Since the early 19th century, garden valerian, a perennial medicinal plant from Europe, has been cultivated in North America. The pulverized roots are used as an herbal sedative remedy to treat insomnia, anxiety, and restlessness. Because valerian, with its attractive flowers and foliage also has ornamental value, it might be tempting to add it to a flower bed or a herb garden. But depending on where you are located, valerian can easily become invasive.
Before you plant garden valerian, check on the Invasive Plant Atlas of the United States whether it is invasive in your area. The same applies to red valerian (Centranthus ruber). It is a botanically different species but similar in appearance to garden valerian.
Invasiveness of Valerian
Garden valerian (Valeriana officinalis) can tolerate both wet and dry conditions, and it is this adaptability to all kinds of locations that enables it to spread vigorously.
Another factor that adds to its invasive nature is that it emerges early in the spring, so it often has a head start over native plants that break their dormancy later. They might not be able to compete for nutrients, water, and sunlight in a location that valerian has already occupied with its vigorous growth.
Valerian is also a prolific self-seeder. Its seeds are powdery and spread easily by the wind.
As a result, valerian forms dense monocultures and takes over natural areas, choking out native vegetation, which in turn affects wildlife diversity.
In a garden setting, the spreading seeds can be very difficult to control due to their powder-like consistency. It also grows via aggressive rhizomes. Therefore, as a gardener dealing with a valerian infestation, you’ll have to battle two fronts at once, controlling the seeds as well as the vegetative growth.
Even though valerian seeds and potted plants are widely available, think twice before you plant this perennial. Once it takes hold, it might be difficult to control.
|Botanical Name||Valeriana officinalis|
|Common Name||Valerian, Garden valerian, Greek valerian, Common valerian, Garden heliotrope, All-heal|
|Mature Size||One to four feet height|
|Sun Exposure||Full sun|
|Flower Color||White or pale pink|
The white or pale pink flowers appear between June and August. The flowers are tiny and form tight, dense, umbrella-like clusters. The scent of the flowers is sweet. After the bloom, the flowers turn into oblong capsules containing numerous powdery seeds.
The pointed, toothed leaves are dark green and grow in opposite leaflets. A characteristic feature of the leaves is their hairy underside. The thick and hairy stems are hollow.
The outstanding characteristic of the roots is their pungent smell. It is somewhere between earthy and foul and funky, often compared to the odor of dirty socks. That smell persists when valerian root is dried and ground as an herbal remedy.
Where Valerian is Found
Valerian thrives in cooler climates with abundant precipitation, especially in sunny wetlands. It also grows in woodlands, forests, grasslands, marshes, woodland swamps, and along streams and disturbed roadsides.
How to Remove Valerian
If there are just a few valerian plants popping up in your yard, remove them by hand. This is best done by lifting them out of the ground with a trowel to make sure you get the entire plant—the stem breaks easily—as well as the roots. Do this as soon as the seedlings emerge, and definitely before they flower and set seed.
If valerian has overgrown a larger area, you can mow it. Again, this needs to be done before the plants go into seed. If you are too late, mowing or any other form of mechanical removal will make it worse because you will just spread the seeds around further.
A heavy infestation might require repeated mowing and a follow-up spray treatment with an herbicide containing glyphosate. Keep in mind, however, that this is a non-selective herbicide that can kill all other vegetation around it.
Varieties of Valerian
Red valerian (Centranthus ruber) is a native of the Mediterranean, both northern Africa and southern Europe. It can also be an invasive plant, in particular along the west coast where it presents a threat to natural areas.
It blooms in May, thus earlier than garden valerian. Its star-shaped flowers are crimson-colored, pink, or white. Just like garden valerian, it also self-seeds easily.
Besides the invasive non-native valerian, there are several native species. They usually grow in the wild and are seldomly available commercially. These include:
- Mountain valerian, marsh valerian (Valeriana uliginosa)
- Sharpleaf valerian (Valeriana acutiloba)
- Marsh valerian, wood valerian (Valeriana dioica)
- Large-flowered valerian (Valeriana pauciflora)
- Edible valerian or hairy valerian (Valeriana edulis var. ciliata)
These native plants are often rare or threatened species and their removal from the wild is prohibited.