I recently made a mistake that almost wiped out my sweet pea seedlings: I left them in cell trays for too long and they started to become root-bound. If your seedlings are looking pale, turning yellow, and won't seem to grow any further, it might be that you're also experiencing the same issue.
Just like other plants, seedlings can become root-bound if they're left in smaller pots or seed trays for too long, often caused by sowing seeds too early. The roots run out of room and start to circle, creating a dense root mass that leaves little soil to provide moisture and nutrients. The result is leggy seedlings, stunted growth, discoloring foliage, and the eventual death of the seedling if not addressed.
But, I was able to successfully save my root-bound seedlings. Immediate action is needed for the best chance, but be aware that it will take some TLC and a little patience to nurture them back to health again. Here, I explain how I did it.
What Causes Root-bound Seedlings?
Root-bound seedlings are caused by being left in small nursery pots or seed trays for too long. This can commonly happen if you started seeds indoors a little too early and the weather hasn't allowed for them to be planted out yet.
As the seedlings outgrow their container, the roots wrap around themselves and create a dense root mass. This reduces their ability to soak up water and nutrients, and causes many different symptoms.
For my sweet pea seedlings, the first sign was the color they turned. They became very pale and some of the foliage yellowed. When I then lifted them from the cells, I could see the hard root mass.
Other symptoms of root-bound seedlings include stunted growth and drying out quickly. You may even find the soil has become hydrophobic and is unable to soak up water, so it rather pools on the surface.
Once root-bound, seedlings become extremely susceptible to heat stress and transplant shock, so you have to approach it carefully.
Here's what I did to save mine.
How to Save Root-Bound Seedlings
By the time I noticed that my sweet pea seedlings had become root-bound, it was time to plant them out. But, if it isn't time to plant yours out yet, you can rather transplant them into a bigger pot.
The first thing to do is gently remove the seedlings from their cells. Using your hands, tease apart the roots. You may even need to prune any particularly tightly packed or damaged roots (using these gardening snips from Amazon).
Leaving the roots as is can encourage them to continue circling, even with more room to grow. This can impact future growth and for crops, reduce yield.
If you're moving the seedlings into a bigger pot, aim for one that is a size or two up to provide more room.
You should water your seedlings deeply to rehydrate them and help them settle into their new position.
Make sure to also reduce stress, for example by keeping them out of harsh afternoon direct sun for the first week. This will help the seedlings acclimate to their new home, establish, and regain strength to put on healthy new growth.
Once my seedlings eventually started to show signs of new growth again, I used my gardening snips to remove the damaged foliage that wasn't going to recover. This helped boost growth by redirecting energy.
What to Shop
This Burpee seed starting tray has capacity for 36 seedlings. It's flexible silicone, so you can easily pop out seedlings without disturbing roots.
This set of nursery pots with humidity domes is perfect for starting seeds and propagating cuttings. You get 30 in this set.
This seedling potting mix a special blend to support seed germination and early seedling growth.
It can be a big seed starting mistake to sow seeds too early for this reason. Make sure to check the bottom of seed trays every few days once seedlings start to take off with rapid growth. If any roots are sticking out of the drainage holes, it's time to plant them up into a bigger home or in the garden.
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