Hardening off is a process that helps plants adjust to the outdoor environment, preventing shock and ensuring they thrive once planted in the garden. Gradual exposure helps the plants acclimate to the conditions they will experience out in the garden or in their containers on your porch before you put them out there.
Today on Just Grow Something we’ll go over the exact steps we need to take to harden off our plants prior to putting them out into the garden. This includes whether you’re growing them yourselves or if you’ve just brought them home from the nursery, garden center, or farmers market. Following these steps and displaying some patience will prevent the heartache of putting those plants out and having them fail. We’ll also talk about how to recover if your plants begin display signs of stress after they are already in their permanent home. Let’s dig in.
Question of the Month:
: “What is your biggest pest in the garden and how do you manage it (if at all)?” Leave a voice message from the link in the show notes, respond to the question in Spotify if that’s where you’re listening, send me an email, drop it in the Facebook group or in a DM to me on Instagram, Facebook or TikTok. We’ve already had some good discussions around this in the Facebook group and I will read all the answers on next week’s episode. You have until March 31st to get me your answer.
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If you follow me on Instagram or TikTok, you may have recently
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seen a video where I talked about my brassicas and sun
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scald. I was attempting to harden off
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my plants and get them out into the garden and I rushed the
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process and therefore ended up with some damaged cabbage and
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broccoli and cauliflower plants. That was due to my lack of
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patience as a gardener. So I had to put those plants
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back into some shade and allow them to recover and then
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continue on with the hardening process, which of course
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defeated the purpose. I was trying to speed up that
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process and I ended up getting myself behind anyway.
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Why is it so important for us to harden off our ceilings properly
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before transplant? The process helps our plants
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adjust to the outdoor environment, preventing shock
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and ensuring that they thrive once they get planted out into
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the garden. Gradual exposure helps the
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plants acclimate to the conditions that they're going to
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experience out in the garden or in their containers on your
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porch before you put them out there.
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Today on Just Grow Something, we will go over the exact steps
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that we need to take to harden off our plants prior to putting
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them out into the garden. This includes whether you're
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growing them yourselves or if you've just brought them home
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from the nursery, the garden center or the farmers market.
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Following these steps and displaying some patients will
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prevent the heartache of putting those plants out and having them
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fail. We'll also talk about how to
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recover if your plants begin to display signs of stress after
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they are already in their permanent home.
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Let's dig in. Hey, I'm Karen.
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I started gardening in a small corner of my suburban backyard
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and now 18 years later, I've got a degree in horticulture and
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operate a 40 acre market farm. I believe there is power in food
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and that everyone should know how to grow at least a little
00:01:58
bit of their own. On this podcast I share evidence
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based techniques to help you plant, grow, harvest, and store
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all your family's favorites. Consider me your friend in the
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garden. So grab your garden journal and
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a cup of coffee and get ready to just grow something.
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OK, so this is your last chance for the question of the month.
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What is your biggest pest in the garden and how do you manage it,
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if at all? Leave me a voice message from
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the link in the show notes. Respond to the question in
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Spotify. If that's where you're
00:02:35
listening. Send me an e-mail.
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Drop it in the Facebook group or in Adm to me on Instagram or
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Facebook or TikTok or wherever you can find me.
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We have already had some good discussions around this in the
00:02:46
Facebook group and I will read all the answers on next week's
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episode. You have until March 31st to get
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me your answer. OK?
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I am hardening off hundreds of plants right now to go out into
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the gardens, and there is a whole lineup of plants waiting
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just behind those for their chance at being hardened off and
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prepared for going out into the garden.
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What is hardening off when we say to harden off a plant, what
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is that? This is the process of gradually
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exposing our young plants to the specific elements in our garden
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before they are being planted into their permanent home
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outside. So this is especially important
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for greenhouse grown plants or plants that we have grown
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indoors, whether they're from seed or from cuttings, because
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the conditions inside our house or a greenhouse are vastly
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different than those that are outside.
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So too much sun and wind too quickly can actually stunt the
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growth of the plants. It can cause transplant shock,
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it can cause damage to the plant leaves, which is going to reduce
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photosynthesis, which is going to stunt the growth, and it can
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even cause those little plants to just die off.
