Caring For Cactus
What is a hardy cactus?
Plants in the family Cactaceae are all native to North, Central and South America and some Caribbean islands. There are many species even in the coldest regions of these places. The term "hardy" is relative to where you live! For a cactus to be hardy in your area, it must be able to withstand the coldest temperatures that occur where you live. For instance, for a cactus to be hardy in Denver, Colorado (zone 5), where I live, they must be able to withstand temperatures to -25 degrees F. (-35 degrees C.). Other things to consider are: the quality and type of soil you have, the amount of precipitation in summer and in winter and how much sunshine you have. If a cactus doesn't get enough cold weather, it will not flower normally in the spring.
How do I grow hardy cacti?
SOIL PREPARATION: In the dry climate of Colorado we actually have to water some cacti occasionally for them to thrive. Our soils are typically heavy clays that do not drain well. In most cases we would create raised beds by mounding the soil. To the heavy clay we add 10% composted yard waste and 30-40% coarse sand (1/16th inch to 1/4 inch in diameter). For Opuntias, this soil mixture provides adequate drainage with our average 15 inches of precipitation a year. For species that require better drainage, we add more coarse sand (up to 60%).
Most of these cacti species prefer slightly alkaline soils. If your soil is acidic, you will have to add crushed limestone or other forms of lime to correct the pH to somewhere between 7.0 and 8.0. If you receive more than 20 inches of rain per year, you will want to increase the drainage material in your soil mix. In extremely wet climates you may have to grow the plants in pots where they can be sheltered from the rain.
How do I plant the cuttings or plants that I receive from ColdHardyCactus.com?
Opuntias will arrive as pad or stem cuttings. You can plant them in pots or directly in your prepared soil. Using kitchen tongs, lay the pads on their side and press gently into the soil. Roots will form on the underside of the pad and give it a good start. New growth will occur in spring and summer from the edges of the original pad. Alternatively, stick the pad with cut end into the soil so that the pad is vertical. The danger in this is that the wound where it was severed from the mother plant could become infected with bacteria or fungus. Erwinia (potato soft rot) bacteria is the common pathogen of newly planted cuttings. Keep the soil slightly moist until growth begins.
If you receive plants that already have roots such as Echinocereus, Coryphantha, Agave, Yucca, etc., plant them in pots or in the ground (in your prepared soil mix) with the root origin just at the top of the soil's surface. Topdress the plant with one inch of crushed stone to support it and to keep the crown drier.
Generally, cacti in the ground are only fertilized when young or when you want to encourage fast growth. I use seaweed extract (0.1 % nitrogen) on young plants in the greenhouse and when they are first transplanted into the ground. Once established, over-fertilization can cause excessively tender tissue that can be more prone to winter damage. I always advise a soil test from your local soils lab or agriculture university to determine what type of soil you have and what minerals and nutrients are present or lacking.
Cacti grown in containers will require regular fertilization, perhaps once a month during the growing months.