5 Signs It’s Time To Repot Your Seedlings
It’s important to be able to recognize when it’s time to transplant seedlings from the seed tray to a larger pot. Transplanting seedlings a few weeks after starting should be part of your seed starting routine.
We start the seeds in smaller containers because we can control moisture and temperature much better that way, and if you’ve heard me talk much about seed starting then you know my motto is that moisture and temperature are the most important factors in getting good germination.
But once the seeds sprout, they quickly outgrow their seed starting container. It would be a bad idea to let them continue to grow in a pot that is too small. They’ll become nutrient deprived and their roots will grow round and round into a big knot.
Transplanting them into larger pots, helps them develop healthier roots and grow faster. By not restraining their growth indoors, you’re training them to grow big and strong when it’s time to put them in the garden.
But how do you know when to repot seedlings?
There are a few simple things you can look for that are dead giveaways your plants need a bigger pot.
1. They have one or two sets of true leaves
The ideal time for transplanting your seedlings is about 3 weeks after they sprout or when you have 1-2 sets of true leaves. It’s better to get them in new containers before they start to show the signs of stress listed below.
2. The cotyledons are turning yellow and falling off
Cotyledons are the first leaves that emerge from a seed. They are different than the “true leaves.” True leaves are the second and subsequent sets of leaves that grow after the cotyledons emerge.
It is normal for cotyledons to yellow and fall off, but if they’re doing it when you only have 1 or 2 sets of leaves, your plants really need to be transplanted.
3. The true leaves are turning yellow
It’s definitely time to transplant if the true leaves are yellow. This is a sure sign that your plants are starved for nutrients.
4. The roots are wound around and around the root ball
You definitely want to see roots in your growing medium when it’s time to plant, but if they’re circling around the edges of the root ball, then they’re getting too crowded.
5. They’re crowded
You don’t want to overcrowd your plants when they’re young. Some plants will grow taller than others and that will affect how much light the others get. You’ll also get the larger plants sequestering all the nutrients and that will stunt the growth of your other plants as well.
Why transplant the seedlings at all?
You might wonder why we would go to the trouble of repotting seedlings at all? Why not just give them some fertilizer, or better yet, start them in a larger container to begin with?
You’ll be much more successful germinating seeds if you start them in small containers. This allows you to have more control over the temperature and moisture in the seed starting container. We’ve found we have much better sprout rates in the smaller cell trays as compared to using other types of seed starting containers.
You can dose your plants with some fertilizer but that will stimulate growth. They’re already telling you they need more space, why stress them by making them grow bigger in the same small space?
Both of those options are viable alternatives, but you’ll have healthier plants if you transplant instead.
How to repot seedlings
Transplanting seedlings is quite easy to do. You simply need a new container and some potting mix. We recommend a container that is twice as big as what they are in now and a high quality potting mix like Fox Farm Ocean Forest.
We like to mix the potting mix and the seed starting mix in a 50:50 ratio. This is especially helpful for young seedlings who still have tender roots.
Before filling your containers, wet down your soil mixture to ensure even watering after you plant. Then nest your seedling in the new container, filling in around the base of the plant and pressing down to seat it in well and remove air pockets.
For tomatoes, bury the stem leaving only 1 or 2 sets of leaves above the soil line. For all others, plant them level or bury the stem about 1/4 inch or less.
Water your transplanted seedlings well and place them back under the light.
What about fertilizing seedlings?
You can fertilize young seedlings after transplanting as needed. Use a liquid organic fertilizer diluted to half strength. If they tolerate the half strength and seem like they need more, you can up it to full strength.
Don’t fertilize your seedlings until after you transplant them. You don’t want to stimulate growth in a space that is too small.
Do you transplant or repot your seedlings?
Tell us about your experience in the comments below!
You've conquered seed starting. Woot! But do you know when to repot seedlings? Transplanting seedlings is a step you can't skip! Learn the signs your plants are telling you they've outgrown their seed starting tray.
Repotting, how to repot a plant and when
Repotting a plant is easy and it’s an important step for plants to grow well.
This provides space for roots to grow, and also has the added benefit of renewing organic matter that plants need.
Indoor plants are often repotted, but even outdoor plants that grow in pots or containers deserve to be regularly repotted. Typical examples are shrubs and fruit trees that grow in garden boxes.
Here is all you need to know on how to repot plants.
Why do potted and indoor plants need repotting?
- Organic matter present in the soil and crucial to the survival of a plant are a limited resource.
- Plants collect these nutrients and feed on them, whereas watering tends to drag them towards the bottom of the pot, effectively washing them out and making them disappear.
- Repotting serves to replenish these organic matter reserves for the plants to feed them and give them space to grow.
Best season to repot plants
The best season to repot is the beginning of spring. The plant then enters a vegetation phase – a leaf-growing phase – and will be better equipped to deal with the changing of pots.
It is also important to repot plants that have just been purchased, because they are generally sold when they have fully maximized their pot.
How to repot a plant
Prepare a larger pot than the previous one.
- Ideal but not mandatory: pour a drainage layer of gravel or expanded clay balls.
- Fill the pot with appropriatesoil mix designed for the plant you are repotting.
- Prepare the clump by removing dead, wounded and fragile roots.
Use very sharp pruning shears to cut them off.
- Place the clump at the center of the pot.
- Fill to the top with soil mix.
- Press down lightly and water in the following few weeks, depending on the needs of the plant.
How to repot very large plants
The alternative for plants that have already reached a size that prohibits repotting is to regularly renew surface soil.
This means to remove as much of the old soil mix as possible, down to where the roots appear. Don’t wound them, and once done removing, simply fill the vacant space with new soil mix.
This is called topdressing. It can be performed on large potted olive, orange or lemon trees to ensure they keep growing and bear fruit.
Precautions when repotting plants
Plants with toxic sap
Some plants have sap that is a bit toxic. When handling these, it’s best to wear gloves.
- If you’re planning on splitting some of the plants, glasses or goggles will keep sap from squirting into your eyes.
Protecting plants when repotting
Plants are fragile and generally don’t like to be handled too much. It may be that repotting triggers transplant shock.
- This is usually very mild when the plant was handled carefully.
- Keep an eye out, though, and check whether you need to apply some of the tricks to avoid transplant shock
- After repotting, try to increase moisture in the air around your plants, at least for a while.
- Plants will draw some of their water needs from the air directly instead of only having to rely on their disturbed root system.
Smart tip about repotting plants
For some plants, repotting is a perfect moment to divide them into smaller plants. This is called crown division, or dividing the clump.
One plant that particularly is fun to split & repot is Zamioculcas, since it grows thick tubers.
Credits for images shared to Nature & Garden (all edits by Gaspard Lorthiois):
Repotting station by Free Photos under Pixabay license
Repotting a plant is an easy operation which is necessary for potted plants and shrubs to grow nicely. Roots have space to grow and nutrients replenished.