We all know that water is essential to the health of our plants. Of course this is true for all stages of a plant's growth; but with seeds and seedlings it truly can be a delicate balancing act. Am I just stating the obvious? Read on and see...
Seeds that are being stored need to stay quite desiccated in order to survive. If kept too damp, their shelf life is drastically reduced. It is usually the introduction of water that breaks them out of their dormancy. Once hydrated, the race is on - there's no turning back after the germination clock starts. The seed coat breaks, a root is sent downward, and the cotyledons attempt to push toward the sky.
Very straightforward, right? It's not always simple, though, because creating the conditions necessary for good germination also tends to encourage molds and fungi, which can attack the developing seedling. Inhibiting these problems involves encouraging air circulation (which of course tends to dry out the soil), and finding the point where the soil is damp enough to provide ample moisture to the seed, but not so damp the fungi thrive. Some types of seeds are very vigorous and resistant to pathogens like damping-off fungi, while others (such as tomatoes, petunias, and their relatives) are rather vulnerable.
Commercial nurseries germinate their seeds on misting tables, and deal with the damping off problem by using chemical fungicides. Some gardeners believe they need to use these as well, but I hope to convince you otherwise. Many gardeners believe seeds need to be kept soaking wet in order to come up, so they create mini-bogs in their seed starting trays. In this environment fungi thrives; the seeds do germinate but then damp off; and the gardener decides to address the symptom instead of the cause. Seeds need less water to germinate successfully than you may realize! For comparison with our hypothetical friend, here's my general watering practice when starting seeds indoors:
Once the seeds are potted up and ready to go, I set the whole group of pots in a tray of water. This allows the soil to soak it up without compacting the surface. I leave the pots in the water until the surface of the soil is damp - the time this takes can vary widely, since it depends on the composition of the potting medium and how dry it was in the first place. At that point I lift the pots out of the water and let them drain for 20-30 minutes (this is much easier if you have some sort of perforated tray to support the pots). Finally, I cover all the pots loosely with a clear plastic lid, set them under the lights, and don't water them again.
There are, of course, exceptions to the rule. Some seeds take weeks to germinate, and those do need to be watered every so often to prevent them from drying out completely. With others such as petunias, which sit near the surface and seem to be extremely prone to damping off, my preferred method is to water them as discussed above, not cover them at all so air can circulate, and mist them lightly once a day. The majority of seeds, though, come up in four to six days and seems to do fine with my usual regimen.
Once the plants are up, I immediately remove the cover. When the soil seems dry (which I usually judge by weight, but you can use whatever method you prefer) I water them. The frequency varies with the ambient air temperature and the size of the plants. My spring transplants often only need water once a week. In summer, it can be every day or two. I like to bottom water them if possible, since I know that it allows the soil to take up all the water it can hold. If you water from the top, the water often just runs down the inside of the container and out the bottom - the soil may look wet but still be bone dry just below the surface.
Finally, the day before the plants are ready to be moved into the garden, I give them a thorough soaking. Since even careful transplanting destroys root hairs, usually the plant will be unable to effectively take up water for a few days afterward. "Watering a transplant in" is a good practice, but its benefit to the plant itself are longer term.
The next article in this series will discuss meeting the nutrient requirements of your transplants.
All contents © Travis Saling
This page was last updated November 18, 2013