Potting soils and containers

Here are a few tips to help take some of the guesswork out of starting your garden from seed.

Potting soil — which one?

Most conventional potting media are soilless mixes that use Canadian peat as the main ingredient, include a chemical wetting agent, and are usually sterilized. The chemical wetting agent helps the mix absorb instead of shed water. Sterile media is supposed to be disease-free, but actually leaves your seedlings vulnerable to disease-causing microorganisms (such as “damping off” disease).

For growing organically, I recommend avoiding the wetting agent and sterile product. Instead, choose a potting mix that is alive. That is, it contains some compost that is rich with living beneficial microbes. The compost component serves as an excellent aid to absorb and retain moisture. It supplies nutrients that peat does not. Those beneficial microorganisms in the compost will actually protect your seedlings from disease.

Two excellent Alaskan choices are Fishy Peat and Alaska Earth brands of potting soil. These are sold at various garden stores. Both are made by Anchor Point Greenhouse on the Kenai Peninsula, by composting fish waste, kelp, and local peat. You may want to fluff the Fishy Peat by mixing in a bit of coco fiber, perlite, or vermiculite. Coco fiber comes in a wettable compressed brick. Perlite and vermiculite are harmless, inert volcanic minerals expanded by “furnacing.” The Alaska Earth already contains perlite for your convenience.

What if you have already purchased a bag of conventional, sterile potting medium? Simply blend some compost into that product to give it life and disease protection. Buy some bagged compost or worm castings, or use your own sifted compost at a ratio of one part compost into three parts of your store-bought potting soil. I don’t recommend that you experiment with additions of outdoor garden soil in your seed-starting mix. OK! You’re ready to fill your containers and set them in your flats.

Which containers?

You have the common choice of those black plastic four-packs or six-packs, or DIY yogurt and cottage cheese containers — just remember to punch drainage holes. Peat pots — and now CowPots — are a convenient alternative because you eventually transplant by setting the seedlings, pot and all, right into the garden bed. Thus you don’t have to tear roots and cause transplant shock in the process. The pots are durable in your trays but break down in a few weeks once planted in soil. (To i2nsure that the roots grow out the bottom when transplanting, gently and partially rip an opening at the bottom.)

Soil blocks allow you to skip the containers all together. You buy a soil block maker and press out soil cubes into your flats. I press 48 soil blocks into a flat, and drop a seed or two into the dimple on the top of each block. Soil blocking works well with dampened Fishy Peat. Like peat pots and CowPots, you plant the whole block, minimizing transplant shock. There are no black plastic six-packs to store at the end of the season, plus each seedling gets about three times more soil in a soil block compared to a cell-pak. Watch the five-minute soil-blocking video at bit.ly/1l9CRbS. Soil blockers are available online from Peaceful Valley Farm Supply.

Ready to sow

You are ready to sow your seeds, about two seeds per cell, and then plant a few extra cells. If your plan calls for 10 broccoli plants, plant 15 to account for some germination failure. If your seed is older, drop three to five seeds per cell, pot, or block. Create a label for each kind of plant you sow, and the date. Water thoroughly. If you have a water-softening system, avoid this tap water — it is too salty. Now, keep that potting soil damp, and watch for the magic of tiny leaves emerging!

Leggy seedlings?

Lighting, temperature, and air movement are crucial for growing sturdy, compact “starts” and bedding plants. I’ll help you navigate those challenges next time.

Ellen Vande Visse operates Good Earth Garden School and offers educational workshops through goodearthgardenschool.com.