Photo: halfpoint, depositphotos
To speed up the growth of certain slow-to-mature flowers and vegetables and thus obtain results more quickly in the garden, gardeners sow them indoors a few weeks in advance. And it’s not even hard to do! Learn here the basics about this almost miraculous yet ever-so-easy technique!
By Larry Hodgson
Almost since humans discovered how to use glass windows to bring bright sunlight into a room without letting all the heat escape, humans have been starting seeds indoors. We know, for example, that Tiberius, Roman emperor from 14 to 37 CE, started cucumbers “under glass” to have them on the imperial table more rapidly and thus impress his guests.
So, sowing seeds indoors with a view to producing plants for transplanting is nothing new. It’s a time-tested tradition and millions of people do it every year. Why not you?
Here are some tips to help you get off to a good start.
You will, of course, need seeds and seed-starting mix. Regular potting mix is also fine. You can easily find both in any garden center or even hardware store. And there are also dozens of seed companies that sell seeds by mail order if you need a wider choice.
As for pots for starting your seeds, you can, of course, buy them too, but no doubt you have small containers that you can easily recycle for that purpose: used pots and 6-paks, margarine and yogurt tubs, plastic or styrofoam coffee cups, etc. Just clean them thoroughly and punch a hole in the bottom (if there isn’t one already), as drainage is important.
You’ll also need a tray on which to place the pots, plus a transparent dome to cover the tray. To this end, think of the clear plastic food containers in which you buy vegetables and pastries. They’re absolutely perfect for the purpose! A large clear plastic bag is also fine.
Finally, you probably already have all the necessary tools: spoon, knife, scissors, pencil, sprayer, etc. Look for them in your kitchen, office or laundry room.
Of course, some seeds are easier to start indoors than others. Here are some interesting varieties for a first experience.
Arugula or rocket
Cleome or spider flower
When to Start?
The recommended dates for sowing seeds vary from one type of plant to another. Normally, it’s printed right on the seed packet (along with lots of other helpful information), usually in a phrase similar to “xx number of weeks before planting outside.” If you don’t have that information, look it up on the Internet (for example, in the article Learn When to Sow Your Garden Seeds) or in a gardening book. Sowing a little late causes no particular inconvenience other than by delaying the harvest by a few days. On the other hand, avoid sowing too early as it leaves weak and etiolated seedlings that rarely do well.
The most common mistake made by novice seed sowers is starting their seedlings too early!
Start Seed Sowing Step by Step
- Pour the seed-sowing mix of your choice into a bowl and add lukewarm water. Stir with a spoon to moisten it well. You want evenly moist soil with a consistency like that of a wrung-out sponge.
- Using a spoon, fill the pots with potting soil up to ½ in (1 cm) from the top.
- Place the pots on a tray.
- With a pencil or pen, punch a hole equal to about 3 times the height of the seeds in the center of the pot.
- Place 2 or 3 seeds in the hole. (Always sow extra seeds in case germination is uneven.)
- Cover the hole with sowing mix.
- Spray with lukewarm water to launch the germination process.
- Place the tray in a warm (70 to 75° F/21–24° C) and brightly lit location, but not in full sun (not yet, at least). Some gardeners like to place their trays on a heating mat, but that’s an extra expense and isn’t necessary if you can otherwise ensure the recommended temperature range.
- Cover the tray with a transparent dome or transparent bag. This creates a “greenhouse effect” beneficial to germination.
- After a few days (3 to 14 for most seeds, but sometimes up to 21 days), small seedlings will appear. At this point, remove the dome to increase air circulation.
- Move the tray to the sunniest location possible. Ideally, also, one that offers cooler temperatures, at least at night, about 55 to 65 °F (12 to 18 °C). That helps keep your seedlings more compact.
Caring for Seedlings
- Monitor the condition of the soil regularly. As soon as it turns pale (a sign that it is drying out), water. The easiest way is to pour water into the tray, let the seedlings soak it up for 15 to 30 minutes, then empty the surplus. The potting soil should be kept “a little moist” for as long as the seedlings are still indoors.
- When the seedlings have 3 or 4 leaves, thin them. That is, cut off the excess seedlings with scissors, leaving just one plant per pot. You have to be ruthless: seedlings growing too densely will compete with each other and that will harm their growth.
- Give the tray a quarter turn, always in the same direction, every 3 or 4 days. This will help produce straight seedlings that don’t bend toward the light.
- When the seedlings have 4–6 leaves, start fertilizing. You could, for example, add an all-purpose soluble fertilizer at a quarter of the recommended rate to the water in your watering can.
Acclimatizing and Transplanting
When night temperatures have warmed up to 54° F (12° C) or more, begin to acclimatize the seedlings to outdoor conditions by placing them in the shade for 3 or 4 days, then in partial shade for 3 or 4 days, and only then, in the sun.
When the seedlings are fully acclimatized, the soil is warm and there is no risk of frost or even cold nights, transplant your seedlings into the ground . . . or into a pot or window box if you’re gardening on a balcony or terrace. Finish by watering well.
From this point on, the “seedling” part of your little project is actually over! Yes, you’ve succeeded and your seedlings are now plants in their own right. You will find advice for the rest of your project, that is, growing your plants on to flower or harvest, in this article: Summer Maintenance Tips for Your Garden.
And there you go! Sowing seedlings indoors is no more complicated than that!