Miniature Conifers: Growing Problems And Solutions

Thuja western Golden Tuffet

Recently, interest in conifers in Russia has grown significantly. This is understandable. A huge number of private territories appeared, the culture of decorating among the population increased, a stream of imported planting material poured in. In addition, it became clear that coniferous plants, like evergreen crops, are able to decorate local areas all year round. This is especially true for our winter, which lasts no less than 6 months. And apart from conifers, nothing diversifies the white landscapes.

The range is huge, but the area of ​​the available garden limits the choice based on the final size of the planted conifers. In small areas, of course, miniature plants will be of greatest interest. Of course, miniature is relative. In this consideration, we will restrict ourselves to dimensions in height that do not exceed 1.5 m. Any lower boundary is possible, on average it is 25-30 cm. Now there are already such crumbs that fascinate with their beauty.

Collection of miniature conifers

Interest in this size range is noticeable not only from the owners of small summer cottages. The fact is that such plants can be used in a garden of any size to fill the lower and middle tiers of various compositions. In addition, miniature plants, which go under the snow in winter, can significantly expand the range of conifers, which in normal sizes have problems with wintering in mid-latitudes. And finally, conifers of this size are a real find for collectors.

Engelman Spruce Dwarf Tree

Balsam fir Prostrata

However, to maintain the decorativeness of miniature forms of conifers in the garden, special care is required. And its features are determined by the history of the appearance of a particular plant variety with a limited size.

How dwarf forms of conifers are obtained

You can get a cultivar with a small size in several ways. This is, first of all, regulation of the ratio of growth hormones in the plant, often not without human help.

Growth processes in plants are controlled by natural growth regulators. One of them is gibberellin. Some plants are known to genetically synthesize very few gibberellins. Therefore, their cells grow poorly, which leads to dwarfism. If this quality is hereditarily fixed, then all offspring will be such. However, if the amount of gibberellins is artificially reduced (treatment with retardants), then a compact, dense, beautiful plant with a presentation will be obtained. But later, the effect of retardants ends, and the plant returns to its original, often not quite attractive, appearance. Many met with such a phenomenon: Kalanchoe, chrysanthemums, gentian, ficuses, platycodons were bought with very pretty blooming balls, which were subsequently "shot" with long shoots in different directions.For conifers, an example of treatment with retardants is the Scotch pine of the Globoza form (round) subsequently turned out to be not at all a "globose".

However, retardants are expensive, and it is difficult to deal with the environment. retardants are poisonous. Therefore, they are now mainly engaged in the creation of varieties in which the natural synthesis of gibberellins is lower than normal, i.e. breeding genetic dwarfs. But once you stimulate them with gibberellins, they will regain their growth again. Gibberellins are already on sale in the form of preparations for stimulating the development of fruits "Ovary".

Other plant growth hormones are brassins. There is also a synthetic analogue of Epin-extra on sale. If the plants lack natural brassins, dwarfism also occurs. Brassin-deficient genetic dwarfs normalize growth after Epin treatment. Therefore, it will not be surprising if, before planting, you treat the plant with Epin, and it begins to grow vigorously, and although after a while the active growth will stop, it will already distort the appearance of the plant.

The third natural growth hormone is auxin. It also affects the elongation of cells, and therefore their division. With insufficient synthesis of this hormone, dwarfism also occurs, but of a different quality. If in the first two cases there is simply a reduced copy of the original plant, then with a lack of auxins the situation changes. In shoots, not only internodes decrease, as in the first two cases, but enhanced branching occurs. Shoots become strongly branched: from almost every dormant bud, an shoot grows on the stem. An example of such dwarfism is thuja western Teddy, from deciduous - viburnum ordinary Nana - dwarf, dense, non-flowering balls. Thus, we considered one of the ways of the appearance of diminutiveness, so desirable for us in this case.

Thuja occidentalis Teddy

But there is another way - this is the use of natural mutations. In the west, from the middle of the last century, they began to engage in breeding and selection of conifers of reduced size. Dwarf forms are usually selected from thousands of seedlings. To increase the yield of plants with deviations from the original size, the seeds are purposefully treated with chemical reagents (colchicine) before sowing, or γ-radiation is used.

Similar mutations occur spontaneously in nature. As a result, "witches brooms" appear on the tree - clots in the crown of abnormally growing branches (similar to rooks' nests). By grafting these branches onto the corresponding stock, a new variety of coniferous plants is obtained. Such mutations are enough in all types of conifers. There are several reasons for this phenomenon. The most harmless is a kidney mutation that can lead to either dwarfism or gigantism. It can be hereditarily fixed (when the damage affects the hereditary apparatus), but it may not persist in the offspring (when only the ratio of hormones in the kidney changes).

