Light and Lighting

Today we will learn about the light and lighting which is one of the most important factors for plants. They use light in the photosynthesis process which is the synthesis of glucose from sunlight, carbon dioxide and water, with oxygen as a waste product. Nearly all life depends on it. It may not look easy to understand but not too difficult to do it. (Actually, I'm not good about science but I've tried to remind the knowledge in science subject that I learnt in high school 555) When you understand the basic of light and lighting, it will help you to recognize how and where to put your plants to be in the right place for them and arrange the articiail light in the necessary case.

Light is composed of mass-less particles ( photons ) moving at a high speed (300 000 000 metres per second ). In one millionth of a second (1 microsecond) light travels 300 metres. The energy carried by the particles determines their colour (wavelength).

violet = high energy blue green yellow red = low energy

We see wavelengths between 400 and 700 nanometers, although the sensitivity of the eye is poor at these limits and more sensitive to the mid-range wavelengths. Most light sources produce a mixture of wavelengths, that we interpret as a particular colour. Different mixtures of wavelengths can produce a perception of identical colours. Light intensity is often mis-understood because of the adaptability of the human eye to a range of lighting conditions. A typical well-lit office environment has about 2000 lux at desk-top level. By contrast, direct sunlight provides at least 8000 lux, more in the tropics where many cacti and succulents originate.

Plants need both red and blue light for photosynthesis. Green light is not used or absorbed, which is why most foliage looks green in sunlight. Plants are frequently seen with leaves of a variety of other colours from shades of red, purple through to black. These colours are caused by other pigments. These pigments are incidental to photosynthesis, but may well only be produced in plants grown in the strongest light especially with a high blue and ultraviolet content.

Red light is very important to plant reproduction. Photochrome pigments absorb the red and far red portions of the light spectrum and regulate seed germination, root development, tuber and bulb formation, dormancy, flowering and fruit production. Therefore, red light is essential for stimulation of flowering and fruiting.

Blue light stimulates chlorophyll production more than any other colour, encouraging thick leaves, strong stems and compact vegetative growth. Carotenoids, the yellow-orange pigment in plants, absorb blue light and control leaf fall and fruit ripening.

Light Sources

• Sunlight colour temperature of about 6000oK is probably the best type of light that you can give your plants for healthy growth, good leaf colour and flowering. Plants have evolved and adapted to the natural light found in their habitat. Natural sunlight has the great advantage of being free, and generates no greenhouse gases. However, the quantity, and to some extent quality, of sunlight on offer depends on the vagaries of climate, lattitude and time of year. Another negative aspect of sunlight is that a sudden burst of sunshine after the dark winter months can lead to scorch and scarring of plant bodies. This can largely be obviated by good ventilation and timely use of shading.
• Tungsten filament lamps, the commonest domestic type of lamp, produce yellowish-white light with a colour temperature of 2750 - 2850°K and a lot of infra-red. The bulbs are cheap but a relatively inefficient method of lighting and unsuitable for high intensity lighting of large areas. Plant growth is "soft" and elongated.
• Quartz halogen lamps produce a clean white light, at a colour temperature of about 3500°K. There is also considerable production of infra-red in the form of radiant heat which, at close range, may scorch foliage and other delicate materials. It is inadvisable to stare at unfiltered quartz halogen lamps as their high filament brightness, heat and ultraviolet emission may cause eye-damage. Quartz halogen lamps are relatively cheap and require no special starter circuits. However, although their higher filament temperature makes them more efficient than ordinary tungsten filament lamps, they are relatively expensive to run compared with the modern discharge lamps mentioned below.
• Metal Halide (HID) lamps produce an intense bluish-white light, at a colour temperature of 5000-6500°K similar to sunlight, and are one of the most efficient ways of lighting large areas. The compact nature of the arc makes it easy to focus the light on a specific area. Plants grow well with compact growth under HID, but it lacks the red required for flowering. Special starter circuits are required. Check that lamps will operate in a horizonal position if this is required.
• Sodium vapour lamps as often used for street lighting produce almost monochromatic yellow light at 589nm from a low pressure discharge in Sodium vapour. These lamps are efficient but lack of red and blue wavelengths make them less suitable for plant growth. Special starter circuits are required.
• High pressure sodium lamps produce an intense pinkish-white light with a colour temperature of 2050°K from an arc discharge in high pressure sodium vapour and are an efficient way of lighting large areas. Plants grow well under this light, but the colour cast may reduce acceptability for decorative illumination. Versions producing more blue light are available to promote compact vegetative growth, but this is not needed if the lamps are used to augment natural daylight which provides sufficient blue light.
• Fluorescent tubes rely on a low-pressure discharge in a mixture of argon and mercury vapour to produce a line spectrum. Ultraviolet light from the discharge excites the phosphor coating on the inside of the glass envelope. Tubes coated with phosphors designed to emit warm white 2700 - 3000°K, cool white 4100 - 4300°K or "daylight" 5000K to 6350°K light are available as well as specialised phosphors designed for optimal use with plants or fish tanks. Fluorescent tubes are moderately efficient to run and suitable for use in a small growing space. Special starter circuits are required but these are freely available in hardware stores.
• Light Emitting Diodes (LED's) are efficient light emitters, available in a wide range of colours. White LED's are really blue LEDs coated in green and red-emitting phosphors which can be adjusted to produce a cool or warm white output. As the prices of these fall they will become more cost effective for illuminating growing spaces or for spotlighting individual plants. LED's produce very little heat so will not scorch foliage.Ultraviolet LEDs are becoming available and could conceivably be added to banks of white LEDs to simulate intense sunlight and develop the strikingly coloured foliage seen in plants from the tropics and high mountains.

