Dibbers
Dibbers are hand tools used for making holes in which to set plants or to drop seeds. They are better than a hoe or a spade for most transplanting. For small plants, as cabbages and tomatoes, a cylindrical Dibber is generally used. (See the lower one in the cut.) It can be made from an old spade handle or any hardwood stick. When broad holes are wanted, the triangular iron Dibber (sold by dealers) is excellent. It is particularly useful in hard soils.
Dicentra includes the Bleeding Heart; also the native little Dutchman’s Breeches and Squirrel Corn, and a few other species. All are hardy perennials of the easiest culture, blooming in spring. In common with all perennial herbs, they are benefited by a winter mulch of leaves or litter. Propagated by dividing the clumps.
Dictamnus. Fraxinella or Gas Plant. An old border plant (perennial herb) with white or pale red flowers. The leaves of the plant emit a strong odor when rubbed, likened to that of the lemon verbena. It has been advertised as the Gas Plant from the fact that the plant exudes an oily matter that may be ignited, especially in warm, dry weather. Propagated by seeds, which should be sown as soon as ripe. The plant blooms the third year, and improves with age. Set plants 3 feet apart. Height 2 to 3 feet.
Dill. An annual aromatic herb that will seed itself if seeds are left to ripen, and an abundance of plants may always be had. The culture is of the easiest. The seeds are often used to flavor pickles.
Diseases. Diseases of plants may be caused by some physiological disturbance to the plant system, or by the incursions of some parasitic organism, as insects or fungi. The work of insects, however, is ordinarily not classed with plant Diseases ([see Insects]). Of Diseases which are caused by plant parasites or by physiological disturbances, there are two general groups:
(1) Parasitic fungous Diseases, such as the apple-scab, black-rot and mildew of the grape, leaf-blight of the plum and pear, black-knot, and the like. These Diseases are characterized by definite spots, discolorations or excrescences, which are more or less scattered over the surface of the leaf, fruit or branch. As a rule, the leaves and fruits which are attacked have a tendency to drop from the tree. The general treatment for these Diseases is to spray with some fungicidal mixture, like the Bordeaux mixture or the ammoniacal carbonate of copper. The treatment is useful in proportion as it is applied early and thoroughly. After the fungus once gets into the tissues of the host-plant, it is difficult, if not impossible, to kill it. If, however, the fungicide is upon the plant before the fungus is, the parasite may not be able to obtain a foothold. Even after it does obtain a foothold, it is probable, however, that the spray will check its spread by preventing the development of its external parts.
(2) The physiological and bacterial Diseases, or those which are termed constitutional troubles. In these cases there are rarely any definite spots, as in the attacks of parasitic fungi, but the entire leaf, or even the entire plant, or a large part of it, shows a general weakening and Disease, as if there were some cutting off of the accustomed source of nourishment. Such Diseases are very likely to be seen in a general yellowing and death of the leaf, in the dying of the leaf along the main veins and around the edges, showing that the difficulty is one which affects the entire leaf, and not any particular part of it. In general, there is a tendency for the foliage in plants so attacked to wither up and hang on the tree for a time. The peach-yellows and pear blight are Diseases of this kind. There are no specific treatments for troubles of this sort. They must be approached by what physicians call prophylaxis—that is, by methods of sanitation and prevention. The diseased plants or parts are cut away and burned. All those conditions which seem to favor the development of the Disease are removed. Varieties which are particularly susceptible are discarded. Careful management in matters of this sort is often much more important than any attempt at specific treatment.
Dolichos. [Mentioned under Hyacinth Bean.]