CACTUS
by Jerry Parsons, Ph.D.
Horticulture Specialist, Texas Agricultural Extension Service in San Antonio

As hot and dry as the summers in Texas are, some people wonder if there is anything that is really easy to grow during the dog days of June through September. For those of you who want to grow a low maintenance plant, you may want to consider cactus.

Why would anyone want to grow cactus?

Primarily, ease--if you can't grow cactus, we can't help you! Can you imagine anyone having the nerve to admit they've killed a cactus?!

Cacti are a group of plants that are not only easy to grow, but offer a variety of shapes, color and form. They can be grown in any sunny, well-drained area. They require little maintenance. They make excellent houseplants and many hardy varieties may be grown outside.

If you want small specimens (less than one inch above the ground), you will want to grow lithops, which is Greek for "living rocks". Other cacti which mimic the appearance of rocks include titanopsis, lapidaria, penestraria and gibbaeum.

Some cactus and succulent types can be used as pot plants. These include Aloe Vera, crassulas, Echeverias, peperomias and kalanchoe.

Larger-growing cactus and succulent plants make dramatic floor plants with heights from 3 to 10 feet or more. These include Cereus peruvianus, Yucca elephantipes, Euphorbias, ponytail palm or bottle palm.

The cactus family (Cactaceae) is one of the most striking, distinctive, diversified and specialized groups in the plant kingdom. It includes about 2,000 species, and all of them are perennial and succulent.

Succulents are plants that have organs such as leaves, stems or roots that are capable of storing water during the rainy or wet season in order to survive extended periods of drought. All the plants in the cactus family (Opuntiacea = Cactacea) are considered stem succulents. During periods of moisture, the stem swells. Then during droughts, the stem slowly contracts. Cactus that have ribs are particularly well adapted to this because the ribs fill in and contract like an accordion.

The cactus flowers are usually conspicuous, and are so different from those of all other plant families that the cacti are unique and alone, without obvious relationship to other plants. Epiphyllum, the orchid cactus, leads this category with its fragrant flowers that grow up to 8 inches across.

The distinctiveness of the cactus family shows itself not only in the flower structure, but also in one characteristic, that, although possessed by every cactus plant, is absent in all species of all other families. This is the spine cushion or areole. Whether or not spines are present, all cacti have areoles. Because these areoles differ in structure on different kinds of cacti, this is one way of distinguishing one cactus plant from another.

An areole is the radial arrangement of spines on pad-like buds where shoots and flowers may appear. The areoles themselves are arranged in a regular pattern, either along the ribs of columnar or barrel cacti, or at equally spaced intervals over the face of pad-like cacti. In some cactus species, such as the Christmas cactus (Schlumbergera sp.), the areoles are difficult to see as they are very small and grouped at the tips and along the sides of the stem segments.

One plant family that is often confused for the cactus family is the euphorbia family (Euphorbiacea) which contains such plants as Cow's Horn Cactus (Euphorbia grandicornis), African Milk Bush (E. trigona) and Crown of Thorns (E. milii). While all these plants have spines, have green stems and few or no leaves, they do not have areoles. If you are still in doubt about whether you have a euphorbia or a cactus, make a small cut in an inconspicuous place. If the sap is milky white and sticky, then you have a euphorbia, since cactus sap is clear and watery.

Here is a frequently asked question: "Is this plant a cactus or a succulent?" This question is nonsensical because cacti are succulents. The true cacti are members of the botanical family Cactaceae and are distinguished from the succulent members of other plant families such as Euphoribiaceae by the structure of the flower and the presence of the areoles on cacti. It therefore should be: "Is this plant a cactus or some other succulent?"

Cacti are native only to the Americas. Christopher Columbus is purported to be the first European to discover this spiny, leafless plant. Of course, Native Americans knew all about cacti. It was incorporated into many Native American cultures. Cactus sap has been used medicinally. Some cactus sap has a narcotic effect and has been used in religious ceremonies. The sap of Stenocereus gummosus is toxic and is thrown into streams where it stuns fish which are then easily caught by hand. The stems of some cacti can be used as a source of food, either baked or eaten raw. Cactus fruit of some species are eaten raw, and also candied or preserved in jams.

Certain parts of the cactus are edible too. In April and May, cactus plants make new growth. The new growth are not new leaves but stems. Leaves are about ¼ inch long and the diameter of a pencil lead. They fall off in a few weeks, before the new stem or pad fully expands. The leaf scar is located at an areole from which the spines begin to emerge after the leaf falls. The areole is also capable of sprouting a new stem (which is the same as an auxillary bud).