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Pachypodium

I think person who likes cactus should not miss Pachypodium because it's a succulent plant and has a lovely and amazing form. Besides, its species are so various and the way to take care of them is not different from one of cacti or succulent. I falled in love with Pachypodium for a while but I don't have it much in my plant collection. I think I will keep it more and here is the brief information about Pachypodium and its sample picture of some species.

Pachypodium is a plant genus that belongs to the dogbane family, Apocynaceae. Pachypodium comes from Greek "pachy" (thick) and "podium" (foot), hence meaning thick-footed.

The pachycaule trunk is a morphologically enlarged trunk that stores water so as to survive seasonal drought or intemitent periods. Whereas there is great variation in the habit of the plant body, all Pachypodium exhibit pachycaul growth. Variation in habit can range from dwarf flattened plants to bottle shaped shrubs to dendroid-shaped trees.

The second general characteristic of Pachypodium is to have spines. The spines come clustered in either pairs or triplets with these clusters often arranged in rings or whorls around the trunk. Spines emerge with leaves, and like leaves grow for a short period before stopping growth and hardending. Spines do not regenerate so weathering and abrasion can wear away all but the youngest spines from older specimens - leaving smooth trunks and branches.

To some extent, branches are a characteristic of the genus. Some caution is warranted in over-generalizing this characteristic. Pachypodium namaquanum is often branchless. Pachypodium brevicaule has no clear branches, and indeed may have evolved an alternative to branching in the form of nodes from which leaves, spines, and inflorescences emerge. In general Pachypodium have few branches. Since the environmental stresses and factors that contribute to branching can vary widely even in small areas, individual plants of the same species exhibit wide variation in branching morphology.

Morpholigically, Pachypodium can be highly flexible in organization. Branching, if present at all, can be from the base either of the plant or at the crown. Freeform branching is a morphological adaptation to factors of the immediate microenvironment which, by their diversity, account for the wide range of habits:

• flattened dwarf species less than 8 cm tall but reaching 40cm in diameter

• bottle- or oval-shaped shrubs to 4 m tall
• both branching and unbranched cigar- and cactus-like trees to 5m tall.

Despite microenvironmental variation, Pachypodium are always succulent and always exhibit pachycaul trunks. Pachypodium are usually spinescent, but individual variation in spinescence as well as weathering/abrasion can result is plants with few if any spines.

