Seed Starting Problems to AvoidBy Tamara Galbraith (TexasTam)
April 18, 2010
Let’s address a few of the more common grumbles, their causes and solutions.
“My seeds never germinated.”
This is pretty common, and the answer is usually pretty simple: your seeds were old and no longer viable. Just buy fresh ones and start over.
In some cases, however, good germination can depend on temperature. Providing consistent bottom heat to a tray of newly planted seeds will, in most cases, promote and speed germination dramatically.
For example, I always start seeds on Sunday, my laundry day. I put the tray on top of the dryer - which ends up running most of the day as I do several loads - and I’ve found that seeds usually sprout within a day or two. You can also purchase heat mats specific to seed starting for this purpose, but I’ve found my dryer method works great.
Conversely, some seeds – usually those with a really hard coat, like spinach, radishes and beets – seem to prefer cooler temperatures for germination. That’s partially why they’re better off just being direct-seeded right into the ground to grow rather than started indoors.
“My seeds sprouted but then the plants fell over and died”
This complaint demonstrates the oft-heard term in seed starting called “damping off” or “dampening off”. Your baby plants come up and all is well. Then, a few days later, the stem gets a pinched appearance right at the soil line, the seedling flops over, and the whole thing soon withers and dies.
Damping off can be a problem for even the most experienced seed starters. Usually, it is caused by planting seeds in soil that is not sterile. I know a lot of gardeners don’t care for the peat or coir (coconut fiber) pellets sold for seed starting, but I do use them purely because of this. Peat and coir are sterile growing mediums. As a result, I rarely have a problem with damping off. Even the best potting soils are not considered suitable for seed starting, as they can contain a lot of other semi-questionable ingredients.
This type of early root rot can also occur if you’re re-using seed starting trays that may have been infected with some type of disease. The bacteria enter the soil and subsequently kill the plants. Either wash your trays with a mild bleach and water solution before re-using them, or buy new trays each time.
Lastly, don’t let your seedlings sit in water for extended periods of time. Keep them moist, but not sopping.
“My seedlings are elongated and pale-looking.”
Seedlings with this affliction are often referred to as being “spindly” or “leggy.” Simply put, they are overextending themselves to reach the nearest light source.
The remedy for this is also simple: move the light source closer. When my seeds first emerge after a couple of days on top of the dryer, I immediately move them under grow lights. A cheap shop light with one warm and one cool fluorescent bulb works just fine. I place telephone books under each end of the shop light to prop it up and I position the light very close to the plants: within 2-3 inches.
As the plants grow, I place more phone books under each end of the light to raise it. (The light bulbs never get hot enough to burn the books or the plants, so don’t worry about things touching them.) Not a fancy or highly-scientific method, but it works. I never have leggy plants.
Also be sure your plants are getting enough direct light; seedlings grow best when given about 15 hours of light exposure. Turn them on when you get up in the morning and off when you go to bed. Timers can be also be handy for this purpose.
I get a lot of questions from gardeners about growing plants on the kitchen windowsill. I generally don’t recommend this method, because that kind of indirect light usually isn’t adequate or reliable. Windowsills can get really hot and/or cold too; the atmosphere next to a window is just too inconsistent for the delicate needs of a seedling, so try to avoid growing them there. Same goes for starting seeds outside, frankly. You want consistent temperature and light levels, and even the sun can’t always provide that.
As I mentioned, a cheap 4-foot metal shop light and a couple of fluorescent bulbs work great, will only set you back about $30 and you can use them for years. Phone books are free and, unfortunately, plentiful.
Fungus or Mold:
Cramming all those moist little plants together in a tray and shoving them under a low-hovering light can cause another problem: mold. Funguses can lead to fatal plant diseases so it’s best to take care of this as soon as you see it. Separate and spread your plants out onto additional trays and turn a fan on the seedlings so a very gentle, continuous flow of air blows across them. You may need to water the seedlings a little more often, since the fan will dry them out faster.
Spots on Leaves:
This can indicate a serious problem, such as blight. Young tomato plants seem to be especially susceptible. I’ve found that in many cases the plant will recover if you catch the problem early enough. Clip off the affected leaves, throw them away and hope for the best. I often follow up by lightly mixing and watering horticultural cornmeal - a natural fungicide - into the soil around the plant. Be sure to also sterilize your cutting tools with Lysol or bleach afterward so if disease is present, the bacteria won’t be spread to other plants the next time you do some clipping.
If somebody has a surefire way to avoid getting these little beasts, I’d love to hear it. Fungus gnats thankfully won’t directly kill your young plants, but they are a nuisance, and the larva can damage plant roots which may later encourage other problems.
Putting a fan on the sprouts does seem to help, both because of the breeze and because your plants won’t harbor a constantly moist atmosphere, which the gnats love. Placing orange peels in the trays around seedlings has also been cited as an effective deterrent. Using a drench of Bt (Bacillus thuringiensis israelensis) will help control the larva population. Sticky yellow fly paper hung around your trays can catch the adults.
Spider mites can also attack indoor plants and cause terrible damage. Regular sprayings of organic Neem oil are effective in controlling mites and mild enough to not hurt seedlings.
Avoid using chemical pesticides on your young plants, especially if you're growing vegetables.
It makes sense to put more than one seed in each growing pellet or cell just in case some don’t germinate. So what do you do when ten of them sprout up all together in a crowded bunch?
Whatever you do, don’t thin them by pulling out the unwanted sprouts. This can result in traumatic root injury to the ones you do want. Instead, choose one or two of the strongest sprouts, and clip the rest off carefully with scissors right at the soil surface. It’s best to ultimately end up with one strong seedling per pellet/cell.
Seed starting doesn’t have to be stressful. In fact, when you know the basics, it can be one of the most rewarding gardening activities you partake in. Success can be boiled down to following these few points:
- Cleanliness: Use clean, sterile soil and growing supplies. Use seed that is either new or has been stored adequately for freshness.
- Environment: Maintain adequate temperatures, light and moisture levels and air flow.
- Maintenance: Monitor your seedlings regularly for fungus, mold, overcrowding and insects and act quickly to correct the situation.
So, later this summer as you groan at the over-abundance of squash popping up seemingly overnight in your garden or the bushels of tomatoes on your kitchen counter, remember and relish the fact that you, literally, were the one who started it.
DG member/author Jill “Critter” Nicolaus has written several excellent articles about seed starting:
Seed Starting 101: Setting up Light Shelves for Starting Plants from Seed Indoors, Without a Greenhouse