Cannabis Seedlings: Care Basics and When to Transplant

Cannabis seedlings need a growing medium that stays moist but never soggy, light as soon as they break the surface, and a transplant into a bigger container once they show their first true leaves and roots poking out the bottom. Handle them gently, because seedlings are ridiculously fragile. Get these basics right and you've set up the whole grow for success.

Seedlings are tiny, freshly germinated plants that need special care to grow strong and healthy. There are few better feelings than nailing germination and watching them come up. Below are the seedling care and transplanting tips that'll help your grow get off to a solid start.

How long does the cannabis seedling stage last?

The window between germinating your seeds and transplanting your seedlings is short. Still, if you don't look after your seedlings properly before transplant, the consequences are brutal. 

It might sound obvious, but plenty of beginners aren't sure how much to water cannabis seedlings.

Remember that a seedling is at the very start of its life, so it doesn't need much to survive. Its root system is miniature compared with that of a mature cannabis plant. So there's no need to drown it: just make sure the medium stays moist (not wet). A steady supply of moisture keeps the delicate roots from drying out without rotting the vulnerable stem.

Once the seedling breaks through the medium, it needs light.

Why do cannabis seedlings need light right away?

They need artificial or natural light for two reasons:

To keep stems from stretching 

Photosynthesis

With natural or artificial light, cannabis seedlings don't stretch too much, which saves you from leggy stems that tend to flop over and snap. On top of that, light lets seedlings photosynthesize, which is how they make the energy they need to grow.

Be careful with seedlings, because one wrong move is all it takes to wreck them. There are ways to nurse a damaged seedling back, but the recovery stunts the whole grow. So handle your seedlings with care to make sure they come through transplanting healthy.

With cannabis seedlings, size matters, but not height. Instead, your seedlings should be showing their first set of leaves and roots sprouting out of the germination medium. Check whether roots are poking out of the bottom. And the arrival of true leaves (not the round cotyledons, or seed leaves) is another sign your seedlings are ready to transplant.

Transplanting cannabis seedlings

One of the first things you learn as a cannabis grower is how to transplant weed seedlings, but maybe nobody ever explained why you're doing it. 

Transplanting gives the roots room to keep growing, and the thing it prevents is a plant getting rootbound. Rootbound means a plant's root system has taken up all the space available in its medium, pot or container. Once rootbound, cannabis plants can't thrive, so it's best to avoid rootbound seedlings at all costs.

Once you move your seedlings into a bigger container, they'll keep growing as the roots quickly colonize the new medium.

Basic care for your seedlings

• Keep seedlings somewhere with natural light, but out of direct sun.
• Keep the growing medium moist but not soaked, watering gently with a spray bottle or a small watering can.
• Keep an eye on room temperature, since seedlings need a specific range to grow properly.

If you don't transplant your cannabis seedlings, they'll get unhealthy because they won't get the nutrition, moisture and oxygen they need. Unhealthy seedlings are more prone to disease. That's why transplanting isn't optional: it helps keep the plant strong enough to fight off problems.

As for the medium, your best bet is to stick with whatever you used for germination. If you germinated your cannabis seeds in soil, transplant the seedlings into a bigger container of soil. If you went with a hydroponic medium, we recommend transplanting into a hydroponic medium too.

A common dilemma for rookie growers is picking the next container size, and there are two ways to go:

Transplant into a bigger temporary container.

Transplant straight into its final container.

Both have their upsides; the choice really comes down to your own growing style.

Transplant them the wrong way and cannabis seedlings are prone to transplant shock. Your number-one goal as a grower is learning to transplant seedlings while avoiding the big stressors that lead to transplant shock.

Things that can cause transplant shock: rough handling, broken roots or leaves, a crushed stem and/or poor transplanting technique.

Symptoms of transplant shock: drooping or wilting leaves, a weak stem, dying branches and/or sudden death.

To keep the impact of transplanting to a minimum, always handle your cannabis seedlings with extreme care. It also helps to start with quality seeds, whether feminized or autoflowers.

Now that you know what seedlings need, it's time to keep moving on your cannabis growing journey.

How to transplant cannabis seedlings successfully

• Before transplanting, make sure the seedlings have at least two true leaves and a developed root system.
• Prepare a suitable growing medium for the plant you're transplanting and make sure it drains well.
• Carefully slide the plant out of its original container and set it in the new one, taking care not to damage the roots.
• Water the plant after transplanting to help it settle into its new home.