Crossandra can also be kept as a houseplant, where its needs are similar. Indoor care may require placing the plant on a tray filled with pebbles and water, and misting it regularly in dry climates or during the dry winter.
Light
Crossandra thrives best in bright, indirect sunlight. This can usually be achieved by planting it outside in a shady garden where it won’t be exposed to direct sunlight. Indoors, your plant will do well in a sunny north or east-facing window or with bright artificial light. Come winter, try to provide as much light as possible indoors.
Soil
A rich, peat-based potting soil that contains perlite is ideal for crossandra. When grown outdoors in the ground, work peat and compost into the soil before planting to provide good drainage and added nutrients. Crossandra likes soil that is slightly acidic (pH 5.8 to 6.5), so test the pH before planting, and use a soil conditioner if it’s not spot-on.
Water
Crossandra is very susceptible to drought and likes slightly moist soil—but not soggy—at all times. Outdoors, water this plant moderately on alternating days during the growing season. Never allow the soil to completely dry out. Reduce the amount of water in the winter to once a week, if you’re growing it as a perennial. Indoors, you can use the same watering guide—decreasing the water in the winter to once a week—but always water your crossandra with warm water. This tropical plant dislikes the cold, and watering it with cold water may shock the roots, causing the plant to die.
Temperature and Humidity
Crossandra is very heat-tolerant and cold-sensitive—befitting a plant from the tropics. This plant thrives best in temperatures of 70 to 75 F. If the temperature drops below 55 F, the plant may experience damage to its leaves. Crossandra also likes high humidity. If you live in an arid climate, mist your crossandra weekly during the growing season to provide sufficient humidity. You can raise the humidity for an indoor plant by placing it on a tray of pebbles that is filled with water, as long as the water doesn’t touch the bottom of the pot.
Fertilizer
Outdoor crossandra can be fertilized with a granular nutrient once a month. Refer to the product’s instructions on amounts, and then use slightly less than what’s recommended to avoid overfertilization. Indoor crossandra can be fed with a liquid fertilizer, diluted to half-strength, every two weeks throughout the growing season. Cut fertilization back to once every other month in the winter for outdoor crossandra, and once a month in the winter for plants grown indoors.
Types of Crossandra
While nearly 50 species of crossandra exist in the wild, there’s only one common species in the garden industry: Crossandra undulifolia (also sold as Crossandra infundibuliformis). That said, horticulturalists have introduced some color variations of this species. Favorites include:
Crossandra infundibuliformis ‘Mona Wallhead’ is a tropical plant that features salmon-pink flowers and grows to a mature height of 12 to 18 inches. This cultivated variety is cold-hardy, withstanding temperatures no lower than 32 F.Otherwise known as " yellow crossandra," Crossandra infundibuliformis ‘Lutea’ bears rich, golden flowers and performs well in containers, where it blooms from spring until the first frost.Crossandra infundibuliformis ‘Orange Marmalade’ boasts excellent disease and pest resistance, and is a consistent performer, showing its bright orange flowers all season long. When used as a houseplant, this cultivar is known to bloom year-round.
Pruning
If you’re lucky enough to live in a warm climate where crossandra grows as a perennial, this plant can benefit from a healthy cutback each spring to encourage new growth. Do so before the plant starts its active growing season. Deadheading crossandra throughout the summer also helps new blooms proliferate and keeps your plant looking tidy. If you want to eliminate seed production to decrease spread, cut the spikes back before they start producing seeds.
Propagating Crossandra
Crossandra readily roots from cuttings taken early in the growing season. This is helpful, should you want to grow the same variety of plants in another part of your garden or in another garden bed. Here’s how to grow crossandra from cuttings:
How to Grow Crossandra From Seed
Crossandra blooms approximately four months after sprouting, so it’s best to start seeds indoors in late winter or early spring. To do so, broadcast seeds across a seed starting tray filled with seed-starting mix and cover them with a sprinkling of soil. Keep the soil moist by misting it regularly with a spray bottle full of water. You can also provide a heat mat to maintain warm temperatures for sprouting. Once sprouted, divide the plants into individual pots and continue growing them inside in a bright window, out of direct light, until outdoor temperatures warm. Plant them into your garden bed when temperatures reach 55 F or higher.
Potting and Repotting Crossandra
Crossandra plant is fussy and can easily succumb to transplant shock, so repot it only when necessary. For best results, repot crossandra once every three years, as this plant grows well, even when rootbound for several years. Twenty-four hours before repotting, give your plant a good drink of water. Select a clay or terracotta pot that is approximately two inches bigger in diameter than its current container, and then line the pot with small pebbles to ensure ample drainage. Next, carefully remove your plant from its old container and place it in the new one, backfilling with rich organic soil that contains perlite. Water it again, and return it to the same growing spot.
Overwintering
Most gardeners treat crossandra as an annual, only keeping it until its blooming season is over and then discarding it. If you choose to overwinter your plant, however, don’t necessarily expect it to bloom indoors year-round, as most varieties of this plant will go through a period of dormancy. Simply water the plant enough to maintain moist soil, and then wait for spring. Come spring, cut off any dead growth and move your crossandra into a slightly bigger container with fresh soil. Provide plenty of indirect, bright light for the transplant to help it adjust.
Common Pests & Plant Diseases
Crossandra plants typically don’t succumb to pests or diseases. Still, a stressed plant can become a good meal for mealybugs, mites, and aphids. Signs of an infestation can include tiny web-like structures on your plant, as well as clumps of white powdery residue or visible insects. Treat infestations as soon as possible to prevent them from spreading to the rest of your plants. As always, start with the least toxic treatment option first, like spraying offenders with a blast from your garden hose, before progressing to products like a 70 percent diluted isopropyl alcohol solution or harsh chemicals.
How to Get Crossandra to Bloom
Crossandra loves to bloom all summer long and requires only a few conditions in order to do so. Make sure your crossandra gets ample sunlight during the day in a shady spot that will not get too hot. Severe low light conditions will cause a halt in flower production. Let your crossandra dry out just slightly before watering, as this will spur new blooms. Deadheading will also initiate new buds and flowers, so tidy your plant throughout the growing season for best results.
Common Problems With Crossandra
Overwatered crossandra plants can fall victim to root rot. To avoid this, use a porous clay or terracotta pot with good drainage, and stick to recommended watering protocols for both garden and houseplants. Crossandra is also finicky about water temperatures. Watering your plant with cold water may cause root shock, which can lead to plant death. Always water indoor plants with room temperature water, and outdoor plants are best watered during the heat of the day.