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Let's put it this way. If you have spent the entire
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winter indoors with very little exposure to outdoor conditions,
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and then you head to a beautiful, sunny, tropical
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location and you spend all day on the beach, the first day,
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you're going to get burned. I don't care how much sunscreen
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you put on. The same thing goes if you live
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in a very warm climate and you decide to go on a trip to
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Antarctica. You can bundle up all you want,
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but you're not going to be used to those conditions and it's
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going to get ugly. The same thing goes for our
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plants. And you do still need to be sure
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that you are taking some of these steps with plants that you
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bring home from elsewhere too. There is no guarantee that those
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plants have been conditioned to take full sun and wind and rain
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and whatever else the garden environment throws at them.
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And it's really lousy to spend a bunch of money on plants, put
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them outside, and then watch them succumb to the elements in
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less than a week. So even if you're not starting
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your transplants yourself, you should still be acclimating
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those purchased ones to your garden conditions before they go
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into the garden. Now.
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Doing this properly is going to thicken the cuticle on the
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leaves, so they're going to lose less water when exposed out to
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the elements. It's going to strengthen the
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stems against wind damage. It's going to cause the plants
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to be more temperature Hardy, which is really important in the
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early spring when you have such wide temperature fluctuations.
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And it's going to help to prevent transplant shock, which
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can cause plant growth to basically completely stall out
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or even cause plants to die from the sudden change in temperature
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and sun exposure. So some tips for this.
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We want to begin the hardening off process about 7 to 10 days
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before the intended transplant date.
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This timing allows the plants to gradually acclimate to the
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outdoor conditions. This is where I messed up.
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I tried to force this process. I tried to move it along a
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little bit more quickly and I exposed those plants to full sun
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sooner than what they were ready and that 'cause them to get sun
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scald. It's better to select a period
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of mild weather for hardening off, avoiding days where you've
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got extreme heat or extreme cold or really, really strong winds.
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Now I know sometimes this can be difficult, especially when we're
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hardening off plants that go in during the early spring, because
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that weather can be very unpredictable in some areas, at
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least in mine for sure. So just do the best that you can
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with some protected areas near your house or near a shed or
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underneath the tables or chairs or near a porch, whatever you
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can do to help sort of protect those plants for those first few
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days. The other thing we want to do is
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start really slowly, just a few hours in a shaded area the first
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few days and then slowly increasing that exposure is what
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we're going for. Just because these plants may
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have been under grow lights for 12 to 15 hours a day since they
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sprouted does not mean that they are ready for exposure to full
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sun right away. Very different light spectrums.
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Plus we're adding in wind and maybe rain, so go slow.
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Again. Exhibit your gardener's
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patience, which is what I didn't do.
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And then each day you're going to gradually increase the amount
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of time the ceilings spend outdoors by about one or two
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hours, maybe three. Aim to expose them to gradual
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increases in amounts of direct sunlight.
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Gradual, gradual, gradual. I can't say that enough.
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Now you're going to want to monitor the weather conditions.
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Be mindful of your weather forecast.
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If there's a prediction of frost or storm conditions while you're
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in this process, then just bring your seedlings back indoors.
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Now, if it's toward the end of the hardening off process, you
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might go ahead and leave them out there, but you might want to
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provide them with some sort of protection like grow covers or
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something, depending on how severe the weather situation is
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going to be. But also keep in mind those
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outdoor conditions are likely to dry out the soil in your
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seedlings more quickly, and this is OK.
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Check the soil moisture daily and water as needed.
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But we don't want to keep them waterlogged because they're not
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going to be consistently moist after they go into the garden.
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Or at least they shouldn't be. So a reduction in watering is
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part of the hardening off process.
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I actually recommend that you start by gradually reducing the
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amount of water that the plant gets a few days before you even
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start the hardening off process. Let them dry out between
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watering to sort of simulate the conditions that they're going to
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face outdoors. No, we don't want them wilting,
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but we do need to get them used to not having water all the
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time. Now along with this, we do not
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want to feed them no fertilizer or plant food during this
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process. Seedlings in the hardening off
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phase are not in active growth mode.
