Feature Articles

Floriculture: Production and care of cacti
There are a large number of cacti genera that are grown as indoor plants. Some of the more popular include: Echinocactus, Cereus, Mammillaria, Gymnocalycium, Rhipsalidopsis, Schlumbergera and Zygocactus.

True cacti have areoles or warts where spines emerge. There are more than 1,500 species of these slow growing plants. Cacti grow and rest in cycles due to their native habitat in the Western Hemisphere. However, harvesting a native cacti is strictly forbidden.

Grafted cacti can be imported from Japan and Brazil, larger specimens are from Texas and California. Cacti require little care and space and are popular in desert dish gardens. Holiday cacti are a group of tree dwelling, epiphytic cacti.

Growth and development
Many growers use gloves, tongs, baskets and specialized tools for cactus production. Optimum light levels are 5,000 to 8,000 footcandles (fc). Temperature preferred when cacti are actively growing is 75 to 85 degrees F.; when dormant, 45 to 55 degrees F. It is important to use substrate with low moisture holding capacity. Use a forgiving mix low in organic matter, high in amendments that improve porosity, such as coarse sand, perlite, shale, crushed granite or pumice (volcanic gravel).

In production, maintain some moisture in the substrate at all times during the production cycle. If the substrate dries out, fine feeder roots die, slowing growth. Dormant cacti in winter need watering only every few weeks.

Holiday cacti prefer a peaty mix with 20 to 25 percent sand, 40 percent perlite and 60 percent peat. They prefer 1,500-3,00fc and a temperature range of 70 to 85 degrees F, although they can survive 40 degrees F. In winter maintain 50 to 60 degrees F for holiday cacti.

During production, leveling, or pinching off leggy growing tips, can be helpful. Cacti have relatively low fertility requielments. Slow release, coated fertilizers may be used.

Apply 150 ppm N of 20-10-20 soluble fertilizer with each watering. Trace elements do not need to be incorporated into substrate for cacti. Watch for nutrient deficiencies of iron, evidenced by veinal chlorosis in new growth, and magnesium, evidenced by yellowing or reddening of the older growth.

Propagation
Cacti are grown from seeds, cuttings, offsets and tissue culture. When propagating form cuttings, do not plant; cuttings may be laid on the substrate and secured with pins or stakes. Large cacti are produced from trunk or large leaf cuttings, which are allowed to air dry away from direct sun before planting. Rooting is completed in a few weeks. Holiday cacti are grown from two leaf joint in dry substrate to allow wounds to heal. Two or three cuttings with two joints are planted in 2-inch pots. Avoid watering until a week after planting. Bottom heat of 7- to 75 degrees F. is helpful in cool conditions.

Seeds germinate quickly when  grown in 50/50 mixtures of sphagnum peat and sand. Fill container to the top, sprinkle the seeds onto substrate, barely cover. Germination time varies from days to months with environment. Bottom heat of 70 degrees F. improves germination time. Most varieties need light to germinate. It takes 12 months to finish a cacti from seed.

Grafting desert cacti is sometimes practiced, often between different species. Use a sharp, sterile knife. popular methods are the cleft graft, much like a tongue-and-groove joint; and flat and side grafting. Line up the vascular bundles to the two pieces to be grafted and secure with rubber bands, tape or cactus thorns.

Disorders
Common problems are rot, caused by excessive watering and inadequately drained substrate; shriveling if excessively dry and cresting or fasciation - development of many growing point resulting in a gnarled appearance. A reddish coloring on seedlings can be caused by too much light. Too little light causes seedling to be pale green and stretch. Low substrate temperatures result in chlorosis. Sunburned tissue occurs when there is a substantial amount of yellow or white tissue. Edema occurs when cacti are kept in hot, dry conditions, then suddenly cooled off or watered heavily, so use careful irrigation. Ethylene sensitivity causes flower drop and yellowing or shriveling. Christmas cacti may turn blue-grey when kept in substrate that is too wet or dry, or poorly aerated, prevented by drying plants our or watering as needed.

Diseases include:

• Drechslera cactivora, stem rot - Over a period of two to four days, the basal part or upper portion (in some cases) or stem turns yellow or dark green to dark brown.

• Anthractnose, leaf and stem spots - Spots appear as soft areas with sunken areas, turning black or tan. Disease is spread by splashed water. Take special care of rooting cuttings.

• Botrytis blight - Appears on areas of cuttings in contact with potting substrate or in center of plant. Water soaked spots spread rapidly. The pathogen prefers cool nights, so reduce moisture on plants at night.

• Cactus Cyst Nematode - Foliage turns brown; growth is stunted; plants wilt. Roots contain tiny, round cysts. To prevent, raise plants above ground, use nematode free substrate, pots and plants.

• Cercospora, leaf spot - Tiny, slightly raised, red or dark green spots appear in lower leaf surfaces. Spots enlarge slowly. To prevent, use pathogen free plants; minimize leaf wetting; remove infected plants.

• Dichotomophthora, rot -  Spots are tan and sunken. Most severe at temperatures 75-91 degrees F.

• Erwinia, blight - A blackened, wet slimy spot starts at substrate line and progresses upwards. Plants wilt and often die during hot months. to prevent, remove and destroy infected plants; water minimally; avoid splashing; and irrigate early in the day.

• Fusarium rot - Spots are tan and sunken with orange spores. Abscission of the cladophylls above the infected portion can occur in warm and wet conditions. Reduce water applications.

• Helmithosporium rot - Blackened, sunken lesions form on plant. Cladophyll abscission is common. Most severe at temperatures 75-91 degrees F.

• Phytophthora, stem rot - Plant truns grey and may wilt, stems become rotted at substrate line, upper portions of plants collapse. Use pathogen free plants, pots and substrate, avoid overwatering.

• Pythium, root rot - Foliage on plants turns a dull grey green and may wilt, stems rot at substrate line, upper portions collapse, cladophyll abscission may occur, roots are darkened and mushy.

Pests

• Mealybugs, root mealybugs - White cottony masses appear on foliage; plants lose vigor and color.

• Scales - Check for infestations periodically.

• Spider Mites - Insecticidal soaps may be helpful.

• Cactoblastis moth - Larvae feed on flowers.

Consumer Care
Fertilize with 20-10-20 at 75-100 ppm N once a month. Cacti perform well in several consumer environments. Provide with as much light as possible. Water more frequently during spring and summer. In winter, water sparingly. Avoid fertilizing dormant cacti. Fertilize in spring and summer. Repot in March and April. Avoid watering right after planting, usually allow one to two weeks to avoid root diseases. Soak seeds at planting, then maintain moisture. Wear heavy glove when handling cacti, if glochids, tiny barbed hairs which feel like fiberglass threads attach to skin, apply cellophane tape to pull off.

Varieties and Cultivars

• Mammillaria zeilmanniana: "Nipple Cactus", small growing and free flowering.

• Gymnocalycium mihanovichii - "Chin Cactus", small growing, colorful body and free flowering.

• Cereus peruvanius - "Column Cacti", popular for large containers.

• Echinocatus frusonii - "Golden Barrel Cactus", low growing, popular for medium sized plants.

• Espostoa lanata - "Peruvian Old Man Cactus"

• Cephalocereus senilis - "Mexican Old Man Cactus"

• Rhipsalidopsis - Christmas Cacti

• Schlumbergera - Thanksgiving Cacti

• Zygocactus - Christmas cacti

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