This may be a novel idea to some of you, but hydroponic sponges are great alternatives to replace coco peat or peat moss when growing plants. We all know that soil can be a hassle when they spill and mess up our hydroponics system. Furthermore, if you’re a large-scale hydroponic grower, sponges are a much more affordable alternative to Rockwool cubes, which are costly.
Sponges are a convenient alternative since they are compact and light. Additionally, sponges can are excellent growing mediums as they help to reduce root damage during the transfer of seedlings.
Why Start Seeds on Sponges?
There are several good reasons to use sponges for seed growing: Horticultural foam has excellent water retention properties, allowing for efficient delivery of nutrients and moisture to the plant roots. It holds moisture well while still providing sufficient aeration to prevent water logging, which is crucial for healthy plant growth.
Unlike soil, horticultural foam is sterile and free from soil-borne pests, pathogens, and weed seeds. This significantly reduces the risk of plant diseases and the need for pesticide applications.
Horticultural foam is lightweight and easy to handle, making it convenient for transplanting seedlings or moving plants within a hydroponic system. It provides a clean and neat growing medium, minimizing mess and making maintenance tasks more straightforward.
You can watch the seeds grow and roots develop. Sponge seed germination happens rapidly. It’s easy to sprout a lot of seeds in a small space. The sponges can be reused if seeds turn out to be unviable. It makes a great experiment for children.
Here are some great plant choices for seed rowing on sponges:
Lettuce
Watercress
Carrots
Mustard
Radish
Herbs
Tomatoes
Peppers
Melon
And many more...
For further information, read our FAQ's, Frequently asked questions about hydroponics.
How to Plant Seeds in a Sponge
First, start with sponges that have not been treated with anything, like detergent or antibacterial compounds. You may want to treat the sponges with diluted bleach to prevent mold growth but rinse them thoroughly if you do.
Use the sponges whole or cut them into smaller squares. Soak the sponges in water and place them in a shallow tray. There are a couple of strategies for putting the seeds in the sponges: you can either press small seeds into the many nooks and crannies, or you can cut a larger hole in the center of each sponge for a single seed.
Planting your seeds
Apart from the vegetables mentioned above, you may also opt for ornamental flowering plants. For the best results, do some research on seeds that can germinate rapidly, and for plants that can grow in the existing climate of your place.
Sprinkle the seeds over the sponge, and pat them into the sponge. Try to leave some space between each seed, if possible. If the seeds are too big, press the seeds and make sure they are securely placed into the sponge holes. An alternative method would be to cut a large hole in the sponge, where you will place your seed to grow.
Using plastic cling wrap, cover the container, and poke holes into the plastic with a small stick or pencil. This step is important to prevent the excessive accumulation of moisture, and to provide air circulation for your seeds. Next, find a warm place in your home or garden to place the sponge, and wait a few days for the seeds to germinate. Note that warmth is essential in ensuring that seeds germinate.
Check under the plastic wrap occasionally to be sure there is no mold growing and that the sponges have not dried out. Give the sponges a regular mist of water to keep them moist but not soaking wet.
Sprouting the seeds
As you wait for the seeds to sprout, you may lift the cling wrap and inspect your sponge for signs of mold or drying. Add water to the sponge using a spray mist bottle, giving only a few sprays to ensure it is not excessively soaked. Remember that overwatering should be avoided, as this can cause mold growth or rotting.
Once the seeds have grown into seedlings, place the sponge garden in any spot that receives plenty of sunlight. This can be on your countertop or windowsill, or any place in your outdoor garden. If there is little sunlight where you live, you may place your mini garden under a fluorescent light instead. Give the seedlings as much light as possible, as plants may grow poorly in shady areas.
Tips for buying leafy greens seeds. Look for pelletized or pre-germinated seeds as they are guaranteed to sprout.
Where to buy seeds
Happy Growing!
Once the seedlings have matured into plants, wait for them to grow to heights of three to four inches. Once they have reached this stage, you may bury the sponge into the soil, or transfer it into a hydroponic system.
Planting seeds in sponges can be a simple and fun family activity. Hydroponic sponges allow you to monitor the progress of plant growth, and you can also see the roots developing inside the sponge. Children would love to take on this little project, and you can carry this out as a science experiment to teach them about plant growth.
Pro tip: Apply half-strength plant nutrient solution 5 days after the seeds have sprouted and gradually increase the strength as they grow.
You can buy horticultural foams on the links below.
Note:
You will have to insert the seedling into a net pot when ready to transplant as shown on the left.
Read our article about net pots here.
Read the full growing process here.
Alternatives to grow sponges
Rockwool
Rockwool has excellent water retention and provides excellent support and moisture retention for germinating seeds and nurturing fragile seedlings.
Coco coir
Coco coir or coco peat made from coconut husks, contributes to environmental sustainability and reduces reliance on non-biodegradable materials.
It also provides excellent drainage and air circulation, preventing root rot and promoting healthy root development.
Perlite and Vermiculite
Perlite and vermiculite mix promotes anchorage for new roots and speeds up root growth, making it great for rooting and cuttings for multiple growing cycles, reducing waste and offering long-term cost savings.
Seed Plugs
Another great way to germinate seeds Seed Plugs They usually consist of a net filled with a mix off soil, cocopeat or peat moss. The seed plugs are compressed in to a convenient size. When the plugs are wetted with about 30ML of water they swell till around 8 times their Original size.
Now they are ready to be sowed.
Seed plugs hold the water for a very long period. After the plugs have been sowed they are best placed inside a heated propagator. As soon as the roots grow out of the plugs they are ready to be transplanted to a wood fibre pot, soil or hydroponics system.
Traditional Farming Method
Seedlings sprouted in horticultural sponges can be directly transferred to soil in pots, raised beds, or other growing mediums. We have collected guidelines below on how to grow your own food after the seedling stage.
What Would You Like To Grow?
