How To Control Japanese Spirea: Tips and Tricks

If you have a Japanese spirea plant in your garden, you may have noticed that it can be quite invasive. This beautiful plant is native to Japan and Korea, but it has quickly become a popular landscaping shrub in many parts of the world. However, its ability to spread aggressively can make it difficult to control. In this article, we will share some tips and tricks to help you keep your Japanese spirea under control and looking great.

1. Know Your Enemy: Understanding Japanese Spirea

The first step to controlling Japanese spirea is understanding what it is and how it grows. Japanese spirea (Spiraea japonica) is a deciduous shrub that typically grows 4-6 feet tall and wide. It produces clusters of small pink or white flowers in early summer and has dark green leaves that turn reddish-purple in the fall.

One of the reasons Japanese spirea is so popular in landscaping is that it is very easy to grow. It tolerates a wide range of soil types and light conditions, and can even thrive in areas with poor soil quality. However, this hardiness also makes it a formidable opponent when it comes to controlling its growth.

2. Prune Regularly: Keeping Japanese Spirea in Check

The most effective way to control Japanese spirea is through regular pruning. This not only helps to keep the plant from taking over your garden, but it also encourages healthy growth and maintains the plant's shape and size.

The best time to prune Japanese spirea is in late winter or early spring, before new growth begins. Use sharp, clean pruning shears to remove any dead, damaged, or diseased branches, as well as any suckers that have sprouted from the base of the plant. You can also selectively prune back some of the older wood to encourage new growth and maintain a tidy shape.

A Japanese spirea bush in full bloom

3. Watch for Signs of Infestation: Dealing with Pests and Diseases

While Japanese spirea is generally quite hardy, it can still be susceptible to pests and diseases. Keeping an eye out for signs of infestation can help you catch problems early and prevent them from spreading.

Some common pests that can affect Japanese spirea include aphids, spider mites, and scale insects. These can be controlled with insecticidal soap or horticultural oils. Additionally, Japanese spirea can be prone to fungal diseases such as powdery mildew and leaf spot. These can be prevented by ensuring good air circulation around the plant and avoiding overhead watering.

Japanese spirea affected by powdery mildew

4. Consider Root Barrier: Controlling Japanese Spirea Spread

Another option for controlling the spread of Japanese spirea is to install a root barrier. This is essentially a physical barrier, usually made of plastic, that prevents the roots from spreading beyond a certain point.

Root barriers can be installed when planting new Japanese spirea, or they can be retrofitted to existing plants. They can be particularly useful if you have a Japanese spirea planted near a sidewalk, driveway, or other area where you don't want it to spread.

Japanese spirea with a root barrier

5. Use Herbicides with Caution: Killing Japanese Spirea

If all else fails and you need to get rid of Japanese spirea altogether, herbicides can be an effective option. However, it is important to use these chemicals with caution, as they can be harmful to other plants and wildlife.

The best type of herbicide to use on Japanese spirea is glyphosate, which is a non-selective herbicide that will kill any plant it comes into contact with. However, it is important to follow the instructions carefully and avoid using it on windy days or when rain is forecasted. Additionally, you should wear protective clothing and gloves when applying herbicides, and keep children and pets away from treated areas.

Japanese spirea being treated with herbicide

Japanese spirea, garden care, gardening tips, pruning techniques, pest control, root barriers, herbicides