How Do You Start Seeds for Hydroponics?

How Do You Start Seeds for Hydroponics?

One of the most common questions from people interested in hydroponics is, “How do you start seeds?”  Most all-in-one systems sell their seed pods for around five dollars each. This ease of convenience may be preferable for some. For those who wish to grow something different, or don't want to pay the price, here is our favorite method for hydroponic seed starting.

Coconut 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 few different forms. It is either bagged loosely like soil or is compressed into dried blocks or tablets. It is also available as short or long fiber, or chunks. 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.

Propagation Trays

Deciding how to start your seeds may depend on the type of hydroponics you practice. For drip irrigation setups, you may be able to sew your seeds right in your pot or grow bag. For other methods, start by placing a propagation tray inside a drip tray. Fill the propagation tray with coco coir, and add water if necessary, so that it’s 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.

Make sure you know the correct depth for the type of seed you are planting, and create a small impression to place the seeds in. For large seeds, like melons, peppers, tomatoes, or hemp, use one seed per cell. For smaller seeds, such as lettuces, you can add a few seeds per cell and separate them once they’ve sprouted. Cover the seeds with coco when you are done, and if you are planting more than one variety, be sure to label them.

Once your seeds are sown, place a humidity dome on top of your tray to keep the coco from drying out too quickly. If you are growing seeds 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 T5 light at a height of 12-18 inches. An LED grow light bulb will also work at this stage in the growing process. During the seed and seedling stage, you can keep your light on for 24 hours. Once your plants are larger, they will require brighter light.

Within 10-14 days your seedlings should have their first true leaves, and will be ready to transplant

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