Many cactus plants have a sculptural quality to them. Those species that also flower are especially striking. Cactus flowers tend to be oversized with petals featuring a shimmery quality. Bloom colors range from dazzling white to everything but true blue and black. You'll often see several colors in the same flower. Most cactus bloom in the spring, opening during the day. Some species flower at night and are pollinated by bats or moths. Cactus flowers tend to last just one day.
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After resting all winter and experiencing spring rain, many cactus plants bloom in the spring months. At that time, temperatures aren't yet excessively hot, so the plants are primed to put on an extravagant floral display. Even if rains are sparse, cacti draw upon their stored water to flower, but not as abundantly.
In Arizona's Sonoran Desert, cacti begin to bloom in March, with April being the month of the most flowering. In May, prickly pears (Opuntia spp.) flower. This species is hardy in U.S. Department of Agriculture (USDA) plant hardiness zones 3 through 9.
Cactus that flower in summer's heat are generally substantial specimens that have stored a significant amount of water. The stored moisture helps them bloom reliably when daytime temperatures climb.
Saguaros (Carnegiea gigantea, zones 9-11), are well known for their striking blooms that open at night for visits by bats. These impressive plants, which reach 40 to 60 feet tall, don't begin flowering until they're 40 to 50 years old. They flower in mid-May to mid-June when temperatures in this plant's native Sonoran Desert regularly surpass 100 degrees Fahrenheit. The plant features many waxy-petaled flowers that encircle branch ends.
Heavy-bodied barrel cactus (Ferocactus spp., zones 8-11) blooms from spring into summer with yellow, orange or bright red flowers, depending on the species. Fishhook barrel cactus (Ferocactus wislizeni, zones 8-11) grows to 5 feet tall and produces yellow blooms.
Some cacti flower at night, which enables the plants to conserve water during the warm months. Peruvian apple cactus (Cereus repandus, zones 9-11) typifies a moth-pollinated flower. The trumpet-shaped blooms are 5-inches in diameter and feature a sweet fragrance. The apple cactus blooms most abundantly in spring, with a fall rebloom possible. The plant is blue-green in color and grows in a 20-foot-tall column, branching at the base.
Night blooming cereus (Hylocereus undatus, zones 9-11) displays another large moth-pollinated white flower. It blooms in spring and summer on flattened stems that resemble long, scalloped leaves. This cactus is cultivated for its oval, red fruits, known as dragonfruit.
The familiar holiday cactus plants announce their seasons of bloom through their common names. With flattened, leaf-like stems, Thanksgiving cactus (Schlumbergera truncata), Christmas cactus (Schlumbergera x buckleyi), and Easter cactus (Schlumbergera gaertneri), all hardy in zones 10-12, grow as epiphytes in tropical forests. Many hybrids and cultivars now exist, with red, white, pink, purple, peach and salmon-colored blooms.
When grown as a houseplant, in order to prompt flower buds to set, holiday cactus plants require cool nights and at least 14 hours of darkness during each 24-hour period until the flower buds form. These plants flower best when they're slightly pot-bound.
- Arizona-Sonora Desert Museum: Desert Wildflower Blooms
- University of Florida IFAS Extension: Opuntia spp. Prickly Pear Cactus
- The Weather Channel: Monthly Averages for Tucson, AZ
- Southern Nevada Water Authority: Saguaro Carnegiea Gigantea
- Online Plant Guide: Ferocactus Wislizenii/Fishhook Barrel Cactus
- Arizona State University: Cereus Repandus
- Online Plant Guide: Hylocereus Undatus
- Missouri Botanical Garden: Schlumbergera Truncata
- Arizona Sonora Museum: Plant Fact Sheet: Saguaro Cactus
- The American Southwest: Ferocactus Wislizeni