Make Your Own Planting Mix
The companion piece to Tuesday's podcast - Ep. 326, "Peat Moss, Coir, & Reusing Old Potting Soil"
In our Tuesday Q&A edition of the Garden Basics podcast, America’s Favorite Retired College Horticulture Professor, Debbie Flower, answered a question from a gardener in North Texas, who is blending his own planting mixes. He is wondering why coir (made from coconut husks, a substitute for peat moss) is difficult to work with, due to its clumping nature. We take many scenic bypasses with this one, including the best formulas to use when reusing your old potting mixes that are just collecting weeds in old containers behind the garage, the remnants of long-ago plants that met an unfortunate demise, for whatever reason. Yes, that soil is reusable! (But watch out for yellowjacket nests buried beneath them if they’ve been sitting there too long!)
Yellowjacket fun fact: Yellowjacket nests in East Texas have been unearthed that were over 6 feet across and contained over 1 million cells!
In Friday’s Episode 327 of the Garden Basics Podcast, we chat with the Fresh Physician, Dr. Laura Varich, about growing a Heart-Healthy garden. What are the foods you can grow in your backyard for better heart health? And how can you grow them? Sounds like a match made in Heaven! One of my favorite tips from her: for a summertime bolt-resistant lettuce variety, try Devil’s Ear Lettuce. Last year when we talked with her, she keyed in on another one of her favorite greens that can take her Florida heat, Tokyo Bekana Chinese Cabbage. Don’t let the name fool you. It actually came here from Japan. And, it looks and tastes more like a mild, looseleaf lettuce variety, and it resisted bolting in our California garden last year!
Homemade Planting Mixes
Note: for all recipes, coir can be substituted for peat moss.
UC Santa Cruz Center for Agroecology and Sustainable Food Systems
Seed Starting Mix (aka “Six-Pack Potting Mix”, for small containers)
By volume:
1 part compost
1 part vermiculite
1 part peat moss or coco peat
Add bonemeal, lime (if peat is used), and kelp meal.
For extra nitrogen, add some blood meal to the mix, as well as fish emulsion when watering.
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Cornell University Modified Peat-Lite Planting Mix: (especially good for seedlings)
for large jobs (1 part=one full wheelbarrow, about 4.5 cu. ft.)
Peat Moss 2 parts
Perlite 1 part
Vermiculite 1 part
Dolomitic Lime (raises pH) 4 cups
Superphosphate (0-20-0) 5 cups
Osmocote or other slow release fertilizer (19-6-12) 8 cups
for small jobs (1 part= a 32 oz. coffee can)
Peat Moss 2 parts
Perlite 1 part
Vermiculite 1 part
Dolomitic Lime (raises pH) 1 tsp.
Superphosphate (0-20-0) 2 tsp.
Osmocote or other slow release fertilizer (19-6-12) 1 Tbs.
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The Rodale Institute Mix (organic):
Finely screened compost 4 parts
Peat Moss 2 parts
Perlite 1 part
Vermiculite 1 part
=======================================Another organic mix (from the book, "Rodale Organic Gardening Solutions"):
shredded peat moss 1 bushel
perlite or vermiculite 1 bushel
ground limestone 1/2 cup
bloodmeal 1 cup
colloidal phosphate 1 cup
greensand 1 cup
(1 bushel = 1.24 cubic feet)
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From: Oregon St. University's E-Organic Program
Seedling mixes for starting transplants
Seed mix (Biernbaum, 2001)
2 parts screened compost
4 parts sphagnum peat
1 part perlite
1 part vermiculite
Lime as needed to adjust pH to 6
Seed mix - standard soilless (Biernbaum, 2001)
50–75% sphagnum peat
25–50% vermiculite
5 lbs of ground or superfine dolomitic lime per cubic yard of mix
Blood meal, rock phosphate, and greensand at 5 to 10 lbs per cubic yard
Organic seedling mix (Biernbaum, 2001)
10 gallons of 2 year old leaf mold, sifted
10 gallons of sifted compost
5–10 gallons of sphagnum peat
5 gallons of perlite
5 gallons of coarse river sand
3 cups blood meal
6 cups bone meal
Soilless potting mix (used by Windsor Organic Research on Transition project, E. Zaborski)
1 part compost
1 part vermiculite
1 part peat moss
Screened with ¼ inch screen to mix together. Per 1 gallon mix add:
0.6 oz blood meal (17.01 grams)
0.4 oz clay phosphate (11.34 grams)
0.4 oz greensand (11.34 grams)
Soil-based seedling mix (Hamilton, 1993)
2 parts loam (stacked turf to kill any weed seed and disease)
2 parts sphagnum peat
2 parts coarse grit (sand)
30 g or 1 oz lime for each 2 gallon bucket (9 liters)
60 g or 1 oz blood meal for each 2 gallon bucket (9 liters)
Organic potting mix (credited to Eliot Coleman in Kuepper, 2004).
