Updated: Apr 17
You have carefully planted your seeds, watched them germinate and grow and now you have realized that they are not looking so healthy. They have become spindly and weak and look like they are about to fall over! Leggy seedlings are a common problem among the best of gardeners when growing seedlings indoors early in the spring. There are a number of things you can do to fix and prevent leggy seedlings.
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Ways to Fix Leggy Seedlings
Pinch Back Your Seedlings
If you are growing a plant that naturally grows as a bushy plant you can pinch or cut off the second set of true leaves. When a plant germinates, the first set of leaves that appear are actually part of the seed and called cotyledon leaves. They are often small and have a rounded tip. These leaves are not the plant's true leaves. The true leaves are the second set of leaves to grow and you can tell them apart as they will look quite different than the first set of leaves. The true leaves look similar to how the plant's leaves will look when it is mature. Do not ever pinch back the first set of true leaves.
To fix leggy seedlings and to encourage your seedling to grow stronger and branch out, you can pinch back the 3rd or 4th set of true leaves that appear on a plant. Never pinch or cut anything back leaving a stem without leaves on the top of it (see photo), rather pinch back just above the lower set of leaves. Never pinch back a plant that is meant to grow up one tall stem without branching out, i.e. sunflowers, luppins, corn or stalks.
Transplant Your Seedlings
Supplies Needed to Transplant Your Seedlings:
A good quality potting soil mix.
A container with drainage to plant your seedlings into.
Marking tags to label your plants.
A good time to transplant seedlings is once they are 1 to 3 inches tall. If seedlings are planted close together in seed trays, transplant when they have grown to be one inch. Seedlings grown in plugs are ready to be transplanted once they reach a 3 inch height.
Most seedlings can be transplanted deeper into pots, planting so the soil level comes partway up the leggy stems. This is a great way to fix leggy tomato seedlings or plants especially as tomatoes will form roots up the stem. Tomatoes can be transplanted as deep as you wish, just be sure not to bury leaves. If you wish to bury part of the stem that has leaves, remove the leaves prior to transplanting. Peppers, basil, cucumbers and squash can also be transplanted up to their bottom leaves. If you are unsure whether or not your leggy plant can be planted deeper into the soil, I recommend burying no more than 1/4 of the stem at once and then waiting a few weeks to allow the plant to adjust before transplanting again.
Do not transplant root crops (like beets), strawberries or leaf plants (like lettuce, spinach and kale) deeper into the soil.
How to Prevent Leggy Seedlings
There are a number of ways to prevent your seedlings from becoming leggy.
Increase Lighting - Seedlings become leggy when they are reaching for sunlight. Most plants require 12 to 16 hours of good quality light a day to grow well. Although it is possible to grow plants from seed in a south facing window, you will have stronger and healthier plants if you supplement indoor growing with good quality broad spectrum lights. If you have grow lights and still have leggy seedlings, consider adding more lights and also check the manufacturer's recommendations on your grow lights to find out how far above the plants they should be spaced. For ideas on grow lights read my blog post about starting seeds indoors.
Provide Air Movement - In the outdoors, seedlings are exposed to wind which helps to strengthen their stems. Indoors, a fan is beneficial for replicating the wind and will strengthen your seedlings as well as protecting them from "dampening off", a condition that happens if the soil is not able to dry out every few days between waterings. Avoid placing a fan on seed trays that have not germinated yet as it is important for this soil to stay moist.
Increase Seedling Spacing - Plants may become leggy when they are overcrowded and competing for the light source. Transplant your seedlings before they become overcrowded to help prevent leggy seedlings.
Move Seedlings Off Heat - If you are using a heat mat to germinate your seedlings, move them off the heat mat as soon as they have germinated. Too much heat will cause your seedlings to be leggy and weak. Aim to keep the ambient temperature around your seedlings from 15 to 23°C (60-75°F).
By keeping a close eye on your seedlings and taking these steps to fix and prevent leggy seedlings as you see problems arising, you can grow strong and healthy plants to maturity, ready to be planted outdoors when spring arrives!
Six easy ways to fix and prevent leggy seedlings:
Pinch back your seedlings.
Transplant your seedlings.
Increase your lighting.
Provide air movement.
Increase seedling spacing.
Move seedlings off heat.
To find a free printable with dates on when to start seeds indoors see When to Start Seeds Indoors.
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