Web Special
Potting Soil Recipes and Recommendations From the Pros
Compiled by Contributing Editor Rita Pelczar

We canvassed a number of professional gardeners, nursery owners, and garden writers for their personal potting mix recipes or favorite commercial mixes. Here's what they had to say:

From Lee Reich, author of numerous garden books:

I do make my own mix for all my seedlings and potted. Why? For the same reasons that I bake my own bread: assured quality, tailored to my plants’ needs, it’s cheaper, and it’s fun. My mix consists of equal parts perlite, peat moss (or coir), garden soil, and home-made compost. For every 10 gallons of mix, I add about a cup of soybean meal and, if handy, some rock phosphate, greensand, and powdered kelp. I pile everything together, moisten slightly, mix, then sift through a quarter or half-inch sieve. I use this mix for everything from tomato seedlings to potted fruit trees. For succulents, I'll add some extra perlite or montmorillonite clay (kitty litter). For African violets and the like, I add extra peat moss. This mix has a broad spectrum of nutrients, and enough of them so that I don't have to add more for many months. It also has good aeration and water holding capacity.

From Becky Heath, co-owner of Brent and Becky’s Bulbs:

We use ‘Bio-Comp,’ which is made from composted peanut hulls and pine bark. We find it to be the very best!

From Tony Avent of Plant Delights Nursery:

Through the years, I've used a number of mixes from homemade to commercial mixes. About 12 years ago, we settled on a commercial mix, BioComp, that is actually made in coastal North Carolina. Most commercial soil companies spend huge amounts of money to accurately measure water, pore space, nutrient capacity, etc. The idea that homeowners have the same ability to properly mix soil doesn't pass the laugh test, yet people will buy commercial soil mixes and add to them. In selecting the proper soil mix for each situation, the gardener must do one of two things: either adapt their watering practices to the soil mix they use or select a soil mix that fits their watering practices. Most folks aren't capable of changing their watering regimen/practices, so they wind up switching their soil mix until they find one that fits their needs.

From garden book author Ray Rogers  (regarding his potting soil for cacti and succulents):

I buy a custom-made mix from Dr. Gerald (Jerry) Barad, a very successful cactus and succulent grower (and a former member of the American Horticultural Society Board of Directors). It’s far superior to the commercially available mixes I've encountered.

From garden writer Tovah Martin:

Except to add custom ingredients for such finicky growers as lachenalias, I found a baseline commercial mix that I’m just wild about: Fafard’s 52 Mix. There’s also a local organic grower who makes a super mix for succulents and outdoor containers. McEnroe’s Organic Potting Soil is so wonderful, why would I search elsewhere? Between these two, my bases are pretty much covered.

From Gene Bush of Munchkin Nursery and Gardens:

The commercial mixes available from company to company are more than adequate for any need we can think up. Many of the new mixes also contain trace elements, and mycorrhizal root inoculants. If you do not see exactly what you want, you can often order custom mixes. Right now we use Sun Gro Redi-earth seedling mix and vermiculite for our seed starting and growing on, with seaweed extract when we water. Our “regular” mix is from Fafard. They make something like 20 different mixes plus custom ones.

From garden writer Jeff Lowenfels:

I use a very special stuff—the soil that makes the famed Alaskan cabbages grow big. It is called Alaska Humus. This is mixed with 1/3 sand or perlite when used as a potting mix.

From National Garden Association’s senior horticulturist Charlie Nardozzi:

One mix recipe I like is:

• 1 part peat moss

• 1 part compost

• 1 part vermiculite

• 1 part perlite

• 1 tablespoon of ground limestone

• 1 teaspoon of organic 5-5-5 fertilizer

From garden writer Pam Baggett:

I like to use compost or bagged cow manure mixed with enough finely ground pine bark to make a well-drained but water-retentive mix. Because the Canadian peat bogs seem fragile and irreplaceable, I try to avoid using peat moss but I have used Hydrogel water crystals to increase water-retentiveness for thirsty plants such as elephant ears and cannas. For succulents, I increase the amount of pine bark and also add sand for extra drainage. I don't have measurements for either recipe; I do it all by instinct.

From garden writer Mary Irish:

I have long grown seeds and started cuttings in a blend of vermiculite and perlite in equal proportions. I find it holds water well and releases me from the need for fungicides which I am loathe to use. Potting soil recipes have ranged over the years but always begin with what is known [in the Southwest] as forest mulch. It is actually ground up leftovers from timber products that is then composted and makes an excellent base for potting soils. I always add some pumice and composted steer manure to it. I make potting soil the same way our grandmothers made sauce, a bit of this and bit of that until it just feels and looks right.

