How to Prepare Seedlings for Transplant into the Garden - Ep. 243

[00:00:00] I will never forget the first time that I successfully started my own transplants from seed indoors and they actually looked healthy and strong. I was so excited to get those tomato plants out into my garden and I lovingly transferred them from their little pots out into the garden, got them all watered in, and I was so excited about the money that I had just saved by doing it all myself instead of going to the garden center.

[00:00:25] Three days later, those plants were flopped over flat on the ground looking like they had seen a hard frost overnight even though I knew they hadn't. Those plants took weeks to bounce back and they started producing way later than they should have. That very next year I did it again, only this time it was cabbage and the plants got completely sun bleached and they never bounced back at all. They dropped most of their leaves and they just didn't grow.

[00:00:53] In both cases, I had failed to give the plants adequate time to acclimate to their surroundings. I moved them way too quickly from their indoor seed starting setup with its perfect light and its perfect temperatures and protection from the elements right out into the full sun with the gusting winds and the wild temperature swings that are very typical for our gardens here in the spring.

[00:01:15] That process of acclimating to the outside world is called hardening off and nobody had ever told me anything about this. It seems obvious if we think about it in terms of anything else in our world. I mean, if we live somewhere warm and travel someplace cold, our bodies need time to acclimate to our new surroundings or need adequate protection to help with that transition.

[00:01:44] If we need it, our little plants need it too. So, today on Just Grow Something, we're walking step by step through how to transition your plants into the garden, whether you've started them yourself or you bought them somewhere else. Will it always end in disaster if you don't do this? No, not always.

[00:02:04] But the number of times it has ended in disaster for me has me checking myself every time that I don't think that I have the patience to wait a week before putting my plant babies in the ground. Let's dig in. Hey, I'm Karen and what started as a small backyard garden 20 years ago turned into a lifelong passion for growing food. Now, as a market farmer and horticulturist, I want to help you do the same.

[00:02:28] On this podcast, I am your friend in the garden, teaching evidence-based techniques to help you grow your favorites and build confidence in your own garden space. So grab your garden journal and a cup of coffee and get ready to just grow something. Okay, I know we've talked about this before. In fact, I'm pretty sure we talked about this at the same time last season. And you know what? That's okay.

[00:02:52] It's important because even very experienced gardeners like myself tend to get overexcited about putting our plants out into the garden on that beautiful spring day when the weather is perfect and the soil is perfect and the plants are ready and we're ready. And so we just grab them and we go.

[00:03:11] So, except the feeling of walking out to the garden and seeing those beautiful little seedlings just completely flopped over and fighting for their life will fill you with such instant regret. And at the same time, you're singing Britney Spears because, oops, you did it again. So let's not do that. Okay. And if you're brand new to gardening and you've not experienced that, then we're just going to try to prevent it.

[00:03:36] So hardening off is the process of gradually exposing our very young plants to the specific elements that are in our garden before we get them planted into their permanent homes.

[00:03:52] This is especially important for plants that we have started indoors ourselves or that have been grown previously in a greenhouse, whether that is from seed or from cuttings, because the conditions inside in our house, in our little seed starting area or the conditions in a greenhouse are vastly different from those outside. And too much sun and wind too quickly can cause the plants to be stunted.

[00:04:17] It can cause transplant shock and it can cause damage to their leaves, which is going to reduce that photosynthesis or even cause the plants to die. So if you as a gardener have never hardened your plants off before and you think that you have never experienced any problems for this, I invite you to think back. It took me a while to figure out what was going on with my plants.

[00:04:43] And even years later, when I had only been hardening off some of my transplants and not all of them, if I went back and I thought about it, I realized, yeah, a lot of my plants were actually having this major transplant shock from not being hardened off. I just wasn't recognizing that that that's what it was.

[00:05:04] So if after planting your plants in the ground, you have ever seen yellowing or even very bleached, almost white leaves on your plants within a few days of transplants with the leaves maybe dropping completely off the plants. Or if you've seen what we refer to as leaf scorch, which is where the edges of the plant leaves turn brown and brittle.

[00:05:27] If you've ever had seedlings that wilt over just completely on their sides and they don't perk up even when they've had enough water. Or if you've just had overall stunted growth or seedlings that just kind of seem to sit in the garden for several weeks without growing at all. Yeah, guess what?

