Hardy Shrubs and Their Protection Against Drought
Some of the things I may say could undoubtedly be better said by some of you, for I know full well that in the growing of trees and plants, many of the members of this association have attained to a rare degree of skill and taste. I hope, however, to interest you in some phases of tree-growing in a climate that is well-known for the frequency and severity of its periods of drought and its long cold winters.
In this climate we lose far more plants from the drying out of the soil, than from the cold atmosphere. In proof of this, most of you can recall that the greatest losses of young trees have occurred in winters following extremely dry autumns.
Therefore the problem of raising trees successfully here is largely one of how to overcome most successfully the droughts to which we are subjected. This is the first part of my subject, and I divide it under the several heads of:
The management of the soil; the selection of the trees and the treatment of the surface of the land around the trees and shelter to protect from drought.
The proper management of the soil will vary as much as soils differ from one another, but in dry locations, we must try to have as good a supply of retentive material around the roots as it may be practicable to obtain. This may properly consist of clay, or material containing much humus, or of both combined. Nothing is better than the sad from clayey land.
In the selection of trees, there is much to be considered, even after the kind is decided upon. As a rule, seedlings which have not had their tap root seriously cut, grow faster, develop into better trees, and are less affected by drought, than those which are much root-pruned, or grown from cuttings. The cottonwood is a good example of this point, and it will be found with this tree that seedlings are much longer lived than cutting plants when grown in the dry soil of our western prairies or in similar situations elsewhere.
As a rule in dry situations, it will be found that small plants with the root undisturbed are far better than are much boasted nursery-grown trees with fibrous roots. Then, too, we must get the roots down deep, and in very dry locations I would often plant so that the roots will be 15 inches deeper than they naturally grew.
The box-elder is one of our hardiest trees, and is seldom, if ever, regarded as tender, yet when grown from seed collected in Southern Missouri, it does not stand well in this section.
The Missouri black walnut is not as hardy as that which was formerly quite abundantly grown in the river bottoms of the southern part of this state. The same I believe to be true of the hard maple, hackberry, red cedar and many other trees. It is also my belief that the Rocky mountain evergreens grown from seed raised on the eastern slopes, where the parents have for ages endured a trying climate, and all the more tender plants have been sifted out, are far more desirable for growing in our northern states than those which have come from the moist, milder and more equable climate of the western ranges. I have recently gone to some considerable pains to get my hard maples from the northern section of this state, for I believe them the hardiest. These statements simply show what the most casual observer must have noted, that there is much in a good pedigree and that there is transmission of qualities of hardiness in the vegetable as well as in the animal kingdom, and that we should think of them in selecting trees and plants. In fact, the qualities of inheritance extend through all organic matter.
The treatment of the surface soil around trees planted on dry land is a matter that calls for much careful attention. The American public has become educated to thinking that a blue-grass sod in such places should extend close up to the trunks of the trees. In a few years this may become so thick and solid that it will shed water nearly as perfectly as a shingled roof. This is an unnatural condition, and under such circumstances plants cannot reach any great degree of development in dry situations. Where trees naturally make a good growth in dry locations, the surface of the soil is covered with a considerable thickness of leaves and branches that have fallen to the ground. These retard the water and allow it to percolate into the ground and reach the roots of the trees. It also prevents evaporation from the surface soil and keeps the surface soil cooler. For instance, this season the strawberry bed at the experiment station has given far better returns than others in the immediate vicinity, and this success was largely due to the practice of heavily mulching, the space between the rows with straw.
At any time during the severe drought, which has prevailed for a considerable period, the soil under the mulch could readily be rolled into pellets, while in adjacent rows, not mulched, the soil was very dry. Analysis of the soil, four inches from the surface, showed that which had been mulched contained 24.3 % of water, while that which was not mulched had 18 % of water. Of the soils three inches from the surface, the mulched contained 20.6 % of water and that not mulched 15.5%. In either case, the mulch increased the amount of water contained in the soil under it 33⅓%. This is equivalent to an increase of 2.2 quarts of water to each cubic foot of soil, which is equivalent, where a tree is mulched for five feet on all sides, to an increase of 44.3 gallons of water in its upper one foot of soil under the mulch, and there is, probably, nearly as much increase in the second foot of soil. Yet in this case, the soil which was not mulched was undoubtedly near enough to be considerably affected by the water in the mulched rows. The surface soil of some other land on the farm was found to contain only 5% of moisture at the same time. It is probably fair to assume that the mulched land contained at least 60% more moisture than that not mulched.
This is a great variation, and often makes the difference between success and failure in growing trees and plants.
People may complain that a mulch is unsightly; but it can often be covered up to great advantage with hardy shrubbery, which also aids the retention of water by shading the ground and protecting it from drying winds. We are apt not to appreciate the value of undergrowth around trees. This is nature's way, and we would do well to follow her in it many times. For covering the mulch symphoricarpos, the hardier spireas, flowering currants, buffalo berry and many other hardy plants are suggested as being desirable; and when properly grouped make pleasing contrast. The best material for mulch will vary with that which is easiest to obtain. Hay, straw, bogasse, coal ashes and hardwood sawdust are good; but any material which is a good nonconductor will answer the purpose.
