Seed-starting made easy: my top tips for success
Someone asked me the other day how I became a gardener. That has to be the ultimate compliment, right? Because I’m not. Yes, I have a flower farm and grow an abundance of flowers from seed, but I never feel like I’ve nailed growing. There’s a lot of trial and error, plenty of failures, and I’m constantly learning something new. That said, growing flowers is probably easier than many people think. As with most things, it’s about having the right conditions and equipment.
What seeds to sow
Some seeds are easier to grow than others. Germination is nearly always 100%, and they come up really quickly (which is both exciting and satisfying). If you’re just starting out, these are great confidence boosters:
Stocks
Sweet peas
Sunflowers (the pale yellow and orangey-crimson varieties, not the garish yellow ones)
Agrostemma
Achillea
Limonium
Zinnia
When to sow them
Sweet peas, stocks, and agrostemma are hardy annuals. They can be sown in autumn, and if you keep them under cover, they’ll get through winter and flower the following year. Or sow them indoors under lights in January and February, on a windowsill in March, or directly outside from the end of March.
Limonium and achillea are perennials, but treat them like hardy annuals for sowing purposes.
Sunflowers and zinnias are half-hardy annuals. They need warmth and light, so they can’t be sown outside until around the end of April, after the last frost. If you want a head start, sow them indoors at the end of March and transplant them outside once frost is no longer a risk.
Everything that follows assumes you’re sowing in pots rather than directly into the ground.
What to sow seeds in
Larger seeds (like beads): Need more space. Use a plug tray (mine has 84 holes, but you can get smaller ones). Square 9cm pots or 15-cell seed trays also work, though they take up more room. Agrostemma, sunflowers, and zinnias do well this way.
Sweet peas: Prefer deeper pots. I sow in 15-cell trays but move them quickly into 1-litre pots (three seedlings per pot). When planting out, I put the whole lot in together without separating them.
Tiny seeds: Can be scattered onto any tray or pot. Once they’re large enough, I prick them out into plug trays. This works well for achillea and limonium.
What compost to use
I’ve said this before, but compost makes all the difference.
Most of my failures are down to poor growing medium. Peat-free is important for the environment, but most peat-free composts are, to be frank, utterly useless—even the big brands.
If you only get one compost, go for Sylvagrow multi-purpose 100% peat-free compost. Shop around, though—some places sell 40L bags for £16, others as low as £5.
If sowing tiny seeds, sieve the compost first.
Or you can get specialist seed-sowing compost. Many recommend Fertile Fibre, though I’ve yet to try it.
Vermiculite or not?
Vermiculite is a naturally occurring mineral that acts as a sponge, retaining moisture and nutrients.
(Just for reference, perlite is different—it improves drainage and aeration, preventing waterlogging.)
If I have vermiculite, I mix some into compost before filling pots and trays. I also sprinkle some on the surface after sowing, especially over tiny seeds, but not enough to block the light.
How to sow them
My best advice is to read the instructions on the seed packet. When I do this, everything is fine. When I think I know better, it all goes awry.
Don’t forget to label them
I make mine from empty 4-pint milk bottles—just rinse them out, cut off the top and bottom, then slice the sides into 2cm-wide strips, trimming one end to a point for easy planting.
A Sharpie works best for writing on them. I include the plant name, the sowing date, and where the seeds came from
Then what do you do with your sown seeds?
Keep them somewhere bright—inside the house, in a greenhouse, or in a polytunnel.
If you don’t have a greenhouse or polytunnel, or (like me) run out of room, you can keep them outside in a clear plastic crate. This idea isn’t mine—I first saw Ben Higgledy, a seed grower, using them on his narrowboat.
Take the lids off during the day if it’s not too cold. If the temperature drops below freezing, bring them inside until it warms up again.
Gnat traps
YYou’ll probably notice fungus gnats in your compost—they reproduce fast, with a single female laying up to 200 eggs. Left unchecked, they can quickly become a real nuisance.
Fungus gnat traps are a good solution. Admittedly, they’re not the prettiest, especially when covered in dead gnats, but they’re far better than having thousands of tiny flies swarming around and damaging your plants.
How often to water your seedlings
If possible, place seed trays in a tray without holes so you can water from the bottom—this reduces the risk of fungal infections (‘damping off’).
How often? It depends on the pot, compost, and weather. The soil should stay moist but not waterlogged. If water collects in the tray, empty it carefully.
I use a small one-pint watering can, which makes it easier to control.
When to pot up your seedlings?
Unless you have frost cloth, wait until after the last frost to plant seedlings out. In Wiltshire, that’s around 21 April, but you can check your local date here.
If roots start poking out of the bottom of their pot before then, they need potting up into something bigger.
When to plant your seedlings
Once we’re past the last frost, get your plants in the ground as soon as you can. They always feel too tiny to survive, but actually do much better.
Once the last frost has passed, get them in the ground as soon as possible. They’ll always look too tiny to survive, but they’ll do much better than you think.
Before planting out, seedlings need to adjust to outdoor conditions – harden them off. Put them outside for a few hours each day for a few days, then all day for a few more days. After that, they’re ready to be planted.
Growing flowers from seed isn’t as tricky as it seems. A bit of patience, the right compost, and some trial and error, and you’ll have beautiful blooms in no time.
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