How to Grow Cilantro in a Greenhouse Float Bed

Place the cilantro seeds in a bowl or glass jar full of water. Soak them for 24 hours to prepare them for planting. Soaking the seeds softens the hard external matrix and allows for easier germination.

Drain the seeds on a paper towel for one hour before planting, but do not let them dry out. Mist the seeds with a spray bottle until you are ready to plant them.

Fill a seedling flat with sterile potting soil. If sterile potting soil is not available, plain garden soil works fine. Cilantro is not fussy about the acidity of the soil, but it must be rich in organic matter and capable of holding moisture.

Create 1/4- to 1/2-inch-deep depressions in the soil at 1-inch intervals. Place one or two seeds into each depression and lightly pinch the soil closed on top of them. Planting the seeds close together creates crowded conditions as the plants grow, thereby shading the roots and keeping the soil cool.

Mist the soil until thoroughly moistened but not saturated.

Fill the float tray with 1 inch of water. Slip the seedling tray inside the float tray, taking care not to splash the water out. Replenish the water once a week to maintain proper humidity for the cilantro.

Open any overhead ventilation windows in the greenhouse to allow heat to radiate out. Place a thermometer near the cilantro flat to monitor the temperature. The temperature must not exceed 75 degrees Fahrenheit or the plants will bolt, or go to seed, prematurely.

Thin the seedlings once they reach 2 inches in height. Remove approximately 30 percent of the seedlings to allow the root systems of the remaining plants to develop.

Harvest the leaves in small batches from different parts of the flat. Continually harvesting the leaves promotes growth in the plants and delays bolting.