The "What Not to Do" photos in my presentations invariably get responses from the audience. People groan or laugh as though only an idiot would do such things. Yet chances are, we've all done at least a few of these. In fact, much of the info that follows originated with mistakes I've made myself.
My what-not-to-do's are simple to avoid, but not necessarily easy to remedy. A smart succulent owner learns what may be expensive to fix and cause prized plants to look dreadful, and what might even kill them.
Watering succulents incorrectly
You probably though my first what-not-to-do would be "overwatering." There's so much angst about watering succulents! Yet watering is one of the simplest things about succulents: Forget to do it and the plant will probably be fine.
That said, succulents do appreciate regular water, and will be healthier and happier if if given it. Water thoroughly; wait until dry or nearly so; and repeat. When in doubt, don't water. [See: How to Water Succulents.]
Assuming pebbles create drainage
Does a layer of pebbles in a nondraining pot provide the drainage succulents famously need? No! In fact, just the opposite. A layer of pebbles traps stagnant water, creating a microbial soup that eventually rots plant roots. However, you CAN grow succulents in nondraining containers, providing you keep soil dry and water only enough to moisten the roots. [Learn more]
Combining succulents with different needs
If you put fat succulents in a pot with thin-leaved ones, you're basically making a temporary floral display. Stonecrop, for example, needs more water and less sun than rotund euphorbias. Enjoy such pretty pairings, but don't expect them to last.
Starting your collection with challenging succulents
Succulents with personality are extremely appealing to owners who are nurturers, but such plants are challenging even for seasoned collectors. I'll never forget the trauma of having my baby toes (Fenestraria, a type of living stones) go squishy. I was 11, and yes, I overwatered them. Another highly desirable succulent that inevitably disappoints is the spiral aloe.
Not bothering with seasonal maintenance
Succulents, like all living things, grow. Three or four times a year, a succulent garden needs pruning, weeding and controlling pests. Gaps need filling and leggy succulents (like aeoniums) need cutting back and replanting. The garden above looks like it may need the irrigation checked, and would benefit from replacing ratty-looking bark with crushed rock. [Learn more: Succulent Garden Maintenance, Part One: Tasks and Succulent Garden Maintenance, Part Two: Referrals]
Not researching how big plants get
You see it all the time: Agave americana planted too close to a curb, walkway, steps or driveway. Century plants get as big as Volkswagens. Because pups are plentiful and free doesn't mean they belong in your garden. What to do? Remove misplaced century plants and any offsets before they get any bigger (which they certainly will). [Learn more on my YouTube channel and in my book Designing with Succulents (2nd ed).]
Pruning agaves badly
This Agave americana 'Marginata' pup probably looked good for a couple of years, but eventually its pointed, fanged leaves threatened passersby. So it got chopped, which ruined the plant's appearance and only temporarily solved the problem. [Find someone who can do it for you.]
Growing Eve's needle
Eve's needle (Austrocylindropuntia subulata) nearly put my hairdresser out of business. She was pruning an overgrown patch of it and got a spine under a fingernail. The hooked barb required surgical removal, and the healing process was long and painful. Unfortunately, this lush cholla is becoming common in Southern CA gardens. It roots readily from cuttings, grows fast, and gets 10 feet tall. When top-heavy, it falls over, breaks apart, and creates its own cuttings. The plant's needle-like spines are a threat to passersby, dogs, and kids who careen into it. [Watch my Instagram video.]
Letting garden pots get waterlogged
Potted succulents that sit atop soil can become waterlogged due to plugged drain holes, causing roots to rot. Prevent this by setting garden pots atop paving stones.
Ironically, the jade plant in the photo survived standing water, only to fall victim of our next don't-do:
Exposing vulnerable succulents to frost
Jade (Crassula ovata) is resilient, often the last plant standing in a neglected garden. Despite being one of the easiest succulents to grow, it does have an Achilles heel: Frost. When temps are forecast to drop to 32 degrees F, throw a sheet over jades exposed to open sky. Better yet, don't plant one in a vulnerable location in the first place. (Apologies to my next-door neighbors.) [See: Frost and Succulents, What You Need to Know.]
Not topdressing bare dirt
Succulent gardens and pots look better and plants benefit if you cover bare soil with gravel or pebbles. In addition to aesthetics, topdressing slows moisture evaporation, moderates soil temperature, diffuses rain, helps prevent weeds from sprouting (and make them easier to pull if they do), and conceals utilitarian items, like pipes. [Learn more about top dressing for succulent pots and gardens.]
Not acclimating new plants
If your newly acquired succulent was under shade cloth at the nursery or in a greenhouse, don't immediately set it in full sun. It may sunburn, and resulting beige patches won't heal. Introduce new plants to greater sun gradually. [Learn more about sun and succulents.]
Giving succulents too little sunlight
Put a red- or orange-leaved succulent in the shade, and it'll revert to green. The plant will be OK, but you may be disappointed. This is especially noticeable with aloes, crassulas, echeverias and kalanchoes. Sun is essential for color...and for flowering as well. [See: How Much Light Do Succulents Need?]
Not treating pests early
Suddenly bugs are everywhere, especially on new growth and flower spikes, or on potted succulents crammed together. Check leaf axils for white bits (mealy bugs) and buds for aphids. Spray pests with Isopropyl alcohol (70%). [More info: Go to this site's Pests, Diseases and Problems page and see the "Pest and Damage Control" section of Designing with Succulents (2nd ed), pp. 137-143]
Assuming you don't have snails
Snails are tiny in early spring, but by summer they're big enough to do serious damage. Snails eat chew holes in succulent leaves, so bait early! I use Sluggo because it's environmentally friendly and affects only snails and slugs.
Opuntia (paddle cacti, prickly pear) typically have spines you can see plus glochids ("glock-ids")---hairlike, hooked ones you almost can't. With the slightest touch, glochids detach from the plant and imbed skin. Bunny ears (Opuntia microdasys) is polka-dotted with glochids. Despite its cute name, this is NOT a plant for children.
Not treating cochineal scale
Opuntia is arguably the easiest succulent to grow, needing no water other than rainfall and tolerating poor soil, high heat and frost. However, pads tend to get infested with cochineal (ko-CHIN-ee-al) scale, which compromises the appearance and health of the plants. Scrub off scale two or three times a year, using a soft-bristled, long-handled brush dipped in a solution of horticultural soap such as Safer. [Go to Cochineal Scale on Paddle Cactus: What to do.]
Installing a dry stream bed above ground
This is a surprisingly common aesthetic error: After having a load of rounded river rock delivered, homeowners make them "flow" atop of the ground... never mind that this never happens in nature. Sure, water flows atop soil, but (have you noticed?) rocks never do. A stream bed in nature is always lower than surrounding terrain...often significantly so. So, dig a swale first! [See: A Colorful Succulent Garden to Copy.]
Not knowing a succulent's origins
You may not be able to provide your cacti with a desert climate, but understanding that the plants come from a dry, hot, sunny region with cold winter nights will go a long way to making them---and you---happy. The secret to growing any succulent successfully (any plant for that matter) is to try to replicate its native habitat. [Learn more in my books.]
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How much light do your succulents need? It depends on the type of plant and where you live. Most haworthias and gasterias prefer shade but can handle some sun along the coast. Many but not all cacti are fine in full desert sun. As a general rule, the majority of soft-leaved succulents want half a day’s sun (in mild climates) and dappled or “bright” shade.