Pachypodium trunks and branches are normally thickened with water-storing tissue. Plants must relie on the food and water stored in their thickened trunks during seasonal drought when leaves have been shed and no water is available from the substrate. In addition to the lower surface-to-volume ratio which aides in water retention, the thickened trunks and branches can also possess photosynthetic surface tissue to allow nutrient synthesis even when leaves are not present.

They should not be mistaken for roots, because the enlargement occurs above the point where the roots branch off the main axis of the trunk.

Pachypodium make use of spinescence as an adaptive mechanism responding to the landscape. Adaptively this spinescence is employed to different degree in various species to collect moisture from fogs and dews. The degree of spinescence demonstrates the degree to which species rely on spines as a means to collect moisture from microclimate conditions, such as localized dews or fogs within microenvironments, and drip to the soil immediately below the spine on a branch or branchlet.

In elevation, Pachypodium in both mainland Africa and Madagascar grow between an altitude of sea level, where some species grow in sand dunes, such as Pachypodium geayi, to 1600 m (5200 feet) for Pachypodium lealii in southern Africa and 1900 m (6200 feet) for Pachypodium brevicaule in Madagascar.

In continental southern Africa, the extreme temperatures range from -10 °C (14 °F) in some locations to as much as 45 °C (113 °F). Whereas in Madagascar, with not such a great temperature amplitude, the temperature ranges from -6 °C (21 °F) to 40 °C (104 °F).
A generalization about precipitation regimes for both southern Africa and Madagascar does not have much meaning because the habitats of Pachypodium vary so greatly with a moisture regime. A precipitation regime for a species of Pachypodium, therefore, depends upon a habitat's location relative to the influences of the Atlantic and Indian Oceans and the various mountain ranges of southern continental Africa and of Madagascar.

Watering for Cacti and Succulent

The last article relates to watering plant. It can give you an idea when and how often to give water to your plant and shrub, recently repotted one, grass and etc.

Today, it's time to learn watering to the lovely cactus and succulent. They needs the different ways to water them and that is one of the most important secret of these plant to grow up.

Normally, I water my cactus 3-4 days/time. It depends on the season and temperature. In summer, I may give them water more often than in winter because it is warm and the plants usually grow up in summer also they need more water.

Cacti, agaves, aloes, sedums and other succulents have special abilities when it comes to storing and utilizing water. To one degree or another, they all have thick, fleshy, water-storing leaves and, or stems. Surfaces exposed to the drying effects of sun and wind are small in proportion to their total mass. This is especially evident in plants like saguaro and barrel cacti. Thick waxy cuticle layers on outer surfaces help seal in moisture. And a smaller than normal number of pore openings in leaves and stems further restrict moisture loss.

When cactus are not getting enough water, their outer skin begins to wrinkle. This is caused by the shrinkage of water-storing tissues in the plant. In the case of segmented cacti, like prickly pear and cholla, the outer pads or segments may also begin falling off. Lack of sufficient moisture in leafy succulents will result in wilting. As water levels in plants such as agave and aloe drop, so does the internal water pressure holding the leaves straight. As a result, leaves begin to bend downward.

Cacti and succulents showing signs of moisture stress can be revived by providing them with a good soaking of water. Keep in mind that the roots of these plants are shallow and widespread, extending out a distance several times their height. Therefore, watering a large area out from the plant, but only a foot or so deep is best. A soaker hose works well for this purpose.
Watering cacti and succulents when they show signs of stress is the way to ensure their survival. However, if you want your cacti and other succulents to thrive, some regular watering will be necessary.

The easiest way to gauge whether or not it's time to water is to stick your finger in the top 1/2 inch of soil. If the soil is dry, go ahead and water. If it's not, wait! Don't let your Cactus go too long without water. If the stem segments are shriveled and the soil is dry, it is probably in need of water. Be careful! If the plant is over watered, the stems will also look shriveled, but the soil will be damp. If this is the case, do not give it more water. An over-watered plant will start to turn yellowish, then get more and more mushy and dark reddish-brown like a rotten apple. This is because the cells took in so much water they broke and are now dead and rotting. This usually happens from the ends first. This will continue even after you stop watering too much, but often you will have enough plant left to start over.

