Reproduction of rhododendrons, diseases and pests


Read the previous part. ← Caring for rhododendrons in spring, summer and autumn

Reproduction of rhododendrons

Species rhododendrons often grow in our gardens, so they can be propagated by seeds. However, this is a rather complex and lengthy process, usually inaccessible to an amateur florist.

Seedlings grow very slowly and are susceptible to many diseases that cause their death. Simpler rhododendrons

propagate by semi-lignified cuttings

... After flowering, when the bases of young shoots begin to lignify, they can be used as cuttings. But here, too, many difficulties await us. The rooting process in evergreen rhododendrons is very long, and in the open field they do not have time to give roots over the summer, therefore they are rooted in closed ground.

Deciduous rhododendrons reproduce more easily. You need to take young shoots as cuttings in late June - early July. It is better not to cut off the shoots, but to break them off (they break easily with a small "heel"), leave a few leaves in the upper part of the shoot, and cut off the rest.


After treatment with a root-forming drug (heteroauxin, root, etc.), plant the cuttings on a special bed (cuttings) or in pots and put

to the greenhouse

... For the winter, the pots need to be dug in, the cuttings should be insulated. Leave the cuttings to root for another summer. Before planting them in a permanent place, rooted cuttings will have to be grown for another 1-2 years.

For hobbyists, the most suitable breeding method is the rooting of cuttings. It is similar to how it is done on most shrubs. Deciduous rhododendrons reproduce better in this way. Most of my deciduous rhododendrons are sourced this way. Everything is as usual: the lower branches are pressed to the ground, for example, with metal hooks, and they are covered with loose soil or peat on top. To improve rooting, you can make cuts in the bark on a branch, cover the rooted place with root. The rooting site must be watered systematically. You can separate the layers after two years, and then grow them before planting in a permanent place.

Diseases of rhododendrons

Subject to all the rules of agricultural technology, plants have a fairly high resistance to various

diseases and pests

... If, nevertheless, some problems have begun, you should, first of all, pay attention to the conditions of keeping the plant. Rhododendrons are intolerant to severe waterlogging, unbalanced feeding, low soil acidity, winter physiological drying, and sunburn.

Often, rhododendrons infect fungal diseases. They often suffer from spots and rust, as well as chlorosis (yellowing of the leaves), which is an acute shortage of elements such as manganese and iron. Chlorosis is usually triggered by low soil acidity.

The main diseases of rhododendrons:

Tracheomycotic wilting - a disease provoked by fungi belonging to the genus Fusarium. The main sign of the onset of this disease is root decay, which subsequently spreads to the entire vascular system of the plant. The plant begins to dry out slowly, acquiring a brown color, and browning begins precisely from the upper organs (mainly from the shoots). As the foliage and stems of the plant dry up, they become covered with mycelium - a bloom of a grayish hue.

Late blight rot - this disease is provoked by mushrooms from the genus late blight. The root collar and base of the stems are covered with purple-brownish spots of rather large sizes, while the roots begin to turn brown and rot away, after which the plant withers and dies.

Rot gray. The source of this disease is considered to be fungi from the genus Botrytis. Many crops suffer from this disease due to the easy spread of fungal spores through the air and water spray. All parts of the plant, including leaves, buds and stems, are covered with brownish-brownish spots, as a result of which mycelium appears on the damaged drying tissues, leading to the death of the plant.

Septoria spot provoked by a fungus from the genus septoria... The leaves of the plant are covered with small spots of a red hue and a rounded shape. The center of the spots turns white over time, becoming covered with black dotted fruiting bodies when the fungi pass into the hibernating stage. Stems affected by the disease begin to shrivel and dry out, and the leaves turn yellow and fall off the plant.

It is very difficult to fight diseases that have gone far, so you need to carefully monitor the condition of the plants and take action in time. Root rot, damage to the bark on the root collar are especially dangerous. If a significant part of the bark has suffered, the plant cannot be saved. Small rotten areas of the bark must be cut off and the wounds painted over with water-based paint with the addition of copper oxychloride (HOM) - 20 g per 100 g of paint.

Effective in the fight against fungal infections of the roots of phytolavines. A good prevention of such diseases is the correct level of planting, filling the neck with coarse clean sand, systematic watering of the soil under the plant with bacterial preparations: phytosporin,

extrasol

and others. Copper-containing preparations (HOM, Ordan, etc.) are used against spotting, and bacterial preparations are used for prophylaxis.

Rhododendron pests

Alley of evergreen rhododendrons

Among the pests of rhododendrons, the following are worth highlighting:
Spider mite. It mainly affects plants in hot, dry weather. Adults are very difficult to see due to their small size, not exceeding half a millimeter. The appearance of this pest on the plant is indicated by the browning of the leaves, they are covered with small brown-yellow dots, you can also notice a cobweb that braids the underside of the rhododendron leaf. Most often deciduous rhododendrons are damaged.