1 part sphagnum peat
1 part peat humus (short fiber)
1 part compost
1 part sharp sand (builder's)
to every 80 quarts of this add:
1 cup greensand
1 cup colloidal phosphate
1½–2 cups crabmeal or blood meal
½ cup lime
Soil block mix (Kuepper, 2004; adapted from Coleman, 1995)
3 buckets (standard 10-qt. bucket) brown peat
½ cup lime (mix well)
2 buckets coarse sand or perlite
3 cups base fertilizer (blood meal, colloidal phosphate, and greensand mixed together in equal parts)
1 bucket soil
2 buckets compost
Seedling mix for soil blocks or seedling flats (from John Greenier of Stoughton, WI in Kuepper, 2004)
2 3-gal. buckets Sphagnum peat moss
¼ cup lime
1½ cups fertility mix (below)
1½ buckets vermiculite
1½ buckets compost
Fertility mix:
2 cups colloidal (rock) phosphate
2 cups greensand
2 cups blood meal
½ cup bone meal
¼ cup kelp meal
Directions for mixing:
Add peat to cement mixer or mixing barrel.
Spread the lime and fertility mix over the peat.
Mix these ingredients thoroughly.
Add the compost and vermiculite and mix well again.
When done, examine the distribution of vermiculite to ensure that it has been mixed in evenly.
Note that all bulk ingredients should be screened through 1/4 inch hardware cloth. Well matured, manure-based compost should be used (avoid poultry manure and wood-chip bedding).
Mixes for larger plants or containers
These mixes require the addition of mined nutrients from natural sources.
Cornell Organic Substitute for Classic Mix (as modified by Biernbaum, 2001)
½ cu yd. sphagnum peat
½ cu yd vermiculite
5 lbs ground limestone
2–4 lbs bone meal
5 lbs blood meal
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Check out all the information about potting mixes for Certified Organic Production at the NCAT Sustainable Agriculture Project Website
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Note: when using peat moss, pre-moisten the peat moss to aid moisture retention. In a hose-end sprayer, put one tablespoon liquid dish detergent in the jar. Set sprayer to mix one tablespoon per gallon of water. Thoroughly water the peat moss with this solution before mixing with other ingredients.
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Purchasing a commercial potting soil or planting mix?
Some tips from the California Master Gardener Handbook:
• Select mixes high in bark, forest materials, or spaghnum peat with vermiculite or perlite.
• Thoroughly leach any potting soil before placing seed or plant material in the mix. Leaching will reduce soluble salts to acceptable levels in most mixes.
•Fertilize with a soluble fertilizer according to manufacturer's directions within two weeks after plants are growing in the new potting/planting mix or potting soil. This will replace leached nutrients and those taken up by the plants.
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The difference between a potting/planting mix and potting soil?
There are no hard and fast rules. Ask 100 experts, you may get 100 different answers. Generally speaking, if the bag says "soil", it probably contains soil and sand, along with ingredients such as perlite, vermiculite, peat moss or bark.
When you buy a garden product with the word "soil" - especially at a low price - you are increasing the chances of buying someone else's problems: a package that contains weed seeds, nematodes, fungal diseases, heavy clay, sludge.
Your best bet, as stated above: choose a product high in forest materials (especially for woody plants), or peat/coir with vermiculite or perlite (for herbaceous or non-woody plants).
Thank you for also listening to the Garden Basics with Farmer Fred podcast!
It’s available wherever you get your podcasts, or at our home page, GardenBasics.net . Please share it with your garden friends.
Fred Hoffman is also a University of California Cooperative Extension Master Gardener in Sacramento County. And he likes to ride his bike(s).