When nopales (nopalito means small) are cut or harvested in the young and tender stage, there are usually no spines yet developed. Nopales are taken only from prickly pear (nopal) cactus. The red fruit are called tuna (a Spanish word) and also have spines. The little stems, or pencos, are light green and as crisp and tender as lettuce. Nopales are a favorite Mexican vegetable, with flavor and texture similar to green beans, but firmer. The smaller leaves are more tender.

To prepare for cooking, the cactus thorns must be removed, carefully, with a potato peeler or sharp-pointed knife. To prepare abut 20 small, tender Nopales, cut the de-spined Nopales into ½ squares and boil in salted water with ¼ teaspoon of soda and one chopped onion for 5 to 10 minutes, or until the Naoales are tender. Drain, season to taste and serve.

Cactus has also had other practical uses. The long, soft spines of Oerocereus celsianus are used as pillow and bed stuffing. Spines of other cacti are used as toothpicks, combs, sewing needles and fishhooks. Yet other cacti are used as building materials and as living fences or hedges.

One the earliest recorded cultivation of a specific cactus species for a specific purpose was by the Aztecs. They grew Opuntia coccenillifera which acted as a host to the cochineal scale insect. It was harvested and crushed to produce a dye that was either a rich purple (from the female scales) or a brilliant scarlet (from the male scales). The dye was used in fabrics and cosmetics.

The first step to successfully growing a healthy cactus plant is to purchase one that is already in good health. Avoid any plant that has damaged spines, obvious signs of bruising, or that has lopsided or uneven growth. A plant that has put on new, spindly growth during its time in the store should be avoided. Even under ideal growing conditions, the spindly growth produced in a dimly-lit store will never broaden out to normal size, leaving the plant with a permanent disfigurement. Ideally, a cactus should be purchased in the greenhouse where it was grown, or as soon as possible after it has been shipped to a retail outlet.

The care a particular type of cactus requires is largely dictated by the climatic conditions where that cactus would be found growing in nature. A good rule of thumb for looking after any plant is to provide conditions that are as close as possible to the environment where the plant would be found growing naturally.

Generally, the 2 most common classes of cactus are those which are l) sun-loving and 2) shade-loving. A potting medium composed of equal volumes of coarse sand, peat and perlite is suitable to grow most cacti. Vertical plants should be planted in a container that has a diameter ½ the height of the plant. Plant Round cacti in containers that have a diameter 2 inches greater than that of the plant. Take care to prevent rot from developing on recently potted or repotted plants. Be sure the pot is dry before transplanting, and transplant into dry soil. Wait a week before watering to allow for the damaged roots to repair.

The quantity and frequency of watering provides one of the biggest dilemmas to cactus owners. Since a cactus does not wilt at the first sign of drought stress, the plant offers few cues that it needs water. A good rule of thumb is to water when the top 2 to 3 centimeters of soil is dry. This should be adjusted with the season.

However, as plants will require more water during the period of summertime growth than they will during the slowed, or halted growth of winter. In winter, the plants may require water only once a month. During winter, you should supply just enough moisture to prevent the roots from drying and dying. One of the most important considerations in watering a cactus is to never let the pots stand in water.

Waterlogged soil can quickly lead to rotting of the roots with disastrous consequences for the plant. Cacti do need to be watered and fertilized, but not as frequently as other plants. Water the pots when they dry out and allow the soil to dry thoroughly between watering. Do not water during rainy spells, during winter or immediately after repotting. Some varieties have dormant periods when watering can be very harmful. Unglazed clay pots require more frequent watering than glazed clay or plastic pots. Small pots require more frequent watering than large pots.

Cactus and succulents need, at the least, very bright light to maintain good color and shape. Spiny, fuzzy or hairy varieties generally require more sun than do the smooth, soft, leafy types.

While most cacti tolerate a wide range of growing temperatures, most will do best at temperatures similar to that of most other houseplants. When temperatures are either too hot or too cold, a cactus will often simply go dormant. An ideal placement for a cactus in winter would be a sunny cool room. During the summer, cacti will appreciate being moved outdoors where they can receive brighter light in combination with cooling breezes during the day and cool humid conditions at the night. If you are moving your cactus outside for the summer, be sure to place it in a position of partial shade for the first few weeks, and slowly move it to a sunnier location. A plant going directly outside into full sun will likely be scorched by the more intense light found outside the home.

Cacti can be propagated from branches or offshoots. The offshoot should be removed from the plant and allowed to dry for 2 weeks. After the broken or cut edge has healed or suberized, plant it shallowly in dry medium. When taking a cutting from a stem section, use a clean, sharp knife. If you are taking several sections from one long stem, you must remember which was the top and the bottom of each piece, because a stem piece that is planted upside down will not grow.

