Flowering Spring Cactus
Spring cactus, also called Easter cactus (Rhipsalidopsis or Hatiora), appears similar to Thanksgiving and Christmas cacti (Schlumbergera truncata and S. x buckleyi), except spring cacti have radially symmetrical flowers that are typically open wider. Flowers of spring cacti come in a broad range of colors, including yellow, pink, peach, red and white.
Spring cactus is a relatively minor floriculture crop in the United States; however, in Denmark and The Netherlands, an estimated 5 million 4- to 5-inch pots are grown each year, with an approximate wholesale value of $4 million (U.S.). Domestic production figures are not available, but most of the spring cacti grown in the United States are propagated and produced in California and are sold from March to May throughout the country.
Flower induction requirements for spring cactus are different from those of Christmas cactus. Spring cactus is induced to flower by a period of cool temperatures with naturally short photoperiods during the winter followed by long-day photoperiods at moderate temperatures. Crops exposed to these conditions in a greenhouse generally flower and are sold in March and April. However, reliably flowering a crop for earlier sales (January and February) has sometimes been a challenge.
We have conducted numerous experiments at Michigan State University to understand the flowering requirements of spring cacti. This article summarizes our research findings and details how spring cactus can be successfully produced in flower for specific dates any time of the year.
Mature pads, or phylloclades, are harvested from stock plants or from plants that have been pinched (leveled or twisted). These cuttings can be propagated immediately after removal from the stock plant, or they may be stored for several months at 52-57¡ F. Treating stock plants with a broad-spectrum fungicide, such as iprodine or chlorothalonil, before harvest can reduce losses in storage and propagation. Time to root after sticking is reduced if cuttings are stored and allowed to callus prior to sticking. ç Dipping pads in a 400-ppm bleach solution (1:250 dilution of 10-percent bleach) containing a wetting agent immediately before sticking also helps prevent losses in propagation.
Cuttings can be stuck into plug trays, or they may be stuck directly into the finish container. Each plug or 4- to 5-inch pot may contain 1-4 cuttings. Using two or more cuttings per plug or pot produces a fuller and sturdier finished plant. A well-drained medium should be used, and bottom heat (75-77¡ F) should be maintained during rooting. Excessive watering during propagation will lead to poor rooting and rot.
As the cuttings root, they will start to grow a new pad or flower. To promote branching, the first new pad or flower should be removed when it is large enough to handle and be fully removed without causing damage to the cutting. If plugs are used, transplant the plug to a finish pot when one new pad has fully formed.
Nutrition and Watering
Nutritional requirements for spring cactus are not unique. Constant liquid feeding with 125-200 ppm nitrogen is adequate. Allow soil to dry between waterings, but do not stress the plant, especially during flower induction and expansion. Maintain EC between 0.5 and 0.8 (1:2 soil:water extract). It is important to maintain soil pH above 6.0 to avoid micronutrient (iron and manganese) accumulation and toxicity, which manifests itself as chlorotic or necrotic margins on the pads. It is recommended to terminate fertilization 2-4 weeks prior to the beginning of flower induction treatments to inhibit vegetative growth and promote flowering. Fertilization should resume during the forcing period following cold treatment.
Spring cactus should be grown under relatively high light levels. Maintain a maximum light intensity at solar noon of 4,000-5,000 foot-candles. Light above 5,000 foot-candles, coupled with high temperatures, may cause pads to yellow and abscise. If plants start to turn yellow from high light levels and temperatures, reduce light to as low as 1,500 foot-candles.
Photoperiodic lighting that delivers at least 10 foot-candles is adequate for long-day treatments, but using supplemental lighting with high-pressure sodium lamps (such as 450 foot-candles) will promote growth and create a stronger plant when natural light conditions are low. Supplemental lighting may also be used before cooling and during forcing to increase bud count.
Prior to the cool treatment (described below), plants may be grown at 62-72¡ F. Following the cool treatment, maintain temperature between 64 and 72¡ F. Warmer temperatures during forcing can cause bud drop. Plants will grow faster at higher temperatures, so schedules should be adjusted accordingly.
Plants are leveled, or twisted, to create a more uniform, upright architecture and to stimulate branching. This practice is not necessary unless more branching is desired, plants become lanky or cuttings are needed. To level plants, pads are twisted 180 degrees and then pulled off the mother plant sharply. It is important not to damage the terminal end of the pad remaining on the mother plant, as this is where new growth or flower buds will emerge. Spring cacti should be leveled about six weeks before inductive treatments begin. Actual timing ç of leveling depends on growing temperature, because temperature influences growth rate. A new set of pads will form after leveling, and these should be close to full size when induction begins. Flowers will appear on these pads that form prior to induction. Depending on plant architecture and pot size, plants are typically leveled so 2-4 tiers of mature pads remain on the plant after leveling. Small, immature pads will not flower and may be removed before or during induction.
Flowering is promoted mostly by short days at cool temperatures followed by long days at moderate temperatures. Optimum temperatures for the cool treatment are 46-55¡ F. If these temperatures are difficult to maintain because of high light levels, shade may be provided during cooling to reduce solar heating of the plants. Preliminary research results suggest that plants may be cooled for a short time in a cooler if greenhouse temperatures cannot be maintained. Cooling plants for up to 4-6 weeks in a dark cooler may be used on an experimental basis if night temperatures cannot be maintained below 55¡ F.
Following cool treatment, forcing under long-day photoperiods is required for rapid production of numerous buds. It has been recommended to raise temperatures slowly (5¡ F per day) following the cool treatment to prevent bud drop; but in our experiments we have not found this to be necessary. To produce flowering plants in March or later, induce plants to flower by using a minimum of 6-8 weeks of cool temperatures under natural photoperiods, then provide long days at warmer temperatures. To create long days, use night interruption (from 10 p.m. to 2 a.m.) or day-extension lighting to create a 14-hour photoperiod. To produce flowering plants in January and February, provide six weeks of artificial short days (10 hours or less) prior to the cool treatment. Supplemental lighting during the short-day treatment increases the number of buds produced during forcing.
Figure 1, left, provides a schedule for growing spring cacti to flower for different dates. Plants are marketed when flower buds are 1?2- to 1-inch long. Some cultivars (usually red-flowered cultivars, for example, 'Jan' and 'Rood') respond better to early-season forcing than others (e.g., 'Phoenix' and 'Capella'). Unlike the Christmas and Thanksgiving cacti, spring cacti typically are not treated with benzyladenine (BA) to increase bud count. However, BA has been shown to increase bud count when applied to plants 12 days after the beginning of the forcing treatment. Exact application timing is crucial, and bud drop is increased. The flowers of spring cacti are less sensitive to ethylene than those of Schlumbergera cacti, so anti-ethylene agents are typically not applied. Production of spring cactus is a time-intensive process. However, if the ideal growing environments and space are available (i.e., proper temperature, photoperiod and cooling for each phase of production), this plant can be a unique and desirable potted plant for late winter/early spring production.