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Watering Plants

Watering home landscape and garden plants properly is one of the most misunderstood problems facing the average gardener. If landscape plants are water stressed during the summer, they may experience severe problems during the rest of the year, such as increased insect and disease susceptibility and decreased winter hardiness.

Water loss from the soil

There are several ways in which water is lost from the soil. Rain, melted snow, or water applied by the gardener may percolate through the soil beyond the root zone. This water is useless to growing plants.

Transpiration is the process by which a plant loses water through its leaves. This is a necessary process for plant growth. A large tree may lose hundreds of gallons of water a day in the summer. Water lost from the soil by evaporation and transpiration must be replaced by precipitation or irrigation.

Soil-Water-Air relationships

Establishing the correct water-air relationships in the soil is essential for the best growth of all plant types. Oxygen in the soil is necessary for plants to grow. Watering too often or too much is likely to exclude the necessary oxygen from the soil pore spaces. Without enough oxygen, plant roots suffocate and die. Plant parts above ground exhibit symptoms of this stress: wilting, yellowing, and drying foliage, leaf drop and twig dieback may all occur. Constant overwatering kills most plants.

Too little water does not allow the roots to replace water lost by the plant through transpiration. The roots may dry up and die, and the top growth begins to show abnormal symptoms.

In both cases, either too much or too little water, the plant suffers from lack of moisture in its tissues.

Heavy clay soils are much more likely to be overwatered than light soils. Conversely, light sandy soils are drought susceptible and tend not to be watered enough. Although light soil allow deeper and quicker water penetration, they dry out more rapidly because they hold less water. Heavy soils, on the other hand, are slower to allow penetration but also dry out much more slowly.

It is essential that gardeners become familiar with how long it takes the root zones of the various plants in their gardens to become completely moistened, and then, how deeply they can allow the soil to dry before the plants begin to show stress and need rewatering. It is also necessary to understand that quick, light sprinkling will not do the job of wetting the entire root zone.

Organic matter Soils to which organic matter has been added will behave differently. For example, clay soils with added organic matter will accept water more quickly. Organically amended sandy soils hold water longer, and consequently do not need to be irrigated as frequently.

Compaction and thatch Water cannot soak into compacted soils, or soils overlaid with a thatch accumulation, particularly if water is applied too quickly. For compacted or thatch-choked areas, or possibly under the canopy of trees and shrubs, the best treatment is to aerate the soil by removing plugs. Mulches around trees and shrubs help restructure the surface layer of compacted soils to allow more efficient penetration of water.



Plants in containers need special attention. Both volume of soil and total water available for plant use are limited. These plants have to be watered more often than plants growing in the ground. Watering should begin when the soil surface feels dry to the touch, but not before. Frequency and amount of water depend on media, location, amount of sun, temperature, type of plant, etc. Containers which have been allowed to completely dry out may need to be soaked in water to rewet the soil.

A plant which uses a lot of water, such as Fuschias, or one that is potbound, may have to be watered daily or several times a day. But for most container grown plants, a thorough watering once or twice a week will be sufficient. Plants in plastic or solid containers will have to be watered less often than plants in porous containers or clay pots. Be very careful not to keep the root system constantly soaking wet. Pathological (disease) problems will occur if air is excluded from the soil.

Trees, shrubs, and landscape plants should be watered just inside and outside the dripline, or outer edge of the plant. In foundation or border plantings, it may be more convenient to water the entire area. A hose, soaker hose, or various kinds of sprinklers are commonly used.

A dished- or berm-enclosed area constructed around the base of a tree or shrub may be filled with water. This allows for slow percolation into the root zone. However, on heavier soils during the rainy season or in the winter, these basin rims are best removed to avoid concentrating too much water.

Shrubs and trees near house foundations, under eaves, have to be watered more frequently. They may get little water from precipitation, and reflected heat from walls leads to increased water and heat stress.

