Hardening Off Seedlings Before Transplant - Ep. 190

[00:00:00] If you follow me on Instagram or TikTok, you may have recently seen a video where I talked about my brassicas and sunscald. I was attempting to harden off my plants and get them out into the garden and I rushed the process

[00:00:15] and therefore ended up with some damaged cabbage and broccoli and cauliflower plants. That was due to my lack of patience as a gardener. So I had to put those plants back into some

[00:00:29] shade and allow them to recover and then continue on with the hardening process, which of course defeated the purpose. I was trying to speed up that process and I ended up getting myself behind

[00:00:40] anyway. Why is it so important for us to harden off our seedlings properly before transplant? The process helps our plants adjust to the outdoor environment preventing shock and ensuring that they thrive once they get planted out into the garden.

[00:00:59] Gradual exposure helps the plants acclimate to the conditions that they're going to experience out in the garden or in their containers on your porch before you put them out there. Today on Just Grow Something, we will go over the exact steps that we need to take to harden

[00:01:15] 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, the garden center, or the farmer's market. Following these steps and displaying some patience will prevent the

[00:01:31] heartache of putting those plants out and having them fail. We'll also talk about how to recover if your plants begin to display signs of stress after they are already in their permanent home. Let's dig in. Hey I'm Karen. I started gardening in a small corner of my suburban

[00:01:48] backyard and now 18 years later I've got a degree in horticulture and operate a 40-acre market farm. I believe there is power in food and that everyone should know how to grow at least a little bit of

[00:01:59] their own. On this podcast I share evidence-based techniques to help you plant, grow, harvest, and store all your family's favorites. Consider me your friend in the garden. So grab your garden journal and a cup of coffee and get ready to just grow something.

[00:02:21] Okay so this is your last chance for the question of the month. What is your biggest pest in the garden and how do you manage it if at all? Leave me a voice message from the link in the show notes,

[00:02:32] 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 or Facebook or TikTok or wherever

[00:02:42] you can find me. We have 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

[00:02:54] answer. Okay I am hardening off hundreds of plants right now to go out into the gardens and there is a whole lineup of plants waiting just behind those for their chance at being hardened off and

[00:03:08] prepared for going out into the garden. What is hardening off? When we say to harden off a plant what is that? This is the process of gradually exposing our young plants to the specific elements

[00:03:22] in our garden before they are being planted into their permanent home outside. So this is especially important for greenhouse grown plants or plants that we have grown indoors whether they're from seed or from cuttings because the conditions inside our house or a greenhouse are vastly

[00:03:43] different than those that are outside. So too much sun and wind too quickly can actually stunt the growth of the plants. It can cause transplant shock. It can cause damage to the plant leaves which is

[00:03:57] going to reduce photosynthesis which is going to stunt the growth and it can even cause those little plants to just die off. Let's put it this way. If you have spent the entire winter indoors with very little exposure to outdoor conditions and then you head to a beautiful

[00:04:12] sunny tropical location and you spend all day on the beach the first day you're going to get burned. I don't care how much sunscreen you put on. The same thing goes if you live in a very warm

[00:04:23] climate and you decide to go on a trip to Antarctica. You can bundle up all you want but you're not going to be used to those conditions and it's going to get ugly. The same thing

[00:04:32] goes for our plants and you do still need to be sure that you are taking some of these steps with plants that you bring home from elsewhere too. There is no guarantee that those plants have

[00:04:43] been conditioned to take full sun and wind and rain and whatever else the garden environment throws at them and it's really lousy to spend a bunch of money on plants put them outside and then watch

[00:04:54] them succumb to the elements in less than a week. So even if you're not starting your transplants yourself you should still be acclimating those purchased ones to your garden conditions before they go into the garden. Now doing this properly is going to thicken the cuticle

[00:05:11] on the leaves so they're going to lose less water when exposed out to the elements. It's going to strengthen the stems against wind damage. It's going to cause the plants to be more temperature hardy which is really important in the early spring when you have such wide temperature

[00:05:26] fluctuations and it's going to help to prevent transplant shock which can cause plant growth to basically completely stall out or even cause plants to die from the sudden change in temperature and sun exposure. So some tips for this we want to begin the hardening off process about seven

