Description of the rhododendron plant, agricultural techniques for planting and care in a personal plot, breeding rules, possible diseases and pests during cultivation, methods of combating them.
Rhododendron (Rhododendron) belongs to the botanical classification of the Heather family (Ericaceae). In the genus, according to various sources, there are 800-1300 species, as well as almost 3000 different varieties and garden forms. They are mainly evergreen representatives of the flora, but among them there are semi-deciduous and deciduous specimens. All rhododendrons have a shrubby form of growth, in some cases they take the form of small trees. Natural distribution occurs in areas with a temperate or subtropical climate of the Northern Hemisphere. But most of these plants can be found on the lands of the southern Chinese regions, in Japan and the Himalayas, and in the southeast of Asia, they are not uncommon in North America. If we talk about the Southern Hemisphere, then rhododendrons grow in the northeast of the Australian continent and on the islands of New Guinea.
| Family name | Heather |
| Growing period | Perennial |
| Vegetation form | Shrub, rarely treelike |
| Breeds | Seeds or vegetatively (grafting, dividing the bush, layering or grafting) |
| Open ground transplant terms | Spring (mid-April to mid-May) autumn (September-November) |
| Landing rules | At least 1 m from other plants or buildings |
| Soil for rhododendron | Well-drained, loose, nutritious - rich in humus |
| Soil acidity values, pH | Below 5 (acidic) |
| Illumination level | Penumbra or full shade |
| Humidity level | Watering is carried out with acidified water so that the soil gets wet to a depth of at least 20-30 cm |
| Special care rules | Pruning and fertilization, high humidity |
| Height options | 0, 3–4 m |
| Flowering period | End of April beginning of June |
| Type of inflorescences or flowers | Racemose or corymbose, occasionally flowers grow in pairs or singly |
| Color of flowers | Yellow, pink crimson purple |
| Fruit type | Polyspermous five-leaved capsules |
| Fruit color | Rusty iron |
| The timing of fruit ripening | September October |
| Decorative period | Spring-autumn, often year-round |
| Application in landscape design | Single or group plantings, hedge formation |
| USDA zone | 4–8 |
The name of this representative of the flora is obtained by merging two words in Greek "rhodon" and "dendron", which translates as "rose" and "tree". This is how the plant has long been called - "rose tree" or "tree with roses". This is because the blooming flowers, with their outlines, very much resemble the "queen of the garden" - a real rose.
The height of all species is very different, some with branches reach only 30 cm, and there are those that approach the four-meter mark. The former grow in the form of shrubs with branches creeping along the surface of the soil, while others take the shape of medium-sized trees. Among rhododendrons, camellias and azaleas are well-known among indoor flower lovers, but mainly because of the addiction to cool wintering, growing indoors is difficult and such representatives of the flora look organically in the garden. After planting, the first years of rhododendrons do not show a high growth rate. Since the root system of lobular root shoots is very close to the soil surface, plant care will be a little difficult, since it will require accuracy. The surface of young shoots is colored green; as it ages, the bark acquires a grayish-brown color.
The shape and size of the leaves of the "rosewood" also directly depends on the species. Here leaves are distinguished annual, biennial or perennial. The arrangement of the leaves is alternate, they are attached to the branches with petioles, but in some varieties the foliage is sessile. Often, the edge of the leaves is entire, but in rare cases, serration is present at the ends. The outlines of the leaf plates can be ovoid or obovate. The surface of the rhododendron leaves on the upper side is usually glossy, bare dark green in color, the reverse has pubescence of white or reddish hairs. The crown of the plant has an attractive appearance even in the absence of flowers because of its color and like a waxy tint on the leaves.
It is not for nothing that the "rosewood" is compared to roses, since very beautiful flowers begin to bloom during flowering. They are bisexual with irregular corollas. It happens that the diameter of the flowers is significant, reaching twenty centimeters when fully opened. The petals in the flowers have a variety of colors: snow-white and yellow, pink in different tones and lilac, crimson-purple and different tones of red color scheme. There are types of rhododendrons that have specks, streaks, and spots on the surface of the petals. The corolla takes the form of a bell, it can be in the form of a tube or spherical. Flowers are collected in inflorescences of racemose or corymbose structure. Only in some cases will the buds be arranged in pairs or singly. The flowers of some varieties exude a pleasant aroma during flowering, which may or may not be very strong. Flowering occurs from mid-spring to June.
