For new and seasoned gardeners alike, there’s nothing quite as concerning as abnormal seedling growth. I know that I will obsess (and stress) over seedlings that grow a little slowly, or too fast, or seedlings that lean a little too much towards the window. There’s just so much that can go wrong with baby plants–it’s common nature to stress over weird things like foliage growth.
Tomatoes and peppers are the most common seedlings to experience the phenomenon of cotyledon leaves pointing up. While perky seedling leaves aren’t necessarily a problem in themselves–this issue usually resolves as the seedling matures–this could also signify a lighting or watering issue.
Read on to understand some potential theories around why seedling leaves might be pointing up, hopefully putting your plant worries to rest.
Reasons seedling leaves might be “praying”
If your seedlings look like they’ve gone to church, that might not be cause for concern.
Stop to think, for a moment, how that seedling sprung from a tiny seed. Each seed contains the seedling’s cotyledons–its first leaves that feed the immature plant until it is able to grow its own true leaves.
It’s no wonder that the cotyledons might be elongated or otherwise wonky, considering that until recently these leaves were wound around each other inside the seed itself. If the cotyledons look strange, they might just need time to straighten out.
Growing too fast
While there isn’t a lot of research around vegetable seedling leaves pointing up, cannabis growers have studied the phenomenon in depth, theorizing that praying cannabis leaves might just signify quick-growing plants.¹
Sometimes, well-fed plants that are getting intense light will send up new growth faster than the rest of the plant. If your plants are healthy and green, that’s likely all that’s going on. It’s not generally an issue, as plants are usually able to catch up to themselves eventually.
Reaching for the light
Foliage is designed to absorb sunlight–that’s how photosynthesis works. Almost any plant, by its own design, will stretch or turn its foliage towards the sun to maximize its ability to photosynthesize.
Seedlings are no different, and they will reach for an indirect light source if it’s all that’s available to them. If you want your seedling foliage and stems to straighten out, try moving a grow light closer to the seedlings themselves.
Heliotropism is the fancy name for this phenomenon of following the sun, and it occurs in seedlings and mature plants alike.
Water stress
Plant dehydration and light stress are closely linked, and plants have developed a response to conserve moisture, called paraheliotropism. Paraheliotropism occurs when plants orient their foliage parallel to incoming light rays in an effort to minimize surface area, slowing down photosynthesis.²
If your seedling leaves are parallel with light rays from a grow light or the sun, it may be past time to water your seedling trays, and back that grow light out a bit.
Reasons seedling leaves might be “curling”
Even if your seedlings are well past the cotyledon stage, there’s still potential for a myriad of foliage issues. While most plants can adapt to a variety of climates, temperatures, and moisture, sometimes less-than-ideal conditions can be too much–and plants will often communicate their needs via varying their foliage.
Too much light
One reason that leaves curl is to protect themselves from too much sunlight. If seedling leaves are at risk for being burned by too much light, whether natural or artificial, you may notice the plant trying to protect itself by shrinking the available surface area.
If your seedlings are under a grow light, remedying this issue is easy. Either back down on the light intensity or put some distance between the light and your seedlings. To start, have at least two inches between seedlings and the grow light. As the plants grow taller, you’ll want to raise the grow light as well.
If seedling foliage looks bleached out and is crispy to the touch, you may be dealing with a case of sunburn. For further reading on the signs of seedling sunburn and how to prevent it, read this article. If you’re using a greenhouse, you might want to hang a shade cloth to offer your plants some protection from the sunlight.
Too much heat
While many of our favorite vegetables are heat-loving annuals, you can have too much of a good thing. Leaves will curl inward if soil and room temperatures are a little too warm.
If you started your seedlings on a heat mat, take the tray off the heat after more than half of the tray has germinated. You should also remove a humidity dome, if you’re using one, during the hottest part of the day to vent the seedlings out.
If your seedlings are in a greenhouse, roll up the sidewalls or crack the windows and doors to allow excess heat to dissipate. You might also consider putting a fan or two in your seed-starting space to improve air circulation and strengthen seedling stems.
Too little water
If plants are overly thirsty, they curl their leaves inward in an effort to retain moisture.
It’s almost more damaging to overwater seedlings than to underwater them, but if the soil is dry to the touch and the foliage has started to curl inwards, your seedlings need more water. Try to water seedlings early, before they are hit with direct light to avoid scorching delicate seedling foliage any further. You might also try bottom watering to protect already damaged plant foliage from unnecessary moisture.
Yellow leaves, on the other hand, are typically a sign of a nutrient deficiency or overwatering. Read this article for more information on yellowing leaves and how to revive a plant that’s struggling from a deficiency of some kind.
In summary
If your seedling leaves are pointing up, don’t worry – it’s likely just a phase that your plants will eventually grow out of. Maybe just spend some extra time in the greenhouse, monitoring conditions closely to make sure that your seedlings are getting the appropriate amount of water, light, and nutrients.
Resources
¹ Haze, Nebula. “Why Are My Leaves Pointing up?” Grow Weed Easy, Grow Weed Easy, 29 Dec. 2019, https://www.growweedeasy.com/why-are-marijuana-leaves-pointing-up.
² Pastenes C, Porter V, Baginsky C, Horton P, González J. “Paraheliotropism can protect water-stressed bean (Phaseolus vulgaris L.) plants against photoinhibition.” J Plant Physiol. 2004 Dec;161(12):1315-23. doi: 10.1016/j.jplph.2003.09.002. PMID: 15658802.
