Hydroponic Herb Gardens
Growing From Seeds 

Watching new plants emerge from seeds is joy. 

New seedlings 1 week after planting. Notice the shell from the seed at the tip of the new leaf.

Growing from seeds is a delicate process however. Too much water and fungus attacks. Not enough water and new tender seedlings shrivel up and die.

Water and temperature have to be just right for success.  

Young, tender seedlings suffer without special care

Starting seeds in soil is a tricky business. If the growing medium is too wet or not sterile, disease can strike. If it is too heavy or sticky, fine new roots won't be able to push through it.

We replace soil with "Rockwool Grow Cubes" - a new and unique way to nurture seeds into seedlings. Rockwool Grow Cubes are a sterile growing medium that resists disease and provides the exact balance of air and water that seeds need to sprout. 

Rockwool Grow Cubes

more on Rockwool Grow Cubes  . . . 

Mature lettuce seedling growing in a Rockwool Cube

Planting Seeds in Rockwool Grow Cubes

1. Soak Rockwool Grow Cubes in clear water until they're saturated - about 10-15 minutes.

Position cubes in a watertight tray for planting. Any type of tray or saucer will work.

Rockwool Grow Cubes in Grower Trays
Rockwool Grow Cubes in a plastic saucer

2. Using a pointed object (like a pencil) poke several holes in the top of each cube. 

Preparing rockwool grow cubes for planting

3. Carefully sprinkle seeds over cubes. Try to get the seeds to fall into the holes - but don't worry if you miss - they will still grow.

Planting seeds

4. Cover seeds with a layer of sand to protect the seed and to block out light. Any type of builders sand will work.

Cover seeds with sand for protection as they open.

Good job!

Be sure to use labels so you know what you've planted.

Getting Your Seeds to Sprout (Germinate)

Getting seeds to germinate is a delicate process that requires two things; 1) warm temperatures and 2) just the right amount of moisture.

Heat mats provide the gentle wramth seeds need to sprout

1. Warm Temperatures

Temperatures in the 68- 75 degree range are imperative. Most seeds simply won't germinate in temperatures below 68 degrees. Heat mats are the best tool for providing the gentle warmth seeds need to sprout.

2. Just the Right Amount of Water

Watering seeds growing in soil is never easy. Soil promotes disease (especially a fungus disease called "damping off") if they're too wet. Seeds are dislodged or damaged without careful watering. 

Rockwool Grow Cubes are a sterile, inert growing medium that prevents fungus and disease. 

And correct watering is easy. Simply pour water into the tray (not directly on the seeds) to about 1/4" deep. The capillary properties of the Rockwool Grow Cubes wicks the moisture up to the seeds gently and evenly. At the same time, air flows through the cubes creating an even balance of air and moisture. 

Always wait until bottom of tray is dry to touch before rewatering. 


Most seeds germinate better in the dark. 

But, when new leaves emerge (in 2-3 days), the new seedlings want cooler temperatures and light - lots of light! Move plants away from the heat and into sunny window that has a couple of hours of direct sun.

New seedlings will grow weak and spindly without adequate light..

Seedlings growing in Rockwool Cubes - 2 weeks after planting.

Most seeds sprout in 5-7 days. In 2-3 weeks you'll have mature seedlings that are 3-4" tall and are ready to be moved into a hydroponic planter.

When roots start growing out of the bottom of the grow cube, it's time to move them into a hydroponic planter.

Grower Tips for Seeds and Seedlings:

  - Use plain water while seeds are sprouting. After new leaves appear apply nutrients at 1/2 strength. I use and recommend Dyna-Gro Grow 7-9-5 formula.

 - As seedlings mature they will gradually use more water. Always wait until tray is dry to touch before rewatering however.

 - Avoid harsh, dry heat when warming seeds for germinatin. Top of a refrigerator or few inches above a radiator simply aren't the best spots. Invest in a heat mat.

Moving Seedlings to Hydro Planters

Hydroponic Herb Gardens - Tools for Success

Why Hydroponics?