It’s seed starting time! And I want to show you why and how I get my seedlings in the sun as soon as possible.
One of the common questions I get is how to keep seedlings from getting leggy and flopping over. Almost always, this happens from growing them indoors in weak light. Maybe you have them next to a sunny window or under a grow light. Well, often that doesn’t work as well as you’d like. Many windows filter the UV rays too much, and your little babies will stretch their stems and bend toward the light, trying to find more. Or you might have your artificial lights too far from the plants. I start seeds under 4-foot fluorescent light tubes (two sets of double tubes), and these need to be just a few inches above the plant tops. Really, really close! Unless you have one of those new LED grow light setups — those can be farther away from the plants. I definitely want to get one – maybe next year!
Closer to nature is usually better
Actually, maybe I won’t get one of those cool, purple LED lights. Because in recent years, I’ve started putting the seedling trays outside within a few days after they sprout. I figure being more like mother nature intended is good for them. Why? A couple of reasons:
- You just can’t duplicate the wide spectrum of light that comes from the sun.
- A little breeze on the seedlings will make the stems stronger, so they’ll be less likely to flop in the garden.
- Your little plants have evolved over millennia to germinate outdoors, and there are probably many benefits to being outside that we haven’t even figure out yet.
But they need some protection!
Most seedlings will struggle if placed directly in bright sun. In nature, they often sprout while last year’s stems and foliage are still providing a little filtration and light shade from the intensity of full sunlight. In a greenhouse, you’d use shade cloth to control how much sun comes in, but if you don’t have a greenhouse, you need to make do. I found an easy solution: we have patio lounge chairs made of a mesh fabric that lets some sunlight pass through. I place my seedling trays under the shade of the lounge chair and use it like shade cloth. I think the warm concrete under the trays is good for them, too. I’m doing this in early spring, so the daytime temps are only in the 60s and 70s (that’s California “early spring” for you!).
After they develop some true leaves (not the little cotyledons or seed leaves they first get), I’ll start gradually giving them some exposure to full sun. But only an hour or so (longer if it’s early morning or late evening) per day at first. Then, maybe a half day, working up to a full day in the sun (if they are full-sun plants — don’t do this if you’re raising shade plants!) about a week before planting them out in the garden.
I made a newb mistake….I just planted some Sun Sugar cherry tomato seedlings into my raised bed last night. I got out to my garden today at about 10 am and the sun was baking them. They’re all wilted. I quickly deep-watered the ground around them and added some garden straw around the base to keep the dark soil from attracting more heat and keeping the water from evaporating. Do you think they’re salvageable?
Oh no! I hope they’re bouncing back. Tomatoes are tough plants, but did you give them some filtered sun at first like I did in the post above? I usually let them have only the filtered sun for a week or so, and then they get half a day of sun. Full sun after a couple weeks, unless it gets hot (like now!) and then I give them some afternoon shade. If yours are still struggling, try figuring out some filtered shade for a while – do you have a patio chair or some other structure you can put over them that lets a few hours of sun hit them (preferably in the morning when not too hot) and gives shade after that?
I have always taken my tomato seedlings directly to my planting area on my roof a the earliest opportunity where they receive hard direct sun, wind, cool temperature, and everything else nature throws at them. No “hardening” or anything else. They thrive. I don’t know why anyone imagines seedlings will be damaged by sun. Of course, latitude matters; I’m at the 42nd parallel. Maybe if you’re somewhere below the 20th parallel, it matters.
I have 30 tomato plants, several varieties including heirlooms, on the roof right now. They’re thriving. I’ve been doing this for 3 decades. I tend to think this idea of protecting your tomatoes from the sun is one more strange internet idea. Plants want sun. Give it to them.
You will always see your plants “wilt” in direct sun when it gets up around 4pm. Keep them watered. Come back in the evening and you will see they’re perked right back up.
This, of course, will be disputed by folks imagining they need to “harden” their seedlings to that thing they’re desperate for….sun. For 3 decades, I’ve been growing tomatoes on my roof in direct sun, hard wind, and every other thing nature throws at them. They thrive.
Your latitude matters; I’m at the 42nd parallel. I suppose if one is in South Florida or thereabouts, it’s another matter.
Hey Kurt, thanks for commenting. How soon do you put your seedlings in the sun? That matters. Most of us are starting them in a protected spot like my garage, under grow lights, to get an earlier start than we can outside. When they’ve been inside for a month or so, they definitely need hardening with filtered light for a while, maybe just a week or so, to gradually get used to full sun. This isn’t just some internet idea. I’ve been gardening 30 years, and I’ve had stuff clearly die when I wasn’t careful about this.
Just thought I’d give you quick update ( some photos to follow).
So far, almost 100% success, I lost a small tray of pepper seedlings, too much of a hurry to get them outside under the shade cloth , they could have done with a few more days under the grow lights. We are now getting 25c regularly, the shade cloth has been a boon, and I’ve been giving the seedlings more and more direct sun gradually. As a novice Gardner, perhaps you can help here, would it be OK to leave the seedlings under the shade cloth all the time ? I believe it’s a 30% cloth. The reason I ask , I’m not able to keep tending them everyday and if it won’t be detrimental it will save me some time. Appreciate your advise
Hey John, good to hear about your success! 30% shade is probably fine to leave them under. When you buy plants at a nursery, they’re usually under some shade that might be even more than that. A quick search online tells me that others are having success growing under 30% shade cloth. If there is any way you can set up automatic watering with a drip system, that would be best, so you don’t have to tend them every day. I set up some half wine barrels on a patio for veggies last year and created a drip system for them. It’s a game changer! I need to post about it, actually!
I have 2 trays of tomato seedlings, outdoors under some shade cloth. They germinated in my basement on a heat mat, I gave them a few days to pop up and moved them straight out . So far they are looking good. Has to be admitted though , I live in Southern Spain. We have had unusual warm weather for March . Some chilli seedlings just starting to peek through on the heat mat , will get them out as well
It sounds like you’re having success, John. Spain in spring also sounds great! This year, I have several varieties of zinnia, gomphrena, strawflower, celosia, amaranth, and rudbeckia starting in seed trays. We’ve created a new cut-flower section of the garden, and my wife is planning to use many of these flowers for our daughter’s wedding in September. Good luck with your growing!
Thanks, John. I usually keep them outside, but I place the trays on the diving board for the pool, which usually keeps them away from slugs and snails exploring at night.
I have 2 trays of tomato seedlings, outdoors under some shade cloth. They germinated in my basement on a heat mat, I gave them a few days to pop up and moved them straight out . So far they are looking good. Has to be admitted though , I live in Southern Spain. We have had unusual warm weather for March . Some chilli seedlings just starting to peek through on the heat mat , will get them out as well
Just came across this article , very interesting, will give it a try. Do you bring the seedlings indoors at night, or leave them out ?