Why do thujas dry out?
Have you noticed a browning of your thujas? The first thing to do is to understand where this problem is coming from so that you can act accordingly. Here are the three main reasons why your thujas may look sad.
A sickness
Most of the time, thujas turn brown when they are sick. It is then necessary to act quickly to prevent other trees from also being contaminated. It can also be an attack by undesirables, whether fungi or parasites, which leads to a weakening and dieback of the thujas.
Inappropriate growing conditions
If you notice that your thujas are losing their green color, a lack of nutrients or soil quality may also be responsible. Once thujas suffer from a deficiency, they can no longer develop properly: they essentially need fertile, fresh, well-drained soil with a neutral pH, as well as a sunny location. To make a diagnosis, ask yourself about the quality of the soil:
- Isn’t it too compact or too clayey? This amounts to asking yourself if the soil does not remain waterlogged in bad seasons and dry when the weather is good.
- Is it sufficiently fertile?
- Does it benefit from sufficient sunlight?
A maintenance problem
If your garden has been neglected for a few years, it is possible that the thujas are turning brown. Indeed, thujas need to be pruned regularly and correctly, their soil must be aerated, etc. In addition, the first years after planting, they must be watered sufficiently, especially in periods of drought. In these cases, depending on the extent of the damage, it is not always possible to remedy the problem.
Act in case of illness
When a thuja turns brown, it may be a sign of disease. Thuja trees can be affected by different diseases whose origin varies, but whose consequences are similar.
Phytophthora cinnamomi
This is a fungus caused by excess water. Its spores attack and destroy the roots of thujas, but also of rhododendrons, heathers, etc. This attack causes the attacked plant to die back. The first symptoms appear at the roots and collars, then move up along the branches. To avoid this disease, it is important to follow the following tips:
- Be careful to avoid excessive watering.
- If your soil tends to be poorly draining, it may be helpful to add sand to the soil.
- If one of your cedar trees is infected, it is necessary to prune the affected areas to prevent the spread of the disease.
Bupreste
The bupreste is a pest beetle which mainly attacks cedars and cypresses. The bupreste is easily recognizable with its metallic green color and brown spots.
It is, in fact, its larvae which are dangerous, because they dig galleries in the branches, which has the effect of hindering, or even stopping, the circulation of sap. In turn, the branches dry out. The larvae then emerge through a small hole the size of a pinhead located at the base of the affected branches.
Here again, it is essential to cut off the affected branch(s) to limit the proliferation of this insect. If you have many thujas, the development of bupreste will be favored. It is therefore better to replace completely dry thujas with shrubs of other species.
Mealybugs
Under their white shield, scale insects can also weaken your thuja and cause it to brown and wilt the shoots. If you want to check if your sick tree is the victim of a mealybug attack, Look for drops of honeydew on the branches.
They are easily recognizable since they stick like honey. If you find any, then it is necessary to spray a mixture of black soap with a drop of vegetable oil over the entire tree. Carry out this operation when it is not raining and, if necessary, repeat the treatment.
Red spiders
Because they feed on the sap of plants, as well as their tissues, red spiders are also a danger for your thujas, because, in addition to weakening them, they suffocate them. If one of your cedar trees is infested with these mites, you may notice the webs they spin, as well as tiny red dots on the plant and brown spots, and you may notice some branches dying.
These undesirables cannot tolerate water, so simplywater the plant to get rid of it. If you decide to cut the dried branches, be careful not to put them in your compost.
Burn or frost spots
It is also possible to notice a browning of certain areas of your thuja following a heatwave: the sun burns the plant. In this case, the best way to help your shrub is to hydrate it.
Conversely, the browning of your thuja can be caused by a cold snap. If very low temperatures are forecast or if you want to protect your thujas and other plants in winter, you can mulch their base. This solution helps protect the roots from the cold, but also keeps the soil moist at the base of the tree and prevents the soil from becoming too compact.
Fight against the lack of nutrients
As we have seen, lack of nutrients can also be the cause of your thujas turning brown. To provide nutrients to your thujas, several solutions are available to you:
- Use a suitable fertilizer for thujas to provide nutrients to yours, but this solution is not the most ecological and requires regular renewal.
- Add compost to provide nutrients to the soil.
- Consider eliminating weeds developing at the foot of cedar trees, because they deprive them of their nutrients.
Remedying a lack of maintenance
Several points must be taken into account:
- Watering thujas : it is important to control it as much as possible, because on the one hand, too much humidity tends to favor the development of diseases, and on the other hand, a water supply may be necessary during the summer during periods of drought. However, you are subject to climatic hazards and watering cannot always be controlled, but the soil also has a role to play.
- Floor : if it is not sufficiently draining, it may be useful to add sand to your soil. Thus, the earth will be less constantly humid. If the soil is too compact, it is necessary to aerate the earth. You can use a manual hoe, for example.
- The size : it is necessary to prune thujas regularly, taking care to rid the plant of dead parts.
Preventing browning of conifers
As we have just seen, attacks suffered by conifers are favored by different stresses. It is therefore necessary to observe your plants carefully and take the following precautions:
- Make sure you choose plants with sufficient hardiness in relation to the climate of the region in which you live.
- Be sure that exposure and type of soil of your outdoor space will suit the chosen plant.
- See to prune conifer hedges in March, April, August or September and in dry weather. To do this, use sharpened and disinfected equipment for a clean and healthy cut, but be careful not to make cuts that are too severe.
- A compost addition is recommended every 3 years.
- Think of space your shrubs at least 1 m apart to allow their proper development and prevent them from mutually asphyxiating each other.
- Mulch the base of your shrub.