The Urban Gardener 31

``` 1

31st Issue Vol. 4 No. 4 ISSN 2094-1765 April 2011

THE UNIQUE WORLD OF CACTI A cactus is a member of the plant family Cactaceae. Their distinctive appearance is a result of adaptations to conserve water in dry and/or hot environments. In most species, the stem has evolved to become photosynthetic and succulent, while the leaves have evolved into spines. Many species are used for ornamental plants, and some are also grown for fodder, forage, fruits, cochineal, and other uses. Cacti come in a wide range of shapes and sizes. The tallest is Pachycereus pringlei, with a maximum recorded height of 19.2 m, and the smallest is Blossfeldia liliputiana, only about 1 cm in diameter at maturity. Cactus flowers are large, and like the spines arise from distinctive features called areoles. (Left) Ferocactus pilosus (Mexican lime cactus) growing south of Saltillo, Coahuila, northeast Mexico

Distribution The cactus family is native to the Americas, where their range extends from Patagonia to southern Canada, but they are densest and most diverse in the regions of northern Mexico and the southern tropics of Argentina and Bolivia. Rhipsalis baccifera is the one exception; it is native to both the Americas and the Old World, where it is found in tropical Africa, Madagascar, and Sri Lanka. It is thought to have colonized the Old World within the last few thousand years, probably by being carried as seeds in the digestive tracts of migratory birds. Many other species have become naturalized outside the Americas after having been introduced by people, especially in Australia, Hawaii, and the Mediterranean region. Cacti inhabit diverse regions, from coastal plains to high mountain areas.

``` 2

Adaptations to dry environment With a few exceptions, cacti are succulent plants and, like other succulents, they have a variety of adaptations that enable them to survive in hot and dry environments. (Below) Pereskia grandifolia: Pereskia is a weakly succulent genus, which also possesses leaves, and is believed to be similar to the ancestor of all cacti.

Organ pipe cactus in Arizona.

In most species of cacti the leaves have evolved into spines which not only defend the cactus against herbivores but also provide shade that lowers the plant's water loss through transpiration. The spines grow from specialized structures called areoles, homologous to the nodes on other plants. Very few members of the family have leaves, and when present these are usually rudimentary and soon fall off; they are typically awl-shaped and only 1–3 mm. long. Two genera, Pereskia and Pereskiopsis, do however retain large, non-succulent leaves 5–25 cm long, and non-succulent stems. Pereskia has

``` 3

now been determined to be the ancestral genus from which all other cacti evolved.[6] Enlarged stems carry out photosynthesis and store water. Unlike other succulents, the stem is the only part of many cacti where this takes place. Cacti often have a waxy coating on their stems to prevent water loss and potentially repel water from their stems. Because of the plants' high water-retention ability, detached parts of the plant can survive for long periods and then grow new roots from anywhere on the plant body when rain comes.

Many species of cactus have long, sharp spines.

The bodies of many cacti have become thickened during the course of evolution, and form water-retentive tissue that is in the optimal shape of a sphere or cylinder (combining highest possible volume with lowest possible surface area). By reducing its surface area, the body of the plant is also protected against excessive sunlight. The plant body itself is also capable of absorbing moisture (through the epidermis and the spines), which is especially important for plants that receive most of their moisture in the form of fog. Most cacti have a short growing season and long dormancy. For example, a fully-grown saguaro (Carnegiea gigantea) can absorb up to 3,000 liters of water in ten days. This is helped by the ability to form new roots quickly. Two hours after rain following a relatively long drought, root formation begins in response to the moisture. Apart from a few exceptions, an extensively ramified root system is formed, which spreads out beneath the surface. The salt concentration in the root cells is relatively high, so when moisture is encountered it is quickly absorbed.

``` 4

Cacti often have very shallow roots that spread out widely close to the surface to collect water, an adaptation to infrequent rains. In one case, a young saguaro only 12 cm tall had a root system covering an area 2 m in diameter, but with no roots more than 10 cm deep.[8] The larger columnar cacti also develop a taproot, primarily for anchoring, but also to reach deeper water supplies and mineral nutrients.[8] Areoles are unique features to cacti. The areole appears like a cushion with a diameter of up to 15 mm, and is formed by two opposing buds in the angles of a leaf[citation needed]. The upper bud develops into either a blossom or a side shoot, while the lower bud develops into spines. The two buds of the areoles can lie very close together or be separated by several cm. (Left) A fully-grown saguaro (Carnegiea gigantea) can absorb up to 3,000 liters of water in ten days.