Acacia false shield. Its larvae appear as small shiny brown outgrowths that cover the bark of the plant. The pest feeds on plant juices, causing it to weaken and dry out.

Furrowed weevil - a small black bug, centimeter-long. The damage to the plant is enormous: the larvae damage the root system, while the adults damage the buds and bark of rhododendrons, possibly an attack by aphids.

From spider mites and

aphids

phytoverm, agravertin and other similar preparations for weevils and many other pests help well, as well as numerous remedies that are used against

Colorado potato beetle

... Against pests wintering in the soil and damaging the roots, it is necessary to spill the soil under the plants with pesticides. Scabbards have to be scraped off, and damaged shoots are painted with water-based paint.

Often damage to rhododendrons by garden

slugs and snails

, which can be dealt with by mechanical collection and destruction, as well as by laying out the "Thunderstorm" granules under the plants.

The main thing for keeping rhododendrons in a healthy state, as for other plants, is checking and disinfecting planting material, quarantine measures, a suitable planting site and proper care, careful observation of plants, timely response to the growth and development problems of these shrubs, and disease prevention.

Read the next part. Using rhododendrons in garden design →

Tatiana Popova, gardener
Photo by Vladimir Popov

Tel .: +7 (904) 631-55-57
Website: http://hydrangea.ru/


Read all parts of the article "Growing rhododendrons in the Northwest"
- Part 1. Species and varieties of rhododendrons
- Part 2. Site selection and planting of rhododendrons, growing conditions
- Part 3. Caring for rhododendrons in spring, summer and autumn
- Part 4. Reproduction of rhododendrons, diseases and pests
- Part 5. Using rhododendrons in garden design

Outdoor rhododendron care

The soil under the rhododendrons should not be dug up so as not to damage the roots. Loosening with a thin hoe is allowed. However, it is necessary to regularly remove weeds before they grow large, as removing large weeds can also damage the small roots of the rhododendron.

Rhododendrons need to be fed with special preparations that can be purchased at garden stores. Nutrient delivery should take place in spring and early summer. However, be careful not to extend this period as the plants will not have time to prepare for winter.

Fertilizers for growth and abundant flowering

Rhododendrons growing near deciduous trees do not need additional fertilization, its function is performed by the foliage falling every year. However, in most gardens, rhododendrons still need regular fertilizing with mineral fertilizers, especially if the bushes are still young.

  1. The first time to fertilize rhododendrons is best in April-May, when the plants are actively growing.
  2. The second - more important - feeding is done after the flowering of rhododendrons, when new shoots appear on the plants (as a rule, in June-July).

Approximate figures: for a plant with a height and width of 40 cm, about 15-20 g (half a tablespoon) of fertilizer is required in spring and summer, for a plant with a height of 150 cm, respectively, 80-100 g.

Removal of faded inflorescences

Do not use liquid fertilizers, it is better to use granular, prolonged release or specially formulated fertilizers for rhododendrons.

Careful maintenance of the rhododendron also includes an annual substrate pH test. If necessary, we also mulch the substrate with a mixture of bark and acid peat.
After the rhododendron fades, the process of seed formation begins. Gently pinch off the inflorescences immediately after they wilt. Thanks to this, the plant will not spend energy on ripening seeds, but will save energy for the formation of new shoots and flowers next year. In addition, rhododendron bushes take on a more well-groomed look.

Pruning

Can rhododendrons be trimmed?

It is better not to cut off at all - rhododendrons look more picturesque over the years

It is better not to cut them off at all - rhododendrons look more picturesque over the years. If you have to cut a too tall bush, then it will soon give new shoots even on old lignified branches (see photo). Note, however, that these slow-growing shrubs will take several years to grow back to their original height.

In spring, cut dried and frozen shoots. Young plants can also be stimulated at this time by pruning them slightly. Old bushes that have lost a lot of lower leaves and look ugly should be rejuvenated by cutting out all shoots, even thick ones. After pruning the branches, many young branches will grow out of the dormant buds in a few weeks. If you are not sure if the bush is strong enough to withstand such a radical cut, you can rejuvenate half of the bush in the spring and the rest next year.

Shelter from frost and wind

Hanging leaves are not a sign of frost damage.

Rhododendrons thrive in temperate climates with warm winters and high humidity. Under such conditions, even in the cold season, metabolism occurs in their evergreen leaves. But the cold winters of Central Europe are not entirely suitable for rhododendrons - on sunny days, the process of photosynthesis begins in the leaves, and the roots cannot absorb enough water from the frozen soil for metabolism, and the leaves begin to dry out. Therefore, for rhododendrons, the winter sun at sub-zero temperatures is more dangerous than the frost itself.

