Potting mix recipes
Also known as Soil mix recipes, Container mixes, Growing media blends
In short
Most potting mixes combine a water-holding base (peat, coir, bark or loam) with an aerating material (perlite, pumice, grit, sand or bark). These widely cited example recipes from extension services and plant societies show starting points for common plant groups; adjust them for your pots, climate and watering habits.
How it looks
General houseplant mix (Clemson): 2 parts peat, 1 part perlite, 1 part coarse sand; or 1 peat : 1 pine bark : 1 perlite. Clemson plant mix: 2 parts pine bark, 1 part peat, 1 part sand, limed to pH 6.0. Texas A&M lists common ratios such as 2:1 peat:perlite and 2:1:1 peat:perlite:vermiculite. Cornell epiphytic mix (for bromeliads, Hoya, Monstera, Philodendron, Peperomia and others): equal parts fine fir bark, sphagnum peat and perlite, plus lime and fertiliser. Carnivorous plants (ICPS): equal parts sphagnum peat and coarse silica sand, with no fertiliser or lime; washed perlite can replace the sand. Succulents and cacti (Debra Lee Baldwin): half bagged potting soil and half pumice, moving to 2 pumice : 1 soil for cacti and 1 : 2 for thin-leaved sedums. Orchids (AOS/Clemson): bark-based mixes of fir or pine bark with charcoal and perlite, often with sphagnum. John Innes No. 2 (UK loam-based): 7 parts sterilised loam, 3 parts peat, 2 parts sharp sand by volume, plus lime and base fertiliser.
Signs
A mix that stays wet for many days, smells sour or grows algae is too dense for its pot or plant. A mix that dries within a day and shrinks from the pot is too open or has become water-repellent.
What favours it
Soilless mixes are light, drain well and are typically adjusted to about pH 6.2. Pick the recipe for the plant group, then adjust for pot size and how quickly the mix dries in your conditions.
Prevention
- Start from a proven recipe and change one ingredient at a time.
- Mix ingredients evenly; do not put gravel or a drainage layer in the bottom.
- Moisten dry peat or coir before mixing.
- Keep carnivorous-plant mixes free of fertiliser and lime.
- Reuse old mix only by blending it 50:50 with fresh mix or compost, as University of Maryland Extension suggests.
Treatment
Start with the first step and move down only if the problem persists.
- If a mix stays too wet, repot with more perlite, pumice, bark or grit; if it dries too fast, add more peat, coir or sphagnum.
Pros and cons
Pros
- Home mixes can be tailored to plant groups and local climate.
- Can use local, lower-impact materials such as coir, bark or rice hulls.
Cons
- Needs several ingredients and some trial and error.
- Home mixes lack the consistency and pre-added nutrients of many commercial products unless fertiliser and lime are added.
Look-alikes
- Garden soil
- Garden soil is heavy mineral soil that compacts in pots.
Typical uses
All container plants; recipes above cover foliage houseplants, epiphytes and aroids, carnivorous plants, cacti and succulents, orchids and general UK loam-based potting.
Related
Sources
- Indoor Plants – Soil Mixes — Clemson Home & Garden Information Center
- Growing Media — Texas A&M AgriLife Extension, Ornamental Production
- Peat, Sand, Perlite — International Carnivorous Plant Society
- About Pumice: The Ideal Soil Amendment for Succulents — Debra Lee Baldwin
- Beginner’s Series — Part 2: Media Mania Revisited — American Orchid Society
- Repotting Your Orchid — Clemson Home & Garden Information Center
- John Innes compost — Wikipedia
- Growing Media (Potting Soil) for Containers — University of Maryland Extension
- Gardening myths — University of Missouri Integrated Pest Management
Written in our own words from these sources. Check a product label before using any treatment.