Growing A Cacti From Seed

Growing plants from seed are not as hard as you might think – even though many of us have tried and failed! One of the most common mistakes people make is planting the seeds too deeply. You should only plant a seed as deep in the soil as the seed is wide. When seeds are planted too deeply the tiny plants emerge and begin to grow but do not reach the surface before they run out of stored food. Follow these instructions for growing cacti from seed and you will surely be successful.

SEED: It is best to use fresh seed when growing most cacti. Seed can be obtained from a commercial source or collected from a plant in your collection. Take care when collecting seed from a cactus collection. Some cactus species hybridize freely and true seed cannot be assured unless pollination has been monitored carefully.

SOIL: A good potting mix, amended with ½ its volume of granite, perlite or pumice for drainage, makes a good mix for growing cacti from seed. It is important that the soil is as pest-free as possible. To pasteurize soil, put it in a shallow heatproof pan, place it in the oven at 300 degrees F for 30 minutes. Most commercial soils are at least pasteurized, if not sterilized. Check the label.

PLANTING: Be sure that all containers to be used are clean. The type of container is not important, but shallow ones are preferred. Water the soil thoroughly and let it drain completely before planting. Spread the seed evenly over the top of the soil. Cover the seed lightly with the mix or very fine sand. When planted, cover the container with any transparent lid. This will retain moisture and allow light to reach the seedlings.

GERMINATION: Cactus seeds need both light and warmth to germinate. A sunny window is a good location, but be careful the light is not too strong and therefore too hot. The moisture retained by the cover should be sufficient to germinate the seed. Most cactus seeds germinate within 3 weeks, but some take much longer – be patient. Once the spines are showing, raise the cover for ventilation during the day. Do not allow the soil to dry out. The amount of water will depend on how much light and heat the seedlings receive. Watch the seedlings carefully. Do not swamp them in puddled water but do not let them dry out completely.

REPOTTING: Seedlings are ready to transplant into larger containers when they are the size of marbles between 6 months to a year after germination. Be sure the soil mix is very well drained, and the container is no larger than twice the diameter of the plant. At this size, plants can be grown in clumps or groups of 6-8 per pot until they are about 1 inch across, then separated and individually re-potted. Lift the small plants carefully from the growing mix, place in the new container, firm the soil around the roots, and water in.
 It is usually best to let the young plants recover from transplanting in a shaded area. Even in cacti that naturally grow with full sun, seedlings will be tender to the full sun until they are older. Acclimate a young plant to the sun gradually beginning when it is about 1 inch across. It is often easier to acclimate young plants to the sun in the winter, and provide some shade in the summer until they are about 3 inches across.

FERTILIZATION: Fertilize young seedlings monthly in the growing season, usually the warm season. Use a formulation specifically for cactus, or an all purpose soluble houseplant formula at ½ the recommended strength.

Care Of Cacti In Containers

Cacti are a group of succulent plants that do well in containers under the right conditions. They are native to the New World. These plants are diverse both in form and color, clumping or solitary. They can range in size from very small to more than 40 feet tall. Most cacti are best grown outdoors in filtered sun or on a bright patio. Some can tolerate full sun. Smaller species may be kept in a container. The larger varieties can start out containerized but will outgrow their pots and can be moved to the landscape, depending on the species, where they can enjoy more growing space.

SOIL: Most cacti should be grown in mineral-based soils consisting of a mixture of sands, silts, and gravel (good drainage) and which does not harden when dry. Cacti from tropical dry forests and high altitude regions benefit from a mix containing 25-50% decomposed organic matter. Epiphytic cacti such as Christmas cacti like a 1/3 – 1/3 – 1/3 mix of bark, pumice and decomposed organic matter. No peat should be used in any of these mixes. Organic matter consisting of well-decomposed plant material or worm castings is acceptable. If you wish to use peat-based soil mixes, you can, provided that you re-pot every 2-3 years. No commercial mixes come up to these standards as of this time, so you will need to formulate your own.