Like other types of succulents, cacti reduce water loss through transpiration by Crassulacean acid metabolism (CAM). Here, transpiration does not take place during the day at the same time as photosynthesis, but at night. The plant stores the carbon dioxide, chemically linking it to malic acid, until nighttime. Because transpiration takes place during the cooler, more humid night hours, water loss through transpiration is significantly reduced. Reproductive ecology

Closeup image of a cactus flower (Echinopsis spachiana) showing large number of stamens. Some cactus flowers form long tubes (up to 30 cm) so only certain species of moths can reach the nectar, and therefore pollinate the blossoms. There are also specializations for species of bats, hummingbirds and bees.

``` 5

Blooming Echinopsis oxygona. The sweet-smelling flower opens towards evening and dies the following morning.[citation needed] The duration of flowering is highly variable. Some flowers, such as those of Selenicereus grandiflorus (Queen of the Night), are only fully open for two hours at night, while other species may flower for a whole week. Most cacti are self-incompatible, and thus require a pollinator. A few are autogamous and are able to pollinate themselves. Fraileas only open their flowers completely in exceptional circumstances; they mostly pollinate themselves or others with their flowers closed ("cleistogamy"). The flower itself has also undergone a further development: the ovary tends to be highly protected by thorns, hairs and scales. Seed formation is prolific, and the fruits are mostly fleshy, pleasant tasting and conspicuously colored. Goats, birds, ants, mice and bats may contribute to seed dispersal.

History Among the remains of the Aztec civilization, cactus-like plants can be found in pictorial representations, sculpture and drawings, with many depictions resembling Echinocactus grusonii. Tenochtitlan (the earlier name of Mexico City) means "place of the sacred cactus." The coat of arms of Mexico to this day shows an eagle perched on a cactus while holding a snake, an image which is at the center of the Aztec origin myth. (Left) Cultivated Notocactus warasii on display at the San Diego County Fair, California, USA

``` 6

Christopher Columbus brought the first melocactus to Europe Cultivation With few exceptions, the vast majority of cacti in habitat almost always are found growing in mineral based soils. Epiphytic cacti are the exception and prefer soils rich in organic materials, however, cacti in this group which prefer these types of soils produce healthier plants when allowed to dry completely between waterings. Some species of cacti such as Toumaya papyracantha (formerly Pediocactus papyracantha -- found in the high mesas of New Mexico) are mycorrhizal symbionts with the roots of various species of grasses[dubious – discuss] and grow underground on the roots of these wild grasses, only emerging above ground and initiating photosynthesis for sexual reproduction and flowering, forming deciduous cactus bodies that die back in winter or during droughts.

Prickly pear is one of the most common types of cacti found in North America The vast majority of commercial "cactus soil mixes" which contain organic materials are unsuitable for growing most terrestrial cacti, and many contain pumice, which exudes traces of heavy metals which will rot the roots of cacti if grown in these medium over a period of years. Surprisingly, most cacti prefer a mineral based soil cut with about half sand and allowed to dry out completely between waterings.

``` 7

Lobivia tiegeliana Astrophytum Super Kabuto

Although cacti are adapted to hot deserts and other xerophytic environments, most cacti evolved in mountainous areas and require moderate cold and/or cool night temperatures for some period of the year to initiate regular flowering. (Left) red flowers of Rebutia poecilantha

Overwatering of cacti is the single biggest cause of plant loss. Cacti are subject to Fusarium infections in their vascular cambium (the bundle of fibers and the "ring" inside the center of a cactus visible when cut in cross section) when overwatered or maintained in soils with high organic content[citation needed]. Fusarium mycelium typically grow into the cambium channels and plug up the plants transport system, causing tissue death and the classic rotting and collapsing observed when you overwater a cactus plant. Cacti are easy to grow if allowed to dry completely between waterings. Many species have specific periods of dormancy and should not be watered during these periods. Uses Cacti, cultivated by people worldwide, are a familiar sight as potted plants, houseplants or in ornamental gardens in warmer climates. They often form part of xeriphytic (dry) gardens in arid regions, or raised rockeries. Some countries, such as Australia, have water restrictions in many cities, so drought-resistant plants are increasing in popularity.

``` 8

Numerous species have entered widespread cultivation, including members of Echinopsis, Mammillaria and Cereus among others.

Escobaria minima

Escobaria wissmannii Oroya peruviana Cacti can be used for fencing material where there is a lack of either natural resources or financial means to construct a permanent fence. This is often seen in arid and warm

``` 9

climates, such as the Maasai Mara in Kenya. This is known as a cactus fence. Cactus fences are often used by homeowners and landscape architects for home security purposes. The sharp thorns of the cactus deter unauthorized persons from entering private properties, and may prevent break-ins if planted under windows and near drainpipes.

Many species of cacti have commercial uses; some cacti bear edible fruit, such as the prickly pear and Hylocereus, which produces dragon fruit or pitaya. The edible cactus, or nopal, industry in Mexico is worth $150 million each year and approximately 10,000 farmers cultivate the plant. Opuntia are also used as host plants for cochineal bugs in the cochineal dye industry in Central America. Particularly in South America dead pillar cacti can yield valuable wood for construction.

Rebutia pallida

Echinomastus durangensis Ferobergia hybride Some cacti are also of pharmaceutical significance. The peyote, Lophophora williamsii, is a well-known psychoactive agent used by Native Americans in the southwestern United States. Some species of Echinopsis also have psychoactive properties. For example, the San Pedro cactus, a common specimen found in many garden centers, is known to contain mescaline.

