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When it comes to gardens, cactus is probably the most maligned and neglected category of plants. While nearly every gardener grows trees, shrubs, perennials, bulbs and annuals, the overwhelming majority find no place for their spiny cousins in the family Cactaceae. This is a shame, seeing that the cactus family is vast, with more than 2,500 species of all shapes, sizes, colors and cold-hardiness. However, the underuse of cactus species in gardens presents opportunities for homeowners looking for something new and exciting to distinguish a garden.
All cactus species evolved in the New World, and in that sense they are truly American plants. Their use dates back more than 3,000 years to Peruvian cultures who used the San Pedro cactus (Echinopsis pachinoi), which contains a hallucinogen, in religious ceremonies. The Aztecs used cacti for medicines, making wine and as a source of dye. Cacti were among the first plants brought to Europe after the discovery of the Americas, perhaps on the return trip from the first voyage. In modern times, cacti have become big horticultural business, and a network of growers and collectors spans the globe. One can find a collection of Chihuahuan Desert cacti atop a Tokyo high-rise rooftop or spiny species from Texas clustered in a Prague windowsill.
As a landscape designer practicing in Tucson, Arizona (which could justifiably be called "Cactus City, U.S.A."), my own 20-year journey into the world of cacti has deepened my plant choices and enriched my design practice. Consider that cacti are the undisputed champions of drought tolerance and can be used in the harshest of garden situations. A wealth of petite and slow-growing species can be wedged into even the smallest gardens, and a wide selection of plants with colored spines offer year-round color. For those afraid of spines, several spineless varieties are readily available. Some species bear healthful and tasty fruit, while others offer fragrant flowers. Cacti can lend themselves to innovative garden designs, some of which I'll share later in this article.
When newcomers began arriving en masse to the Sunbelt in the 1950s and '60s, they were intrigued by cacti but didn't have many creative ideas for what to do with them. Many gardens from this era feature mounds of rocks and cactus species corralled in brick circles. I like to call these "cactus ghettos" because of the way in which they typically only include cactus species that are physically separated from the rest of the garden. While there is nothing wrong with grouping cacti together, softer textured approaches are possible if you include other plant types.
As xeriscaping and native plant gardens caught on in the 1980s and '90s, gardeners realized that, just like in nature, many cacti can grow in the ground planted among plants such as shrubs, grasses, trees, wildflowers and other succulents. The key to a successful cactus garden that is integrated with the larger garden is to group them with plants that have similar watering needs. An example of this technique is the planting of the Mojave Desert native Beavertail cactus (Opuntia basilaris) paired with perky Sue (Tetraneuris acaulis).
Some cacti happily grow right alongside perennials. Cool season growers benefit cacti planted nearby in that they wick water away from cactus roots during cold seasons when cacti are not actively growing, helping to prevent rot.
Another way to create cactus combinations is to seed annuals in a garden bed. Many wildflowers are quite compatible with cactus culture. Consider the following wildflowers, all of which will grow side-by-side with your cactus species: Mexican gold poppy, Parry penstemon, arroyo lupine and desert bluebells.
Many native grasses also happily pair with cacti. Plants such as sideoats grama (Bouteloua curtipendula), blue grama (Bouteloua gracilis) and purple three-awn (Aristida purpurea) are excellent for growing with prickly pear cactus species and also will grow next to several barrel cactus types.
One trend that can add impact to an in-ground planting is to group several plants of the same species together. This provides visual punch and is often done with barrel cacti with brightly colored spines. Although cactus flowers are spectacular, most species are not long-blooming, and therefore many cactus aficionados seek out plants for their distinctive spines rather than for their blooms. Many barrel-shaped cacti sport particularly brilliantly colored spines. Consider species such as the compass barrel (Ferocactus cylindraceus), which can have blonde, red or yellow spines. Another native barrel – this one with lemon-yellow pineapple-shaped fruit – is the fishhook barrel (Ferocactus wislizeni). Clusterings that include fishhook barrel planted among wildflowers can be visually strong. Other cactus species with colorful spines include the Texas rainbow cactus (Echinocereus dasyacanthus) and glory of Texas (Thelocactus bicolor var. bicolor).
Because many of the intricate spines and flowers on many cactus species are relatively small in scale, raising the height of your containerized cacti closer to eye level is desirable. Plants such as pincushions (Mammillaria spp.) bear small flowers in concentric circles along the tops of their stems and are best appreciated up close. Also, species with fragrant flowers – like the northern Mexico natives "Lemon Pledge" pincushion (Mammillaria baumii) and chocolate-scented flowered hedgehog (Echinocereus carmenensis) – are small plants with flowers that are better close to nose level. Placing container plants on benches, shelves and pot stands will raise the stature of the cacti in your garden. Displaying your cacti on shelves has the added benefit of keeping them off the ground and away from potential rodent damage.
Another great way to bring cacti closer to eye level is to plant them in hanging pots or baskets or arrange them vertically in pots attached to trellises. Whereas growing annuals in hanging baskets can require twice-daily watering in hot climates, cacti are perfectly adapted to growing in hot hanging containers and even in the harshest of climates require no more than twice-weekly watering during the hottest months of the year. A Texas native with flamboyant pink flowers and a trailing habit that is often used in hanging baskets is the ladyfinger cactus (Echinocereus pentalophus). Of course, you'll want to avoid hanging really spiny species next to pathways or porches where people could accidentally brush against them, but there are many less thorny species, such as blooming bishop's cap (Astrophytum myriostigma), a Mexican species that has almost no spines to speak of. For cold climate gardeners, one of these is the claret cup cactus (Echinocereus triglochidiatus), which makes a great addition to a rock garden.
In regions where cold, soggy weather makes growing a wide variety of cacti in the ground difficult or impossible, many gardeners turn to pots. Although most cacti don't make good long term houseguests on account of their preference for strong, bright light, the good news is that they work fine as seasonal houseplants. That is, you can bring them indoors just before the first frost and bring them back outside in spring after your local last frost date. However, just like humans coming outdoors after a long, dark winter, you will have to slowly acclimate them to the intensity of full sun to avoid burning them.
For hardy cacti, one design trick is to plant them in an attractive pot (preferably a good-quality high-fired glazed pot that can withstand some freezing weather) and place the pot out in the middle of a garden bed rather than on a deck or patio. The design impact is strong, often setting the cactus apart like a sculpture on a plinth. New Mexico plantsman David Salman has done this effectively with the beautiful white lace cactus (Echinocereus reichenbachii ssp. baileyi) planted in a wide, shallow blue pot that complements the white spines and pink flowers of the plant. Other cold-hardy cactus specimens that look great in pots are the Missouri foxtail cactus (Escobaria missouriensis). This low-grower has a wide native range and looks good in colorful glazed pots. When creating an attractive garden sure to withstand drought, cacti must not be overlooked.
Scott Calhoun is author of the book "The Gardener's Guide to Cactus: The 100 Best Paddles, Barrels, Columns and Globes," Timber Press, 2012.