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They kind of go into a survival mode.
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They're they're getting ready to go out into the garden.
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Fertilizer is really most beneficial when plants are
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actively growing and they can utilize those nutrients
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efficiently. So if we apply plant food during
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this sort of transition period, this is likely not going to
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result in any kind of significant growth benefits and
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it actually could lead to more plant stress.
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Plus, we want the plants focusing on developing strong,
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healthy roots that can anchor them into the garden soil when
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they go out. Too much plant food is actually
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going to more encourage that top growth growth on the leaves and
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the stems, and that's at the expense of root development.
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So save the plant food or amendments for after the plants
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are established in their new home.
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Now, depending on where you put your seedlings out to harden
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them off, you may need to keep them under some insect netting
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to let the light in. But to keep the bugs out, if you
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have slugs or snails, you may need to elevate the plants up
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onto a table. If you have cats or dogs, you
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may need to harden them off somewhere where your furry
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companions aren't likely to get into them.
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I have made the mistake of starting to harden my plants off
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on the table on my back deck only to find a squirrel smack
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dab in the middle of the table digging into one of the
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containers to hide an acorn. So consider your particular
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version of pest and protect your seedlings accordingly.
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So, step by step, how do we harden off our seedlings?
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Start this process when the daytime temperatures are
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generally staying above 45°F, or 7.2 Celsius for your cool
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weather crops, and at least 50 Fahrenheit or 10 Celsius for the
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warmer weather plants. Keep your long range forecast in
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mind too. Just because I have a warm spell
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in the beginning of February where it's 60° outside, it
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doesn't mean the temperatures aren't going to plummet down to
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10° in the overnights in the next week.
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And that's not going to be good for my lettuce if I moved into
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the garden too early. So plan according to the
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preferred growing conditions for whatever you're planting, and
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then start the process about 10 days before you want to put them
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out into the garden. Now if you have put a garden
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plan together that includes a calendar based on what your
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usual conditions are for that time of year, this is going to
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be a little bit easier and you may actually decide to add that
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as a date. But learn to be flexible with
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this. So when we start this process on
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the first day, we want to put the plants outside in a
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protected area in the shade or in dappled shade somewhere
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outside of direct sunlight for just a few hours.
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Now the next day you want to add a couple of hours to that, and
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the third day we're going to add a few more hours to that.
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We don't want to expose them to too much sun too quickly, we're
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just allowing them to get outside.
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We also don't want too much wind right away, which is why I say a
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protected area at first. A very gentle breeze is fine,
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but avoid putting them out into any gusting winds.
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Now conversely to this, if there isn't enough air movement on the
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days that your plants are outside, then you can go ahead
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and just run your hands across the plants several times a day,
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and that's also going to do the trick.
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If you started these plants yourself, hopefully you have had
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a fan on them for at least a few hours a day, simulating a light
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breeze, and this has helped to strengthen them up beforehand,
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so this might not be as necessary.
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Now, after a few days of increasing time outside in the
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shade, you can place them in direct morning sun for just a
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couple of hours and then move them back into the shade in
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their protected area for the afternoons, and then gradually
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expose them to more direct sun each morning.
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This is not only exposing them to increased amounts of
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sunlight, but it's also adding more wind and the other elements
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as you move them out of that protected area in the morning.
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You also want to gradually reduce the amount of water they
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get each day as you do this. Again, we don't want to bring
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them to the wilting point, but we want to prepare them for the
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fact that they won't be constantly wet in the garden.
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And then if we water them really well on the day we transplant
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and we make sure they're watered in very well, when they go in
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the ground, they'll be less prone to transplant shock
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because they won't have to focus on getting water.
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They can focus on stretching their roots out into the soil.
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We want those roots to search downward for moisture once they
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go out into the garden. So when you do water them during
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this hardening off period, try to water them from the bottom.
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Just place them in a tray with some water and let them soak it
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up from underneath. Now following these steps,
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within about 7 to 10 days your plants should be used to the
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outdoor temperatures and the elements and the sun exposure.