Capillary action can cause dissolved salts to be carried from moist zones into the dry soil under eaves. A salt concentration is then left behind as the water evaporates. Thorough leaching of such areas may occasionally be necessary, particularly in the drier regions of the state, to remove salt buildup.

Recently transplanted woody plants need special attention. The soils in which balled and burlapped and containerized plants have grown are often radically different than the soils into which they are planted in the home landscape. When this occurs, interfaces are created between the original nursery soil and the soil at the new site. Because of these interfaces, water does not move readily between the different media. Therefore, it is most important that water be applied to both the nursery soil and the surrounding soil during the critical establishment period. Roots grow only where there is moisture, and unless both media are moist the roots may never grow out of the original nursery soil. Plants in such a situation may ultimately girdle themselves and die.

Many native woody plants should not receive summer watering. Once they are established, they are drought tolerant in the summer, and some may be damaged by moisture at this time. It is especially important to keep water away from the crowns and larger roots of madronas and western dogwood in western Washington. They often succumb to root rot problems with summer watering. Avoid planting moisture demanding plants underneath them.

Other drought tolerant shrubs and trees also do not need to be watered. For lists of drought tolerant shrubs and trees, a good reference work should be consulted. Many plants in the following genera have proven themselves drought resistant: Caragana, Ceanothus, Cotoneaster, Cytisus, Eleagnus, Genista, Juniperus, Koelreuteria, Pinus, Quercus, and Robinia. There are also many more.

Lawns are best watered by overhead sprinklers. The deeper the wetting, the deeper the roots will grow. Deep-rooted grass plants are much healthier and better able to withstand drought stress.

Grass should be watered when the soil begins to dry out, but before the plants actually begin to wilt, and certainly before they begin to desiccate. Grass should be irrigated when it begins to be less resilient and springy and does not bounce back up after being walked on. The amount of water to wet the root zone is determined by soil type, amount of thatch accumulation, and several other variables. To determine when a sprinkler has put out an inch of water, or any specific quantity, simply use several coffee cans or jars spaced at intervals from the sprinkler itself to the edge of the watering pattern.

Important factors to remember

• Frequent, shallow waterings lead to shallow roots. Shallow roots lead to more rapid stress under drought or hot conditions.
• Too much water is as bad as, or worse than, too little. Rate of water application should be no more rapid than the rate at which the soil can absorb it.
• Fertilizer spread around plants (including lawns) does absolutely no good at all unless it is dissolved in water. Therefore, fertilizers have to be watered in, and soils have to be moist to get the full effect of the fertilizer application.

Madagascar Climate

In the last articles, I mentioned about South Africa climate and here is about the Madagascar climate. I see that many cacti come from there orginially especially Pachypodium also I think this information should be helpful, too.

Madagascar has three main plateaus. The highest point on the island is the ridge of Androna, which is a volcano rising 9,439 feet. There are also three main river basins. The coastline is straight and has sand dunes and mangrove swamps on the southeastern side and estuaries and bays on the northwestern side.

Madagascar is an island off Africa's southeast coast. It is the fourth largest island in the world. It is in the Indian Ocean and is separated from Africa by the 500 mile wide Mozambique Channel.

There are really only two seasons in Madagascar: wet and dry. The hot, wet season lasts from November to April, and the cooler, drier season lasts from May to October. July is the coolest month, having temperatures between 54 and 77 F degrees (12-25 celsius). December is the hottest month with temperatures between 68 and 82 F degrees (20-27 celsius)

Plant Fertilizer Why does the plant need it?

In order for a plant to grow and thrive, it needs a number of different chemical elements. All plants need the same main nutrition for their growth. The most important are:

• Carbon, hydrogen and oxygen - Available from air and water and therefore in plentiful supply


• Nitrogen, phosphorus, potassium (a.k.a. potash) - The three macronutrients and the three elements you find in most packaged fertilizers


• Sulfur, calcium, and magnesium - Secondary nutrients


• Boron, cobalt, copper, iron, manganese, molybdenum and zinc - Micronutrients The most important of these (the ones that are needed in the largest quantity by a plant) are nitrogen, phosphorus and potassium.

