All living matter lives in water. More than 90 per cent L of the bulk of plants is water. Without continuous access to water there would be no plant growth. As a result, water becomes the limiting factor in our gardens. When and how much to water perplexes many gardeners.

In rearing orchids watering is no problem. It is subject to exact rules. The amount of water orchids should receive, and when, is prescribed by their root structure, botanical classification, and type of compost. This is the wonder of orchid culture. It is reducible to simple rules and practices.

The procedure to be followed in watering orchids can be summed up in four simple statements:

1. Don't overwater.

2. The composts of terrestrial and monopodial orchids are kept moist and not allowed to dry out.

3. The composts of sympodial orchids are dried out between waterings.

4. Watering increases in frequency and quantity as growth and roots develop and may decrease after flowering.

Orchids are killed by overwatering, never by an occasional lack of water. Excess water sogs composts and keeps orchid roots wet too long. They get soft, flabby, turn brown, and rot. The foliage often becomes pliable, wrinkles, and frequently falls off. This is particularly true of epiphytes, or most orchids if they are grown in osmunda. Overwatering is nothing but carelessness and ignorance, yet it is the common fault of beginners and even of more experienced growers.

A visual check may be made on epiphytal orchids. Their roots, when dry, are white in color. When surcharged with water the roots turn greenish. When they do not return to their original white condition between waterings, look out! Green roots, if that color remains, soon become sick roots. Usually there are several months between the warning and the rot; and an alert gardener should never allow a plant to reach the stage at which the foliage wrinkles and the plant dies.

The old English orchid growers had perhaps the most satisfactory approach to watering: never too little and never too much. They reduced the quantity of water to two tablespoons per day to each plant in a four-inch pot. They made it a point of honor not to let enough water accumulate to scum the outside of their pots. Scum, weeds, and moss in or on orchid pots are danger signs of overwatering; orchids are staying wet too long. Their results were not spectacular because, in part, they didn't give the plants enough water; only the top of the compost was moist, but their plants didn't die.

The idea, however, of a little water more or less continuously applied is the correct approach to watering terrestrial and monopodial orchids. In nature terrestrials and monopodials are rarely dry; sympodials, however, are accustomed to brief periods of dryness, and a day or two in a dry compost sometimes benefits them.

In culture, it is customary to water terrestrials and monopodials enough to moisten thoroughly but not to soak the compost. It is not wise, even though drainage may be perfect, to permit water to accumulate above the level of the compost. The second that water drips out of the bottom of the pot, stop; you have watered enough. Every few days check the compost until you have some idea of how long it takes for it to get nearly dry. Base on that your time schedule for watering. It will vary, of course. Water more frequently in summer, less often in winter; and no water on cold, damp, dark days.

It is easy to tell the degree of moisture in composts. Scratch the surface of a leafmold compost or thrust your finger into it. Wet leafmold is black, compact. As it dries out it becomes fluffy, brownish. The moisture content of osmunda is even easier to determine. Best test for osmunda still is the finger test. Push your index finger down into the compost along the inside of the pot. If the compost is cool, black, and moist there is enough water. If it is warm, powdery, and dry, add water. A few practice trials will familiarize you with the feel of the compost. Another trick is this: when water stands on the surface, the osmunda is dry; water penetrates quickly only when osmunda is moist all the way through.

The English rule—not too little, and not too much—is extraordinarily well suited to sympodial orchids. They, above all others, suffer quickly and irreparably from over-watering. Their roots, unconfined in nature, react unfavorably to the cultural necessity of being tucked into clay pots. You will find that their roots tend to reach out of the pots and over the sides, particularly if the compost is too wet and humidity too high. It is debatable among orchidists whether to leave these free roots alone, to cut them off, or to put them back on the surface of the compost. Most commercial growers try to confine the roots only when repotting, although there is nothing you can do about Vanda coerulea and similar monopodial orchids that develop aerial roots. They are not unlikely to have more roots out of the compost than in it.

Often epiphytal orchids fail to develop the abundant roots typical of native plants. The few roots produced in pot culture must be made to do the work of the many that failed to grow. Sympodial tree orchids, therefore, must be treated considerately. Water should be applied to the pots slowly until it dribbles from the drainage holes, then no more. A week to ten days may elapse before another watering becomes necessary. That depends on the dryness of the osmunda. Before watering again, make the finger test for dryness. When the osmunda is dry—definitely dry, not questionably so—water again. It may be said that this drying-out period for pseudobulbous tree orchids is next in importance to their demand for atmospheric moisture. Allowing the osmunda to dry supplies roots with enough air to prevent rotting. It helps, also, to force the extra roots so essential to support growth. Balancing the ratio between roots, air, compost, and water is the cultivator's method of simulating nature.

From the beginning of orchid culture until the present the corollary that watering increases as growth increases, decreases as orchids become dormant, has been followed blindly by many English and American amateurs.

