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Finding out that the boxwood has turned yellow is a very unpleasant discovery for any gardener. After all, it takes years to grow even a small beautiful bush. Loss of decorativeness is not the worst consequence of yellowing evergreen leaves. If you do not understand the causes of chlorosis in time and do not correct the situation, over time you can lose the entire plant.
Why does boxwood dry out and turn yellow?
Indispensable in landscaping, evergreen boxwood can be easily formed into beautiful shapes, dense hedges or borders. Small, tough foliage delights with bright colors all year round. But boxwood grows extremely slowly - under the most favorable conditions, its annual growth does not exceed 15 cm. Therefore, discovering that leaves have turned yellow or entire branches have dried out is a serious problem.
It is sometimes very simple to correct the situation by changing the care of the boxwood. In other cases, complex procedures will be required, but the probable cause must first be determined from among many possible causes.
Adverse climatic factors
Boxwood is considered a hardy plant that can cope with heat and cold, but sudden changes in weather or growing conditions can cause the plant to weaken.Leaves are the first to respond to stress factors. If boxwoods turn yellow, it means one of the following problems has arisen:
- A sharp change in light after winter. The bright spring sun can burn the awakening shoots while the roots are not yet functioning at full strength. If you do not shade the boxwood in the first sunny days, the leaf blades around the circumference of the bushes will inevitably turn yellow.
- The leaves can acquire a reddish tint in the hot summer when two factors coincide: bright midday light and drying out of the top layer of soil near the trunk. Boxwood is thermophilic, but at temperatures above + 35 °C it requires partial shade or diffuse lighting.
- For central Russia, you should choose specially bred frost-resistant varieties. The first sign of hypothermia is if the tips of the leaves turn yellow. Boxwood easily tolerates mild winters, but during severe cold snaps the entire part not covered with snow can freeze.
Improper care
Not only natural factors influence the fact that boxwood leaves turn yellow. Sometimes care does not meet the needs of the plant, to which the bushes react by changing color.
The most common causes of yellowing of boxwood:
- Insufficient hydration. Boxwood does not require watering, but prolonged drying of the top layer of soil is contraindicated for it. It often happens that boxwood turns yellow after pruning if the mandatory watering after the procedure is missed.
- Dry air. If there is insufficient humidity, it is useful to spray young bushes with a spray bottle.This will stop the yellowing. It is useful to combine the procedure with foliar feeding.
- Excessive moisture. Stagnation of water in the soil is unacceptable when growing boxwoods. Systematic overwatering provokes rotting of the roots. In this case, the leaf blades gradually turn yellow, and signs of general wilting are observed.
- Lack of nutrition. A lack of microelements may manifest itself as yellowing of the tips of the leaves or the interveinal space. Over time, the entire green part changes color and the plant may die. Yellowing is usually due to a lack of phosphorus or potassium.
- If the boxwood is yellow mainly in the middle of the bush, and there is also a change in color in the lower part, it means the plant lacks nitrogen.
Diseases and pests
The most dangerous diseases for crops are fungal infections. The most difficult types to defeat are two types of infection: tissue necrosis and root rot. The smallest spores of the fungus are carried by air masses and mainly affect weakened plants located in conditions of excess humidity.
Necrosis
The disease manifests itself in early spring. If the youngest shoots turn red, then turn yellow and dry out, then it is a matter of infection with a fungus. Affected bushes should be treated with fungicides, dried shoots should be removed and burned. Deep pruning is carried out to healthy areas of wood, after which the treatment with preparations is repeated.
Root rot
The lesion is also caused by a fungus present in the soil.The disease actively develops with excessive watering with stagnant moisture, mainly in the cold season. Root disease is manifested by general inhibition of growth and lethargy of boxwood. As root rot progresses, it causes the leaves on individual shoots to turn yellow, and then the entire plant.
At the early stage of the disease, when only individual branches have turned yellow, the boxwood can be removed from the soil, all damaged areas of the roots can be cut off, and the substrate in the planting hole can be replaced, with drainage required. Sand must be mixed with fresh soil. At a late stage, with the loss of more than half of the green mass, it is almost impossible to save the boxwood.