[00:05:48] to ten days before the intended transplant date. This timing allows the plants to gradually acclimate to the outdoor conditions. This is where I messed up. I tried to force this

[00:06:01] process. I tried to move it along a little bit more quickly and I exposed those plants to full sun sooner than what they were ready and that caused them to get sunscalded. It's better to select

[00:06:14] a period of mild weather for hardening off avoiding days where you've got extreme heat or extreme cold or really really strong winds. Now I know sometimes this can be difficult especially when we're hardening off plants that go in during the early spring because that weather

[00:06:30] can be very unpredictable in some areas at least in mine for sure. So just do the best that you can with some protected areas near your house or near a shed or underneath the tables or chairs or near

[00:06:43] a porch whatever you can do to help sort of protect those plants for those first few days. The other thing we want to do is start really slowly just a few hours in a shaded area the

[00:06:55] first few days and then slowly increasing that exposure is what we're going for just because these plants may have been under grow lights for 12 to 15 hours a day since they sprouted does not mean that they are ready for exposure to full sun right away. Very different light spectrums

[00:07:13] plus we're adding in wind and maybe rain so go slow again exhibit your gardener's patience which is what I didn't do and then each day you're going to gradually increase the amount of time

[00:07:24] the seedlings spend outdoors by about one or two hours maybe three aim to expose them to gradual increases in amounts of direct sunlight gradual gradual gradual I can't say that enough. Now you're going to want to monitor the weather conditions be mindful of your weather forecast

[00:07:44] if there's a prediction of frost or storm conditions while you're in this process then just bring your seedlings back indoors now if it's toward the end of the hardening off process you might go ahead and leave them out there but you might want to provide them with some

[00:07:58] sort of protection like row covers or something depending on how severe the weather situation is going to be but also keep in mind those outdoor conditions are likely to dry out the soil in your

[00:08:10] seedlings more quickly and this is okay check the soil moisture daily and water as needed but we don't want to keep them waterlog because they're not going to be consistently moist after

[00:08:22] they go into the garden or at least they shouldn't be so a reduction in watering is part of the hardening off process I actually recommend that you start by gradually reducing the amount of water

[00:08:34] that the plant gets a few days before you even start the hardening off process let them dry out between watering to sort of simulate the conditions that they're going to face outdoors

[00:08:45] no we don't want them wilting but we do need to get them used to not having water all the time now along with this we do not want to feed them no fertilizer or plant food during this process

[00:08:59] seedlings in the hardening off phase are not in active growth mode they kind of go into a survival mode they're they're getting ready to go out into the garden fertilizer is really most beneficial

[00:09:12] when plants are actively growing and they can utilize those nutrients efficiently so if we apply plant food during this sort of transition period this is likely not going to result in any kind of

[00:09:25] significant growth benefits and it actually could lead to more plant stress plus we want the plants focusing on developing strong healthy roots that can anchor them into the garden soil when they

[00:09:36] go out too much plant food is actually going to more encourage that top growth growth on the leaves and the stems and that's at the expense of root development so save the plant food or amendments

[00:09:49] for after the plants are established in their new home now depending on where you put your seedlings out to harden them off you may need to keep them under some insect netting to let

[00:10:00] the light in but to keep the bugs out if you have slugs or snails you may need to elevate the plants up onto a table if you have cats or dogs you may need to harden them off somewhere

[00:10:10] where your furry companions aren't likely to get into them i have made the mistake of starting to harden my plants off on the table on my back deck only to find a squirrel smack dab in the middle

[00:10:20] of the table digging into one of the containers to hide an acorn so consider your particular version of pest and protect your seedlings accordingly so step by step how do we harden off our seedlings start this process when the daytime temperatures are generally staying

[00:10:41] above 45 degrees Fahrenheit or 7.2 Celsius for your cool weather crops and at least 50 Fahrenheit or 10 Celsius for the warmer weather plants keep your long range forecast in mind too just because i have a warm spell in the beginning of february where it's 60 degrees outside it

[00:11:02] doesn't mean the temperatures aren't going to plummet down to 10 degrees in the overnight in the next week and that's not going to be good for my lettuce if i moved them to the garden too early so plan according to the preferred growing conditions for whatever you're planting

[00:11:16] and then start the process about 10 days before you want to put them out into the garden now if you have put a garden plant together that includes a calendar based on what your

