Last week I explained the principles of how to sow most bedding plants as well as some vegetables. These were plants that needed to be sown indoors, usually in March, and protected from frost. I now want to explain what to do next, once the seedlings have germinated, and then discuss other ways you can sow seeds.
Most plants produce seedlings with two seed leaves when they germinate. After sowing in the seed trays or pots, these seedlings will need to be transplanted (pricked out) into small pots or cell trays to grow on and get bigger, ready to be planted out.
Some seedlings, such as cosmos and marigolds, are large and easy to handle. Others, like petunias, are tiny! The best time to transplant your seedlings is when the seed leaves are fully expanded and the first true leaf is starting to grow from between them.
If you try to handle the seedlings when they are very small it is almost impossible to avoid damaging them.
On the other hand if you leave it too long, the roots will have branched and will be tangled and it is difficult to separate them without causing lots of damage.
When the first true leaves start to grow the roots will be ‘single strands’ and just starting to branch so are easy to untangle. This is the ideal time.
So fill your trays or pots with compost and tap to firm, ready for the job and have a can of water to hand.
You can remove your seedlings in various ways but an old kitchen fork, to push under the plants and lift them, under the roots, is a good option. Never just pull them out! To be honest, I usually use the pencil I use for writing labels!
Make sure the compost in the pot of seedlings is moist. Ideally water the night before. Transplanting the seedlings is much easier if the seedlings’ leaves are dry so don’t sprinkle water over them just before the job.
Only handle the seedlings by their seed leaves: NEVER by their stems.
If you crush the stems the seedling will die. If you damage or even break off a seed leaf the seedling will probably survive. Carefully lift the seedling by a seed leaf, make a hole in the compost with your pencil, and lower the roots in so the seedling is at the level it was in the seed-sowing tray or slightly deeper. Firm by pushing your dibber (or pencil) in the compost beside the seedling and pushing from the side gently. Do not ‘over-firm’. If you press down the compost you will squeeze out the air and this will lead to roots suffocating and dying. The compressed compost will become waterlogged and green algae will grow on the surface.
Try to get the root in as straight as possible but it is not too critical as long as you do not break or severely bend the root.
Water as soon as possible once you have transplanted a batch. Water from above so you settle the seedlings into the compost.
It is best to give the newly transplanted seedlings some shade for a few days to help them recover from the move.
Most plants are not unduly affected by transplanting but a few really dislike it. Among flowers, the most important are zinnias (below) which should not be transplanted. And never transplant root crops like parsnips and carrots.
Some seeds are best sown in individual pots. This can be because the seeds, and seedlings, are large or because they do not respond well to root damage.
Among these are courgettes and sweetcorn. Because not every seed will grow it is common practice to sow two seeds per pot or per cell and remove the weakest if both grow. But F1 hybrid seed is expensive so sow just one per pot to avoid waste but you will have some empty pots.
Flowers with large seeds like nasturtiums and sunflowers can be sown in individual pots but do not sow till April.
Sowing seeds direct in the soil
Hardy annuals are flowers that can be sown direct where they are to bloom. They include favourites such as cornflowers, calendulas and most poppies. If you have fine, ‘crumbly’ soil you can sow direct but if you have ‘less perfect’ soil you can sow these in cell trays. Sow a pinch of seeds in each cell and plant out the small clusters of two or three seedlings. This is how I grow zinnias and a wide range of hardy annuals to pop into gaps in the border. I sow in April.
But if you prefer, you can sow patches in the border in April to early June. A pack of calendulas or nigella is great for this – just sow a short row here and there as you get gaps in the border. Fork over and rake the soil, take out a shallow trench (drill) about 1cm deep, sow the seeds, cover and water.
You can fill large areas with hardy annuals too. My soil is still pretty awful (it was a field five years ago) and the only place I can really sow hardy annuals direct is in some raised beds where I have improved the soil with sand and lots of compost. Fork over to remove weeds and rake several times so it is fine in texture.
In a bed like this I will mark the areas for different plants with sand. Although you can just scatter the seeds around it is then difficult to weed the seedlings. It is best to sow in rows, about 20cm apart. You can then identify the seedlings and be able to remove weeds. You can make the rows at different angles in each area. You will need to ‘thin’ the seedlings as they grow, to about 10cm apart in the rows and as they grow they will merge and you will never know they were in rows.
Thinning is important because if they are crowded they will bloom prematurely and only for a short time as they struggle for light, moisture and nutrients.
Rake the soil over the seeds and water well. You will need to keep the seeds watered in dry spells until the seedlings are well grown and established.
Next week
Sowing and growing vegetables
Spring talks
My second talk this spring is next week. The topic is on four garden favourites: How to get the best from hydrangeas, clematis, roses and camellias. So if you struggle to grow or prune these popular plants I hope to give you the confidence to grow them well. And the following month my talk is about growing veg. It is designed for anyone wanting to get started but with plenty of tips for more experienced growers too. You can find details and book HERE