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Their final Test is to place them still in their containers,
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out into the place where they will reside permanently and
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leave them there for at least 24 hours. 48 hours if you can
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manage it, watering them as usual but providing no other
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protection other than to protect from critters.
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If they still look good, well then go forth and transplant my
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friend. But if they show any signs of
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stress or shock at that point or anywhere along the way with this
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process, slow down, back up and introduce them more gradually.
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What are those signs of plant stress?
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Very wilted plants or sagging leaves that don't seem to perk?
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Back up spots on the leaves or leaf edges that look like burn
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marks, discoloured leaves, leaves turning purple or
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blanching, leaves dropping off the plant.
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Plants that lean over and don't seem to stand back up very
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readily, especially after being watered or when facing heavy
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wind gusts. These are all signs your plants
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need to be acclimated a little more slowly.
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You are much better off delaying your planting than to continue
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to move forward with transplanting and shocking your
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plants even further. This could set back your harvest
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by a full month or more because it will stunt the plant growth.
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Or worse, you may not get a harvest at all because the
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plants die after being transplanted, or they don't
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bounce back quickly enough to reach maturity before their
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season ends. If your plants do show these
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signs of stress, just reduce the amount of exposure that they're
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getting for a few days and then start to increase again a little
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bit more slowly. Some plants are much more prone
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to sun scald like my brassicas, and it may take them a while to
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bounce back, so give it some time.
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Most of the ones that I scalded bounced back in a matter of just
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a few days and I was able to finish the hardening off process
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and get them transplanted. However, I have an entire tray
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of cauliflower that got so scalded the older leaves didn't
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bounce back at all, and I'm waiting on the new green growth
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to mature before I start the process all over again.
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It's very possible that I won't get a harvest from those
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depending on our weather, but it's a very fast maturing
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variety so I'm not giving up hope.
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If I was relying on those to produce for me though, and they
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are something that maybe took longer than 60 days to mature,
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then I would likely replace them with plants from the nursery.
00:16:40
You have to decide what's best for your specific growing
00:16:43
situation and the specific plants you are growing.
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direct.com now. Just because you buy plants from
00:17:41
the store or the market instead of starting them yourself
00:17:44
doesn't mean you're off the hook and you get to skip this
00:17:47
hardening off process. Purchased plants might be
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hardened off to the best of the growers ability before being
00:17:53
sold to you, and they might not be hardened off at all.
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So whether or not there has been an attempt to harden those
00:18:01
plants off, the conditions at the greenhouse or the farm or
00:18:04
the retail center that those plants came from are not the
00:18:07
same as the ones in your garden. If they've been hardened off at
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all to some extent, those plants have likely been hardened off as
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a large group, not individual plants facing the outdoor
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conditions alone. This makes a difference.
00:18:23
So if the nursery has dozens of trays of 18 to 24 plants sitting
00:18:30
outside together facing the wind, those plants have each
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other for support and a little bit of protection just by the
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sheer volume of plants and their proximity to each other.
00:18:39
That is very different from a single plant whose nearest
00:18:43
neighbor is 18 to 36 inches away, like they will be after
00:18:47
they're transplanted. So you don't necessarily have to
00:18:51
take the entire 7 to 10 days to harden nursery plants off,
00:18:55
especially if you bought them from a garden center where
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they've been sitting outside somewhat.
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But you should give them at least five days to acclimate to
00:19:04
your unique gardening situation and just watch how they react.
00:19:08
Put the plants out into the sun for a few morning hours the
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first day you bring them home, and then back into the shade
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again in the afternoon. Just increase those hours over
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the next three days and then give them that 24 hour test on
00:19:22
day 5. You should also be letting them
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dry out between waterings each day too, to acclimate them to
00:19:29
those less than ideal conditions.
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Keep an eye out for those stress indicators I talked about
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earlier and adjust your schedule accordingly based on how the
00:19:39
plant reacts. So what happens if you get
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through the hardening off process and you think everything
00:19:45
is good to go and you transplant everything outside into their
00:19:48
new homes only to see your plants start to show signs of
00:19:52
stress once they're out in the garden.
