Soil Mix, Cactus Care
A few years ago I experimented and concocted a versatile, high performing and well-draining soil mix for the columnar cacti that I grow, and it has proven outstanding for my plants and those of my customers. The more water-loving, tropical columnar cacti, and even the big desert Pachycereus and barrel cacti, thrive in this mix despite excessive rain on potted plants and outdoor amended beds here in N. Florida. All of these ingredients plus pellet fertilizer can be found at Lowes.
Mix into a large rectangular plastic tub 1 bag Miracle Gro Cactus, Palm & Citrus garden soil ($9), 1/2 bag Cowabunga compost with manure (under $3) and 1.5 bags of Perlite. Break up clumps in the Miracle Gro soil using a coarse mesh sifter, or by hand, then mix with a shovel all of the ingredients until uniform. I use a thin layer of pea gravel to cover the dirt, in order to prevent soil from washing out and Perlite from floating to the top.
Dynamite brand pellet fertilizer added every six months has increased growth and height dramatically, and it is far less likely to burn plant bases that it touches.
For less frequent repotting in large vessels or outdoor raised cactus beds, though more expensive, adding 1/8″ black scoria to the mix will give it more permanent body and lessen settling from composting over time. I use Eco Complete black aquarium gravel (lava) because of its off-the-charts micronutrient/rare earth element content.
Cactus Conservator’s Mix from Botanic Gardens
When I visited Fairchild Tropical Botanic Garden and Montgomery Botanical Center a couple of years ago, their native/endemic Florida cacti were growing beautifully in a mix that is more mineral, and thus more stable for a permanent large pot or display bed. Their Harrisia and Pilosocereus looked fantastic at large sizes and I used it with great results when up-potting large specimen native Florida species at Cactus Island. Here is that recipe:
“The mix I use for the cactus is a 1/3 standard potting mix, 1/3 crushed limestone, and 1/3 Turface. The Turface comes in 3 sizes. I use the coarsest grade (largest size) in the mix. For every 5 scoops of these components I add 1 scoop of organic soil for a little extra kick. The limestone provides the correct pH, the Turface provides the high CEC capacity (cation exchange capacity) and since it’s fortified with calcium clays, the appropriate pH, and the potting media to hold moisture. I use a time release fertilizer made specifically for growing in Florida, Nurticote 18-6-8, Florikan CRF 18-6-8, or Osmocote 18-6-10 as nutrition.“
Turface and crushed limestone of the same 1/8″-1/4″ grain size. Quickcrete crushed limestone (Ace Hardware) is what I use, and it must be rinsed several times until water runs clear and not milky white.