Every amino acid contains nitrogen.
Every molecule making up every cell's membrane contains phosphorous (the membrane molecules are called phospholipids), and so does every molecule of ATP (the main energy source of all cells).
Potassium makes up 1 percent to 2 percent of the weight of any plant and, as an ion in cells, is essential to metabolism. Without nitrogen, phosphorus and potassium, the plant simply cannot grow because it cannot make the pieces it needs. It's like a car factory running out of steel or a road crew running out of asphalt.

If any of the macronutrients are missing or hard to obtain from the soil, this will limit the growth rate for the plant. In nature, the nitrogen, phosphorous and potassium often come from the decay of plants that have died. In the case of nitrogen, the recycling of nitrogen from dead to living plants is often the only source of nitrogen in the soil.

To make plants grow faster, what you need to do is supply the elements that the plants need in readily available forms. That is the goal of fertilizer. Most fertilizers supply just nitrogen, phosphorus and potassium because the other chemicals are needed in much lower quantities and are generally available in most soils. Nitrogen, phosphorus and potassium availability is the big limit to growth.

The numbers on a bag of fertilizer tell you the percentages of available nitrogen, phosphorus and potassium found in the bag. So 12-8-10 fertilizer has 12-percent nitrogen, 8-percent phosphorous and 10-percent potassium. In a 100-pound bag, therefore, 12 pounds is nitrogen, 8 pounds is phosphorous and 10 pounds is potassium. The other 70 pounds is known as ballast and has no value to the plants.

So why don't people need fertilizer to grow? Because we get everything we need from the plants we eat or from the meat of animals that ate plants. Plants are factories that do all of the work to process the basic elements of life and make them available to us.

Cactus Diseases

Although we take care of our cacti carefully, it is perfectly sure that our plant will not have any diseases. And when they happen, it will be a serious problem because it can cause the plant die if we don't know how to deal with the disease properly. Today I also give you information of some diseases that always see.




Bud drop: The premature dropping of flower buds. The cause of this problem is primarily environmental. Temperature fluctuation due to drafts is commonly seen as a cause. Bud drop can also be caused by the lack of or excess water and changing light levels. In Christmas cacti, a lack of potassium or an excess of nitrogen can also cause this problem. Sometimes buds fall off a cactus simply because the plant has too many blossoms. Rough handling or turning a plant also will cause buds to abort.It is important to maintain the care that a flowering cactus is used to when it is in bud. Resist moving your cactus to another site if it has buds or open flowers.

Corky scab: Brown, irregular spots developing in older parts of a stem. Most of the spots affect the epidermis of the plant only, so, damage is superficial and only affects the appearance of the plant. More severe or widespread attacks can destroy entire shoots or decrease flower production. Corky scab is normally the result of poor cultivation (i.e. overwatering, poor ventilation).To control, increase light exposure and decrease humidity. The prickly pear (Opuntia sp.) are particularly prone to corky scab.

Etiolation: The abnormal elongation of cactus stems due to insufficient light. Stems may be pale or yellow with unusual spine characteristics. Commonly seen in plants taken from a commercial nursery into a dimly-lit retail environment. This may also occur if a cactus is fertilized while in its normal Winter dormancy period.

To correct etiolation, move the cactus into stronger light. While this will prevent further etiolation, the spindly elongated section of stem will remain as proof of improper care. You may also choose to prune the etiolated stem back to the healthy part; this acts to promote the growth of 'perfectly-shaped' offshoots or stems that may be removed and re-planted.

Rot: Rot is caused by microorganisms: fungi and bacteria. It may affect the roots, stem, and/or the crown of the plant. Typically, the diseased tissue takes on a watery, slimy, soft, and blackened appearance. Damage often starts at the base of the plant and progresses to the top. Plants start to lean, then often collapse and die.

Overwatering, particularly in cold weather when cacti are dormant, is the chief cause of the problem. Cold temperature and plant wounds exasperate the problem.