00:19:55
Signs of stress or shock are going to include wilting,
00:19:58
yellowing leaves, stunted growth, or drooping that doesn't
00:20:02
recover after being watered or after the sun goes down.
00:20:05
So here are some steps to assist your plant in recovering from
00:20:08
transplant shock. Ensure the soil around the
00:20:12
transplanted seedlings is very moist when you transplant.
00:20:16
If the plant starts to show signs of stress over the next
00:20:19
few days, then continue to water deeply and evenly, providing
00:20:23
enough moisture for the plant to establish its roots.
00:20:26
If you've backed off the watering a bit during the
00:20:29
hardening off process, this extra water is going to take
00:20:32
some stress off the plant and allow it to focus on tissue
00:20:35
repair. If the plants are wilting
00:20:38
excessively or show signs of sun scald, provide temporary shade
00:20:42
using garden fabric, a shade cloth, or even a simple
00:20:45
makeshift cover like a cardboard box with holes for circulation.
00:20:49
This helps reduce stress from overexposure to intense
00:20:52
sunlight. Then gradually reintroduce
00:20:56
sunlight to the plants. Over the next several days,
00:21:00
apply a layer of organic mulch around the base of the
00:21:03
seedlings. Mulch helps retain soil
00:21:06
moisture, regulates soil temperature, and reduces stress
00:21:10
on the plants. If the plant has lost a
00:21:13
significant portion of its foliage, consider pruning back
00:21:17
the damaged leaves and stems. This reduces the load on the
00:21:20
plant and allows it to focus on recovery.
00:21:24
Hold off on applying fertilizer immediately after transplanting
00:21:27
and during the recovery period. Fertilizer can stress already
00:21:31
weakened plants. Allow the plant to recover fully
00:21:34
before introducing nutrients, and if the plant is tall or top
00:21:39
heavy, consider providing A stake to provide support until
00:21:43
it establishes stronger roots and can stand on its own.
00:21:47
And sometimes the best remedy is just time and patience.
00:21:51
Most plants are pretty resilient and they will recover given the
00:21:54
right care. So avoid overreacting and making
00:21:58
too many drastic changes at once.
00:22:00
I know it's hard not to panic when it looks like all our hard
00:22:04
work or money is just shriveling up out in the garden.
00:22:07
So just continuously monitor the plants progress and if it shows
00:22:11
signs of improvement then continue with what you're doing.
00:22:14
If conditions worsen or they just don't improve at all, well
00:22:17
then maybe re evaluate and sort of adjust your approach
00:22:20
accordingly. And sometimes transplant shock
00:22:25
is going to happen. No matter how well we harden the
00:22:29
seedlings off beforehand, we are changing their environment and
00:22:32
some plants are just less resilient to this change than
00:22:35
others. So some tips for preventing
00:22:37
transplant shock include transplant during cooler, milder
00:22:42
weather. Cloudy days are great days for
00:22:44
transplanting. Handle the seedlings gently
00:22:47
during transplanting to minimize the root damage.
00:22:50
Ensure that your planting hole is large enough for the root
00:22:53
ball without cramping the roots, and that you've loosened up the
00:22:56
soil around the hole enough for those roots to start to spread.
00:23:01
And then be sure to water thoroughly before and after
00:23:04
transplanting to help settle the soil around the roots and to
00:23:07
reduce the stress on the plant. By following the steps from this
00:23:11
episode, we can ensure that our seedlings are properly
00:23:13
acclimated to outdoor conditions and we are able to help them
00:23:17
recover from any transplant shock and thrive in their new
00:23:20
garden environment. It just takes patience.
00:23:25
Until next time, my gardening friends, Keep on cultivating
00:23:27
that dream garden and we'll talk again soon.
00:23:30
Thanks for listening to another episode of the Just Grow
00:23:32
Something Podcast. For more information about
00:23:34
today's topic and to find all the ways you can get in touch
00:23:37
with me or support the show, go to justgrowsomethingpodcast.com.
00:23:41
Until next time, my gardening friends keep learning and keep
00:23:44
growing.