Raising Really Good Seedlings

corn seedlings growing in toliet rolls

Really good seedlings are an important part of an abundant garden. If your seedlings are strong and healthy, the grown ups will be too. It takes a bit of dedication to pull off, but its so wonderful to watch seeds curl up out of the soil and to grow robust little guys. You wont mind the chore of it, one little bit. Infact, prepare to fall in love. It all begins with a good set up.

A good setup

A seed propogator is awesome for warming and protecting seedlings

Seed raising needs a toasty, sunny spot that’s secure from birds, rats, mice, slugs, dogs, cats and curious children (in other words in heaven 🙂 ). Seed propagators, like the one in the photo above, tick all these boxes, plus they’re easily mobile in the event you need to drive them over to your besties place when you go away. Or just take them with you – seeds and seedlings are babies, right, they need daily, attention. It’s great to raise your seeds handy to a hose, or if not, have a small watering can with an upward facing rose on stand by. Go the extra mile and leave water in it to keep it ambient for your babies.

Stock your seed raising place with small, shallow trays (small seed) and 6 cell plug trays (larger seed) and a selection of small pots for moving the newly sprouted seedlings into.

Make a stash of labels by cutting plastic into strips, or give your old labels a scrub with a wet steelo. A waterproof pen, for obvious reasons, a teaspoon for pricking seedlings out and seed raising mix completes your kit.

And lucky last – go through your seed stocks. Make sure you have enough of all your favourites and remember to get plenty of greencrops and companion flowers. Its so hard not to go over board seed shopping!, but it helps to know that seed has a used by date. If you cannot swap or share with friends then be careful or you’ll end up tossing alot out. Storage makes all the difference. Keep them somewhere dry, dark and at a steady temp – extremes of hot and cold impact, as does the damp.

Longevity of seed differs from crop to crop – some, like tomatoes, last for years and years, but others like parsnip, start to loose viability after only a year. Its useful to buy seed with the date stamped on it, and to date your home saved seed. Find out if your old seed is viable by chitting it.

Seedtray prep

Bottom watering - these pots are sitting in water wicking the moisture up
Bottom watering gets water right to the bottom of the pot

Fill your tray with seed mix, pat it down firmly, then water until its barely moist. I like to bottom water. Sit the tray in enough water so it comes about a third of the way up the tray/ pots. As soon as the water darkens the soil on top, whip them out. You want it damp, not saturated. Sit them on the bench to drain.

Next is perhaps one of the most important steps – be sure the seed raising mix has reached the ideal temperature for the seed you are sowing. Warm/ hot season crops will need somewhere in the range of 15°C – 25°C soil in order to sprout. Here’s a useful guide. This means sitting your trays/ pots on a heat pad, under a cloche, in a propagater (like above) or under an old window – somewhere toasty in other words, until the perfect temperature is reached. Once it has, you are ready set to sow.

Seed sowing

Seed sown thickly, ready to be pricked on
These lettuce seedlings are ready to prick on into cell trays. Poor germination, in rows 3 + 4, is old seed.

If you use small trays and sow thickly you’ll make your seed raising mix go a lot further and it helps to not sow too many seeds! Home gardens thrive on little and often sowing – small, shallow containers fit the bill. It doesn’t matter that the seeds come up like a thicket. Stage 2 follows hot on the heels of the thicket stage – moving them into a container that’s a little bigger than the one they came from.

As a good general rule, sow seed to a depth of twice its width.

  • For fine seed (eg lettuce) sprinkle it on top of the firmed down seed mix, and lightly sprinkle seed mix on top. Lettuce and celery need a bit of light to germinate so cover sparsely, then lightly pat the top down.
  • Do the same for middle sized seed (eg cabbage) only spread a little more seed mix on top. Firm down.
  • For bigger seeds like pumpkin, beans or corn – use plug trays or toliet paper rolls. Make a hole twice as deep as the seed, with the end of your upside down teaspoon, pop the seed in, cover it and firm down.
a 6 cell plug tray
6 cell plug trays are awesome for larger seed and for pricking smaller seedlings like lettuce or beetroot into, for stage 2

Pricking on

Lettuce seedlings in plug trays nearly ready to harden off

When your seedling babies have grown 2-4 leaves they need to be pricked on to new accommodation. Please don’t loose interest at this part, this is the best bit, the bit that makes for fast growing, strong seedlings. Do this in the cool of the evening. If you do it in the sun they’ll be finished before they’ve begun.

If you’ve sown seed thickly, like I do, you mustn’t let your seedlings linger in this state. Our goal is robust stocky plants with strong stems – not weedy, woobly, vulnerable ones.

soak your seedlings pre planting
This cabbage is about to be transplanted in the garden. I grow them big to beat the slugs. Here you can see the robust, root ball – neither stringy and weak, nor choked up – just right! Plug trays or the right sized container are what creates this. Roots like this adapt and grow fast!

For all the small seed in trays, I move seedlings into plug trays. For seed that starts in plug trays, I move into pots that are about 10cm deep. Don’t waste your seedling mix going into big pots, and besides tiny seedlings prefer to hit an edge, to be cosy. Its awesome at planting time for the seedling to have a solid root mass – the plants grow super fast this way.

  • Prepare a new tray or plug trays (my go to). For heat lovers, like tomatoes, prep the pots then sit them on the heat pad overnight to be sure they are warm enough.
  • Prepare the seedlings about to be moved, by lightly watering them. Choose the biggest, straightest, best-est seedlings, compost the weak, weedy ones as you go.
  • Seedlings in a thicket – lever a clump out with your teaspoon, take a seedling by the leaf (not the stem – you’ll wreck the plumbing), and gently pull it out. Otherwise, holding the seedling by the leaf, scoop it out with your handy dandy teaspoon.
  • Turn the teaspoon upside down and push it into the soil of the newly prepped tray/ pot, while at the same time drop the root of the seedling into the hole, deep enough so that the leaves are sitting just above the soil. This will at times bury a goodly bit of the stem, but that is AOK – this makes for stocky, strong plants which have far better resilience than weedy straggly ones, once out in the garden.
  • Still holding the leaf, sweep the disturbed soil around the seedling, lightly firming it as you go.


bottom watering
Bottom watering prior to pricking out.

The perfect moisture level for seeds and seedlings (plants in general) is barely wet – err on the side of dry. The best way to achieve this is with bottom watering. It ensures the tray is moist right to the bottom encouraging the roots to stretch out, prevents fungus and mold because the foliage stays dry, and it saves time – trays retain moisture for a few days. Great to do if you go away for the weekend and can bear to be parted.

I leave an old sink, in the greenhouse with water in it. This keeps the water ambient. You want the water to come about a third of the way up the seedtray. The soil will wick the moisture the rest of the way, up to the top, thereby not disturbing your seeds. As soon as the top darkens with moisture, lift the tray out. It’s time to water again when the top has completely dried out (it’ll still be moist underneath).  About 4 days for me in cool spring.

Once your seedlings are pricked on and growing well, switch to light overhead watering. In an ideal world the rose on your watering can or the attachment on your hose end, would be facing upward so the water makes like an arc. Create this as best you can – sweeping back and forth a few times like a passing drizzle, not a downpour.

Direct or Tray Sow

Seeds that do better direct sown carrots, parsnip, rocket, coriander.

Seeds that can be either direct or tray sown beetroot, peas, beans, corn, zucchini

Seeds that germinate faster with an over night soak pre sowing beetroot, chard, silverbeet, spinach.