A soilless approach to growing plants indoors

It is that time of year when gardeners are salivating to get out to the garden and get growing. With piles of snow still getting deeper, we have an opportunity to get started inside. Many of the vegetable crops we love need more time to mature than our climate offers. Tomatoes and peppers first come to mind when I think of starting seeds inside. The foundation of any garden is the soil. The soil supplies nutrients, filters water, breaks down organic matter — it is the one thing that can make or break your garden.

Soilless media is the choice for starting seeds inside. Soilless media is any sterile medium for growing plants that does not involve soil. Characteristics of good soilless media include good aeration and drainage, durability, porosity, sterile, neutral pH and good cation-exchange capacity, and functionality. Several options of soilless media are available and can be mixed by hand or can be purchased from local hardware or garden stores premixed.

Potting mixes usually have a combination of peat moss, pine bark, coir, perlite, and vermiculite. Peat moss makes up most potting mixes but can be replaced with coir. Peat moss decomposes slowly and retains moisture while still supplying plenty of air and water space. It is acidic and limestone should be added to neutralize the pH. It is also hydrophobic, so it is difficult to keep wet. Coir is a byproduct of coconut production. Coir fiber is easier to rewet when it dries out. Shredded pine bark is usually used in epiphytic mixes where moisture needs to be low but can also be mixed in a general potting soil. Perlite, a white, irregular, small volcanic rock that is sterile, odorless, light weight, and used to improve drainage and aeration. Vermiculite is made when mica chips are heated and supplies added moisture retention for the potting mix.

Several types of potting soil are available for starting seeds, make sure to buy a germination mix. The mix will be ground finer so seeds will have more surface area contact to the soil. When I prepare the potting mix for planting, I make sure to mix in warm water to help the seeds get started sooner. Peat moss holds moisture well, but once it dries out it becomes hydrophobic and becomes difficult to wet again. Most germination mixes have vermiculite, which helps keep water in the media. A good mix for germination is three-parts finely ground peat moss, one-part perlite, and one-part fine vermiculite.

I avoid using garden soil in anything I grow indoors. Soil contains minerals, organic matter, air, and water space. And although they are well suited for gardening, several factors make them unacceptable for container gardening. Soil is easily compacted in containers, decreasing the amount of air and water space available to the plant. Soils can easily be saturated with water limiting air space roots need. Unpasteurized soils are a source of weeds, insects, and disease. Soil also makes the containers very heavy, which makes moving them difficult.