How to Plant Seeds in a Sponge
Channel: J & C Industries
Date: 2020-05-16

Planting seeds in a sponge may not be the most practical method of growing large number of seeds, but the method works well for planting a few flower seeds or fast-growing seeds such as watercress, which is ready to harvest after a few weeks. Planting seeds in a sponge is also a hands-on way for gardeners of all ages to learn how plants grow with only water, air and sunlight.

Purchase fast-growing seeds to plant in your sponge. Fast-growing vegetable seeds that are ready for eating as sprouts in a few days include watercress, radishes, lettuce, alfalfa or mustard. You can also plant annual flowers for planting outdoors. Fast-growing annuals include nasturtiums, marigolds, bachelor's buttons or cosmos.

Rinse a sponge thoroughly under running water. Squeeze the sponge until it is moist but not dripping. You can use a kitchen sponge or a sea sponge.

Place the moist sponge on a plate or shallow dish such as a pie pan.

Plant the seeds in the small holes in the sponge, using tweezers. Allow about 1/2 to 1 inch between each seed.

Place the plate in a sunny area such as a countertop, table or windowsill.


Check the sponge daily, as the sponge must remain constantly moist. Water the sponge when it feels slightly dry, but don't overwater, as the seeds may mold or rot. To avoid overwatering, add only 1 tablespoon of water at a time.


Harvest radishes, mustard or lettuce by snipping the seedlings with clean scissors in about four days. Allow watercress to mature for about two weeks. Eat the seedlings or add them to sandwiches or salads.


Plant annual flowers in a sunny garden spot when the roots are about 1/2 inch to 1 inch long. Cut the sponge apart between each seedling, leaving only a small amount of sponge attached to each seedling. Space the seedlings according to the directions on the seed packet. You can also plant annual seedlings in a flower pot filled with commercial potting soil.