A simple way of keeping track of the top and bottom is to cut the bottom of each segment on a slight angle, and the top straight across. For pad-forming, or branching cacti, the cuttings should be taken at the joints so that the mother plant is not significantly disfigured. A single oval pad from a pad-forming cactus makes an ideal sized cutting.

The primary problem with cactus cuttings is the development of fungal soft rot. This condition begins at the cut surface and eventually reduces the entire cutting to a slimy mass. Two techniques are recommended for avoiding this problem. The first is to simply allow all fresh cuttings to sit in a warm dry place from one to 14 days before they are placed in the rooting medium. The larger the cut surface, the longer they should be allowed to dry. During this time, the cut, moist surface will form a dry callus that is far less prone to rot. Although leaving a new cutting exposed for several days may seem like a radical idea, remember that a cactus is able to survive periods of drought. As long as the cutting is not noticeably shriveled, it is probably okay to leave it dry. Newly cut stem segments may also be dipped in garden sulphur before planting to prevent the onset of soft rot. Do not water the cutting for a week, then water sparingly.

Cacti can also be grown from seed, and many seed companies offer packets of mixed varieties. These can be fun to grow if you can stand the suspense. Some cacti seed take a year to germinate, and it may take a few years to see what your young cacti will look like.

Despite their slow germination, cacti are no more difficult to raise from seed than many half-hardy plants. Many can be flowered within 2 years or even earlier after sowing the seed. It's possible to get a fine collection within in a few years.

The time of the year for sowing seeds depends on what conditions are available. If you have a greenhouse and a small, heated propagator, it is possible to sow your seeds at the end of January or early February. However, if heat is not available, it would be better to wait until late April or early May before attempting to sow your seed.

The earlier the seed is sown the larger the seedlings grow before the winter sets in. This is a very important point. It is never easy to get small seedlings through the winter without heat, and the stronger they are by the middle of October, the better the chances are that you will see them through the cold season. Some varieties are extremely slow while others are much faster. Maintaining the heat in your greenhouse in the 40 to 45 degrees F range will help considerably, and the seedlings will make an earlier start into spring growth.

The best compost for raising cacti is a potting mix. The addition of extra sharp sand is very helpful, especially for the top inch of compost.

Four-inch half-pans have been found to be very suitable for seed growing because they do not dry out too quickly. Make sure all pans are sterilized and clean before sowing. If only a small quantity of seed of each variety is being sown, the pan can be divided into sections using thin strips of plastic. Care must be taken not to get the seed mixed. Put one inch of unsifted compost into the pan. Then, fill the pan up with a mixture of sifted compost and sharp sand, gently pressing down the soil and leaving ½ inch at the top of the pan. Place the dividing slips in the pan and label all of the sown seeds with the date. Do not cover the small seeds with potting mix but very gently give a sprinkling of silver sand to anchor them. Large seeds should be pressed gently into the soil.

After sowing the seeds, place the pans in a container with water sufficient enough to reach about 2/3 of the way up. Once the top of the soil is visibly damp, the seeds are ready to be put into the heated propagator-70 to 90 degrees at the end of January or early February. The base of the propagator can be sand, but the spaces of the pans can be filled with damp peat up to the rim. Place the cover over and shade with dark paper. However if it is not possible to maintain a temperature of around 70 degrees F, it is better to wait until late April or early May, when general temperatures should be much higher, before sowing. The initial watering should be sufficient until some of the seeds are showing but be sure to watch them carefully and water with a fine spray if necessary.

Some varieties take longer than others, depending on the species. However, some seedlings may show within 7 to 10 days while others will take much longer. Mammillarias may be up in a fortnight or sooner. And, again, if the seed is a mixture of varieties, a few will germinate much quicker than others. It is really much better to sow each variety separately. Opuntias, ferocactus and some types of cereus can take a long while to germinate. It has been found that large seeds will germinate more quickly if they are well washed with hand-hot water before sowing.

Cover seeds after sowing. It is really a must with most cacti seed. But whichever covering you choose--a propagator of frame and glass over the boxes or pans-or even polythene bags over the pans--it is very important to wipe the coverings daily to remove any moisture that has formed, as dripping moisture will rot the seed or seedlings.

As soon as the seedlings appear, the paper or covering must be removed to allow for light. But, if they are exposed to too much bright sunlight, they can turn red in color and may stop growing for a long while. Once the seedlings germinate, raise either the glass or frame cover daily so they can get light and air. Otherwise, the seedlings will damp-off.