When pollination is completed at the rhododendron, the formation of fruits that look like polyspermous capsules occurs. This period stretches from September to the end of October. The capsules are made up of five leaves, which, when ripe, open from top to bottom. When fully ripe, the color of the capsules becomes rusty-iron. Inside there is a large number of small seeds, the length of which is 0.5–2 mm. The seeds are rod-shaped. They are used for seed propagation.
Plants, of course, require growing experience, but if you do not violate the below-mentioned cultivation rules, then "pink trees" will delight you with just wonderful flowering for many years.
Planting rhododendron in the open field, rules of care
- Landing place it is worth in our latitudes to select in accordance with the natural preferences of this plant, and also take into account the climate in which the cultivation will be carried out. In middle latitudes, varieties and species characterized by frost resistance are recommended. A location in partial shade is well suited for a "rosewood", but a certain amount of direct sunlight is desirable for planting flower buds - preferably in the morning or evening hours. Therefore, a western or eastern location is suitable, you can plant such bushes on the north side of the buildings. It will be nice for rhododendrons under the crowns of trees, which give diffused lighting and protection from the scorching sun on a summer afternoon. The proximity of groundwater, despite the moisture content, is undesirable. It is also necessary that an increased air humidity is provided at the landing site. When the groundwater on the site lies at a depth of less than 1 m, it will be necessary to build a raised bed for cultivation. It is important that chestnuts, lindens and elms are not planted nearby, the presence of alder, poplar or willow will negatively affect the rhododendron, since their root system will be practically nearby and the “rose tree” will lack moisture and nutrients. If such a neighborhood cannot be avoided, then the edges of the landing recess should be protected with slate, plastic wrap or roofing material. Nearby pears or apple trees will not cause harm.
- Soil for rhododendron should be selected devoid of lime (sour), well moistened, but with high rates of drainage and looseness. Moisture in the soil should not stagnate. It is also recommended that the substrate is nutritious and acidic. You can buy the necessary soil mixture in specialized stores or mix it yourself from pine (spruce) needles, which are collected in the forest from coniferous trees, garden soil and high peat. A small amount of a complex mineral fertilizer (for example, Agrecol or Fertis) is mixed there.
- Planting a rhododendron It is held from mid-spring to the second half of May, and the time is also suitable throughout September-November. However, gardeners with extensive experience in cultivation are engaged in planting "rose trees" throughout the growing season, excluding only the flowering phase and subsequent 1-2 weeks. Pits for planting are prepared with a depth of 40 cm with a diameter of 60 cm. But here they are guided by the rule that the deepening should be twice the volume of the container in which the rhododendron seedling is located (or the earthen coma surrounding the root system). If the soil is clayey on the site, then a sufficient drainage layer must first be laid on the bottom. Pieces of broken brick, crushed stone or expanded clay can act as such material. The thickness of the drainage is 15 cm. The above soil mixture is placed in the pit, or it is filled with a substrate consisting of loam (or clay, but a smaller amount), high-moor peat in a ratio of 3, 5: 8 buckets. Everything is thoroughly mixed and compacted after filling. Then a recess is made in the soil, suitable in size to the earthen coma of the seedling. Before planting, the rhododendron seedling is immersed in a basin of water and only when air bubbles cease to rise from the soil surface, it is removed. A seedling with an earthen clod is placed in a hole and filled with soil mixture to the top. When planting, the soil is compacted so that there are no voids. The seedling in the hole is installed in such a way that its root collar is flush with the soil of the site - deepening is prohibited! After planting, abundant watering is carried out. If the planting was carried out in a dry substrate, then moisten it until it gets wet 20 cm deep. The trunk circle of the rhododendron is then mulched. The mulch is peat, dry oak foliage, pine litter (needles) or moss. The thickness of the mulch layer will be 5–6 cm. If the seedling has a large number of buds, they are removed so that the plant does not waste energy on flowers, but directs them to adaptation. When one rhododendron bush is located on the site, it is recommended to tie it to a support, which is removed after engraftment. But with a group planting, the distance between plants or buildings is not less than 1 meter.
