Evergreens, such as yuccas and pines, resist desiccation because their leaves have a tough cuticle and so do not lose water rapidly when exposed to wind and sun. Some plants lose all or many of their leaves and exist through the times of stress entirely or mainly by virtue of the tenacity of life of their underground parts. In many cases these parts are fat and swollen and serve as storage organs for elaborated food materials and for water. Such organs the gardener calls "bulbs."
The chief regions in which bulbs occur naturally are those that have a "Mediterranean" climate-where an extended dry warm period alternates with a moist warm period, areas such as the steppes of Russia, where a cold winter is succeeded by a short growing season and that in turn by a hot dry period, and the woodlands of temperate regions, where winters are cold and summers reasonably moist. This last-named locale permits a short spring growing season before the overhead canopy becomes too dense to admit sufficient light and before the roots of the trees become so active that they absorb most available moisture and keep the soil about the bulbs much drier than might be supposed. California, Mexico, South Africa, and the Mediterranean region and its eastward extensions are all regions where bulbous plants abound naturally; most are sun-lovers. In eastern North America, central and northern Europe, and parts, of eastern Asia a considerable selection of chiefly woodland bulbs have their homes; the majority of these are shade-lovers.
Most soils in which bulbs grow naturally are dry or definitely dryish during those periods when the top and root growth of the bulbs is inactive, that is, when the bulbs are at rest. There are just enough exceptions to validate this rule-a few swamp lilies, the lesser celandine, and certain camassias, for example, grow in soils that are always moist. In the long evolutionary development of plant life these may represent dry-region species that have invaded humid soils and have not yet lost the organs that served them well in droughty areas.
Care in handling bulbs
There are some important general principles to be observed in the cultivation of bulbs. Because they are fleshy they must be handled carefully to avoid physical injury. When lifting bulbs and when digging and cultivating among mixed plantings of which they form a part they are easily mashed, punctured, and scraped unless particular care is taken to prevent this. Any wound provides easy access for disease and encourages decay, which may spread rapidly to kill the entire plant. A spading fork is the safest tool to employ for lifting bulbs; if a spade is used too many are apt to be sliced. By marking with stakes or in other appropriate fashion the locations of bulbs planted in areas where soil operations are likely to be carried out during times when the bulbs have no top growth, the risk of damaging the bulbs is greatly reduced. If bulbs are injured unavoidably, prompt treatment consisting of smoothing the edges of the wounds and dusting them with sulphur of Fermate is advisable.
Most bulbs prosper in what we speak of as good garden soil-an earth midway between sand and clay and containing a generous measure of organic matter. Because their roots extend well down it should be made agreeable to a depth of at least eight inches and more for kinds that are planted deeply.
Manner of planting
Although there are exceptions, bulbs are generally set with their tops about three times the diameter of the bulb below ground; small bulbs deeper proportionately. In most cases it is the pointed end of the bulb which should be uppermost-but some tubers are planted horizontally. Some few, such as anemones, give no clear indication as to which end is "up" but close examination will usually disclose some sign of previous stem or root sources, and of course the stem scar should face upward.
Moisture and drainage
It is essential that all bulbs have plenty of moisture when growing actively. Efficient drainage to prevent water from standing around them is very necessary for nearly all. An overabundance of water during the dormant period is particularly harmful.
Storage of nourishment
Bulbs are warehouses in which the plant stores food to provide nourishment for next year's crop of foliage and flowers. In many spring-flowering kinds embryonic leaves and flowers are completely formed within the bulb before winter comes, and these remain quiescent until spring warmth stimulates growth; in others no foliage or flower parts are present, but the foodstuffs needed for their development are stored. Most summer-flowering bulbs have enough food within themselves to provide a vigorous spring start, but that needed for the production of later foliage and flowers is manufactured by the leaves from elements taken from the soil and air as growth proceeds. The nourishment that the plant stores for the next season is prepared by the green leaves of the current year; therefore it is imperative not only that enough green leaves to carry out this process be developed and retained but also that they be kept in good condition until their work of food manufacture is complete, which is indicated by natural yellowing and eventual browning. When cutting flowers from bulbs, it is always important not to remove too many leaves if the bulb is expected to produce flowers the following year. When bulbs must be dug before the ripening process is completed, it is just as important that the leaves be given as good a chance as possible to complete their work and to ripen normally. Success with bulbs demands that everything possible be done to encourage and retain healthy leaf growth.
Like all plants, bulbs respond to fertile soil, but manures and fertilizers must not be used carelessly or more harm than good may result. The value of well-rotted manure to improve soil structure and to provide nutrients is recognized. It may be used to great advantage as long as there is a good protective layer of soil between the bulbs and the manure. Fresh manure coming in contact with the underground parts of any plants in this group is likely to be disastrous and should not be permitted; neither should manure mulches be used except with great caution.
Slow-acting fertilizers other than manure are particularly recommended for feeding bulbs. Bone meal is one of the best, and five or six pounds to a hundred square feet is not too heavy an annual application. Other good fertilizers are cottonseed meal, dried blood, tankage, and wood ashes, as well as complete commercial fertilizers in which the nutrient elements are neither too rapidly available nor too concentrated; a regular 5-10-5 fertilizer such as is used in vegetable gardens is suitable.
