Most of us who start seeds indoors occasionally get a sinking feeling from watching some of our seedlings sinking onto their faces. That toppling is caused by fiendish fungi—such as Rhizoctonia or Pythium--biting into the stems at the soil line.
Actually, damping off also can occur beneath the soil before the seedlings emerge. That means the seed companies aren’t always to blame for your low rates of germination! Granted, though, such premature damping off is higher in outdated seeds than in fresh ones.
To help prevent such tragedies, you should either use new containers for planting your seeds or sanitize the old ones in a solution of 9 parts water and 1 part bleach. You generally can find inexpensive plastic planting packs at your garden store. (In my rural section of the country, that usually means the local feed mill!) For the initial seed sowing, I use the packs which aren’t divided into cells, but that is a matter of preference.
Fill your packs or pots with sterile, soilless seed-starting mix, preferably from a just-opened new bag. (Soilless mixes usually contain peat moss and/or coir rather than actual garden soil.) If you must use a mix that contains soil, it’s a good idea to cover the seeds with a product which isn’t likely to harbor fungi—such as milled sphagnum moss, fine chick grit, or sand.
To germinate plants which prefer dry conditions, I use cactus mix. Although it isn’t ideal—i.e., not always sterile—it does seem to work better than the damper seed-starting mixes for such species. A safer solution would be to mix sand with your seed-starting mix, but I always have problems finding clean bagged sand hereabouts!
You may also want to give your seeds a fungi-killing bath before you plant them. For instance, you can immerse them overnight in chamomile tea or for just 15 minutes in a solution of 1 teaspoon bleach mixed into 1 quart of water.
Be sure to space those seeds far enough apart that the seedlings won’t be crowded when they emerge. Scattering tiny seeds can be difficult, so you might want to mix them with sand before you sow them so that they will be dispersed more widely. Or you can buy your fine seeds in pelleted form, as the pellets are much easier to space.
For the best results, use containers with drainage holes for your seed starting and water them from the bottom with room-temperature rather than cold water. You may want to add a fungicide of some sort to that water such as vinegar (1 tablespoon per gallon of water), weak chamomile tea (one tea bag brewed in one quart of water), or peroxide (1 tablespoon of peroxide per quart of water). If you have hard water, the vinegar also can keep your seed-starting mix from becoming too alkaline. Just don’t combine vinegar and peroxide, as that creates an acid which can irritate your skin and damage your lungs.
Although rainwater is good for larger plants, avoid using it for baby ones, as it is more likely to harbor fungi than tap water is. If possible, irrigate your seedlings in the morning so that any drops on their foliage will dry off by evening, and try to get the seed-starting mix lightly moist rather than sodden.
Since many of us keep our seedlings in cool garages or basements which are on the dank side, it’s a good idea to have a fan running at all times to keep the air moving. Just position it so that it isn’t blowing directly onto the seedlings.
If my seeds don’t require cool temperatures for germination, I usually start them upstairs--where conditions are warmer--and give them a couple weeks to get growing well before I move them to the basement. Although the cooler temperatures down there generally produce healthier, more stocky seedlings, chilly soil also can increase the chances of those seedlings damping off.
To keep your baby plants standing straight, provide them with plenty of light directly overhead, preferably 12 to 16 hours of it per day. You don’t necessarily need grow-lights for this, as regular shop lights with fluorescent tubes work well for seedlings. However, you may want to buy longer chains for those fixtures—rather than the almost-always-insufficient ones included—so you can adjust them upward or downward as need be.
I usually try to transplant my seedlings as soon as they are large enough to handle, moving the smaller ones into six-cell planting packs and the larger ones into four-cell ones. I often use a combination of seed-starting mix and regular potting mix for that--to make the transition easier--and I also water the just-shifted seedlings with a vitamin solution recommended for transplants.
No matter what precautions I take, I still suffer some losses, probably because I have too many older plants in close proximity to the new ones. Without those losses, though, the victories would be far less sweet. Perhaps, after all, we need threatening villains such as the disease mentioned here to keep ourselves challenged and growing!
Photos: The banner image is by [email protected], the chamomile image by [email protected], and the seeds image by [email protected] The antique damping-off image is from Agricultural Botany, Theoretical and Practical by John Percival, courtesy of Flickr Creative Commons.