- In the germination stage, light levels are not critical for growth.
- But as soon as the seedlings produce true leaves, they require different conditions than the germination area.
In the vegetative stage, they are one of the most critical areas. You really want good grow lights sitting a few inches over the leaf surfaces for continued growth and more importantly, short blocky growth.The first sign that seedlings are not getting enough light is their long and lanky look.
Crowded seedlings – even in adequate light – will also be lanky-looking. So the more room you give them to grow, the better your transplant will be. Optimum spacing is one plant per 4-inch pot – the pots are tight-together.
In the germination stage, we were looking for a soil temperature of 70F.
We’re now looking for an air temperature of 65F and we’re happy with the resulting soil temperature. We water with tepid water instead of warmish water (still not “cold”).
So cool and well-lit will give you the starting points for a good seedling.
The Major Problem
The major problem faced by home gardeners is that the seedlings are usually overcrowded. In the excitement of sowing seed, the seed is too close together so that when it grows, the seedlings are crowded and air movement across the soil is restricted.
This leads to damping off – a fungal infection that causes your seedlings to fall over as if they’re a chainsawed tree. You’ll see a rot right at the soil line or a streak of black at the soil line where the plant has fallen away from.
Air circulation! You need it. The easiest way to get it is to space your seedlings apart as far as or further than recommended rates. In the greenhouses, we’d have fans blowing air across our seedling flats to keep those areas dry. And yes, this meant we had to watch our watering even more because the soil would dry out faster.
A garlic drench works really well to stop damping-off problems.
Having the right light and air temperatures, the other leg in the production stool is feeding.
Here’s my ultra-scientific method of feeding seedlings. I use a regular plant food (I prefer fish emulsion) at half strength once a week or twice a week when the plants start to really grow.
It’s mostly be by gosh and by golly (that’s the scientific part) and the measuring is mostly right but I do feed.
Can you use Miracle-gro or other chemical fertilizer? Sure. It isn’t organic but you can do exactly the same thing. I have seen houseplant fertilizer made from soybeans that does a great job (but it doesn’t have the “I’m a gardener” smell of fish emulsion) 🙂
You can tell when your plants are healthy and getting enough food when their leaves are a deep, lustrous green. Light green means they aren’t getting enough food.
When the seedlings get to the 4-leaf stage (they have 4 leaves that look like the plant rather than seedling leaves) they are ready to be transplanted into their own pot or cell pack area for growing on.
Growing On from There
Continue the feeding regime, continue the light, continue the temperature. That’s about it.
I always harden off seedlings. This means I follow a bit of schedule for introducing the transplants to the outdoors.
Day 1 – outdoors for an hour
Day 2 – outdoors – 2 hours
Day 3 – outdoors 4 hours
Day 4 – outdoors 8 hours
Day 5 – outdoors 8 hours
Day 6 – outdoors all day till dark and bedtime
Day 7 – outdoors all night
Day 8 – into the garden
Now, this assumes the weather is not freezing, is not frosting and looks like it’s going to be gardening season. If it’s cold or a high-cold wind, your tender seedlings will be burned by that wind. Do not put them outside at this point or you’ll stress them / stall their growth rate. The objective is to acclimatize them, not traumatize them.
Plant in garden. Grow. Eat. Smile