Rose branches have turned black: why and what to do

Content

1 What blackened rose branches look like
2 Why does a rose's trunk turn black?
3 What to do if the stem of a rose turns black
4 Preventive measures
5 Conclusion

Roses are an “eternal” trend in landscape design. However, they are susceptible to diseases that negatively affect the decorativeness of the bushes. One of the common symptoms is the branches of the rose turning black. In this case, it is necessary to be able to correctly identify the disease by “associated” signs and know what to do in each specific case. Naturally, it is easier to prevent a disease than to fight it, so the gardener needs to pay attention to preventive measures.

What blackened rose branches look like

When the stems and other parts of a rose turn black, it may look different. And often this is not the only symptom indicating the disease.

The blackness on the stems of roses can be “solid” or “spotty”. The affected areas themselves are dry or “wet”, as if slimy to the touch. Fabrics that turn black, in some cases become very soft, and in others, on the contrary, “harden” unnaturally and crack.

However, in garden and house roses, when their trunk has turned black, some similarities can be identified, in addition to the fact that their decorative effect greatly suffers:

The disease does not stop on one stem; it first spreads to the entire already infected bush, then “spreads” to neighboring roses.
Plants “refuse” to form buds, their development practically “freezes”, their tone decreases literally before our eyes.
Already existing buds on bushes whose stems turn black dry out and fall off without opening, or become severely deformed.
The stems of roses themselves, when they turn black (even on top), cannot be used for propagation (cuttings do not produce roots).

To correctly “make a diagnosis”, you need to evaluate it holistically, taking into account all the negative changes

Important! If nothing is done when the rose branches turn black, the disease “spreads” to other parts of the plant. Most often, the buds and petals of opened flowers “suffer”, then the leaves and root system.

Why does a rose's trunk turn black?

It is often the gardener’s fault that the rose’s stems turn black. Diseases are much more often “caught” by bushes whose immunity is weakened due to serious errors in care or incorrect choice of planting site.

Basically, rose stems turn black for the following reasons:

Excessive “crowding” in the flowerbed. Thickened planting prevents normal air circulation and access of light to the inside of the bush. Such a “stagnant” atmosphere is very suitable for pathogenic microflora.
Excessively abundant watering. High humidity and a “swamp” in the flower bed contribute to the activation of many pathogenic fungi.
Excess nitrogen in the soil. “Overfeeding” with nitrogen fertilizers greatly “undermines” the immunity of roses. They become more susceptible to diseases, including those that cause the stems to turn black. Calcium deficiency has a similar effect.

Improper watering is the cause of many problems with bushes

Bacterial cancer (burn)

When the stems of roses turn black due to bacterial canker (also known as bacterial burn), “pressed-in” black-brown small spots of a fairly regular round shape appear on them along the entire length. Gradually they grow, the tissues affected by the bacteria dry out and die, as a result of which the spots turn into “ulcers”. The shoots dry out, the above-ground part of the bush dies, and it dies.

If nothing is done, not only the stems of roses turn black, but also the leaves. “Wet” rounded black spots appear on them. When tissues die, holes remain in this place. Eventually the leaves fall off.

Bacterial cancer often causes the stems of old roses to turn black, the shoots and roots of which are prone to cracking

The activation of bacteria is promoted by:

temperature in the range of 25-30 °C;
alkaline substrate (pH 6.0-9.0);
heavy clay soil;
excess nitrogen in the soil.

However, despite the relatively high favorable temperature, the stems of roses turn black from bacterial cancer quite early, even before flowering. The pathogen “seizes the moment” and begins to actively progress when the bushes have not yet recovered from the “stress” of wintering.

Important! The causative agent of bacterial cancer remains viable in the soil for several seasons. The disease is also transmitted through tools, gloves, and work clothes of the gardener; it is carried by insects, wind, and raindrops.

Gray rot

When gray rot develops on roses, not only do their stems turn black. The buds are the first to suffer: “clumps” of dark mucus appear in the core and at the base, the petals soften and turn brown.

Then similar damage in the form of “wetting” dark spots is noted on the leaves and stems. Gradually they become covered with a layer of “fluffy” gray plaque with small black “grains” (clusters of fungal spores). The last pathogen attacks the root system, the rose stems turn black completely, the leaves fall off, and the plant dies.

Young roses are most susceptible to gray rot; The disease manifests itself quite late, at the end of summer

The following factors are favorable for the development of gray rot:

cool weather (about 20 °C), high air and soil humidity caused by frequent rains and fogs;
excessive “crowding” in the flowerbed;
mechanical damage to rose stems.

