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How Long Can Seedlings Stay In Peat Pots – A Timeline

A lot of work has gone into preparing for this year’s gardening season. These seedlings are a few weeks old for gardeners who start their seeds indoors. While we wait for warmer weather, you may be wondering how long can seedlings stay in peat pots?

Seedlings can stay in peat pots for 14 – 21 days before they need to be transplanted to larger containers or garden beds. As the roots develop, they will need more room to expand. The entire peat pot can be placed into the dirt at transplanting time which keeps the roots intact.

You can look for some signs to be sure when seedlings are no longer comfortable in their starter pots and need to be moved into a larger pot or transplanted out into the garden.

Why seedlings don’t need to be removed from peat pots

Peat pots are derived from a species of moss called Sphagnum. Peat moss is a mixture of decayed Sphagnum moss and other organic materials like dead grasses. Peat pots are biodegradable and, when planted into dirt, will break down over time, especially with moisture.

There is no need to remove seedlings from the pot when transplanting, unlike clay or plastic pots. This prevents damage to seedling roots and dramatically reduces transplant shock. Buried in dirt, the seedling will continue to grow through the pot’s walls.

This doesn’t mean that seedlings should be kept in peat pots any longer than pots made from other materials. Ideally, you don’t want your seedling roots to grow through the pot before you’ve had the chance to bury it under the soil. We’ll get more into how this affects the plant below.

What happens if seedlings stay in their pot too long

  • Root Bound – Roots that have outgrown their space don’t just stop growing. The root growth structure becomes unhealthy because the roots keep growing in the small space, becoming a tight, tangled mess. In severely root bound plants, the growth continues until there are several layers of roots at the bottom of the pot where no soil is left.
  • Stunted growth – One consequence of root bound seedlings is stunted growth. With the plant lacking the adequate space and nutrients from the soil for proper root growth, plant growth stalls. Vertical growth and development of leaves slow, and the plant can appear to be dwarfed.
  • Exposed roots – Some plants with stronger roots, like squash, can break through the walls of the peat pot. While this is cool to see, exposed roots can be easily damaged because they are directly exposed to light and heat. They are also prone to breaking when moved since there is no soil to protect them.

Avoid these issues by moving seedlings when they begin to show that they’re outgrowing their first home.

Ways to tell that seedlings need to be moved to a larger space

  • True leaves – The first two leaves that emerge from the soil once a seed germinates are called cotyledons. If you have several different plants growing, you may not be able to identify them without labels. Many cotyledons from different seedlings are identical. They are often oval or teardrop shaped with very fine veins.
  • Two more leaves then emerge, growing in the opposite direction. Those leaves look different from the first two. They have a different shape and have more distinct veins; some may have a different color and appear to have very fine hairs or a texture like a tomato and squash leaves.
  • The plant can be identified once the second set of leaves appears because those are the true leaves. These leaves are responsible for photosynthesis, and the seedling can now use up nutrients to make its own food. When your seedlings have at least a couple of sets of true leaves, they can be transplanted.
  • They are twice as tall as the pot – Now that the plant has doubled in height, it’s a good indication that it could do with more space.
  • They are becoming crowded – Like fully grown plants, seedlings will encroach on each other’s space to compete for light, water, and nutrients. The taller plants will shade out the shorter plants and affect their growth. Seedlings may begin to touch each other and need to be untangled.
  • They have been planted indoors for the amount of time suggested on the seed packet – Often, seed packets may give recommendations on when to sow seeds indoors. This will usually state the number of weeks before transplanting, for instance, “sow six weeks indoors before transplanting.” Once the six weeks have passed and it’s near the transplant date or last frost date for your area, it’s an ideal time to move your seedlings.
  • There’s a root ball– If you pop the seedling out of the pot and see the root growing in a continuous circle, the plant has outgrown the pot, and letting the seedling continue to grow this way can permanently affect the plant.

How to transplant seedlings grown in peat pots

Once it’s been established that the seedlings need to be transplanted, there are a few steps to follow before placing the peat pots into the ground.

  1. Ideally, plants benefit when they have been hardened off before transplanting. Place seedlings outside for a few hours each day for about a week before you plan to move them. This slowly introduces them to their new environment’s bright light and wind. This reduces some of the stress the seedling will experience when the conditions it’s used to sudden changes.
  2. Prep your soil. This can include tilling, weeding, and adding soil amendments like compost.
  3. Dig a hole wide and deep enough to bury the entire peat pot.
  4. Wiggle the seedling gently at its base to loosen the roots stuck to the pot. Some gardeners slit the sides of the peat pot to make it easier for the roots to push out. This can be nerve-wracking since it’s possible to slice the roots using this method accidentally. Alternatively, tear off a piece of the pot from the sides or bottom. If the seedling is root bound, submerge the entire root system in water and let it soak. This will soften the roots and soil. Gently detangle the roots; some will break off. Once you’ve detangled as much as you can, continue with the following step. You don’t need to place the seedling back into the pot.
  5. Place the seedlings into the soil and fill the peat pothole.
  6. Always water thoroughly after transplanting.

Final thoughts

On a positive note, your seedlings can bounce back into good health if they are root bound, stunted, or have exposed roots. Once you have detangled a root-bound seedling, moved a stunted plant into a larger space, or buried exposed roots, offer a little extra care to these seedlings—water well and feed with a quality seedling fertilizer.