An important factor in determining the suitability of a plant to your home and envisioning the care it will need, is to know the origin of the plant. Plants that are native to desert regions will require substantial amount of sunlight and loose, fast-draining soil. Plants from the floor of a rainforest will need some protection from strong sunlight and generous humidity.
Rhipsalis is a genus of numerous species, many of which are commonly known as mistletoe cactus or coral cactus. These plants are epiphytic or lithophytic* ,tropical cacti, primarily native to the tropical and subtropical forests of Central and South America. Tropical cacti typically grow in a pocket of moss or debris in the crook of a tree branch or a rock. So despite the humid, jungle conditions of their native habitats, these cacti are adapted to grow in a media that is prone to dryness.
Tropical cacti are succulents, with areoles, but differ considerably in appearance from desert cacti. Like Christmas or Easter cacti, mistletoe and coral cacti are leafless and composed of branching stems. Many are admired for their attractive, pendant architecture more than their flower display, though the flowers can be numerous and, in some species, are scented.
Imagine the understory, filtered light of a tropical cacti’s natural habitat. These plants prefer a medium source of light year-round and will die if exposed to prolonged, direct, summer sun. Morning sun only is ideal. Rotating the plant is beneficial but not essential.
Water frequently in spring and summer, keeping the soil consistently moist but not standing in water run-off. Watering frequency should vary as your house heats up and cools down with the seasons. During the pre-flowering period, reduce watering, letting the top ½ inch of soil dry out between waterings. After flowering, water only enough to keep soil barely moist for a period of three to six weeks. Rhipsalis do not like hard water and should, ideally, be watered with rainwater.
Mist your mistletoe or coral cactus daily to compensate for the inhospitable dryness of a Northeastern home.
Tropical cacti like warm household temperatures most of the year, but with a rest period after flowering and again while setting buds to re-bloom. To form flowers, mistletoe and coral cacti need to be moved to a spot with lower temperatures (below about 65° F.) for a month or two after flowering and again before setting buds. (See Encouraging your Rhipsalis to flower below). Do not expose them to temperatures below 50°F.
Mistletoe and coral cacti prefer a rich soil with excellent drainage. Many commercial cacti and potting soil mixes rely too heavily on peat, which holds moisture in the soil longer than is desirable for these plants. In general, mixing one part perlite (for drainage) with one part potting soil, one part peat and one part coarse orchid bark (for structure and nutrition) creates an excellent soil for most jungle cacti. You will notice that while this mix is fast draining, it will hold more moisture than a desert cactus mix. Plants that are potted in the wrong mixture will initially do well but may later suffer from root rot associated with excess water retention in the soil.
Re-potting your plant annually after flowering is essential for your mistletoe or coral cactus, even though its small roots are unlikely to outgrow the container. Generally, a clean pot of the same size with fresh soil is fine as slightly tight conditions benefit flowering. Handle the plant carefully as you move it so as not to break off the delicate segments.
When flower buds begin to form, use a tomato-type fertilizer every two weeks through the flowering period and then monthly for the rest of the year, except for the rest period following flowering. Do not use a high nitrogen fertilizer on these plants or any other succulent.
Mistletoe and coral cacti do best if they have a period of rest after they finish blooming of a month or two and they need to experience lower temperatures and longer nights to set new buds. If your mistletoe or coral cactus will not re-bloom, it is most likely that one of these elements has been missed in its yearly routine. In particular, your cactus will not set buds if kept at normal household temperatures above 68° F. in the bud formation period. Bud formation and bloom may also inhibited by the presence of artificial light at night, so household lamplight and even streetlights can be a problem. Once the buds are set, do not move your cactus.
During the flowering period, keep temperatures above 60°F and water normally, as directed above.
Your cactus then needs a rest period for about two months following flowering. During this time the cactus should be watered less frequently, not fed, and kept relatively cool (around 55°F).
After the rest period, you can increase water, temperature and re-start your feeding program. About two months before bloom-time, keep your plant dry-ish and cool again until buds form, at which point you can resume regular watering.
Mistletoe and coral cacti benefit from the air circulation when placed outdoors during the summer months but keep them in medium shade. The stems will harden with this outdoor exposure and your chance of a strong flower display will improve.
Do not overwater; if your plant begins to turn yellow at the tips you are giving it too much water and causing the cellular structure to rupture.
*epiphytic = growing on but not feeding from another plant; lithophytic = growing on rocks.