- Humidity and watering when growing rhododendron are of particular importance. It is necessary that these parameters, both air and soil, be high, especially during the period of budding and subsequent flowering. Correctly performed moistening of the soil will be the key to laying flower buds, which will bloom in the next season. Watering is carried out only with soft water (you can defend it or collect rainwater). If this is not possible, then a gauze bag filled with several handfuls of high-moor peat is dropped into a bucket of water. The peat is kept there for a day and the solution is ready for use. Watering is carried out when the leaves of the rosewood lose their turgor and become dull. When moistened, the soil must be impregnated to a depth of at least 20-30 cm. Important! You should not bring the soil to acidification, since the root system of the rhododendron reacts negatively to waterlogging. Folded and lost leaves will be the signal. In order to prevent waterlogging of the substrate even on dry and hot summer days, the irrigation regime is not changed, but the crown is often sprayed from a finely dispersed spray bottle using soft water.
- Pruning when growing rhododendron, it is practically not performed, since by nature the shape of such bushes is more or less correct. Only those branches that have become too stretched are cut off, it is necessary to rejuvenate or remove shoots damaged by frost over the winter with the arrival of spring. In the spring, pruning should be carried out before sap flow begins. If branches are cut, the thickness of which varies within 2-4 cm, then all sections must be carefully coated with garden varnish. After about 4 weeks, dormant buds will begin to awaken, and at the same time, the process of the beginning of the renewal will begin, which stretches for the whole year. When, with the arrival of spring, after inspection, it is found that the branches are severely damaged by frost or the plant is too old, then all the shoots are shortened by 30-40 cm. But here it is important not to cut off the entire bush with a rhinestone - in the first year one half should be ennobled, the other half in the second. Rhododendron has a peculiarity: if the year turned out to be with lush flowering and fruiting, then the second one will be scarce. However, some gardeners correct this aspect by breaking out all the inflorescences that have already grown pepper. Then the rose tree will direct all the remaining forces to laying the buds for the new season.
- Fertilizers for rhododendron, you will need to make it if the planting was carried out in the current year. The first time feeding is introduced in March, and the last one at the end of July, when the flowering ends. Preparations are used in liquid form, containing horny flour and well-rotted cow dung. To prepare such a solution, manure is mixed with water in a ratio of 1:15 and left to infuse for several days. Then it is filtered and ready to use. Thorough watering is recommended before fertilizing. It should also be borne in mind that rhododendrons prefer to grow in acidic soil, so it is necessary to use mineral products that will not change the acidic reaction of the environment. Therefore, it is recommended to use drugs such as: ammonium sulfate and magnesium; phosphate, nitrate, potassium sulfate and calcium, the concentration of which will be 1, 2: 1000. If potash dressings are used, then they are taken of very weak saturation. In order for the "pink trees" to please with growth and lush flowering, it is recommended with the arrival of spring, as soon as the snow melts, for the rhododendron you need organic matter or complete mineral complexes, which contain nitrogen. For this, 50 grams of magnesium sulfate and ammonium are used per 1 m2. Then, in the first week of June, when the flowering is over, potassium sulfate and superphosphate (20 grams each) and twice as much ammonium sulfate are added to the same area. Already in the middle of summer (about the middle or end of July), a third feeding with potassium sulfate and superphosphate will be required, which are used in 20 grams of each per 1 m2.