WATER: It is completely false that cacti need no water; after all, they are composed principally of water. What is true is that they require less water than violets, but more than a rock. Water cacti when they are actively growing or are wilting. Wilting appears as shrinkage of the plant or wrinkling of the surface. Most cacti grow actively in the spring and summer, but some grow in the other seasons as well so you will need to watch them carefully. Water only when the soil is nearly dry. You can test for dry sub-surface soil with your finger, a wooden pencil or popsicle stick (damp soil will cling to the wood), or (best) with a moisture meter. Water all of the soil thoroughly until the water runs out of the drain holes. Use only pots with drain holes, and if you use pots with saucers, be sure to empty the saucer after watering. The rule is ―no swamps.‖ The warmer the weather, the more frequently water is needed, unless the plant is dormant. In winter, little or no water is needed, even for cacti in active growth, because it is cool. Natural rain is very beneficial, and water may be applied from overhead (which helps clean the plant), at the soil line, or from below. Remember not to let the plant stand in a saucer of water.

LIGHT: Cacti, excepting epiphytes, are best grown outdoors. Interiors are usually too dark for good growth unless assisted by high-intensity lights. Cacti grown indoors very frequently develop pointy heads or other forms of stem stretching. Cacti should be grown outdoors in conditions ranging from full sun to 50% shade, depending on the species and on the size of the plant. If the cactus gets too much sun it will sunburn, which results in a yellowing of the skin, progressing to a browning (killing) of the skin on the sunniest side. If this occurs, provide shade immediately. Eastern exposures are gentlest, western sunlight is fiercest.

FERTILIZATION: Container grown plants need fertilizer because the soil will be exhausted of nutrients over time. The frequency of fertilization depends on how fast you want the plant to grow and the strength, or  concentration, of the fertilizer that you use. Remember that fast growth may produce weak cells, leading to over-tenderness. Fertilize at least once every four weeks during the plant’s growing season. Use the concentration recommended for ornamental plants on the fertilizer package. If you fertilize with each watering cut the strength of the solution accordingly. Use a low nitrogen fertilizer, such as 10-30-20. As a slow-acting organic fertilizer, fish emulsion is effective.

TRANSPLANTING/REPOTTING: Transplanting should be done when the plant has filled the pot, or, in the case of tall species, when the pot becomes top-heavy. If the soil in the new destination is the same or similar to that in which the plant is growing, simply shake the plant free of its container, keeping the soil ball intact if possible. Rough up the edges of the soil ball and then replant, keeping the soil level the same as the former location. If the soil/root ball collapses, wait a week to let the roots callus, then plant, using dry soil. If you are changing soil types from organic to mineral, first remove all old soil from the roots using an old toothbrush to get at the most stubborn bits. Cut off any broken roots and let dry until all wounds have callused over, then re-pot or plant using dry soil to fill in so that the soil will flow and fill in all air pockets. Wait a few days, then water in to settle the soil. It is best to transplant when the plant is actively growing, but if you must, you can do it anytime.

PESTS AND DISEASES: Cacti have few diseases and pests. Most problems are environmental. Pointy heads in globular cacti or stringy narrow stems in others–Etiolation caused by too little light–give more light. Yellowing or browning of the skin: especially on the sunny side—Sunburn—give more shade immediately. Wilting, wrinkling, shrinkage: dry soil, needs water. If the soil is wet, then roots have died due to swamping—remove from damp soil, re-root, and transplant. White cottony masses or white rice-like objects on plants: Cochineal scale or mealy bug—wash off with a hard jet of water, or apply alcohol or a pesticide for scale insects. Inspect plant often to check for recurrence. Very fine spider webbing in the spines: sometimes with red bead-size mites, and graying of the skin—Red spider mite. Wash off the water and use overhead watering to prevent reoccurrence. In severe cases use miticide treatment. Large larvae (grubs) tunneling inside stems, large black adults feeding on tips of plant: Longhorn beetle—remove adults at dawn and kill, or place them in a large prickly pear cactus clump some distance away.

Plant being eaten: Rabbit, rodent or javelina damage—Protect plant with a wire cage or move out of reach. Wet rot anywhere on the stem: Bacterial rot (Erwinia carnegieana)—Cut away all rotted tissue down to fresh, discolored tissue. Air dry. Do not fill in holes. Dry rot on tips or in the whole plant: Fungal dry rot (Helminthosporum cactivorum)—Cut away all dried and discolored tissue. Air dry.

