Reproduction Of Rhododendrons, Diseases And Pests

2024 Author: Sebastian Paterson | [email protected]. Last modified: 2023-12-16 13:47

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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. It is easier to propagate rhododendrons by semi-lignified cuttings. After flowering ends, 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, so 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.

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After treatment with a root-forming agent (heteroauxin, root, etc.), plant the cuttings on a special bed (cuttings) or in pots and put them in a 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, the rooted cuttings will have to grow 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. In this way deciduous rhododendrons reproduce better. 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 up to planting in a permanent place.

Rhododendron diseases

Subject to all the rules of agricultural technology, plants have a fairly high resistance to various diseases and pests. If, nevertheless, some problems began, 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 desiccation, and sunburn.

Often, rhododendrons attack 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 is a disease provoked by fungi belonging to the genus Fusarium. The main sign of the onset of this disease is root rot, 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, after which the plant withers and dies.

Rot is gray. Mushrooms from the genus Botrytis are considered the source of this disease. Many crops suffer from this disease due to the easy spread of fungal spores through the air and with 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 spotting is provoked by a fungus from the genus Septoria. The leaves of the plant are covered with small spots of a red hue and a round shape. The center of the spots turns white over time, becoming covered with black dotted fruit 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, backfilling of the neck with coarse clean sand, systematic watering of the soil under the plant with bacterial preparations: phytosporin, extrasol, etc. Copper-containing preparations (HOM, Ordan, etc.) are used against spotting, and bacterial preparations are used for prevention.

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 brownish-yellow dots, you can also notice a cobweb braiding 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.

Phytoverms, agravertin and other similar preparations for weevils and many other pests, as well as numerous remedies that are used against the Colorado potato beetle, help well against spider mites and aphids. Against pests that hibernate in the soil and damage 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 well 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 →

Tatyana Popova, gardener

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