[00:05:56] All of those are signs of severe transplant shock and that can generally be avoided with proper hardening off and the proper timing of when to plant those seedlings. Yes, sometimes transplant shock is going to happen no matter what, but we can do our best to prevent it and give our little plants the best chance. And the steps that I'm sharing are just as important with plants that you bring home from elsewhere as they are with the ones that you've grown yourself.

[00:06:23] There is no guarantee that those plants that you've bought at the nursery or at the farmer's market have been conditioned to take full sun and wind and rain and whatever else your garden is going to throw at them. It's a really, really lousy feeling to spend a bunch of money on some really nice plants and then put them outside and then just watch them succumb to the elements in less than a week.

[00:06:47] So even if you're not starting your own transplants yourself, you should still be acclimating those ones that you purchase to your garden conditions before they go in the garden. So what are we actually doing physically to the plants when we harden them off? Number one, we're thickening the cuticle on the leaves so they're going to lose less water when they're exposed to the elements out in the garden, especially like wind and the sun.

[00:07:15] Second, we're strengthening the stems so they are better able to stand up to the wind. Thirdly, we're helping the plant to be more temperature hardy so it's better prepared for the wild temperature swings that can occur from the daytime into the overnights in a lot of areas, especially in the spring. And then finally, we're working to prevent that transplant shock, which can cause plant growth to completely stall out or even cause plants to die from the sudden change in temperature and sun exposure.

[00:07:45] Now, before we go step by step into how to do this, I want to mention that Heirloom Roses is back as a sponsor of the podcast this season. I am super excited about this because I have now seen firsthand the quality of their plants. I got a rose bush from them toward the end of the season last year specifically to plant in a container. It bloomed beautifully within about two weeks of being planted in the fall, and I was super impressed with that.

[00:08:14] But I figured our harsh Missouri winter was going to be the true test of how good their own root roses are. So I pushed the pot up against the side of my house once the plant went dormant, and I mulched in and around the pot with straw, and I left it there all winter. So since I'm in the process of hardening off a lot of my seedlings to go into the garden right now, I thought it would be a good time to pull that pot away from the house and get it back out into the sun and kind of allow that rose to come out of dormancy.

[00:08:42] Well, wouldn't you know it, when I went to go move it out, there were already leaves opening up on that bush, and it hadn't even been out in the sun at all yet. So I'm already thinking really good things about this rose, and I'm expecting, you know, really good things, and I'm excited to see what happens as it starts to bloom this season. If you want to experience the charm of heirloom roses for yourself, head to heirloomroses.com and use code JUSTGROW at checkout to save 20% on your own rose plant.

[00:09:12] Heirloomroses.com with code JUSTGROW, and the link will be in the show notes. Okay, step by step, how do we harden off our transplants? You really want to do this, and you want to kind of plan this according to whatever the preferred growing conditions are for whatever it is that you're transplanting. So generally speaking, we're going to want daytime temperatures that are staying above 45 degrees Fahrenheit or 7.2 Celsius for our cool weather crops,

[00:09:40] and then at least 50 Fahrenheit or 10 Celsius for our warmer weather plants. Now, I actually prefer those air temperatures to be closer to like 55 to 60 degrees Fahrenheit consistently, but that's because I wait until the soil temperatures are higher. So this is all about personal preference for whenever you are transplanting your plants. No matter what, you do actually want to start this process, though, about 7 to 10 days before you want to put them out into the garden.

[00:10:07] So yes, this takes some planning, and I know for those of you who aren't planners, this is going to be a little bit difficult. And honestly, it's difficult for me, too. I mean, when the weather is beautiful and your plants are just ready to go, you want to just grab them and go. But patience is going to be key here, okay? So on the first day, you want to put the plants outside in a protected area in shade or sort of mostly shade,

[00:10:34] somewhere where they're definitely outside of the direct sunlight and just for a few hours, and then bring them back in again, okay? Usually you want to start doing this in the morning. And then the next day, you want to add a few more hours to that. And then the third day, you want to be able to put them out for most of the day. And you still want to do this all in, like, the shade or the dappled light. We don't want to expose them too much sun too quickly. We also don't want too much wind right away, which is why I say a protected area at first.