The importance of shelter, by this I mean wind-breaks, can hardly be overestimated. It has been clearly shown that evaporation under the influence of the wind is dependent not only on the temperature and degrees of the same, but also on its velocity, which if impeded, reduces the rate of evaporation. Careful experiments made by the U. S. Signal Service in 1887, showed that with the temperature of the air at 84° and a relative humidity of 50%, evaporation, with the wind blowing at five miles an hour, was a little more than twice what it was in calm. At 15 miles an hour, the wind would evaporate about five times as much water as in a calm atmosphere of the same temperature and humidity. These figures state in exact terms the value of shelter belts and many other similar observations could be given to show the value of wind-brakes.
This protection is sometimes best given by a wind-break. It certainly may be given by planting in groves where the trees protect one another from the wind and sun. Newly transplanted trees will often be greatly helped by covering their trunks with hay, straw or other material that will keep off the wind and sun. The hard maple is found in the extreme northern limit of this state in large quantities, forming great forests, yet even at Lake City, 300 miles south of this limit, is liable to serious injury to its trunk, and is not considered a safe street tree, unless the trunk is shaded. The same is more or less true of the bass-wood, which is greatly improved by covering its trunk. The mountain ash makes a large tree 200 miles north of this city and yet, here, is liable to sun scald if its trunk is not protected. I have made a considerable study of this subject and have always found the bark much healthier and fresher when protected than when exposed.
To sum up this matter, I would say, in dry locations it is of the utmost importance to have a retentive soil, to mulch and to protect the whole plant from wind and the trunk from the sun as far as possible.
In the extreme north, we do not have the variety to use in grouping which is found in milder climates, but by careful management we can produce very pleasant contrasts with the material we have at hand, and there is no need, even here, of any great sameness in plantings.
Among the larger trees that are most useful for planting along our drives, is, first of all our American white elm, which will endure greater extremes of temperature and moisture than any of the fast-growing larger trees and is the best of all for general use, but it is well to vary this occasionally by planting a few sycamores, or even a whole drive, with the rock and the slippery elm.
The English elm I do not consider hardy enough for planting in this climate. The sugar and soft maple are both good; the latter being especially desirable for quick effects on retentive land where not too much exposed. The Norway maple is unreliable. The hack-berry is a rival of the white elm for planting in good soil; but in dry situations it is not so reliable.
The green ash is the hardiest of its kind; the white is not so well adapted to severe conditions, yet in favorable locations it makes a fine tree.
The box elder is rather too small for general street planting but for drives or alleys, especially in trying situations it is one of the best trees.
The poplars and willows are generally neglected; but some of those introduced from Russia, and a few of our natives, could often be used to good advantage. Among the best of these are the certinensis, and laurel-leaved poplars, and the white and Russian golden and laurel-leaved willows. These are of rapid growth, very desirable as pioneer trees, and of great value in producing pretty effects on the edges of timber plantings.
I fear there is a general tendency to neglect the oaks on account of their slow growth, but in every large planting there should be a judicious mixture of the trees of this genus. They will grow in almost any situation and develop in size much more rapidly than we think, and always command attention. As for myself, I always feel like taking off my hat to a fine oak. The best of all is the Burr or Over-cup oak, which is one of the most magnificent trees in form, foliage and hardiness in the world. Then the scarlet oak is a very desirable tree. No other plant approaches it in beauty of autumn coloring, and it soon becomes large enough to give good landscape effects, and it may be transplanted with considerable certainty if nursery grown.
Among the smaller trees of special merit are the American canoe birch, the European birch and its variety of cut leaves. They are especially desirable for effective grouping in moist land, and to contrast against a back ground of evergreens.
The Balleana poplar is a form of the silver poplar, with a close, upright, distinct and pretty habit, and as hardy as the ordinary white poplar. It is destined to be popular as a specimen tree, where a bright; striking effect is wanted. An occasional white poplar is also desirable.
The Catalpa is worth planting in a small way in very favorable locations on account of its distinct foliage and beautiful flower clusters; but it is unreliable.
The mountain ash is pretty at all times, and is a satisfactory tree as far north as Fargo, and can be used to great advantage along the borders of groves to enliven them with its bright flower clusters in spring, and its fruit clusters in autumn.
The oil-berry (Elaeagnus Augustifolis) is a very hardy small tree and desirable for its pretty habit and downy light green colored foliage.
The Kentucky coffee tree, with its large, conspicuous compound leaves, is valuable for variety and occasional use in good locations.
The Butternut, too, may be used for variety, and for general use should take precedence over the black walnut, which is only reliable in the best locations.
Van Gert's golden poplar, if used occasionally, gives a bright pleasing effect to the landscape by its pleasant contrast with trees of dark foliage, but if used too largely the effect is sickly and unpleasant.
Among the willows, the Russian golden is far superior to the common form. It can be used to great advantage in enlivening the landscape of the late winter and early spring months. The laurel-leaved is especially pleasing with its large, bright, glossy foliage; and can often be used for brightening the effect of more somber kinds.