In theory, rot in its early stages may be checked by moving plant to a dry, temperate environment. It has been our experience that once you spot rot it is already progressed past its early stages. If rot is above ground, cut out the diseased portion of the plant with a sharp knife and dust the wound with a fungicide. In many cases, the top of the plant appears healthy above a rotten base. This healthy top may be cut off, allowed to dry, and then re-rooted in a sandy medium. Remove and destroy infected plants and/or plant parts.

Proper cultural practices help to prevent rot. Sterilizing the potting media and placing a layer of gravel on top of the soil will kill or reduce bacterial damage. Water plants early in the day and avoid spreading disease by splashing water from one infected plant to a healthy plant. In Winter, the normal dormancy period for most cacti, water sparingly.

Sunburn: A change in the appearance in the plant due to too much exposure to the sun. The entire plant epidermis will turn a whitish, yellowish or reddish-brown color. In extreme cases, a
sunburned plant may become sensitive to other diseases.

As mentioned, this disease is caused by too much light exposure. Typically, this occurs when rapidly bringing plants used to artificial light into intense natural light. Epiphytic cacti and seedlings are especially sensitive to sunburn. To prevent, a cactus should be gradually introduced to more light over a period of time. Plants should be placed into the shade, then into partial sun, and finally into full sun; this process may take one month. If you notice signs of sunburn, move the plant temporarily back into the shade. Also, sunburn is exasperated by hot weather and lack of water, so, make sure the plant is properly watered.

South Africa Climate

As many cactus have origin in South Africa, their growth depends on the same weather according their root. The climate in South Africa is different from another part of the world. Therefore, it is good and useful to learn about it also we can know how to take care of our plant properly.

Climatic conditions generally range from Mediterranean in the southwestern corner of the country to temperate in the interior plateau, and subtropical in the northeast. A small area in the northwest has a desert climate. Most of the country has warm, sunny days and cool nights. Rainfall generally occurs during summer (November through March), although in the southwest, around the Cape of Good Hope, rainfall often occurs in winter (June through August). Temperatures are influenced by variations in elevation, terrain, and ocean currents more than latitude.

Temperature and rainfall patterns vary in response to the movement of a high-pressure belt that circles the globe between 25ฐ and 30ฐ south latitude during the winter and low-pressure systems that occur during summer. There is very little difference in average temperatures from south to north, however, in part because the inland plateau rises slightly in the northeast. For example, the average annual temperature in Cape Town is 17ฐC, and in Pretoria, 17.5ฐC, although these cities are separated by almost ten degrees of latitude. Maximum temperatures often exceed 32ฐC in the summer, and reach 38ฐC in some areas of the far north. The country's highest recorded temperatures, close to 48ฐC, have occurred in both the Northern Cape and Mpumalanga (formerly Eastern Transvaal).

Frost occurs in high altitudes during the winter months. The coldest temperatures have been recorded about 250 kilometers northeast of Cape Town, where the average annual minimum temperature is -6.1ฐC.

Climatic conditions vary noticeably between east and west, largely in response to the warm Agulhas ocean current, which sweeps southward along the Indian Ocean coastline in the east for several months of the year, and the cold Benguela current, which sweeps northward along the Atlantic Ocean coastline in the west. Air temperatures in Durban, on the Indian Ocean, average nearly 6ฐC warmer than temperatures at the same latitude on the Atlantic Ocean coast. The effects of these two currents can be seen even at the narrow peninsula of the Cape of Good Hope, where water temperatures average 4ฐC higher on the east side than on the west.

Rainfall varies considerably from west to east. In the northwest, annual rainfall often remains below 200 millimeters. Much of the eastern Highveld, in contrast, receives 500 millimeters to 900 millimeters of rainfall per year; occasionally, rainfall there exceeds 2,000 millimeters. A large area of the center of the country receives about 400 millimeters of rain, on average, and there are wide variations closer to the coast. The 400-millimeter "rainfall line" has been significant because land east of the rainfall line is generally suitable for growing crops, and land west of the rainfall line, only for livestock grazing or crop cultivation on irrigated land