There are many ways of seed sowing in a protected environment, but I fluctuate between either putting all the seeds I want into one pot or tray, and then pricking them out when they are big enough, or starting out with single tiny pots or modules into which I sow just one or two seeds, anticipating that the emerging plant will remain in that growing medium until it is planted out into its final location. There are pros and cons with both practices.
Sowing & Pricking Out
I currently use this technique for the majority of my seed sowing.
Taking either a shallow seed tray or a small pot, I fill it with compost (more on compost in a later post), gently flatten it down a little, sprinkle sparsely with seeds and cover very thinly with more compost before firming down again gently. I water by standing the tray or pot in a shallow trough of water and allowing the compost to pull the water up. Watering from overhead risks washing all the seeds into one corner; I know because I've done this! And that's it - the initial sowing session is quick and easy, indeed the longest part of the exercise is the preparation: sorting out containers and compost, writing labels etc.
The pots or trays can then be left in a suitable place, be that a heated propagator or simply outside but sheltered from the rain.
Once the seedlings have emerged and have grown a set of true leaves, meaning that they have also produced a root system, they can be pricked out and moved on to individual pots. This is the bit that can take the time, and needs a little skill.
First prepare enough individual pots; for the big plants where we harvest the fruit over a long period such as tomatoes and aubergines, this is the time to decide how many plants of each you want, or perhaps can accommodate. This will be the number of pots you want to prepare.
So for example, I am growing sixteen varieties of tomatoes this year, initially sown into sixteen pots, from which I will want forty plants in total. Because I only want one or two plants of quite a few varieties, I only sowed five or six seeds into the pot. Tomatoes are generally good germinators but it is still wise to sow a few more than you need. For forty plants I need to prepare forty pots, filling them three-quarters with compost. Make a deep hole in the pot with a pencil or small knife, or even your finger. Ensure that the pot or tray of seedlings is very well watered and then with a small knife or pencil gently ease down into the compost beside the selected seedling. Hold the seedling itself by one of the leaves, but never the stem; plants can grow new leaves, but if the stem gets damaged it is unlikely to do well, if it survives at all. Ease the seedling from the compost, supporting the weight by the knife and by holding the leaf. Don't pull as you don't want to snap the roots. When the seedling is free, lower it into the prepared hole, tucking all the roots in and firm in place. Top up the pot with compost firming carefully around the stem.
Don't forget to label the plants, and again water by standing the pot in water. If you have a lot of spare seedlings you can double up in the pots, later discarding the weaker of the two seedlings. The seedlings may well initially wilt and should be kept somewhere sheltered while they recover from the shock.
If your compost is stored outside, think about bringing it into the same environment as the seedlings to allow it to warm up, and likewise, watering with freezing water from the outside water butt may also shock the plants. I keep a small watering can inside the house and my two big ones full in the greenhouse at this time of the year.
Modular Sowing
This is the method I used to use and because they begin life in their bigger pot or container it avoids the need to prick out seedlings.
The basic method is simply filling a small pot or other container (yoghurt pots or tin cans with holes punched in the bottom, loo roll inners ...) with compost and sowing into it just one or two seeds.
You can also buy small discs made from coir, a by-product of the coconut industry. These are packed dried, each in a small individual biodegradable bag and need to be rehydrated before use. Rehydration causes them to swell to four or five times the original size. A seed (or two) is then popped in the top and lightly covered with a little coir. When it is time to plant out, the whole thing goes straight into the ground. It is a simple and clean process. The coir is a great medium for sowing, but doesn't have a huge amount of nutrition, so the plants may need potting on if planting out is delayed.
It is also possible to make soil or compost blocks for modular sowing, but I've not tried this as yet.
I would sow two seeds in each pot or plug and thin out the weaker of the two once they are showing good growth.
Pros & Cons
Bulk sowing in trays or pots is initially a quick job.
If the seed fails to germinate, only one pot is lost, rather than a whole load with modular sowing.
Pricking out can damage the plants and is fiddly; Modular sowing cuts out the pricking out stage.
Modular sowing uses fewer seeds unless you are meticulous about counting them into your tray.
Modular sowing takes up more space in a heated propagator - I would not have room for forty tomatoes, and twenty each of chillies, peppers, aubergines, for example, but I do have room for one pot per variety. This is my main reason for moving away from the system. (Seedlings come out of the heated propagator as soon as they appear.)
Modular sowing disturbs the plant less, the roots don't have to adapt to the pricking out process.
Modular sown plants may run out of nutrients and need to be potted on before they are planted into their final positions, especially if the weather doesn't play ball!
Ultimately, it is down to the individual grower to choose their own way forward, but for beginners I would recommend module sowing, especially if you're only starting off a few plants. Personally, I love pricking out - I find it very therapeutic and love having spare unused seedlings to pass on to friends and neighbours.
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