Boxwood gall midge
Pest infestation first appears as yellow swellings on the surface of the leaves. On the back side of the plate, tubercles form in which worm-like orange larvae develop. Young gall midges feed on boxwood leaves, and during the winter they go deep into the wood, only to come to the surface in the spring and repeat the breeding cycle as adult insects.
With prolonged infection, boxwood leaves and entire shoots dry out. Gall midges should be combated comprehensively, removing the affected areas of the shoots, treating them twice with chemicals (Tagore, Aktara) with a break of 10 days. Be sure to spray the plants next season in early May, when the surviving gall midges enter the breeding season.
Boxwood moth
An insect similar to a small moth, the most dangerous enemy of boxwood plantings in Europe, entered Russia in 2012, but managed to spread over large areas and destroy hectares of groves on the southern coast of the Black Sea. Once on plants, insects quickly multiply and cover the bushes with sticky webs. Boxwood leaves turn yellow and curl; they are eaten by small, bright moth caterpillars.
If a pest is detected, the plantings are immediately treated with specialized biological products. Moreover, separate insecticides are provided for insects at different stages of development: Dimilin, Decis pro, Fastak, Fury. Spray the crown, trunks and all the soil near the trunk, as well as between the plants.
Spider mite
If the leaves become covered with yellow spots, and later lose color and dry out, you should check the boxwood for the presence of small mites on the underside of the leaf blades. Pests appear in hot weather with low air humidity and feed on sap from living leaves.
At the initial stages of infection, microscopic mites can be washed off the plants with a soap solution. This way you can prevent the entire bush from turning yellow. In case of severe damage, the plantings will have to be treated with chemicals.
What to do if boxwood dries and turns yellow
If individual leaves or entire branches turn yellow, and no pests or diseases are found, a number of measures should be taken to save the plant.
Basic measures for treating drying boxwood:
- If the reason that the bush has turned yellow is sunburn, you should place a screen next to it, protecting it from direct sunlight.
- When the soil compaction is high, the plantings are dug up by making a shallow groove, slightly enlarging the tree trunk circle.
- Boxwood roots occupy the very top layers of the soil and can suffer from changes in humidity. Around a boxwood that has turned yellow, mulch should be laid in a layer of 1 cm, with a diameter of at least 15 cm from the trunk.
- Regulating watering often helps bushes recover quickly. Proper, abundant fertilizing allows you to increase the leaf mass and avoid further yellowing.
- An important stage in treating bushes is the complete removal of all parts of the plant that have dried out or turned yellow. The shoots are removed down to healthy leaves, checking the condition of the wood at the cut.
Preventive actions
It will not be possible to return the color to boxwood that has turned yellow. The affected branches will have to be removed and the formation of the bush must begin again. It is much easier to take care of the plants in advance.
Prevention of discoloration and drying of boxwood includes the following measures:
- Regular removal of garden debris (leaves, branches) from the tree trunk and center of the bush. This way you can avoid the proliferation of pathogenic spores and bacteria.
- Annual crown thinning, especially in the center. Excess shoots are removed until the location of the internal branches in the bush can be accurately seen.
- Early installation of screens or canopies from the spring sun. Work is carried out no later than mid-February. You can simply cover the boxwood with an opaque, breathable material.
- Ensuring a sufficient drainage layer even at the stage of laying planting holes.If the bush has already turned yellow from waterlogging, you can try to carefully dig it out, pour at least 10 cm of pebbles, bark, coarse sand, and crushed stone under the roots. After this, plant the plant in place again.
Be sure to regularly fertilize boxwood. In autumn - with potassium content to maintain frost resistance. In spring, with complex formulations with the obligatory presence of nitrogen. In the middle of the season, if the leaves are bright, green and not a single shoot has turned yellow, boxwood can only be watered without adding fertilizer.
Conclusion
If the boxwood has turned yellow, it is not time to despair and discard the bush. By finding out the cause in time and providing proper care, you can restore the plant’s attractiveness. When individual leaves or shoots turn yellow, this is a signal from the boxwood about trouble, and having dealt with it, you can safely grow more than one beautiful plant, garden sculpture or an entire hedge.