For sensitive varieties and standard plants, it is advisable to use shade shelters. They protect the plants from the wind and, by creating shade, prevent the leaves from drying out. These shelters are best made from breathable materials such as agrofibre, otherwise mold can develop underneath. Dehydration is especially dangerous for container rhododendrons, so they should be watered abundantly in winter.

Small feet under tubs and pots will drain excess water

Rhododendrons growing in the shade, for example under tree crowns, usually do not need to be covered for the winter.
Dangling leaves are not a sign of frost damage, but the plant's natural reaction to it. The tent will protect you from wind, cold and winter sun, which can dry out the leaves in case of frost on the soil. In standard plants, both the crown and the trunk should be covered for the winter.
Small “LEGS” under the tubs and pots will drain excess water.

Optimal watering

Rainwater is ideal for irrigation as it does not contain lime.

Rhododendrons prefer uniformly moist soil. They are equally sensitive to both drying out and waterlogging. When watering, you need to know when to stop: a large amount of water washes away nutrients and leads to decay of the roots, with insufficient watering, the bushes wither and dry out. If the leaves fall from the heat during the day, then this is normal, the plants usually recover overnight. For irrigation, it is better to use rainwater, which, unlike tap water, does not contain lime. The mulch layer prevents water evaporation and retains moisture in the soil. The same function is performed by ground cover plants, which create a favorable microclimate. For dry soils, computer-controlled drip irrigation is suitable, evenly moisturizing the soil.

Important: Evergreen rhododendrons should be watered in winter as well.


Garlic in the garden - what to plant nearby

Gardeners can also take advantage of the benefits of garlic as a plant that helps fight disease and pests using coordinated cultivation. Planted next to carrots, a garlic row will scare away carrot flies, next to strawberries will reduce the appearance of strawberry mites, and near currants will help fight leafworm and spotted rust.

Cloves of garlic placed in the earthen pits of vole mice can permanently scare away rodents and force them to leave the site.


Diseases and pests

When the scabbard appears, the leaves of the ctenants will begin to become covered with brown spots, then dry up and fall off. The spider mite leaves behind whitish spots on foliage and traces of cobwebs. The reason for their appearance may be in too dry air. To combat pests, you must first use insecticidal solutions, and then restore high humidity in the room.

The ktenant is sick mainly due to non-compliance with the rules of care:

  • At temperatures below 15 degrees and severe waterlogging, the stems lose their stability and begin to rot.
  • At very low humidity, growth slows down and the tips of the leaves dry.
  • With a lack of moisture and when exposed to direct sunlight, the leaves curl up and lose their usual color.

Ktenanta is a rather unpretentious plant and will not cause much trouble when grown at home.


Description of calathea

The vast majority of calathea varieties have underground shoots located near the surface of the earth and forming a root system. They store the moisture necessary for the flower. It is from them that new rosettes appear, formed by large oval leaves. They are up to 40 cm long and are located on long petioles. The calathea bush itself can reach almost a meter in size.The outer surface of the leaves is painted in different shades of green, and may also have splashes of white, yellow or pink. The seamy side of the leaf blades is most often painted in pinkish-purple tones, but there are also species with completely green leaves.

Up to 6 new plates can appear on the bush per year. In the spring, during the flowering period, the plant forms nondescript inflorescences-spikelets of white or lilac flowers that do not have much decorative effect. The exception is two calatheas - Varshevich and saffron. Their flowers are located behind bright bracts, painted in tones of white, orange or pinkish colors.

As a representative of Marantovs, calathea also has an interesting feature characteristic of them. The nubs, located between the petiole and the leaf blade, control the leaves themselves, turning them closer to the light. Because of this, every evening the leaf blades of the calathea rise upward, folding like hands in prayer. With the onset of the morning, they return to their original position. Due to this feature, calathea and arrowroot are also known as "prayer flowers".


Rhododendron

The genus of rhododendrons is considerable and diverse. Its genus includes deciduous, evergreen and semi-evergreen shrubs, and sometimes trees.

Rhododendron is a plant of the Heather family. The genus unites about 1300 species of evergreen and deciduous trees and shrubs.

The genus rhododendron also includes azaleas known in the greenhouse and indoor culture, distinguished by some classifications in the subgenus.

Rhododendrons are common in the Northern Hemisphere, with the greatest diversity of species found in the Himalayas, southern China, Southeast Asia, Japan and North America. Rhododendrons vary greatly in size: some species grow up to 30 m tall, while others are simply creeping shrubs.

Under natural conditions, 18 species are found in Russia, in the Caucasus, Siberia, and the Far East.


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