Leggy Cilantro: Why Hydroponic Plants Stretch and How to Fix It

Leggy cilantro has long, thin, pale stems with few leaves, and it often flops over. The plant is stretching, because something is making it reach. The step-by-step Kratky method guide for cilantro mentions legginess in its expert tips, and this post goes into the causes and fixes.

The main cause: not enough light

Plants stretch toward light. If the light is too weak, too far away, or only on for a few hours, the stems grow long and thin as the plant tries to reach it. The guide recommends at least six hours of sunlight a day, or grow lights. If your plants are leggy, light is the first thing to check.

Other causes

• One-sided light. A plant beside a window leans toward the glass. The guide says to rotate your plants occasionally to promote even growth and prevent leggy stems.
• Crowding. Seedlings packed together stretch to reach the light above their neighbors.
• Too much warmth. Warm conditions speed up stem growth at the expense of leaves.
• Weak nutrition. A solution that is too weak, or a pH outside 6.0 to 6.8, slows healthy growth.

How to fix it

1. Add light. Move the plants to a brighter window, or lower the grow light within its instructions.
2. Rotate the container a little every few days.
3. Thin the plants. Snip the weakest seedlings at the base so the rest have room.
4. Check the solution. Test the pH, and make sure the mix matches the nutrient label. See hydroponic cilantro nutrients: what to mix.
5. Harvest. Regular harvesting encourages bushier growth. Leave enough foliage for the plant to keep growing.

Will leggy plants recover?

A stem that has already stretched will not shorten. What you can do is fix the cause so that new growth comes in sturdier, then harvest the stretched stems. If a plant is very weak, it may be quicker to start a new container, as described in how to grow cilantro from seed hydroponically.

Prevent it next time

Choose a bright spot from the start, as covered in grow cilantro indoors, and do not sow the seeds too thickly.

How close should a grow light be?

There is no single answer, because lights differ in strength. The maker's instructions give a recommended distance for herbs and leafy greens. If plants stretch toward the light, it is usually too far away or too weak. If leaves look bleached or crisp at the edges, it may be too close.

Common questions