- General advice on care. Since the root system is superficial, weeding and loosening of the soil is carried out only manually, they do not use a hoe. If he talks about the priorities of cultivation, for example, in the Moscow region, then preference should be given to species and varieties that can withstand the harsh winter. Heat-loving varieties and their garden forms should not be planted, since, even providing them with thorough cover, it is noticed that freezing cannot be avoided. In such climatic conditions, it is recommended to plant deciduous species: Japanese rhododendron (Rhododendron japonicum) and yellow (Rhododendron luteum), Schlippenbach (Rhododendron schlippenbachii) and Vaseya (Rhododendron vaseyi), Canadian (Rhododendron vaseyi), Canadian (Rhododendron) and pukchatron canachat (adodendron) Rhododendron poukhanense). Of the semi-evergreen species, the most popular is the Rhododendron ledebourii. In mid-latitudes for cultivation, the following species will be the best choice: Rhododendron catawbiense and its hybrid forms - Alfed, Abraham Lincoln, Nova Zembla, Cunningham's White. It also includes short-fruited rhododendron (Rhododendron brachicarpum), as well as golden (Rhododendron aureum) and the largest (Rhododendron maximum), Smirnov (Rhododendron smirnovii) and his hybrid forms Gabriel, Dorothy Swift (Dorothy Like)In Finland, breeders have developed varieties that have proven to be quite frost-resistant, among them the most popular are Elvira, The Hague and Mikkeli. The following hybrid groups showed particular resistance to wintering in mid-latitude conditions: Northern Lights (Northern Light or Nose Light), Pink lights or Rosie Lights (Rosie Lights), Spicy Lights (Spicy Lights).
- Preparing for winter. If there was no precipitation when growing rhododendron in the fall, then watering should be carried out regularly, while 10-12 liters of water are added under each bush. With normal precipitation, soil moistening is not needed. In November, it is recommended to insulate the root system of the "rosewood" by mulching it with a layer of peat chips. It is also necessary that the protection of the crown is provided, and for this, pine or spruce paws are pushed between the branches, and then the crown is neatly pulled together with twine. After that, she is wrapped in burlap. With the arrival of spring, when the snow melts, such a shelter should be removed so that the plant does not fall out. A cloudy day is chosen so that leaves and branches are not immediately exposed to direct ultraviolet currents. If the region has a warm climate, then a shelter is not needed for growing.
- The use of rhododendron in landscape design. Since the "rosewood" in nature prefers to grow in acidic soil, the best neighbors in this regard are such trees as pine, larch or oak. This culture looks good both singly and in group plantings. Some gardeners use rhododendron bushes to form hedges.
Read also about growing wild rosemary at home.
Breeding rules for rhododendron
In order to get a young plant of the "rose tree", you should use seed or vegetative methods. The second option includes grafting, dividing the bush, rooting cuttings or grafting.
Reproduction of rhododendron using seeds
For sowing, nutrient soil should be poured into the container, which is combined with peat or heather soil with river sand in a ratio of 3: 1. After that, the substrate is moistened and the seed is distributed on its surface. From above, the crops are powdered with dry, pre-washed sand. A piece of glass is placed on top of the landing containers. Place the pots in a place with good lighting. When caring for crops, it is recommended to moisten the soil, preventing it from drying out, and also to ventilate daily in order to remove accumulated condensate. You can expect the first seedlings a month after sowing. After that, the shelter is removed. When two real leaves unfold on the plants, it is necessary to dive - to plant the seedlings in other containers using the same soil mixture. The planting scheme for rhododendron seedlings should be maintained within 2x3 cm. When replanting seedlings, the deepening is carried out along the cotyledon, so that this serves to form the root system. When growing seedlings in the first year, they are kept in cool greenhouse conditions. Only after another year, you can transplant into the open ground in a school (training bed). On it, the soil is made up of garden soil, combined with a small part of river sand and peat chips. However, it is worth noting that the growth rate of such seedlings will be very slow and such “pink trees” will start to delight in flowering only 6–8 years after the transplantation.
