Make Your Own Planting Mix (updated 2024)

Note: for all recipes, coir can be substituted for peat moss.

 

The Rodale Instute Mix (organic):

Finely screened compost  4 parts

Peat Moss  2 parts
Perlite  1 part
Vermiculite 1 part

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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 gallon 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:

1. Add peat to cement mixer or mixing barrel.
2. Spread the lime and fertility mix over the peat.
3. Mix these ingredients thoroughly.
4. Add the compost and vermiculite and mix well again.
5. 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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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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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).

Pepper Seeds Won't Germinate? Some Tips.

Home gardeners who grow their tomatoes from seed usually get fairly quick results after sowing the seeds indoors. Given the right germinating conditions - a soilless planting mix, good drainage, plenty of light, plenty of warmth - tomato seeds can pop up in 8-10 days.

  

Pepper seeds are a different story. Why is it some peppers can take weeks to germinate?

"The important thing in getting your (pepper) seeds to germinate is to keep them warm – the soil temperature should be in the 80's", says Renee Shepherd of Renee's Garden, a popular seed catalog based in Felton, California. "Germination is very much related to even moisture and warm temperatures. You should see germination within 2 to 3 weeks if it's warm enough. I strongly suggest using bottom heat to achieve the warmth the seeds need – most good nurseries carry good little electric seed starting mats which will keep your seeds at the right temperature to sprout. A local mail order source is Peaceful Valley Farm Supply."

For those who want to comparison shop, another source for heating mats for your pepper seeds: Amazon.

Another trick that some gardeners employ is soaking the pepper seed for a few hours before sowing to soften the seed coat. The value of that is open to debate.

"I have never heard of soaking pepper seed overnight and have never done it in 20 years of running a trial garden,"  says Shepherd.

On the other hand, Professor Debbie Flower of the American River College Horticulture Department sees the benefits of some "immersion therapy" for pepper seeds. "We soaked our pepper seeds in hydrogen peroxide for 10 minutes," explains Flower. "That's not enough time to scarify (soften or break the seedcoat), or even get them soaked, but enough to kill exterior diseases."

Many sweet pepper varieties will show their initial leaves about two weeks after planting the seeds. But some varieties of peppers take longer to pop up than others. "The hot pepper varieties take longer to germinate, some to three weeks," says Flower.

But if you are experimenting with the really hot pepper varieties, such as the Bhut Jolokia (Ghost Pepper), it could take up to four months, says the Trade Winds Fruit website:

"Chinense species (e.g. Habanero's) generally take longer to germinate than most common peppers. Keep soil warm to very warm (75-90F) for better germination. Do not use acidic soil. Some Chinense peppers, in particular Bhut Jolokia, Naga Morich and related peppers are very slow to germinate, averaging 1-4 months germination time."

By the way, if you are growing the Bhut Jolokia...you're playing with fire. The Ghost Pepper is rated at 850,000 Scoville units of heat. For comparison, the habanero rates 200,000; the Jalapeno is 5,000; the Anaheim equals 1,000. And sweet bell peppers? 0.

This is as hot as I can stand. The Inferno: 4,000 Scoville Heat Units

Another factor that can determine the rate of germination of pepper seeds: the pH of your seed starting mix. One of the most common ingredients in most seed starting mixes is peat moss, which is highly acidic, with a pH around 4.0. Pepper heads, including the Horticulture students at American River College, have found quicker germination when Coir (coconut fiber) is substituted for peat moss. Coir has a closer-to-neutral pH: around 6.5. The tests at American River College bear this out after trying Coir in their pepper seed soil mix. "We've had the best germination of peppers ever!" says Flower.

And don't be in a rush to set them out in their permanent garden home. "Pepper seedlings need to be grown out until they have at least several sets of true leaves, and it is at least 55° at night before you plant them out," explains Renee Shepherd.  "And they will need a little time to get used to being outdoors, as well."

Here in the Sacramento area, that would be around  mid-May. Be patient.