Problem Guide For Southwest Gardens

A noticeable, fine web may be present on your Palo Verde trees (Parkinsonia spp.) and even from time to time on the Whitethorn Acacia (Vachellia constricta syn. Acacia constricta).  This “webbing” is produced by the Palo Verde webworms often called Palo Verde webbers. The webworm is a small caterpillar that feeds on the leaves and occasionally the bark of the small stems.  The Palo Verde tree and Whitethorn Acacia are resilient to webworm infestations so control methods are unnecessary. The caterpillars and adult moths are an important food source for many lizards and birds.
If you notice a tattered appearance on your landscape plants such as Evening Primroses (Oenothera spp.), Sacred Datura (Datura wrightii) and Gaura (Gaura lindheimeri) it may be the flea beetle in action. A different species of flea beetle may also harm your vegetables including tomatoes and eggplants. The flea beetle larvae and adults can be destructive and they can be difficult to control. To find out more information on flea beetles go to the following link:
Agave snout weevils become active during the warm months and infestation may not be apparent until it is too late. For detailed information on the life cycle, symptoms,
While sitting underneath your desert trees, you may notice a light “rain” falling. This is the smoke tree sharpshooter insect expelling sap as it draws from a variety of plants including Palo Verdes (Parkinsonia spp.), Beebrush (Aloysia gratissima), Bird of Paradise species (Caesalpinia spp.) and Hackberries (Celtis spp.). These sharpshooter insects have gone virtually unnoticed until they threatened oleanders, shrubs widely used in low-desert landscapes for screening hedges. They gained notoriety because they are able to transmit a deadly bacterial disease called oleander leaf scorch. Our native plants do not appear to be adversely affected by the smoke tree sharpshooter so no control is necessary.  To find out more about oleander leaf scorch check out the University of Arizona Extension Plant Pathology at
As the weather warms, whiteflies may be present on your landscape, vegetable and herb plants. These tiny, white insects have sucking mouthparts that cause leaves to yellow, wilt and drop prematurely. The immature nymph stage does more harm to the plant than the adult. Whiteflies can be difficult to control. Allow natural predators such as spiders, ladybugs, lacewings and even hummingbirds to control the population. Yellow sticky traps can also be used to control the adult population.
Noticeable leaf damage may be seen on the Texas Mountain-laurel (Calia secundiflora syn. Sophora secundiflora) during the warm months. The damage is caused by the sophora pyralid caterpillars feeding on the tender new growth. These ravenous caterpillars are approximately an inch long with orange bodies and interesting black spots with white hairs.
Psyllids can still be active during the month of May, but activity will decrease as the temperatures climb.  Psyllids are sap feeders and many are plant specific or feed on a closely related group of plants. High populations of psyllids can cause distortion and die back of new growth, and in some cases defoliation. To keep populations under control do not overwater or over fertilize your plants as this causes excessive growth. Yellow sticky traps can also be used to control the adult population.
Cochineal scale, the cottony, white substance on your Prickly-pears (Opuntia spp.) and Chollas (Cylindropunita spp.) may be active now. Remove by using a fast stream of water or spray insecticidal soap.
Fine webbing between leaves or stippling on leaves may indicate the presence of spider mites. These plant mites cause damage by sucking contents from the leaves and are difficult to detect due to their small size. Plants that are water stressed may become susceptible to infestation. Dusty conditions can also lead to spider mite outbreaks. Make sure your plants are well-watered and wash off accumulated dust on plants to manage spider mite problems. You can also remove by using a fast spray of water or by spraying insecticidal soap to control populations. There are many biological controls that feed on spider mites including lacewings, predatory mites, lady bugs and big-eyed bugs. Using insecticides is not recommended as insecticides do not help manage the population, but can actually cause the population to intensify because insecticides used will often kill their natural enemies. Some insecticides can even accelerate mite reproduction.
If you notice a rank odor and black ooze dripping down the saguaro stem(s), the plant may have developed an infection as a result of an injury or frost damage. The infection is caused by the Erwinia bacteria, a common bacterium found in the environment.
For more information on diseases or problems of landscape plants go to the University of Arizona Cooperative Extension publication/sites/dbg.dd/files/pldiseases_urban-1124.pdf or the University of California UC IPM Online at