``` 10

Some species have become endangered in the wild because of overharvesting for sale as an ornamental plant. All cacti are covered by the Convention on International Trade in Endangered Species of Wild Fauna and Flora, and many species, by virtue of their inclusion in Appendix 1, are fully protected.

How to Grow Cactus A common misconception is that cacti require special care, as these plants are unique compared to conventional plants. But the truth is that cactus plants are popular for their low maintenance. Here are a few tips on how to grow cactus successfully...

Cactus plants are unique for their anatomical and physiological features. Most of them have fleshy stems and spines, but lack leaves. There are many types of cacti, which differ in the size and color. While some of the cactus plants sport leaves, some others lack spines. Usually, cactus plants denote those which have spines and succulent stems, but jungle cacti, which are natives to rainforests, lack these features.

They are very different in their appearance and growing conditions. Hence, it is important to understand the type of plant, before buying it or growing it. It should be taken care of as per the requirement of the particular species. In spite of all the misconception, cactus remains a very popular plant for both indoor and outdoor use. But there are still people who think that it is very difficult to take care of these plants. The fact is that growing cacti is very easy, as they require less care and maintenance.

Lobivia cinnabarina Lobivia peclardiana

``` 11

How to Grow Cactus? The popularity of cacti is attributed to their unique looks and low maintenance. These plants are available in a wide range of sizes and shapes, which can attract any person. If you are a plant lover, you too can grow cactus with the help of the following guidelines regarding how to grow cactus.

• The first step is the purchase of a cactus plant. Decide on the variety of the cactus plant you like and search for it in greenhouses and gardens. Make sure that you are buying a healthy plant of average size. If you go for very small ones, it may sometimes take years to grow to a standard size.

• Due care must be given while choosing a planting medium or soil for the cactus plants. Special potting soil, which is meant for these plants are available in the market. You can use that or make one by mixing coarse sand, peat and pearlite. Clay pots are the best option for cactus plants. The pot should be three to four times the size of the plant. Fill the pot with the planting medium, which should be dry.

• Refrain from watering for a week after the planting. During this time, the plant will be able to adjust to the new soil or planting medium. Avoidance of water during this time will prevent rotting of the roots. After one week, water the plant and repeat the watering weekly. During winters, watering should be restricted to once a month.

• Most of the cactus plants love sunlight, especially the ones with spines. They should be placed in direct sunlight. Others, which do not prefer sunlight, should be kept in shade. If the sun loving cactus are kept indoors, then place it near a heat lamp.

• Make it a point to check the plant for any unhealthy symptoms like drooping, or change of color. The problem can be over watering or deficiency of sunlight. Adjust these factors and see the difference.

Growing Jungle Cacti There are two types of cacti, the conventional ones with succulent stems and spines, which are suited for desert-like habitats, and the ones which are natives to the rainforests. Some plants of the latter category lack the features of conventional cacti and may look different. These cacti need a different medium to grow. A good potting mixture for such plants can be made by mixing 25% of orchid bark and same quantities of potting soil and peat with 20% pearlite and 5% coarse gravel. Water these plants once a week, or in very hot conditions, twice.

Mammillaria slevinii

``` 12

The Urban Gardener is an official electronic publication (in PDF Format) of the Plant Biotechnology Project, Research & Development Center, Rizal Technological University, Boni Avenue, Mandaluyong City, Philippines. It is published monthly. For more information, please inquire thru email: [email protected] or [email protected] and landline (+632) 534-8267 Local 135 or Fax (+632) 534-9710.

Edited by N.R. Bautista © April 2011

The Plant Biotechnology Project Committee is composed of: Alexander B. Quilang,

Norberto R. Bautista, & Jovita A. Anit.

These plants need the sun in the mornings and shade in the afternoons. Take care that this plant is not in full shade, full sun, morning shade or full afternoon sun. These conditions can prove detrimental to the health of the plant. There are some jungle cacti, which prefer full sun for their growth. So if you are selecting a jungle cacti, it will be better to study the growth conditions of the plant and then proceed. Cactus Plant Care Tips Even though this plant is touted as low maintenance plants, there is some information on cactus plants that can help you take care of your plant properly. The following are some tips regarding growing cactus plants.

• Adequate sunlight is very necessary for cactus plants. Keep indoor cacti on windowsills or other places, where they get sufficient sunlight.

• The pots in which they are planted should have good drainage, as water retention can cause rotting of the roots.

• Cactus plants that grow in a vertical direction need pots with a diameter of about half the length of the plant. If the plant has a horizontal growth, the diameter of the pot should be two inches more than the width of the plant.

• The golden rule regarding growing cactus is that you should not over water this plant. Water retention is fatal for the plant, as they may die due to rotting. Water the plant if the planting medium is absolutely dry.

Now you are ready to grow cactus plants. Start with the type you like the most and you will be surprised at how easy it is to grow cactus plants. You can gradually increase the number and variety of such plants in your house and add to the decor.