[00:11:27] usual conditions are for that time of year this is going to be a little bit easier and you may actually decide to add that as a date but learn to be flexible with this so when we start this

[00:11:39] process on the first day we want to put the plants outside in a protected area in the shade or in dappled shade somewhere outside of direct sunlight for just a few hours now the next day

[00:11:53] you want to add a couple of hours to that in the third day we're going to add a few more hours to that we don't want to expose them to too much sun too quickly we're just allowing them to get outside

[00:12:05] we also don't want too much wind right away which is why i say a protected area at first a very gentle breeze is fine but avoid putting them out into any gusting winds now conversely

[00:12:18] to this if there isn't enough air movement on the days that your plants are outside then you can go ahead and just run your hands across the plants several times a day and that's also

[00:12:26] going to do the trick if you started these plants yourself hopefully you have had a fan on them for at least a few hours a day simulating a light breeze and this has helped to strengthen them up

[00:12:37] beforehand so this might not be as necessary now after a few days of increasing time outside in the shade you can place them in direct morning sun for just a couple of hours and then move

[00:12:52] them back into the shade in their protected area for the afternoons and then gradually expose them to more direct sun each morning this is not only exposing them to increased amounts of sunlight

[00:13:05] but it's also adding more wind and the other elements as you move them out of that protected area in the morning you also want to gradually reduce the amount of water they get each day

[00:13:18] as you do this again we don't want to bring them to the wilting point but we want to prepare them for the fact that they won't be constantly wet in the garden and then if we water them really well

[00:13:29] on the day we transplant and we make sure they're watered in very well when they go in the ground they'll be less prone to transplant shock because they won't have to focus on getting water they

[00:13:40] can focus on stretching their roots out into the soil we want those roots to search downward for moisture once they go out into the garden so when you do water them during this hardening

[00:13:51] off period try to water them from the bottom just place them in a tray with some water and let them soak it up from underneath now following these steps within about seven to ten days your plants

[00:14:04] should be used to the outdoor temperatures and the elements and the sun exposure their final test is to place them still in their containers out into the place where they will reside permanently and

[00:14:16] leave them there for at least 24 hours 48 hours if you can manage it watering them as usual but providing no other protection other than to protect from critters if they still look good well then go

[00:14:29] forth and transplant my friend but if they show any signs of stress or shock at that point or anywhere along the way with this process slow down back up and introduce them more gradually

[00:14:43] what are those signs of plant stress very wilted plants or sagging leaves that don't seem to perk back up spots on the leaves or leaf edges that look like burn marks discolored leaves leaves turning purple or blanching leaves dropping off the plant plants that lean over and

[00:15:03] don't seem to stand back up very readily especially after being watered or when facing heavy wind gusts these are all signs your plants need to be acclimated a little more slowly you are much better

[00:15:15] off delaying your planting than to continue to move forward with transplanting and shocking your plants even further this could set back your harvest by a full month or more because it will

[00:15:27] stunt the plant growth or worse you may not get a harvest at all because the plants die after being transplanted or they don't bounce back quickly enough to reach maturity before their season ends

[00:15:40] if your plants do show these signs of stress just reduce the amount of exposure that they're getting for a few days and then start to increase again a little bit more slowly some plants are much more

[00:15:53] prone to sunscald like my brassicas and it may take them a while to bounce back so give it some time most of the ones that I scalded bounced back in a matter of just a few days and I was able

[00:16:04] to finish the hardening off process and get them transplanted however I have an entire tray of cauliflower that got so scalded the older leaves didn't bounce back at all and I'm waiting on the

[00:16:17] new green growth to mature before I start the process all over again it's very possible that I won't get a harvest from those depending on our weather but it's a very fast maturing variety

[00:16:28] so I'm not giving up hope if I was relying on those to produce for me though and they are something that maybe took longer than 60 days to mature then I would likely replace them with plants from the

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[00:17:40] you buy plants from the store or the market instead of starting them yourself doesn't mean you're off the hook and you get to skip this hardening off process purchased plants might be

[00:17:50] hardened off to the best of the growers ability before being sold to you and they might not be hardened off at all so whether or not there has been an attempt to harden those plants off the