Propagation of rhododendron by cuttings
This breeding method is more complicated here. The tops from semi-lignified branches will act as blanks. The length of the cuttings should be about 5–8 cm. All lower leaves should be removed and the rest should be cut in half so that moisture does not evaporate from them. The cuttings are placed in lower cuts in a solution of a root formation stimulator (using Kornevin or heteroauxinic acid). There the workpieces are kept for 12-16 hours. Planting is carried out in containers filled with a peat-sand mixture in a 3: 1 ratio. After planting, the pots are covered with plastic wrap or a plastic or glass container is placed on top. You can take a plastic bottle, cut off the bottom of it and place it on top of the cuttings. This will help to conduct subsequent ventilation, simply by removing the cap from the neck. Rhododendron cuttings take root very difficult and for a long time. If the species is evergreen, then the duration of this process stretches for 3-4, 5 months, but cuttings from deciduous species will release root shoots after 6 weeks. The seedlings are grown in planting boxes, which are filled with a soil mixture based on peat crumbs and coniferous pine litter (fallen needles), in a ratio of 2: 1. During the winter months, when caring for cuttings, it is recommended to provide a high level of lighting and temperature indicators that do not go beyond the range of 8-12 degrees. When spring comes, this box is buried in the garden, where the seedlings will spend another 1–2 years, and only after the specified period is transplanted to a prepared place in the open ground.
Reproduction of rhododendron by layering
This method is the easiest, always giving a positive result. In the spring months, it is recommended to choose a young and flexible branch growing at the bottom of the bush. It is placed in a pre-dug groove, the depth of which will not be more than 15 cm. In the middle, the shoot is fixed with a stiff wire or hairpin in the groove. After that, the layering is sprinkled in the attached place with a soil mixture from garden soil in half with peat chips. The top of the branch, which remains on the surface of the substrate, is tied to a peg vertically dug in next to it. Layering care is carried out in the same way as for the parent bush. With the arrival of autumn or when the next spring comes, the cutter will have a sufficient number of its own root processes and separation from the mother rhododendron can be performed. Transplanting a seedling to a new place should be immediately after separation. This method is most suitable for the propagation of deciduous rosewood species.
Fight against possible diseases and pests when growing rhododendron
Of the diseases that gardeners face when caring for a "tree with roses", they distinguish: cancer or spotting of leaf plates. Often the reason for their occurrence is the lack of proper aeration of the soil, then the root system does not receive enough oxygen. With spotting, all the leaves begin to dot spots of various sizes of a light shade, which gradually merge and the leaves turn yellow and fly around. Used to treat fungicides (such as Fundazol or Bordeaux liquid).
When a rhododendron suffers from cancer, then on the surface of its branches, convex specks of a bright orange-pink color are clearly visible. Then it is recommended to cut off all affected shoots to healthy tissue or remove them altogether. All sections are carefully coated with garden varnish. Copper sulfate is used for disinfection, and so that infection does not develop, prophylactic treatment with Bordeaux mixture should be carried out in the spring.
Rust is a fungal disease that is clearly visible due to the appearance of small cushion-like formations on the leaves. High humidity and lack of aeration can also be the reason. This disease not only leads to foliage falling, but also reduces the frost resistance of the rhododendron. It is important to immediately take measures to eliminate it. At the same time, spraying with copper-containing preparations, for example, Bordeaux liquid, is performed.
Often, many representatives of heather are struck by chlorosis, in which the leaves take on a light green tint, in the veins opposite they are painted in a pronounced dark green color. Gradually, the foliage turns yellow and flies around. The reason for this is a lack of iron or watering with too hard (not acidified) water. Then it is recommended to use iron chelate or preparations with iron in the composition (for example, Mr. Color Anti-chlorosis).
The following pests cause a problem when growing rhododendron: scale insects and mealybugs, spider mites and weevils, rhododendron flies can also settle on bushes. All such insects are removed by treating the plant with broad-spectrum insecticides, such as Aktara or Karbofos. In this case, the trunk circle is also subject to processing.
Trouble happens when slugs or snails settle on the rosewood bushes. These "uninvited guests" have to be picked by hand or sprayed with Tirama or TMTD (8%), as well as a preparation containing Groza-Meta metaldehyde.
You can find out about popular types and varieties of rhododendrons in our article "Rhododendron: a general description of the plant, popular species and varieties."
Video about growing rhododendron outdoors:
