Spring Greenhouse – Guttation and Other Funny Things
Guttation, Transpiration and Edema – How Water moves through Your Spring Greenhouse Plants
If you are inclined to have a long, lingering coffee before you pop out to your spring greenhouse in the morning you may never see this “problem”. If, however, you are an early bird, you may panic when you see your plants leaking water from the leaf edges. This is a condition called guttation.
In the early season of tomato growing when the soil is nice and moist but the air temperatures are still cool inside the morning greenhouse the humidity approaches 100% overnight. That is when guttation is common. Guttation is simply water popping out of special pores on a tomato or strawberry leaf first thing in the morning. It is just a way for plants to get rid of extra moisture, minerals and other small matter and it won’t harm the plant.
During the day, plants transpire or lose water throughout their leaves but at night the transpiring holes in the leaves close and special pores on the edges of the leaves open to allow excess water to leave the plant. It’s enough to scare an early bird gardener and make them wonder if there is anything wrong. In good news this is normal in small plants in spring so you can relax. Read more here: https://www.nature-and-garden.com/gardening/guttation.html
Clear, White or brown bumps on leaves
Some plants can’t weep or lose extra moisture through guttation. Instead, these plants, including ivy-leaf geraniums and certain edible peppers, suffer from edema when the conditions are too wet at night.
Oddly enough I had never seen this “problem” before and suddenly got it on only one variety of peppers this spring. Ironically, the peppers were growing in my house under lights while I waited for the temperatures in the greenhouse to be high enough overnight for my peppers.
The single affected variety is an heirloom called Szentisi. I was excited to grow it so of course at first sign of trouble I moved it away from my grow lights and onto a wire shelf in my greenhouse where there is more air movement. I love my grow lights but they are in my stuffy office with little to no air movement. I also ignore my plants more in my house and then either underwater them or overwater them, a problem that can trigger edema.
Once moved to the greenhouse I lost a few leaves but with warmer evenings, everything is settling down now and the plants are blooming and starting to develop small fruit. For more info about this edema-sensitive variety read more here: https://www.sweetrockfarm.ca/peppers/pepper-szentesi
What might scare a new gardener is that edema can look like warts or possibly even like an insect pest. The rule of thumb is if it doesn’t rub off when touched lightly then it is probably edema. To be sure, get yourself a magnifying glass and you will see these bumps don’t have any eyes or legs. They are simply a “grower” problem. Check these excellent references if you see clear, white or brown bumps on the underside of your leaves: https://peppergeek.com/edema-in-plants/ and https://www.greenhousemag.com/article/gm0413-manage-edema-plants/
Meanwhile, crank up the heat a bit in your spring greenhouse or simply increase the air movement because heavily affected plants may shed leaves and that will worry a new grower even more.
For more great tips from Donna, visit www.donnabalzer.com.
You can also read Donna’s gardening books: No Guff Vegetable Gardening with Steven Biggs and her just released Gardener’s Gratitude Journal: Part Diary, Part Personal Growing Guide.