[00:18:01] conditions at the greenhouse or the farm or the retail center that those plants came from are not the same as the ones in your garden if they've been hardened off at all to some extent

[00:18:14] those plants have likely been hardened off as a large group not individual plants facing the outdoor conditions alone this makes a difference so if the nursery has dozens of trays of 18 to 24 plants sitting outside together facing the wind those plants have each other for support and a

[00:18:34] little bit of protection just by the sheer volume of plants and their proximity to each other that is very different from a single plant whose nearest neighbor is 18 to 36 inches away like they will be after they're transplanted so you don't necessarily have to take the entire seven to

[00:18:52] 10 days to harden nursery plants off especially if you bought them from a garden center where they've been sitting outside somewhat but you should give them at least five days to acclimate to your unique gardening situation and just watch how they react put the plants out into

[00:19:09] the sun for a few morning hours the first day you bring them home and then back into the shade again in the afternoon just increase those hours over the next three days and then give them

[00:19:20] that 24 hour test on day five you should also be letting them dry out between waterings each day to to acclimate them to those less than ideal conditions keep an eye out for those stress

[00:19:33] indicators I talked about earlier and adjust your schedule accordingly based on how the plant reacts so what happens if you get through the hardening off process and you think everything is good to go

[00:19:46] and you transplant everything outside into their new homes only to see your plants start to show signs of stress once they're out in the garden signs of stress or shock are going to include wilting yellowing leaves stunted growth or drooping that doesn't recover after being watered or

[00:20:03] after the sun goes down so here are some steps to assist your plant in recovering from transplant shock ensure the soil around the transplanted seedlings is very moist when you transplant if the plant starts to show signs of stress over the next few days then continue to

[00:20:21] water deeply and evenly providing enough moisture for the plant to establish its roots if you've backed off the watering a bit during the hardening off process this extra water is going to

[00:20:31] take some stress off the plant and allow it to focus on tissue repair if the plants are wilting excessively or show signs of sunscald provide temporary shade using garden fabric a shade cloth or even a simple makeshift cover like a cardboard box with holes for circulation

[00:20:49] this helps reduce stress from overexposure to intense sunlight then gradually reintroduce sunlight to the plants over the next several days apply a layer of organic mulch around the base of the seedlings mulch helps retain soil moisture regulates soil temperature and reduces

[00:21:10] stress on the plants if the plant has lost a significant portion of its foliage consider pruning back the damaged leaves and stems this reduces the load on the plant and allows it to focus on recovery hold off on applying fertilizer immediately after transplanting and during

[00:21:27] the recovery period fertilizer can stress already weakened plants allow the plant to recover fully before introducing nutrients and if the plant is tall or top heavy consider providing a stake to provide support until it establishes stronger roots and can stand on its own and sometimes

[00:21:48] the best remedy is just time and patience most plants are pretty resilient and they will recover given the right care so avoid overreacting and making too many drastic changes at once i know

[00:22:00] it's hard not to panic when it looks like all our hard work or money is just shriveling up out in the garden so just continuously monitor the plant's progress and if it shows signs of improvement

[00:22:12] then continue with what you're doing if conditions worsen or they just don't improve it all well then maybe reevaluate and sort of adjust your approach accordingly and sometimes transplant shock is going to happen no matter how well we harden the seedlings off beforehand we're changing their

[00:22:31] environment and some plants are just less resilient to this change than others so some tips for preventing transplant shock include transplant during cooler milder weather cloudy days are great days for transplanting handle the seedlings gently during transplanting to minimize the root damage

[00:22:50] ensure that your planting hole is large enough for the root ball without cramping the roots and that you've loosened up the soil around the hole enough for those roots to start to spread and then

[00:23:01] be sure to water thoroughly before and after transplanting to help settle the soil around the roots and to reduce the stress on the plant by following the steps from this episode we can ensure that our seedlings are properly acclimated to outdoor conditions and we are able

[00:23:16] to help them recover from any transplant shock and thrive in their new garden environment it just takes patience until next time my gardening friends keep on cultivating that dream garden and we'll talk again soon thanks for listening to another episode of just grow something podcast

[00:23:33] for more information about today's topic and to find all the ways you can get in touch with me or support the show go to justgrowsomethingpodcast.com until next time my gardening friends keep learning and keep growing