Echinocacti are all stout-spined, globular plants, and only one species is likely to flower as a pot plant. Echinocactus Horizonthalonius can be expected to flower indoors, is small and slow growing. Its pink bell-shaped flowers are about 2 inches wide at the mouth. They open during the Summer months and each flower lasts for several days.
Water moderately when in active growth, give enough to keep the potting mixture moist throughout and allowing the top half-inch to dry out before watering again. Keep dry from late Autumn to Spring.
Use a standard tomato-type fertilizer during the active growth period. Apply the fertilizer once a month if the plant is growing in soil-based potting mixture, once every 2 weeks if the potting mixture is peat-based.
If the plant has grown so much that the roots fill the pot, re-pot into a pot one size larger in Spring, using either soil-based or peat-based mixture.
Potted Echinocactus can be propagated only from seed.
Echinocacti need to be given direct sunlight throughout the year, in order to produce strong spines. Indoor Echinocacti should be given Winter rest period.
Spraying occasionally overhead keeps the spines clean and yellow.
A healthy Echinocactus Grusonii is one which makes plenty of bright new spines in the Summer and is not marked with brown cold marks after Winter. Mealy bug may be a problem, dab and remove woolly patches with small paintbrush or cotton bud dipped in methylated spirits. Brush all dead pests out from between the ribs, or moulds may set up. Toothpick helps to remove any bugs from between the spines.
Use 1 part coarse, gritty sand to 2 parts of soil-less or good loam-based no. 2 potting compost, no. 3 for larger plants.
Less than 2 percent of the insects in the world are harmful. Most are beneficial.