The secret to caring for any plant is to understand its native habitat and to try to replicate that as much as possible in your garden, greenhouse or home environment. Succulents by and large come from warm, dry regions with low humidity and minimal rainfall, and the majority can’t handle freezing temperatures. After all, these are plants that survive some of the planet’s harshest growing conditions by storing water in their leaves. The plants may go dormant, close their rosettes, and their roots may desiccate during long dry spells. When the rains (i.e., you, wielding a hose) come again, they rehydrate and grow new roots. In this respect, they’re among the easiest plants to grow. But what you want to avoid is letting them get scorched by too much sun, having their roots rot by too much rain or watering (rot quickly spreads up the stem), or making them susceptible to insect infestations due to high humidity and poor air circulation.
If you live in the desert, move your container-grown succulents outdoors when daytime temperatures drop below 90 degrees. Give the plants bright shade and occasional water. Keep in mind that many need nighttime temperatures below 45 degrees (but above freezing) in order to bloom in spring.
If you live in southern or coastal CA from the Bay Area south, your succulents likely will be fine year-round, in the ground or in containers (provided they’re protected from occasional frosts). If your area gets drenching rainstorms combined with cold temperatures when the plants are winter-dormant, they may rot. Protect your container-grown succulents by moving them beneath an overhang. Grow in-ground succulents atop berms so water flows away from the roots. Amend the soil with crushed volcanic rock, such as pumice or scoria, to enhance aeration and to absorb excess moisture.
Before a rainstorm, spread a granular pre-emergent herbicide wherever you don’t want weeds; it contains an enzyme that prevents seeds from sprouting. Pre-emergent is available at most nurseries. I wouldn’t be without it, but I also am keen to be green, so I use it mainly around my large, spiky agaves and cacti. Also before a rainstorm, boost the growth of in-ground succulents by fertilizing with Ironite. Don’t let granules land in rosettes or on hardscape, because they can leave rust stains.
If you live where temperatures drop below freezing (32 degrees F), most succulents (except for sedums and sempervivums, which are frost-tolerant) will need to be covered. Translucent frost cloth, which protects the plants but allows them to photosynthesize, is sold at most garden centers, or you can simply use bed sheets. Overwinter container-grown succulents indoors or move them against a structure that radiates enough warmth to raise the the temperature above freezing—such as your home’s south-facing wall. In colder climates, options include moving the plants into a sunroom, greenhouse, or basement with lights on a timer to simulate daylight. As the plants’ growth slows and they begin to enter a three-month dormancy, they’ll need less water. Give enough to keep roots from desiccating, but not so much that they rot. When in doubt, err on the side of dryness.
Watch for mealy bugs and treat the plants at the first sign of an infestation. I spray with isopropyl alcohol. Succulent grower Petra Crist (Rare Succulents Nursery) uses Windex. There are commercial insecticides as well. Isolate infested plants, and destroy any that are severely infested. Mealy bugs, which resemble bits of white lint, tend to live in leaf axils (where leaves join the stem). The best preventative is good air circulation. Indoor plants are especially susceptible, so keep a fan running. If you find pests on one plant, be sure to check the rest.