All growing starts with planting. Planting a hydroponic garden is no different. We love to start our plants from seeds, it is part of the gardening fun.
With discovering hydroponics and indoor gardening a whole new gardening world opened up to us. Now planting a garden is not limited to springtime anymore, we can grow a garden 365 days a year! And plant new seeds over and over again.
It was a steep learning curve on how to start plants for hydroponic growing. As always, we like to share with you what we learn.
There are many ways to plant a hydroponic garden, what we share here is what has worked well for us. This method is great for all kinds of hydroponic growing, the aeroponic Tower Garden, high-pressure aeroponics, NFT hydroponics setup, as well as the simple Kratky Hydroponics.
Since hydroponic is not using any soil, we do not plant seeds in the soil. We started our hydroponic growing with the Tower Garden that came with everything we needed to start growing. It worked well, so we have kept the same method for many years.
Things that you need for planting a hydroponic garden.
Rock wool starter cubes come in different sizes. We grow everything in 1.5×1.5 inch Rockwool. The Rockwool plugs are made from molten rock spun into cotton candy-like fibers. Rockwool is maybe the most popular hydroponic growing medium and for good reasons, it simply works. But you can also use Oasis Rootcube, Rooter Plugs or any other hydroponic growing medium of your choice.
Vermiculite works great to cover the seeds to keep them moist.
A planting tray without holes to hold the Rockwool cubes in. Quality trays are great, but we often also just use recycled containers for example from mushrooms.
Net pots are there to hold the rockwool and the plant. The planting medium has to be a bit smaller than the net pots. We use net pots that are 2 inches in diameter. In a usual container garden, you would not be able to grow a big plant like a tomato in a 2-inch pot. That is different with hydroponics. As long as there is room in the system for the roots, the pot can be small.
The hydroponic nutrient solution will be needed once the seedling has true leaves. We like to use the dry General Hydroponics MaxiGrow. You do not need it to start seeds, but have it ready since some seeds grow fast.
Having a PH and PDS meter ready is helpful too. Again, these will be needed once the selling has grown true leaves and will need a solution.
Rock wool needs to be soaked in water for a few minutes up to a few hours until wet throughout. Especially if your water is very acidic, you can soak the wool in lower PH water – the water will neutralize the PH. Rock wool has a PH of its own that is a bit higher, you can use the PH down or simply a lemon to lower the PH in the water. You want the wool to be moist, not wet. So after soaking let the water drip off a bit.
Now you are ready to plant.
Planting from seeds
The seeds for hydroponics are just the same as for any gardening. You might want to try new varieties depending on where the garden will be.
Plant 1-3 seeds in one hole of the Rockwool cube to make sure one germinates. Sometimes the Rockwool cubes have nice cut-out holes, sometimes however it’s just a small opening. In this case, I use my finger to make a bigger hole.
Since many seeds are very small, a toothpick can help to plant them. Wet the pick in some water and the seed will stick to it. Now you can plant the seeds precisely. There is no need to waste seeds.
After adding the seeds to the hole, cover them with some vermiculite. Do not overfill the holes, the idea is just to help keep the seed moist. Now spray each hole with a little water. You can also add a little water to the bottom of the tray to add moisture.
Seeds need warm temperatures to germinate, not so much light. Find a warm spot in your house. The top of a fridge would be a better place than a cold but bright window. Some have great results by placing the tray on top of a heating vent in the winter. You want about 85 degrees (Fahrenheit) for fast germination. A Germination Station with Heat Mat can be helpful too.
To speed up germination you can also sprout seeds before planting them. I use the Biosta sprouter. Especially in the winter I find it helpful to sprout seeds.
Sprouted seeds are a bit sensitive. If you just plant the dry seeds they will sprout and grow whenever the conditions right. If you sprout them prior to planting, you have to make sure the conditions are right at all time till they become robust little plants. Keep them moist and warm with lots of light.
As soon as your seed germinate, they will need sunshine or a grow light. Keep your seeds and seedlings moist by adding about 1/4 inch of water each day. Once your seedlings start growing true leaves, water them with a hydroponic nutrient solution.
Thinning out seedlings
It is tempting to grow several plants in one rock wool cube. However, we have learned that this is not a good idea, even if the plants are small. In fact, we have lost a whole Tower Garden to over planting. If you have multiple seedlings in one rock wool cube, thin them out to just one plant per cube. You will end up with healthier plants and a cleaner root system in your garden.
Use garden snips or scissors and cut out the crowded seedlings always leaving the healthiest plant.
In 2-4 weeks, when your seedlings are about 3 inches tall, they are ready to be planted into the hydroponic / aeroponic garden. It is not so much the size of the plant, a more healthy root system that is growing out of the rock wool cube that we are looking for.
Growing healthier roots
To ensure there are health roots growing out of the net cup you can plant the seedlings into the net cups prior to planting them into the system. This is especially helpful for plants who have tiny roots at the planting stage, or if the seedlings for some reason need to wait longer to be planted. In any case, this little step will give you healthier roots. In the video below I explain it in detail. (You will not be able to see the video with an add blocker)
Planting from seedlings
If you have a hydroponic greenhouse selling seedlings nearby, you can purchase the seedlings instead of growing your own. You can also buy normal seedlings to use in a hydroponic system.
Choose seedlings that have a longer root system. Now gently wash all the soil off of them. Cut a rock wool cube in half and place the seedling into it. Lay the other half on top and hold them together with a rubber band.
If planting strawberries, make sure to have the crown above the rock wool.
Note of caution: By bringing in seedlings you might bring in some diseases or insects, too.
Planting from cuttings
After taking a cutting you can simple put it into the rock wool cube so the end is showing on the other side. Keep the cube moist and the cutting will grow roots.
Or you can place your cuttings as per usual in a glass of water (I have had great results with this), and when roots are established proceed planting it like a seedling. Cut a rock wool cube in half and place the cutting with an established root system into it. Lay the other half on top and hold them together with a rubber band.
Planting seedlings into the system
Your seedlings are ready to be planted into the system, when you can see the roots growing out of the rock wool cube. In our tower garden system we push the cubes a bit down into the net pots. Roots that do not reach the watering will dry out and die. To prevent that see the video above on how to grow healthier roots.
In a vertical system like the Tower Garden, make sure to plant smaller plants on top and bigger, heavy plants with a massive root system at the bottom. This way you will insure a good water flow and also have an easier time supporting the bigger plants as they grow.
Also if you have a problem with insects like aphids, plant plants that are known to be liked by them (like herbs and cabbage family plants) at the bottom, this way they will stay mostly on those plants and not go all over the garden. You can even grow a trap for insects with some beautiful nasturtiums. Nasturtiums attract many insects, meaning if there are any in your garden they will be on them and not in your salad.
Generally speaking, labeling your plants is very important. How else will you remember what was planted, what did well, and what you should never grow again ;)? Labeling the rock wool cubes can be a bit challenging simply because of their size. Little homemade labels out of a milk carton or a diagram on a peace of paper works well.
Most of the time though, I prefer to make a list of things I planted. This is not as accurate, but still works well for the purpose.
Start new plants
Since plants grow in aeroponics system much faster than they do in soil, you will need to start new seedlings approximately every 8 weeks for fast growing plants like letuce. The hydroponic / aeroponic garden is a real green food machine, so keep on growing.
Grow an indoor edible garden
Hydroponics is one of the best ways to grow an indoor edible garden. Take a look at all the posts we already shared about growing food indoors, and seedlings for the summer garden.