If your cactus do not have mealybugs, you can use horticultural oil sprayed in a strong squirt to get through the “cotton” to the insect below. Keep an eye on it, because mealybugs love succulents. Inspect the roots very carefully before potting up.
Pots for cactus
Have clean pots and dry cactus potting soil handy. Clay pots are always preferred for succulents; clay (terra cotta) is porous, although some clay pots have glazed interiors or are fired at higher temperatures, making them non-porous. The pot should be just big enough to fit the root system, but no bigger.
Sunlight for cactus
Lack of sunlight will make life difficult for cacti, and their owners. Find a spot where they will get the most sunlight. If you have overcast skies most of the time, add some artificial light (LED’s) above and around the plants, within inches of the stems and kept on for several hours each day, and more than that if that’s the only source of good light. Place the pots on large white saucers or table covers to reflect light onto the plants.
If there are several stems, you may plant them in clusters instead of individually. Azalea pots (shorter and wide) can make the cactus easier to manage…but it does cause shadows (less light). Grouping them will help dry the soil faster, which is critical for cacti. Space them an inch or so apart, to allow for future growth.
Start by covering the drainage hole (must have at least one) with polyester fiberfill (from a hobby shop). That is like a white synthetic “cottony” material (real cotton will rot) that does not let any sandy soil erode through the hole, but allow water to pass through. Poke a small amount through the hole to form a short cone of white fiberfill. That little bit, hanging unobstructed below the pot, will help draw more water out of the soil. This is especially important if you are using a wide shallow pot and where growing conditions are not ideal.
Fill the bottom of the pot with dry potting soil. If it does not feel gritty enough, mix in some horticultural grit, coarse sand, or some other expanded mineral matter. Materials with angular edges are better than those with smooth rounded edges. Nestle the bottom roots into the soil.
It will be challenging to get the cacti to stay standing. Use a few rocks to hold them in place. Bamboo stakes and twine might help until they root. Plant them so the roots are below the surface and the entire stem is above ground.
If one of the stems seems to have a soft tan spot, use an old towel to hold the stems will prevent nasty little pricks from the spines.) If it is soft, cut the stem with a sharp knife, discard the bottom part, and lay the cutting (4″ or 5″ long) on dry soil to let it callus over. It can be planted when the cut end heals.
Fill between the roots with soil, packing it lightly. If any roots are dried up or soft and mushy, cut those parts off. Continue filling up to the crown of the plant (where roots meet stem), which should lie about an inch below the rim of the pot.
When cacti receive less light, their stems grow narrower and maybe faster—they are stretching toward the light. When light levels increase, the stem will grow thicker but slowly. Compact growth is what you want. With limited sunlight, it will be hard to keep them happy, as in desert happy. Do the best you can, but consider other families of plants in the future….
Sun and water
The 2 most important things are sun and water. Direct sun is what cacti need. Without it, they stretch and run a high risk of root rot from the smallest excess of water in the soil. While the plants are recovering and trying to make new roots, keep them quite dry. If in doubt and if it is cloudy, do not water!
After a week, add a small amount of water. Do not saturate the soil. Keep the temperature in the 60’s or 70’s F. No fertilizer yet. Never mist the plant, never let it sit in water, and water only when the soil has thoroughly dried.
Sun, sun, sun!!