Confused why there seems to be soil within the seed capsules when aspara is meant to be soil free? The compact, brown material in the capsule is in fact a special hydroponic growing media that is needed for your plants to grow.
When plants are grown hydroponically, they need a medium to hold the seeds in place so the seeds cannot float to and fro on the water. This helps secure the seeds so the roots can support the plant’s weight and keep the plant upright. This medium needs to be inert so it will not decay or break down quickly in water for the plant to be able to absorb nutrients but otherwise there are virtually no other conditions to be met for something to qualify as a hydroponic growing medium. However, porous materials are generally preferred as these materials can contain the water and oxygen plants need to grow better than non-porous materials. Non-porous hydroponic growing mediums may need more frequent watering for the plant to grow. After the seeds are placed in the media and it is inserted into a hydroponic machine, the media is doused in a nutrient solution that provides the plant with the nutrients it needs to grow.
One of the most common materials used for hydroponic growing media is rockwool. A sterile, porous medium that is made primarily of granite and/or limestone spun into thin threads, it is then formed into blocks, sheets, or even slabs. Although it has a porous structure that allows for extensive root development and does not easily leach minerals, rockwool is also prone to becoming saturated and thus suffocating your roots.
Another material that is becoming increasingly popular is coconut coir, known as coco coir. This sweet smelling material is made from ground coconut husks and has been shown to form a great growing medium for your seedlings. When the husk is still wrapped around the coconut, it protects the seed and the flesh from sun damage as well as helping the coconut germinate into a new tree. In the same way it does for coconuts, coco coir can help seeds germinate while providing an unmatched air to water ratio so your roots will never be drowned.
Peat moss is a classic hydroponic medium that has been tried and tested for a long time. Formed in peat bogs, these bogs are drained and processed to be used as a hydroponic growing medium. Peat moss is popular due to its ability to hold water and its slight acidity that makes pH adjustments easier. To seal the deal, it is also one of the cheapest mediums out there.
Finally, biochar is an option for home users of hydroponic technology as well as commercial hydroponics. Biochar is very kind to nature and can contribute to sustainability when it is used. As a hydroponic medium, it stabilizes nutrients for the plants to use.