From gardener writer Jo Ann Gardner (regarding potting mixes for "happy" container plants):

Fill container to within 6 inches of the pot’s rim with compost; for smaller containers, add a couple of handfuls of compost (small containers, though, dry out faster than larger ones). Top to within an inch of the rim with a pre-moistened commercial potting soil that includes fast-release and slow release fertilizer (read the label carefully). The compost will slowly provide nutrients, too, and is an economical way to fill larger containers if you have a compost supply on hand. For plants that like leaner soil, stir in one quarter to one third seeding mix into the potting soil.

From Kathy LaLiberte of Gardener’s Supply Company:

I usually choose among the different potting mixes that Gardener's Supply carries. I often fill the flats or cells about three-fourths full with moistened Transplant Mix, which has a slightly coarse texture. Then I fill to the brim with about an inch or so of the more finely textured Germinating Mix. I also tend to cover newly planted seeds with Germinating Mix because the fine texture makes it very easy for the newly germinating sprouts to get through. This technique makes the Germinating Mix go further (it’s a little more expensive than the Transplant Mix).

When potting up, I always add about 20% compost to whatever growing medium I’m using. I save a tub trug or two worth of good compost from the fall – put it in the basement so it doesn’t freeze. I also add a little bit of worm castings (they’re potent!), which I produce during the winter in my basement worm bin. I add this only when potting up. Seedlings develop an increasing resistance to bacteria and fungi as they get older – so I germinate in a sterile mix, but “grow on” in an amended mix.

From garden writer Felder Rushing:

I did graduate level research on potting soils “way back when” and to this day am confused by all the recipes I see. So my special mix, which is just fine for everything I grow in containers—from tomatoes and peppers to heirloom shrubs and bulbs - is pretty simple: One part cheap potting soil (whatever is on sale) for moisture- and nutrient-holding capacity, and one part finely ground bark mulch for bulk and drainage, plus a handful of agricultural lime per wheelbarrow load to compensate for the acidity of the peat and bark. If I have a plant that needs super drainage like sansevierias, cacti, or on my green roof entry arbor, I add either perlite or lightweight expanded clay. For cuttings I use one part potting soil and one part perlite, and for seeds I use potting soil and vermiculite.

From Bob Polomski, Consumer Horticulture Information Coordinator at Clemson University:

When I was young with little disposable income, I made my own mixes from raw ingredients. When I had a bit more disposable income, I graduated to commercial potting mixes. The good ones are pretty fool-proof because they have the right kinds and quantities of ingredients. Most importantly, they come with wetting agents to facilitate moistening and even distribution of water throughout the mix.

One thing I've learned about potting mixes is knowing how to pick the right one. I’ve been promoting this quick “flow-through test” to determine the quality of the potting mix. Fill an ordinary pot with mix (a 6-inch pot is fine) to within an inch of the rim and add water. As you water, hold the pot away from you to watch the flow of water from the bottom of the pot. It should look like a shower head with water flowing out uniformly from all of the drainage holes. This even stream of water from the bottom of the pot indicates that all of the mix is getting watered. There are no wet or dry pockets, which can be found in low quality mixes. Keep adding water until the potting medium is completely saturated. With a good potting pix, water should continue to slowly seep through the mix. Expect to see standing water in poorly drained, low quality mixes. Often these inferior mixes appear swampy-looking.

From gardening coach and writer Barbara Ellis (for starting perennials from seed):
I start with a commercial mix that is fairly heavy when wet (bark mixes are too difficult to wet and re-wet) then doctor as follows by mixing ingredients in a large dishpan or other container:

• 10 parts purchased mix

• 3 parts vermiculite

• 3 parts perlite

• 4 parts compost or leaf mold

If the mix still seems heavy or if you are sowing plants that require well drained conditions, add more vermiculite or perlite (I keep a mix of the two on hand for rooting cuttings) as well as more compost. After sowing, mulch the pots with a layer of pea gravel (the kind sold in aquarium stores) or with large-size poultry grit (developer size).

From Rose Marie Nichols-McGee, president of Nichols Garden Nursery:

Our blend of potting soil is 50 percent aged fine fir bark, 25 percent grower grade peat moss, 12.5 percent unscreened pumice and 12.5 percent coarse perlite. The advantages of this mixture are rapid growth because of well oxygenated roots and lighter weight for plant shipping. Drawback -- plants do not hold well without regular watering. Our seed starting mix is pure organic vermiculite and for cuttings we use a 50/50 blend of perlite and vermiculite. With the last two we’ve tried other formulations and this has proven reliable and readily available.