Important! Rose bushes affected by gray rot, whose stems turn black, should not be covered for the winter along with healthy ones. By spring, all plantings will almost certainly die.

Black spot

Also sometimes found under the name “marsonina” (from the name of the fungus that causes the disease). In this case, the stems of roses are affected and turn black much less often than the leaves, only if the process of development of the disease is “started” to the state of a “severe case”.

Rose leaves are the first to suffer from black spot. Purple “blurry” spots appear on the front side. They quickly turn black and become covered with a “scabbing” of accumulations of fungal spores.

The process goes from the bottom up, most often the rose fungus is “picked up” from the ground. If nothing is done, the leaves turn brown, curl up and fall off. Then the disease “spreads” to the stems of the roses, they turn black.

In bushes affected by black spot, not only their decorative properties suffer. They become more susceptible to other pathogens, and their cold resistance is greatly reduced.

The fungus, which turns the leaves and stems of roses black, overwinters in plant debris. In the spring, he waits long enough for favorable weather, so symptoms appear closer to mid-summer.

Spores are transferred from diseased bushes to healthy ones by wind, drops of rain, and dew; The gardener himself can “contribute” to this

Powdery mildew

An extremely common disease in which mainly young stems of roses turn black, and subsequently leaves. At first it looks quite “harmless”: like a grayish powdery coating on the shoots.

Gradually it thickens and darkens. The tissues on the stems underneath turn black and, depending on air humidity, dry out or rot and die. The shoots themselves become deformed.

The fungus then “moves” to the leaves. They also gradually turn black, curl and fall off. Rose buds are rarely affected by powdery mildew, only in the most severe cases - they dry out without opening, and the outer petals of already blossoming flowers curl and die.

The “damage” is not limited to the fact that the stems of the bushes turn black. The immune system suffers greatly, the bushes lose the ability to normally tolerate temperature fluctuations. They most likely will not survive the winter.

Roses are especially susceptible to powdery mildew when there is an excess of nitrogen in the soil and a deficiency of calcium.

Important! Roses with thin and “delicate” leaf plates are especially prone to infection with powdery mildew.

What to do if the stem of a rose turns black

There are no methods for treating bacterial cancer: if the stems of roses turn black because of it, the bush can only be dug up and burned to prevent the spread of the pathogen. Only fungal diseases can be treated with “therapy”, and it is worth starting as soon as possible after symptoms are detected.

What to do if you see that the rose trunk has turned black and have identified the pathogen:

Using a sharp, disinfected knife or pruning shears, cut off all parts of the plant that show symptoms, even slightly. All “wounds” are immediately disinfected by sprinkling with sifted wood ash, crushed chalk, and activated carbon.
Burn the resulting plant debris as quickly as possible. Adding it to compost is a very bad idea.
Spray the roses themselves, whose stems are turning black, and the soil in the flowerbed with a solution of any fungicide. It is not advisable to use folk remedies in this case; it will simply be a waste of time. All processing is carried out in strict accordance with the manufacturer's instructions. This is especially true for the concentration of the solution and the frequency of procedures.
Provide the highest quality aeration. In climbing varieties and hybrids, the stems are removed from the support and fanned out so that they do not touch each other. In creeping ground cover shoots, the shoots are raised above the ground, laid on “horns”, and the mulch layer is completely changed. The rest are pruned, “opening” the middle of the rose as much as possible.
2-3 weeks after the condition of the bushes improves and their stems stop turning black, it is advisable to carry out foliar feeding with any biostimulant.

When pruning, it is advisable to capture some healthy-looking tissue - most likely, the pathogen has managed to spread there too

You cannot endlessly spray rose bushes whose stems turn black with fungicides. If after 3-4 treatments their condition has not improved, you may not continue further. Plants are dug up and burned.

Preventive measures

Preventing roses from becoming infected with diseases that cause their stems to turn black is much easier than fighting them later. Preventive measures are simple, they will not take much time and effort from gardeners:

regular inspection of plantings for the presence of suspicious symptoms;
weeding flower beds;
cleaning the soil at the end of autumn from plant and other debris, deep loosening, updating the mulch layer;
proper care of plantings during the season;
timely and high-quality shelter for the winter;
choosing a place for a seedling according to the “requirements” of the culture;
planting in accordance with the scheme recommended for a given variety or hybrid in order to avoid “crowding” in the flowerbed;
targeted pest control.

You cannot neglect the inspection of even absolutely healthy roses - this is what will allow you to notice the development of the disease in time

Conclusion

If the branches of a rose turn black, this indicates that the bush is infected with a dangerous disease. The gardener is required to determine as quickly as possible what exactly he is dealing with, otherwise it will not be possible to “prescribe” the correct “treatment”.