The Clever Way Smart Gardeners Stop Seedlings Dying

Watching seedlings struggle is very frustrating, and your plants may never recover from a poor start. But growing strong seedlings isn’t just luck – it’s a skill that anyone can learn. And after years of growing many thousands of plants, I’ve learned exactly what works to get perfect seedlings every time…

1. How to Transplant Seedlings Successfully

One of the problems first-time gardeners come up against is knowing how and when to transfer seedlings into their own plug trays or pots, which is a process known as ‘pricking out’. Leave it too long and roots become increasingly tangled, making it hard to separate them without damaging them. Overcrowded seedlings also tend to become drawn and leggy, resulting in weaker plants further down the line.

Prepare your new pots or plug trays by filling them with potting mix. Then lay your container of seedlings on its side, and carefully jiggle the pot to jump the seedlings out into your waiting hand. This way the potting mix won’t land on top of the seedlings, which would snap the fragile stems. You can then gently coax them apart.

I like to work in batches, separating out several seedlings at a time and planting them in pre-filled pots and trays to minimize how long roots are exposed to the air. This doesn’t matter so much at this cooler time of year, but if you’re working with seedlings in warmer, sunnier weather then it is important to prevent roots from drying out and dying.

Make a hole in the fresh potting mix with a chopstick or similar tool (or even just your finger). Pick up a seedling carefully by a leaf to avoid the risk of damaging that delicate stem. Water and nutrients are drawn up through the stem to the leaves, so even slightly crushing it can cripple the plant. Transfer the seedling into the waiting hole, feeding the roots down into the hole. Tuck the potting mix back in around the roots to fill the hole. Once you’ve transplanted all your seedlings, give them a drink of water to settle them in. They might look a bit sorry for themselves at first, but they’ll quickly perk up.

I like to do prick out seedlings when they are only just big enough to handle, and that’s simply because it’s easier to guide the roots into the holes while they’re still quite small. In some cases you can just glide the seedling straight in, without the help of a thin stick to guide them in. If they’re not overcrowded, you can leave them til they’re a little bigger. Young seedlings quickly settle into their new home, and it won’t be long before they perk back up and continue growing apace.

Often I sow seeds into pots or plug trays where they can be left to continue to grow until they need to be potted on into a larger container, but sometimes I sow into pots, which I then have to prick out. The main reason for sowing multiple seeds into pots is to save space. Many plants will be germinated indoors, in the house, to speed them along. But indoor space is at a premium, particularly under grow lights or on narrow windowsills, so starting several seeds in a single pot makes the best use of space early on.

Sowing into pots also means I can ensure exactly one plant per plug once I’ve pricked them out, with no wasted seedlings if not all germinate.

But most of my vegetables get sown into plug trays (you can also sow one plant per small pot). Plug trays avoid the pricking out stage entirely, and are especially handy for crops that can be multisown (sown as a pinch of seeds in each plug, and the seedlings later transplanted as a little cluster).

Vegetables suitable for include both most types of onions, radish, beets, peas, spinach, turnip – a whole host of crops – and this is a great way to save time without compromising on final harvest quantities.

2. Begin With Homemade Seed-Starting Mix

Both seeds and young seedlings require a good, free-draining potting mix to thrive. It doesn’t need to be especially fertile – it’s drainage that really matters, so they have enough moisture but aren’t sitting in sopping-wet conditions that will cause them to rot.

I rarely bother with purpose sold seed-starting mixes as they are a lot more expensive. You could absolutely use an all-purpose potting mix for sowing if you first sift it to give a finer texture. But pre-mixed potting mixes can be expensive too, so to cut costs you can mix your own.

My seed-starting mix uses just three ingredients that you can easily buy from any garden center: coconut fiber or coir, which comes from the husks of coconuts and is essentially a waste produce of the industry; some perlite for improved drainage; and a little vermiculite to help the mix retain just enough moisture. This is just a cheat’s option for saving the pennies, but I reckon it also leaves us with absolutely the perfect potting mix for these early stages of life!

Mix together seven parts by volume of the coconut fiber (screened if necessary to remove some of the longer strands of fiber and make it easier to handle), two parts perlite, and one part vermiculite.

3. Get Watering Right

Getting watering wrong is one of the main reasons seedlings fail. But I promise it’s easy to get right!

To avoid blasting out the potting mix when watering, we’ve got two options. My favorite is to use a pump-action hand sprayer to mist the surface of the potting mix several times to really moisten it. The other option is to use a trusty old watering can fitted with a rose – ideally a fine rose for seeds and very young seedlings. Quickly pass it over your sown trays or pots a few times.

Consistent moisture is a must, and always avoid leaving seedlings sopping wet. This is why a good, free-draining potting mix is so important – it will allow water to pour away easily, and greatly reduce the chances of fungal diseases like damping off.

Check seedlings every few days, and if the container feels light, water it. If it feels fairly weighty in the hand and you can see the soil is dark with moisture, leave it. Sometimes it looks dry on the top but it’s actually still moist just below the surface, so picking it up to feel the weight is a better way to decide if it needs watered. With time and experience you’ll be able to better judge when and when not to water.

4. Ensure Plenty of Light

Low light levels are often the biggest drawback for seedlings started very early in the season, especially in a less-than-sunny climate like mine. Poor light leads to stretched, weak seedlings, instead of the strong and stocky ones we’re after.

For this reason, sometimes the simplest approach is just to delay starting seedlings until light levels have begun to improve. For me, that’s usually from late winter.

But, of course, it’s hard to wait! So, if natural light levels just don’t cut it but you’re itching to get growing, use grow lights for those first sowings. Keep the lights on for at least 12 hours per day to power your seedlings on. This makes all the difference in the depths of winter, especially for sun-loving crops like peppers and chilies.

5. Keep the Air Moving

Stagnant air can be a killer for tender seedlings because it gives pests and diseases an opportunity to settle in and do their worst. Whenever it’s not too cold outside, I like to open up greenhouse windows and the door to let the air circulate and begin to toughen up my seedlings a bit. You could also prop up cold frame lids or place seedlings outside for a little while on warmer days. Overcrowded seedlings won’t get enough airflow, so thin out or prick out seedlings promptly so they never get to this point.

Inspect seedlings regularly – at least every few days – and act quickly if you do spot any problems. This might include pests like aphids or fungus gnats, which can then be nipped in the bud promptly.

As planting time nears, help seedlings and young plants acclimatize to the great outdoors by leaving them outside for increasingly longer spells. A gentle breeze or gently brushing your hand over the tops of the seedlings can help toughen them up in preparation, though in my airy, unheated greenhouse I don’t find this necessary for cool-season crops.

When the time comes to plant, carefully push your seedlings out of their plugs or pots from the bottom, then lay them out where they’ll be planted. Make a hole with a dibber or your finger, and pop in one seedling (or cluster of seedlings if multisown) together with its plug of soil. Firm the soil lightly back around it, and finish by watering to settle it in.

Early in the season you may need to give newly-planted crops a little extra protection by tucking them in with row cover fabric, which will also protect the seedlings from birds.

Then all you have to do is wait. Follow these 5 key steps and you’ll find that it’s hard not to raise fantastic seedlings every time!