Starting Tomato, Pepper Seeds Indoors

Every summer, I make the same promise to myself: "Next year, fewer tomato and pepper plants!" And every winter around this time, I try to start small. But somehow, things get out of control...

Late January and early February is the ideal time here in Northern California for starting tomato and pepper seeds indoors. And while you're at it, why not start a few others, such as more cool season leaf crops and summer annual flowers from seed. Those leaf crops (lettuce, spinach, chard) can be transplanted outdoors after about three weeks worth of growth indoors (take a few days to gradually introduce them to the outdoors, perhaps bringing them and their containers back in at night).

Those tomato and pepper plants, along with the summer flowers you started from seed? Keep them protected, indoors, until mid-April. Then, gradually acclimate them to the outdoors as well.

The main problem with outdoor planting of tomato and pepper plants this time of year? Soil temperature. Those summer vegetables do not start actively growing until soil temps reach the mid-60's, and don't really take off with food production until soil temperatures are above 70. Right now? Soil temperatures are hovering around 50 degrees here in the Sacramento area.

Another good reason to delay outdoor planting of those young vegetables until late April-early May: the wind. March is a very windy month in the Central Valley, with northerly winds hitting 20-30 miles per hour, for several days.

What you need to start your seeds:

• A sunny, indoor window or greenhouse.

• Small pots or flats with good drainage. Clean thoroughly.

• An easy draining, pathogen-free soil mix, preferably soilless.

• No greenhouse? Use good quality light fixtures.

• Air movement.

• Small amounts of fertilizer.

• Seed heating mat (optional).

If you are starting your seeds indoors, you would benefit from an extra lighting system, such as fluorescent bulbs hung a few inches above the plants. If the light source is too far away, the plants will get leggy.

I like to use 3"- 4" azalea pots for starting seeds of tomatoes and peppers. I will plant three or four seeds per pot. When they come up and put on two sets of leaves (about three weeks after germination), I'll transplant them to their own pot.

(NOTE: this is how a small number of plants becomes wayyyyy too many, in a hurry!).

Those old six packs and partitioned flats are ideal for starting green, leafy crops. Thin out the seedlings so that there is only one remaining in each cell.

The real key to seed starting success? The soil. More exactly, the soilless mix. Using soil from your garden to start seeds is filled with threats to seed survival: competition from weed seeds, soil-borne diseases, and too heavy a soil. Damping off, a common malady of new seedlings, is due to cool, wet, heavy soil, a perfect environment for pathogens, especially pythium.

Using a soilless mix to start seeds helps avoid introduction of those pathogens. You can purchase bags of "Seed Starting Mix" at your favorite nursery. 


Or, make your own. The recipe I use:

4 parts well aged compost

2 parts peat moss or coir (be sure to thoroughly moisten the peat moss first)

1 part perlite (aids drainage)

If you are worried that the mix you are using is too heavy, you can help your seeds get off to a good start with bottom heat, via a seed heating mat. These are especially useful for germinating pepper seeds, which need higher temperatures to germinate.

Put the seed starting mix in each pot or flat, and then thoroughly soak it. Although it isn't necessary for starting seeds, you can add a diluted liquid fertilizer at this time. I tend to use fish emulsion (5-1-1 NPK) and a sea kelp product, which promotes root production. Generally, there is no need to fertilize until the seed has produced two sets of true leaves. 

"True Leaves" look like the finished product. The first two leaves that emerge from a seed are usually oval shaped cotyledons, which are embryonic leaves.

The seeds are planted just below the soil surface in each pot, no more than a half inch deep.

Once the seeds are up and growing, introduce some air movement into the room, such as a house fan. This helps the new plants avoid diseases. And, air movement can help strengthen tomato stems, according to Debbie Flower, professor of horticulture at American River College, where they use fans in their greenhouses, for up to 16 hours a day.

Coming in March: those containers of tomato and pepper starts will easily become many more containers of tomato and pepper plants, after separating out the three or four starts per container.

Yep, another year of too much.