The disease called "damping-off" is a very troublesome enemy of tiny seedlings. It is, therefore, very important that the seed compost is correctly sterilized and pure clean water is used for spraying and watering. Once seedlings are attacked, they are sure to die. If mildew forms on the surface of the pans, it could be caused by some seed pod husk when sowing the seed. It is very important to see the seed is free of all impurities.

Do not let the pans dry out while germination is taking place. Once the seedlings are up, it is then much safer to allow pans to become almost dry before applying any water.

It is also important to prick out the seedlings as soon as they are ready. If left too long in the seed pans, they may stop growing. Once this happens, it can be a long time before they begin growing again, and very rarely make good plants.

The seedlings should be ready for pricking out when they are about 3 months old, but some varieties may have to be left much longer. The best time to transplant is after the cotyledon (first seed leaf) has been absorbed by the plant proper. You will find that the seedling will have a good root system and can be potted without damage. The seedlings are best planted about one inch apart in good, strong trays which have been washed with disinfectant to prevent any diseases from occurring. Potting mix can be used but add about one part of sharp sand to every 5 parts of compost by volume to make it more porous. Level off the soil around the plants and firm gently.

When removing seedlings from the seed pan, it may be possible to raise all of the seedlings together and then gently separate the roots. Make sure the roots go well into the soil and try to spread them out. Label each kind of seedling with its name and the date when it was potted. Then, water very carefully. The seedlings must be kept in a shady place. Under no circumstances should they be placed in the sun. It is also important not to apply too much water until the seedlings start to grow again after transplanting.

The temperature still needs to be near 70 degrees F. If the temperature drops during the night, it should not hurt the seedlings as long as it does not go below 50 degrees F.

Water the plants so the soil is quite damp. Then, do not water again until the soil shows signs of drying out. Make sure there is plenty of circulating air during the day, but close the ventilators fairly early in the evening.

The primary reason why seeds do not germinate is that they have been sown too deeply. Also, stale seed often has a very small chance of germinating, especially if it has been kept in poor conditions. Use fresh seed and buy from a reputable company. Do not expose seed pans to strong sun and be sure to bring them into light as soon as they are up.

Be patient and don't be too quick to pot up small seedlings. Leave them in the pricking-out boxes until they are touching one another. At the first potting, the seedlings should be put into 2 or 2 ½ inch pots, depending on the variety or species. Some seedlings, such as mammilarias, may even flower in their seed boxes or pans following the year of sowing, but other flowering cacti, such as rebutias, notocactus, gymnocalycium, lobivias etc., generally take 2
Years. Others, such as opuntias, cereus and ferocactus, may take much longer.

After the plants are potted up and growing well, with a few exceptions, they should be able to stand a winter temperature of 45 degrees F, so long as they are kept dry.

A weak solution of liquid fertilizer can be used about once a month during spring and summer on most varieties of cacti.

The cactus family extends to many thousands of varieties and species. We have only covered a small number, but the basic instructions will apply to raising practically all of the varieties.

An exception may be the following epiphytes that grow naturally on trees. They require slightly different growing instructions, especially as they flower from Christmas forward.

Examples include Zygocactus truncatus, Schlumbergera bridgesii (Christmas Cactus), Schlumbergera gaertneri (Easter Cactus) and Rhipsalidopsis rosea (Whitsum Cactus). All of these types require low to medium light, porous yet moisture-retentive compost, and a need for watering when the soil becomes dry. They should be kept drier in autumn to encourage bud formation. They need a humid atmosphere and from spring to late August will benefit from a weekly misting. Just as the buds begin to form, place the plants in a cool place where, as long as the temperature does not drop below 45 to 50 degrees F, they can be kept in darkness at least 12 hours each night.

Epiphyllums are different still, and require full light from early autumn to spring, then partial shade after flowering. They can be plunged outside in a shady position. It is necessary to check all pots before bringing them in to ensure that there are no worms in the pots. After flowering, plants should be rested for 6 weeks when they will need only enough moisture to prevent the soil from becoming completely dry. At all other times, the compost should not be allowed to become too dry. Water less frequently in late autumn and winter. Overhead spraying is also beneficial, when they need only enough moisture to prevent the soil from becoming completely dry. Aporocactus (Rat's Tail Cactus) needs rich, open compost and plenty of water in summer.

Care must be taken to ensure that the propagating area is free from pests. Here are some to watch for:

Mealy Bug As hot and dry as the summers in Texas are, some people wonder if there is anything that is really easy to grow during the dog days of June through September. For those of you who want to grow a low maintenance plant, you may want to consider cactus.