How Do You Start Seeds for Hydroponics?

How Do You Start Seeds for Hydroponics?

One of the most common questions we get from people interested in hydroponics is “How do you start seeds?”  While there are many options, our favorite is coco coir.

Made from the outside husk of a coconut, the fine fibers are porous and soak up water while leaving room for air pockets. A quality coco coir brand, like OrganicMechanics Cocodelphia, comes thoroughly washed and buffered to provide an inert, pH neutral growing media free from salts (<0.7 EC). Because it uses the waste from coconut processing, it’s more sustainable than peat pods, rockwool, or rooting cubes made from floral foam.

Coco coir comes in a couple different forms. It is either bagged loosely like soil, or is compressed into dried blocks or tablets. If you choose a compressed form, you need to soak it in water to soften and break up the fibers before you can use it for growing.

Deciding how to start your seeds may depend on the type of hydroponics you practice. For drip irrigation setups, you may be able to start your seeds right in your pot or grow bag. For other methods, you may want to start by placing a seed or propagation tray inside a drip tray. Fill the seed tray with coco coir, and add water if necessary, so that its damp and sticks together slightly. Now you’re ready to plant your seeds.

Seed tray filled with coco coir sitting on a table. In the center of each cell of the seed tray a small depression is waiting for a seed.

For large seeds, use one seed per cell. For smaller seeds, you can add a few seeds per cell and separate them once they’ve sprouted.

Once your seeds are sown, a humidity dome can help to keep the coco from drying out too quickly. Depending on the type of seeds you are growing, such as tomatoes, peppers, or similar, a heat mat can aid germination (if equipped with a thermostat, 75℉ is the optimal temperature).

Seed tray under an LED T5 light. In the background a vertical deep flow hydroponic system is full of tomatoes and peppers.Inside a grow tent, 4" pots with seedlings, and a seed tray covered in a humidity dome sit below a grow light.

For seed starting, a bright shop light is sufficient; or you can use a florescent or LED T5 light at a height of 12-18 inches.

Within 10-14 days your seedlings should have their first true leaves. Now they’re ready to transplant.


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