[00:11:03] A gentle breeze is fine, but you really don't want them out there, like, in the gusting winds, right? So then after a few days of increasing the time outside in the shade, then you can start placing them in the direct sun in the morning, so the morning light, for just a few hours and then move them back into the shade again for the afternoon. And then you gradually just expose them to more and more of that sunlight each day. So this is not only exposing them to increased amounts of sunlight,

[00:11:32] but also to more wind and the other elements as you kind of move them out of their little protected area in the morning, right? So days one through three, shade only. Days four through seven, we're gradually increasing that sun exposure beginning with the morning sun. Now I know that not everybody is home all day to be moving plants in and out all the time, and that's fine, I get that. If you can start by putting them outside in the shade during the day for the first three days

[00:12:02] and bringing them back in when you get home in the evening, then the next time see if you can put them in a spot where they're going to get the morning sun, but that morning sun is going to move beyond so that it naturally is going to be put into the shade in that afternoon. And do that for the next couple of days and then maybe scoots it out just a little bit more until it's finally sitting outside, you know, for the full 24 hours without any ill effects.

[00:12:27] You also want to be gradually reducing the amount of water that they're getting each day as you do this. We don't want them to get to the wilting point, but we do want to prepare them for the fact that they're not going to be constantly wet out in the garden. At least they shouldn't be. I'm hoping that you're not soaking them every single day when they're out in the garden, right? So if we let them sort of dry out a little bit in between waterings while they're in this hardening off process,

[00:12:55] and then we water them really well on the day that we transplant them and we make sure that they're really well watered in when they actually go in the ground, then they're going to be a lot less prone to transplant shock because they're not going to have to focus on getting water. They can just focus on stretching their roots out into the soil, but they've been kind of acclimated to not having that water, see? So after about seven days or so, your plant should now be used to the outside temperatures in most of the elements, right?

[00:13:24] You have to give them a little bit of a final test. So you can take them still in their containers and put them out in the place where they're going to go permanently in your garden and just leave them there for 24 hours, 48 hours if you can manage it. Watering them as usual, but don't provide any other protection other than to protect them from, like, critters, okay? If they still look good after that 24, 48 hours, then they're good to go. It's time to transplant.

[00:13:49] But if they show any signs, any major signs of stress or shock at that point or anywhere along the way with this process, then slow down, back up. We want to reintroduce them a little bit more gradually. This is why I say seven to ten days because this is giving you some wiggle room just in case the plants have a negative reaction somewhere along the way. It gives you the flexibility to be able to slow down the process. So some tips for this. When you're doing the hardening off process,

[00:14:17] if you can pick a time when the weather is kind of mild, I know that's hard to do, especially in the spring. But, you know, we really want to avoid days where it's extremely hot or extremely cold or it's super, super windy outside. So, yes, we're all about kind of keeping to a schedule, but we have to work with the elements, to be honest, okay? And just do the best that you can with a protected area near a building or under tables or chairs if you need to. Start slowly, okay?

[00:14:46] Be patient with this process. I know we want to hurry up and just be done. But just because these plants have been under lights in a seed starting room or in a greenhouse somewhere for 12 to 15 hours a day since they sprouted does not mean that they are ready for exposure to the full sun and the elements outside. So go slow. You also just kind of want to be mindful of the weather forecast. I mean, if there's a prediction of frost or storms coming, you know, bring the seedlings back indoors. This wild weather that we're having here in Missouri this spring

[00:15:16] where it's 74 degrees one day and then all of a sudden we're in a blizzard morning the next day and then we've got heavy winds and everything else. I've been hardening off brassicas to go out into the gardens and I've already had to kind of bring them back into the greenhouse twice because the weather was supposed to be so severe. So not only am I trying to harden them off during periods where the weather is just a little bit more mild, but I will also be timing my planting for when the weather is a little bit more wild. Mild. Not wild.

[00:15:45] It's already wild. Mild. Technically speaking, I should be planting those, you know, in the next day or two, but I likely am going to wait about three or four days until our weather kind of evens out a little bit and I can have a good predictor. So just be mindful of your weather forecast when you're doing this. You also do not want to feed your seedlings. No fertilizing your seedlings during the hardening off phase. During this part, they are not actively like in growth mode, right? We're kind of stressing them out a little bit.

