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Hardly any plant is as versatile as the boxwood. Whether as an opaque hedge, edging for beds or a beautifully shaped eye-catcher, it remains green day after day. You just have to be patient because he's growing at a snail's pace. If unexpected yellow or brown leaves appear on the box tree, the horror is all the greater. Has all the years of effort been in vain or can the cause be found easily and fixed promptly?
When all the causes are listed that can cause yellow or brown leaves in Buxus sempervirens, as the box tree is botanically called, this list becomes really long. Broadly speaking, they can be divided into the following four categories:
- bad site conditions
- care mistakes
Don't let that put you off. Some of them can be effectively combated or eliminated with appropriate measures. Before doing so, however, the reason for the discolored foliage must be clearly identified. It is advisable to check all possible causes, because several of them can be active at the same time as unwanted "leaf color change".
Poor site conditions
A location that is not quite optimal, in combination with the weather elements, causes unwanted leaf discoloration on the boxwood. If additional balancing care is missing, yellow or brown leaves on the boxwood are inevitable at some point. In summary, any site that has one or more of the following characteristics is unsuitable:
- offers no protection from the winter sun
- is very sunny throughout the summer
- tends to waterlogging
- is too sandy, tends to be dry (nutrient absorption is also disturbed)
If yellow leaves appear on the box tree directly in the winter show, it is very likely that the cold combined with the winter sun is to blame. Especially when the boxwood leaves are covered with hoarfrost, the winter sun has a devastating effect. Forms a boxwood, however, in the summer and yellow leaves or entire leaf sections on the south or south-east side facing the sun, he has one sunburn to get. Such burns can occur especially after pruning, since previously well-shaded leaves are then exposed to the full sun. When it comes to water balance, you need to take a close look at the soil at the foot of the boxwood to draw the right conclusions in this regard.
If you have identified an unfavorable location as a possible cause, you do not immediately have to think about giving up or transplanting. First try to get the problem under control with the first measures and wait and see whether the tree recovers. Only if the location is very unfavorable and the measures taken are not sufficient does the plant have to be transplanted.
- Cut back sunburned shoots
- If possible, plant other trees in front of them to provide shade
- they also protect the tree from the winter sun
- allow the wet floor to dry properly first
- only then water again if necessary and, above all, moderately
- Dry soil, on the other hand, should be regularly moistened
- amend sandy soils with compost
- if necessary, fill up the nutrient depot with horn shavings
Fortunately, not every summer in this country is extremely hot and not every winter is bitterly cold and sunny at the same time.
If your boxwood thrives in a pot, you can immediately move it to a new, more suitable location. If necessary, repotting can also be useful, for example to add a missing drainage layer.
A boxwood can very quickly suffer disadvantages through carelessness and a lack of knowledge about the care needs of this evergreen plant. The care must also be flexibly aligned to the given location and the current weather conditions. The most common maintenance mistakes are:
- undersupply of nutrients
- caused by incorrect dosage
- irregular fertilizing
- wrong time (fertilizing time is April to September)
- wrong fertilizer, e.g. blue grain
- soil that is too wet or too dry due to incorrect watering
- no need-based amount of water
- an unsuitable watering interval
- Giessen was neglected in winter and summer
Bronze discoloration is a sign of nitrogen deficiency. But the boxwood can also be damaged unintentionally, for example if weed killers are applied in its immediate vicinity.
It is high time to inquire in detail about the needs of the boxwood in order to avoid care mistakes from now on. In addition, you should take the following measures:
- immediately water a dry soil copiously
- Water daily on hot summer days
- Loosen the soil regularly
- Apply a layer of mulch to protect against drying out
- allow a wet soil to dry before further watering
- down to the deeper layers
- Cut back yellow or brown plant parts in autumn
- Provide boxwood with a long-term fertilizer
- e.g. B. with compost or horn shavings
- or use special boxwood fertilizer
tip: A box tree must occasionally be watered in winter, especially if it is growing in a bucket. This is the time when he develops his roots.
The headline could also be fungal diseases, because these are the ones that have been causing problems for Buxus sempervirens in recent years. Not all of them cause yellow and brown leaves on boxwood. In the case of fungal diseases, not only are the leaves blotchy or completely discolored, there is usually also a fungal coating, which is often only discovered after a closer look.
Four fungal diseases in particular can cause yellow and brown discoloration of the leaves and even cause them to die or fall off.
The tree canker spreads with preference in cool summers. The first sign, the orange fungal coating on the underside of the leaves, is usually overlooked. This is followed by discolored leaves, which, however, remain on the shoots for a long time. This fungal disease does not appear very bad, but that is deceptive. Without help, the box tree can die from it.
This fungal disease is usually found on already weakened box trees. It shows symptoms similar to tree cancer, but can be easily combated with pruning.
Tree rust also has an easier time with weakened or old plants. This fungal pathogen does not discolor the entire leaves. Rather, small and slightly raised spots of rust are visible on the upper sides of the leaves. Their color is reddish brown.
This fungal disease is initially recognized by orange-brown leaf spots. The spore stores are hidden on the underside of the leaves and are white in colour. The shoot tips, on the other hand, are criss-crossed with black stripes.
combat fungal infestation
Fungal diseases cause the Buxus sempervirens even more trouble than an unfavorable location or incorrect care. If fungal diseases go undetected or if the plant gets help too late, it can perish completely.
- Act quickly at the first symptoms
- Cut back affected shoots
- down to healthy wood
- always use disinfected cutting tools
- Discard removed shoots and fallen leaves
- Change the soil underneath the plant
- inside are fungal spores that would strike again
- only then supply again with organic long-term fertilizer
Due to the very slow growth, it can take several years for the boxwood to fully recover from pruning caused by disease. If you are considering chemical treatment, seek advice from a specialist retailer. However, keep in mind that fungicides also have a harmful impact on the environment.
Buxus sempervirens is delicious food for some pests. Many species are seen on it, but two of them in particular lead to a change in leaf color right from the start.
box tree moth
When the plant turns yellow to light yellow and only the veins of many leaves remain, the caterpillars of the box tree moth have been well protected inside the plant and have eaten through them for weeks. The caterpillar is about 5 cm long, green and patterned with black dots. The moth lives less than 10 days while hiding under the leaves. It is mostly white with black patterns.
boxwood spider mite
The spider mite causes a significant loss of green color. But at the beginning she sends small yellow speckles ahead, which to a trained eye are an alarm signal. Later, the leaves are recolored to bronze. This mite species likes dry and warm weather. It is very small at 0.5 mm and is therefore easily overlooked.
get rid of pests
In its fight against the pests, the boxwood needs the help of its owner.
- Combat spider mites naturally with predatory mites
- use commercially available preparations if necessary
- in the spring, treat eggs with oil-based agents
- collect caterpillars of the box tree moth in spring
- alternatively spread foil around the plant
- Remove caterpillars with a leaf blower or high-pressure cleaner
- Discard caterpillars with foil
- Use pesticides if the infestation is severe
You can prevent fungal diseases and pest infestation by strengthening the plant's resistance. Always good care is the most important means. You can also regularly administer special plant strengtheners. To what extent preventive fungicide spraying makes sense, everyone has to decide for themselves, after all, these agents are not exactly environmentally friendly.
When planting new plants, you should immediately pay attention to an optimal location. In addition, the market offers some less susceptible boxwood species.