Salix Regalis is hardy here and is a beautiful, graceful tree with white, silvery foliage. On account of its rapid growth, it is very valuable for an immediate effect.
The Conifers are especially good for winter effects. They do much the best here when grouped, and a much stronger effect is produced in this way than by single specimens. The ground around them should be kept clear of grass, and if practicable they should be mulched.
When once established such trees as the white spruce, Scotch, Norway and dwarf pine, red cedar and arbor vitae will stand well in almost any location. These are the hardiest of our evergreens, and are generally satisfactory.
I think the dwarf pine is the hardiest of the pines, and the best for a dry situation. It is especially valuable for outer specimens of evergreen beds.
The Juniper sabina, or trailing juniper, is one of the neatest of all for a low evergreen. It is pretty when allowed to assume its natural habit, and by pruning can be made to take on almost any low form.
Among arbor vitaes, the common form and the pyramidal are very satisfactory. Those with either golden or silver foliage have not done well here.
Of the Rocky Mountain evergreens, our best is the Picea Pungens, which is hardy enough for us and is certainly very desirable for fine effect among evergreens.
The Picea Concolor is somewhat unsatisfactory. The Douglass spruce is doing nobly, and is destined to be popular for favorable locations. It grows much faster than the Picea Pungens, and its form as well as its color is very pleasing.
The Pinus ponderosa or Bull pine is of promising hardiness, and will probably prove valuable in dry situations. The Norway spruce is good, but does not hold on like the white spruce. The Hemlock is a little uncertain, and needs a favorable place to do well; but adds much by its grace and beauty to the groups in which it is placed.
The Retinosporas, with which such charming effects are produced in more favorable locations, are almost useless here, and we must get along without them.
Among the shrubs there are a multitude of kinds that suggest themselves and a few are worthy of special notice in this connection. The Caraganas are generally neglected in this country, and yet they are among the hardiest plants in the world, and in Russia they are used as pioneer plants to prepare the land for tree growth. They have a very pretty habit. The young foliage is especially delicate and pretty, and the yellow flowers make a bright and pleasant contrast in the spring. Our best Cornus is the native one with red bark, (Cornus stolonifera), and it is of much value for enlivening shrubberies in winter and is a good plant at all times.
The hardy hydrangea does well here, and if it did require some coddling to make it grow it would be well worthy of it. It is the most popular shrub grown. The Polish privet is the only one that stands even fairly well, but is hardly worth growing. The bush honeysuckles and lilacs are successful everywhere and are grand shrubs.
The Syringas do fairly well, but are peculiarly liable to injury from drought. The P. Columbian is a new form with large white flowers that I think, will prove a great addition to our flowering plants.
The shrubby Cinquefoil (P. fruticosa), is one of the best and hardiest under shrubs, and its bright yellow flowers add to its attractiveness.
Many of the sumacs are hardy, and though somewhat coarse, their rich autumn coloring is a special inducement for growing them.
The Missouri flowering currant is the best of its class, and is a grand shrub which never fails. The Alpine currant may be used in a small way.
Broad leaved evergreens do not thrive.
Rosa rugosa is perfectly hardy with us, and most satisfactory as a shrub. It is not well known as it should be. It is valuable for effective grouping or as a specimen plant.
Of the Elders, the native red-berried form, though somewhat coarse, is very useful in many places, and is conspicuous in flowers and in fruit. The golden elder is a beautiful thing and almost indispensable for enlivening shrubberies, and while it is frequently killed to the ground in winter, it is generally very satisfactory.
Of the Spireas, the Van Houten is the best; but Obovata, Fortunei, Lanceolata and Lobifolis are all good. The delicate Thunbergii is too tender to be satisfactory here. The golden spirea, though no longer put in that class by botanists, is the most satisfactory golden-leaved plant we have.
The Buffalo-berry, (Sheperdia argentea), is a large, clean, graceful and excellent shrub and as hardy as any. There is some difference in the color of specimens. It is not well known, but is destined to be largely used as an ornamental plant. The light green color of the leaves and branches may be used in striking contrast to evergreens and dark-foliaged plants.
The Snowberry is so hardy it may be used in almost any location.
The Tamarix Amurensis is a beautiful, graceful shrub, with feathery foliage and pretty small flowers. While it generally kills to the ground in winter, yet it starts so quickly in the spring that it is very desirable for the edgings of shrubberies. The Snow-ball is well known and satisfactory in good locations. The original form of it, the high bush cranberry, has the advantage over it in bright fruit, which holds on well into the winter, and I like it much better than the snow-ball.
The prickly ash is a good plant for giving variety to lawn planting.
The dwarf June-berry is a nice, quiet looking shrub in the edges of groups and shrubberies, and its pretty flowers are admired by all.
The common buck-thorn is useful and makes either a specimen plant or a good low hedge. Of its hardiness, Prof. Prendergast, who has much experience with it in a very trying location, says: "Plant without fear."
By the use of these plants we may secure a good effect the year around, and even in winter, have our parks and cemeteries objects of beauty and admiration
From the publication:
AACS - Proceedings of the 7th Annual Convention
August 22, 23 and 24, 1893