Homemade Potting Soil Mix

It's nearly time to start sowing seeds for your spring gardens. Of course you can buy commercial potting soil mixes, but read the label carefully. Do you want chemically enhanced soil? Watch for Miracle Grow and other "helpful" additives.

Mixing potting soil at home is easy and economical. It takes a few basic ingredients and a dish pan to mix it in. I usually start with compost from my bins, but alas, it's frozen solid. Instead, I purchased a 40 lb bag of ordinary potting soil without any additives. This should cost about $5.

For my seed starting mix, I use equal parts of soil, peat moss and horticultural vermiculite. This mix is light enough for seeds to germinate. If I need to transplant healthy seedlings into larger containers, my transplant mix contains equal parts of soil, peat moss and Turface for drainage.

If you can afford it, choose coir rather than peat moss because coir is far more sustainable than raiding the peat bogs. Horticultural vermiculite is available at garden centers. I buy it in super large bags, but it's also available in smaller amounts.

Turface is tiny bits of clay used for drainage on golf courses and athletic fields. It's sold at landscape suppliers for about $12 per 40 lb bag. (I learned about Turface from the bonsai community.)  If you can't find Turface, you can substitute chicken grit for drainage, which is easily available at farm stores. The baby grit is quite fine and can get dusty; granny grit is slightly larger. Caution: even a small bag of grit is very heavy.

Now go play in the dirt!

Seedling Soil Mixture

We're off to a good start. So far this year we've planned the gardens (Jan. 26 blog), researched seed purchases (Jan. 27 blog), warmed up our seedling heat mat (Feb. 1 blog) and assembled our lighted plant stands (Feb. 14 blog).

Today let's think about creating a soil mixture suitable for planting seeds. It's much cheaper to make your own soil mixture rather than buy bags prepared at the garden center. At Red Bucket Farm, our approach is simple. We create a soil light enough for seeds to emerge using compost, peat moss, and perlite or vermiculite.

If you haven't started composting yet, you can purchase finished compost at any garden store. But remember that you can begin composting in the winter by mixing a combination of green and brown ingredients in a plastic tub in your basement or garage. (See my May 6, 2011 blog post for more details on composting.)

For many years I've purchased peat moss from the garden center. Recently, though, I've become concerned about depleting our peat bogs. Coir--coconut husk fiber and peat--is a more readily renewable option. It's sold in dense blocks and requires simple hydration. Perlite and vermiculite are also available at garden centers.

Using a hand scoop, dump approximately equal amounts of compost, peat/coir and vermiculite/perlite into a bucket and stir, keeping the mixture light and loose. Distribute seeds over the soil mixture and stir very gently to just barely cover the seeds with soil. Then mist with water from a spray bottle, and/or water from beneath using a drip tray. It's important to keep the seeds moist enough to germinate but not soggy enough to rot. I check my seeds twice a day to maintain proper moisture levels. It's not difficult, but you must be attentive.

The snow is melting and spring is approaching. It's not too late to start your seeds indoors---vegetables, herbs and flowers all benefit from an early start. What are you planting?

Custom Soil Mix

Last week I potted up my veggie seedlings. The peppers, lemon cuke, eggplant, cantaloupe and basil went into large glazed containers. They'll live in the greenhouse for the summer, where I hope the extra heat will boost crops. Using so many containers requires quite a bit of potting soil, and the quality of the soil is especially important for container plants.

I learned from the bonsai community years ago that mixing your own potting soil is cost effective and far more convenient than purchasing heavy bags of the right blend. The bonsai experts in my area recommend equal parts peat moss, Turface and chicken grit. Now that I'm focusing on vegetables, fruits and herbs, my soil mix has evolved to include plenty of sifted compost, rich in nitrogen from chicken manure.

Turface is a soil amendment that keeps soil loose and aerated. It stores and releases moisture and nutrients and helps produce a deep root structure. Red chicken grit is made from granite and helps promote good drainage. (White chicken grit is made of oyster shells and increases calcium in the chicken's diet.)

I blend my soil mixes in a wheelbarrow. It's easy to adjust the blend for the needs of various plants. For example, too much nitrogen in the pepper containers will grow lush leaves and little fruit, so I cut back on the compost. On the other hand, cantaloupe plants love the compost, so I gave it to them straight. I keep plastic tubs of Turface, chicken grit and peat moss in my potting area. Our compost gets sifted out back and wheeled up the hill as needed.

There is no need to purchase bags of special potting soil from the garden center. Just mix your own!