Although it was once believed that all dormant orchids needed little, if any, water, it has been demonstrated in laboratories that most orchids are never truly dormant. Continuously maintained warmth and humidity nearly always stimulates continuous growth. But some species flower only once a year no matter what is done to stimulate them. Others flower several times a year in culture. Some hybrids, cattleyas particularly, have no definite blooming season, renewing their growth and blooming as often as three times a year. They haven't time to be dormant.

The only truly dormant orchids are the deciduous, particularly those with tubers or corms such as Bletia hyacinthina or Disa grandiflora. The rest period, as dormancy is called, is the reaction of orchids to the harsh conditions of nature. It is their method of self-protection. The old or-chidists believed that dormancy was a necessary forerunner of flower development, and they withheld water in an attempt to ripen and harden pseudobulbs. The results were not always satisfactory. Orchid pseudobulbs most often can be ripened better by adjusting temperature and light. High temperatures produce growth; low temperatures and abundant light ripen and harden growth.

If an orchid has leaves and roots, it will transpire water at nearly the same rate when at rest as when actively growing. Since such orchids never stop transpiring, their water requirement doesn't vary materially. The only case in which the rule: "Watering increases or decreases with the growth," applies is for deciduous orchids—those which lose their foliage and roots. Water to them, when dormant, is useless excess that makes the compost soggy. Such dormant orchids, like propagations, should be kept barely moist until growth commences and roots appear. A little water added occasionally will help the roots struggle out farther and begin burying themselves in the compost. As the roots lengthen, watering is increased. Since you can't follow the progress of the roots, the growing lead is the visible indication of water requirements. New growth will be six or eight inches high before water is again applied in amounts sufficient to wet the compost thoroughly. This is continued until the symptoms of dormancy again appear and less water is given.

Incidentally, the practice of barely moistening the compost when orchids were in bloom was, also, once thought to be the only method of hardening flowers and making them last longer. This is now more easily and healthfully accomplished by removing flowering plants to a cooler, drier atmosphere.

There is a debate—now a hundred years old—on the ideal water for orchids. Rain water only, insist the English growers, because rain water contains no alkaline impurities that may be injurious. But rain water is difficult to collect in many areas and is unhandy to store much more than two months.

Many American growers use ordinary tap water if chemical analysis does not show too high an alkalinity. Water for orchids should be neutral or acid. Unfortunately, most of the tap water in the United States, except for some eastern and northwestern areas, has too high an alkaline content, which must be decreased in some way for orchids. A few commercial growers and amateurs have installed water softeners which relieve them of work and worry. The rest of us must use less costly means. Three to four drops of concentrated, technical grade, phosphoric acid to each quart of tap water will make it suitable for orchids. Don't use sulphuric acid; it's too dangerous to handle—nor hydrochloric acid; it often is injurious to plants.

Your local water bureau can tell you whether or not the tap water in your city has a high or low alkaline content. But if you like to experiment you can make your own chemical tests. This is a good practice besides being fun. It gives you more accurate control of the condition of your water; it also helps you to determine if the compost is suitable for your orchids.

The measure of alkalinity or acidity is called the "pH" (potential hydrogen ion concentration), and a scale is used to determine the degree of pH. Numbers from 1.0 to 7.0 indicate excessive acidity to a neutral condition. From 7.0 to 14.0 the numbers indicate increasing alkalinity. Most orchids require a pH between 4.5 and 5.6—definitely acid— although, Cypripedium bellatulum is most successfully grown in neutral (7.0) to mildly alkaline (8.6) composts.

You can buy pH kits for a reasonable price in many garden stores. Usually they will be colorimetric, graduated hues indicating the degree of pH. Other methods may utilize chemically impregnated strips of paper which are sufficiently accurate for most general tests. Directions for making tests always are included in the kits. With such equipment you can test your water supply before and after you condition it, making absolutely certain that it is at the correct pH for your plants. You also can test your composts. If you pour distilled water through freshly potted osmunda, and collect it in clean containers and test it, it will have a pH of about 4.8. When osmunda has decayed too much and the plants need repotting, distilled water poured through it tests about 5.6 or higher.

A peculiarity of orchids is that they do better if the water given them is not cold. Cold water applied to roots or sprayed on foliage may stun orchids, temporarily hindering growth. Equatorial rain may be heavy, but it is slightly on the tepid side, not cold. Tree orchids are accustomed to this and adjust with difficulty to colder water. Terrestrials adjust more easily. In the milder sections of America the temperature of the water is not of great consequence. In cold regions water may have to be stored in large jars for a few days at room temperature before using.

While most orchids in captivity are benefited by syringing with water, if foliage is sprayed on a cold day with cold water rots may develop. Water on some new growth may damage it, even in warm weather. Water on the wide, succulent leaves of some warm monopodials (phalaenopsis) may produce rots. Make it a practice not to let water touch new growth; make it a practice not to spray foliage unless the day is dry, warm, and clear; spray preferably in late morning or middle of the afternoon—never in the evening. Of course, in home culture where windows or cases may be used for growing orchids, the too frequently dry air of a house makes it necessary to syringe foliage on all possible occasions except the worst dark, cold, miserable days. Be careful; water is as dangerous to orchids as it is valuable.

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