DIY Potting Mix: Cheap, Custom Blends for Container Gardens

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Container gardening is on my mind as winter's chill eases. I like to get a jump on summer by growing vegetables and flowers in pots before our last frost date, May 15.

How to Make Your Own Potting Soil

Years ago I discovered it's far cheaper to mix my own potting soil and store it in an old trash can than to buy bagged mixes. Plus, I can customize the blend for different plants.

Light, porous mixes are ideal—they make containers easier to move and transport water, fertilizer, and air to roots quickly.

This stunning window box needs only about 20 quarts of custom mix. It's on the acidic side, with extra peat moss to retain moisture for begonias and callas. Credit: Doreen G. Howard

The perfect growing medium contains no garden soil. It's composed of peat moss, vermiculite or perlite, sand, and shredded bark or compost. Plants like lettuce, Russian sage, and marigolds prefer a neutral pH around 7.5. Acid-lovers like ferns, asters, and strawberries need 5.5–6.0. Start with the basic recipe below, then add soil sulfur to lower pH or lime to raise it—both sold in 4-pound bags at garden centers.

For rapid drainage (cacti, succulents, lavender), add extra sand. For moisture-loving ferns and woodland flowers like primrose, increase peat moss.

Homemade potting mix stores well in a sealed container. Credit: Doreen G. Howard

Basic Container Mix Recipe

1 bucket (2½ gallons) peat moss
1 bucket (2½ gallons) vermiculite or perlite
½ bucket (1¼ gallons) screened compost or composted cow manure
2 cups fine sand
2 cups pelleted time-release fertilizer
½ cup lime (counters peat acidity, keeps pH near neutral)

Mix thoroughly. Fills two 14-inch tubs or five 12-inch hanging baskets. Double or triple for larger containers.

How Much Mix Do You Need?

Potting mix is sold by volume (quarts), while pots are measured by diameter. Use this quick reference:

Container Size & Amount Needed

Pots & Tubs
8-inch: 3 quarts
10-inch: 6 quarts
12-inch: 8 quarts
14-inch: 12 quarts
16-inch: 20 quarts
20-inch: 24 quarts
24-inch: 28 quarts
30-inch: 72 quarts
36-inch: 96 quarts

Hanging Baskets
12-inch: 6 quarts
16-inch: 10 quarts

Window Boxes
24" × 6": 12 quarts
36" × 6": 20 quarts

Next week: the right fertilizers for containers and tips for success. Ask your questions in the comments below!