Mulches can be employed with excellent effect. Those used in summer can be very helpful in aiding to retain moisture in the soil, in keeping the ground cool, and in discouraging weeds. Peatmoss, buckwheat hulls, clippings from lawns, and even decayed sawdust can be used successfully. Mulches intended for protective winter cover should be applied after the top surface of the ground has frozen and be removed after bulb growth is well started in the spring. For this purpose, branches of evergreens, buckwheat hulls, pine needles, salt hay, and leaves of deciduous trees that do not pack down ( because of their tendency to do this maple leaves are not very suitable) are recommended. The purpose of winter covering is not to keep the bulbs warm but to lessen the hazards of alternate freezing and thawing which may lift and expose bulbs that are not far below the surface and may tear and break the roots of others. Winter protection should not be applied until the top couple of inches of soil are frozen.
Good housekeeping-seeing that cultivated and adjacent areas are kept free of debris and that injured and infected foliage is diligently removed-is essential. Incurably diseased plants should be promptly removed and burned. When seeds are not desired, the early removal of faded flowers channels plant energy which would normally be used for seed production into building stronger bulbs. It also aids in keeping the garden neat.
Insects and diseases
In dealing with insects and diseases, proper diagnosis of the trouble is of primary importance; it is not reasonable to resort to medication, surgery, or more drastic measures without being sure what is wrong. Such practices may be both expensive and wasteful of time. Particularly when rare or expensive varieties are concerned is it desirable to know what the chances are of a diseased plant being saved by removing the affected parts and nursing what is left back to a healthy condition. Frequently when disease appears among a planting, lifting the healthy bulbs, disinfecting them, and moving them to an area not previously used for growing bulbs of the same kind will save them from infection.
Many bulbs are dug, transported for great distances, stored in stock bins of bulb merchants, and displayed at retail outlets for extended periods before they are delivered to the customer. After delivery there may be further delay before the bulbs can be set in the garden. Some bulbs-like narcissuses and tulips-withstand this treatment amazingly well. They are often dug in July and are not put back in the ground until late November or December. It is agreed, however, that most bulbs should not be out of the ground longer than necessary. New bulbs should be procured from retailers as soon as they are available and, except in a very few cases, be planted as soon as is practicable. A few, such as amaryllises and lilies, have fleshy perennial roots attached to their bases when dug. These are usually removed or are very seriously battered before they reach the purchaser. Because these roots are so essential and must be replaced before the plant can fully resume its normal activities, it may take a year or more for such bulbs to re-establish themselves after planting. Lily bulbs which have soft fleshy scales and a maximum amount of exposed surface ( as well as other kinds known to be very susceptible to serious drying) should be kept in sawdust, peatmoss, buckwheat hulls, vermiculite, or similar material while out of the ground. A storage atmosphere that is either too dry or too damp can be disastrous to all kinds of bulbs. Dahlias, cannas, and some others often benefit from the protection of being packed in dry soil, peatmoss, or other material which may even have to be sprinkled occasionally to lessen the water loss which causes them to wither. The know-how of handling bulbs in storage is in most cases a matter of realizing the effect of atmospheric conditions on their physical make-up and using common sense.
When purchasing bulbs avoid "cheap jack" offers of extraordinary "bargains." Deal with suppliers of known integrity, place your order as early as possible, and expect to pay fair prices. Good bulbs should be heavy for their size, firm of flesh, and plump. They should be free of bruises and scars, their coats intact ( except that tulips sometimes tend to lose their skins and this does no harm provided the flesh beneath is not damaged ).
Bulb sizes often puzzle the amateur. They are expressed in different ways for different kinds and, unfortunately, dealers are not always consistent in their application. "Top size," "jumbo size," "exhibition size," "extra size," "number one size," and similar terms are freely used-and sometimes misused. When sizes in inches or centimetres are given they usually refer to the circumference of the bulb, but in some cases-freesias and tuberous begonias, for example-to the diameter. Such sizes are a good guide when comparing bulbs of the same variety and sometimes when making comparison between different varieties of the same kind. This latter does not always hold, however; some varieties of narcissuses, for example, have consistently larger bulbs than others, the very biggest bulb of a poeticus being of a size that would be small for a "King Alfred." It pays to buy large bulbs, but not always the largest. "Bedding size" hyacinths, for instance, are more suitable for outdoor planting than exhibition size; freesias not over three quarters of an inch in diameter are generally preferred to bigger ones.
No matter how fine the bulbs you purchase are, if you mistreat them afterward they will deteriorate. Open the packages immediately upon arrival. Examine the bulbs carefully for defects and, if you find any, request a replacement at once. If planting has to be delayed, store the bulbs in the bags they come in with their tops opened in a cool, well-ventilated place where mice, squirrels, and other rodents cannot get at them, or spread them out in flats or shallow trays and store them under the same conditions. Keep them away from furnaces and other sources of dry heat. Too high temperatures and excessive dryness will cause shrivelling and may work other serious harm. The best temperature for storing is between 60 and 65 degrees.
This border, set against a background of shrubs and planted almost solidly with tulips arranged in informal groups, provides a rich picture that is much more pleasing than if the bulbs had been planted in geometrical patterns.