[00:16:14] So if we were to give them any plant food or any fertilizer during this period, it can actually lead them to more stress. Plus, we want them focusing on developing really strong, healthy roots so that they can anchor the plant really well in the garden soil when they go out. If we give them fertilizer right now in their little containers, that's actually likely to encourage more top growth. So the leaves and the stems and not focus at all on that root development.

[00:16:42] So wait until after you're transplanting them and after they've gotten established in their new little spot in the garden to feed them then. And then finally, you want to make sure that you're sort of protecting them from pests. So depending on where you put your seedlings out to harden them off, you may need to put them under some insect nettings so that you're letting the light in but you're keeping the bugs out. If you have slugs or you have snails or something, you can put them up onto a table. If you have cats or dogs or chickens,

[00:17:12] you may have to put them someplace where those little companions aren't going to get to them. I have made the mistake of hardening them off on a table on my back porch only to have squirrels in the middle of them digging to bury their nuts in the soil. So just consider whatever your particular version of pest is and just protect your plants accordingly. So what happens if you get through the hardening off process and you think everything is good to go

[00:17:41] and you transplant everything outside into their new homes, but your plants still start to show some signs of transplant shock. Sometimes it's just going to happen. It really does depend on the plant. Some of them handle transplant better than others. A little bit of stress, a little bit of transplant shock is not going to be the end of the world. They usually will sort of bounce back after being in place for a week or so. But if you're seeing very severe things like, you know, severe wilting, yellowing leaves, very stunted growth,

[00:18:11] drooping that doesn't recover after being watered or after the sun goes down, there are some ways that you can kind of help the plant recover a little bit from that transplant shock. The first thing that kind of starts as we're transplanting. And that is number one, like I said, make sure that your plant is very, very well watered beforehand and then make sure that the soil around the seedling is very moist when you transplant it. You can continue to water very deeply and very evenly over the next couple of days to kind of provide enough moisture

[00:18:40] for the plant to establish its roots. We don't want to overwater it, obviously. But if you've backed off of the watering a little bit during the hardening off process, then this extra water is going to take some of the stress off the plant and allow it to focus on tissue repair if it has been damaged in the process. If they are showing signs of like excessive wilting or sun scald, you might want to provide some temporary shade. So if you can use a shade cloth,

[00:19:10] if you can use some row cover or some sort of a garden fabric to just make a makeshift kind of cover over them, even if you've got a cardboard box with some holes in it for air circulation that you can put over it like in the afternoon, this is going to help to reduce that stress from overexposure to the sunlight. And then you would just sort of gradually reintroduce that stronger sunlight over the next several days. Another thing you can do is make sure that you have put down a really good layer of mulch on the base of the seedlings.

[00:19:40] This is something else that you can do at transplant time. Mulch is going to help to retain the soil moisture. It's going to regulate that soil temperature. So that is going to help reduce the stress on the plants. And if the plant has had significant damage to its foliage, like I mentioned, those really bleached leaves, you can go ahead and prune back some of that damaged part. That's going to help reduce the load on the plant a little bit and help it focus on its recovery. And then finally,

[00:20:09] don't apply fertilizer or plant food immediately after transplanting or during that sort of recovery period, especially if it's showing any kind of stress. That, we already mentioned, the fertilizer can actually stress a plant that is already weakened. So allow it to recover fully before you introduce any type of a fertilizer. Now, if you have something like, you know, I use Elm Dirt's plant juice and it is more supporting the microbes in the soil versus actually feeding the plant itself.

[00:20:38] That I have actually found to be beneficial when I do transplanting. So I will actually water in with the plant juice mixture, but I wouldn't use something like a Miracle-Gro or a Schultz or anything like that to feed them until well after they have already gotten themselves sort of re-established. Sometimes it just takes some time. You just kind of have to wait for them to recover. Most plants are resilient and so long as they haven't been irreparably damaged,

[00:21:08] they should bounce back for you. It's kind of hard not to panic. It looks like all of our hard work or all of our money just shriveled up out in the garden. Just keep an eye on it. Continue with what you're doing and, you know, just see how the plant reacts and just re-evaluate and adjust accordingly when you need to. So if we follow the steps from this episode, we can help to prevent our seedlings from having any type of adverse reaction from severe transplant shock when we put them out in the garden.

[00:21:37] We want to make sure they are properly acclimated to the outdoor conditions before we move them and we are able to help them recover from any transplant shock and just kind of 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.