Korean fir Blauer Eskimo

Gray spruce Aurea

The latter phenomenon is very common in the world of roses (at claimings) - the Iceberg and Gloria Day varieties often give mutations in color and flower size, the size of the whole plant is not an inherited mutation.

The second reason for the occurrence of "witch's brooms" is a bacterial or fungal infection. Pathogens secrete plant hormones (in this case, cytokinins) and characteristic signs appear. Usually, dwarfism persists only as long as the parasite is active in the plant. After recovery, the symptoms disappear. This does not apply to agrobacteria (this case cannot be cured), with the help of which genetically modified plants are obtained. Often, although not always, due to the imbalance of hormones, plants obtained from witch brooms are sterile (without seed reproduction) and reproduce only by grafting.

Sitka spruce Silbergzwerg

Spruce Glen Chitosemaru

All this hormonal and genetic educational program aimed to show that plants with reduced forms must be handled competently, and, if stimulants are applied to them, then very carefully. Otherwise, you can cause a reversion - a return to the original form. The end result is a mutant freak.

Sometimes diminutiveness can also be associated with the action of external conditions: their improvement and approaching the necessary increases the size of plants, and vice versa. For example, for thermophilic plants moving north, winter temperature is the decisive factor. As a result, the tree sometimes turns into a bush or turns into a herbaceous form (for example, buddley). A deficiency of mineral nutrition elements or, conversely, an excess can also lead to a decrease in geometric dimensions. Therefore, dwarf forms should not be intensively fed, especially with nitrogen fertilizers.

Regular mechanical damage also contributes to a decrease in the size of plants (on windy coasts, during the formation of bonsai).

In addition to dwarfs, there are simply plants that slowly develop at the beginning of life. An example is the specific mountain pine (Pinus mugo): in the first 10-30 years it does not exceed 1-2 m in height, but in the future it can reach 10-12 m. This does not mean genetic dwarfs, which this species has plenty of.

Recently, in order to give the required size and habit, the technique of molding has been increasingly used for conifers. Depending on their types, the ways to achieve the required size and habit are different. But this is a completely different direction in caring for such conifers. However, in this case, restraint in the use of fertilizers, especially nitrogen fertilizers, is necessary.

Molded larch

And, of course, the general principle when choosing a cultivar in a retail network is the size of the last increase. It is she who will determine what the plant will be like in 10 years. And if the annual growth is 10-15 cm, then in 10 years you will get a far from miniature plant. But such characteristics as winter hardiness and resistance to the spring sun (especially important for conifers) are determined not by the variety, but by the botanical species to which it belongs.

Caring for dwarf conifers

Generally, the smaller the plant, the greater the density of the branches. And this fact makes adjustments to the care of them. A brown "cocoon" of dead needles always forms inside the plants. This is not a disease, but a physiological phenomenon. The growing young twigs shade the inner part of the plant, which leads to the death of the needles. Many plants, especially dwarf ones, cannot free themselves from it on their own. Such internal thickening, which prevents airing and contributes to outbreaks of fungal diseases, which can not only significantly spoil the decorative effect, but also lead the plant to death (very rapid drying and falling of the needles for no apparent reason).

Korean fir Kohouts

This fact should be taken into account. To enhance ventilation, and, consequently, to eliminate the conditions of an outbreak of fungal diseases, it is necessary to periodically (1-2 times per season) "shake out" the dried needles from the inner areas. This procedure will not be superfluous even for medium-sized plants with a dense crown. A textbook example is the Canadian spruce Conica (Picea glauca "Conica"). There are no complaints about winter hardiness. However, very often her death is discovered in the spring. There are several reasons for this. It is a canopy plant of dark coniferous forests, and therefore prefers moist air and shading. And our winter temperatures (not taking into account the winter of 2013-2014) dry it out a lot. And frozen roots do not work to replenish moisture in the needles. As an option for a tolerable existence - landing in the shade.But often the root cause of spring death is fungal infection of needles in the fall, which is facilitated by dense backwoods. Winter only makes the situation worse. Therefore, such plants also require regular (mandatory in autumn) cleaning of the inner brown "cocoon".

Canadian spruce Conica from the north side

Canadian spruce Conica from the south side

However, providing ventilation inside the plant is only a prerequisite to prevent disease. And sufficient - preventive spraying with fungicides inside and on the surface of plants. It is preferable to do three sprays (spring-April, summer-July, autumn-October). A prophylactic agent - your choice: one of the chemical fungicides or a biological product. With such care, it is highly likely that your miniature plant will not get sick and, moreover, will not die.

And in general, to ensure a high decorative effect of all conifers, without exception, do not spare water. Water from head to toe, spray more often with clean water, mulch root balls to retain moisture. But use all the recommendations taking into account the nature of the soil on your site and the preferences of the crop. All conifers prefer humid air, but cannot tolerate even short-term root ball locking.