Standing out among ornamental grasses for its blue-green foliage, blue oat grass (Helictotrichon sempervirens) offers a unique aesthetic and easy maintenance for gardens and landscaping. This perennial grass is evergreen or semi-evergreen in regions with mild to moderate winter seasons, providing visual interest even after the growing season has ended.
A clumping plant with a rapid growth rate, blue oat grass has been described as dramatic and yet well-behaved. It produces abundant shoots of blue-green grass stalks during the spring, but rarely self-seeds and doesn’t have the reputation of taking over in a garden.
In summer, spikelets of tiny blue-green flowers bearing seeds appear at the top of the tall grass stalks in groups called panicles. These gradually turn to wispy brown plumage as fall approaches, imitating the appearance of oats.
|Common Name||Blue oat grass|
|Botanical Name||Helictotrichon sempervirens|
|Mature Size||2-3 ft. tall, 2-3 ft. wide|
|Sun Exposure||Full sun|
|Soil Type||Dry and well-drained|
|Soil pH||Slightly acidic to neutral|
|Hardiness Zones||4-9 (USDA)|
Blue Oat Grass Care
Blue oat grass is a great option for planting in your garden since it is not invasive and requires little regular maintenance to maintain its beautiful appearance. These plants require just average to dry soil moisture conditions, rarely self-seed, and just require occasional cleaning of dead growth by hand or with a rake.
The plant is also very tolerant of environmental salt, pollution, and urban environments—making it adaptable for use in all types of landscaping. However, it does not prefer very hot or humid summer seasons, since it is a cool season grass.
Plant a single blue oat grass plant for variety in your garden, or a whole row as a landscape border, a beautiful accent to your sidewalk or driveway, or as part of a xeriscaping plan.
Blue oat grass thrives in full sun conditions. It can grow in areas with part sun and part shade, but it may become leggy under these conditions. Ideally, look for a location that receives at least six hours of direct sunlight per day for this plant.
Ensure that you plant blue oat grass in well-draining soil. Retained water leads to rotting of the roots or crown. For this reason, heavy clay-like soils are not ideal.
Blue oat grass does best with an alkaline to neutral pH level in soil; a pH of 6.5 to 7.5 is considered best. These plants are also tolerant of environmental salt in the soil and are not adversely affected.
Generally speaking, you won’t need to water blue oat grass often or much once established. This plant typically thrives just on the rainfall it receives. Keep in mind that the soil moisture should be average to dry at all times, so don’t overwater these plants or you could cause rotting of the root or crown.
Blue oat grass is considered drought-tolerant, though it should be noted that periods of drought can induce a semi-dormant state in the plant.
Temperature and Humidity
Blue oat grass prefers a dry and cool climate. The distinctive blue hue that this plant is known for is most prominent in dry climates. In cool weather, these plants are semi-evergreen and retain their blue-green foliage through the majority of the winter—if conditions are not too harsh.
In hot weather climates, summer temperatures may become too warm for the preference of blue oat grass, and the plant may not flower as expected.
Hardy and healthy, blue oat grass doesn’t generally need supplemental fertilizer. When deciding whether or not your plant needs fertilizer, consider the health and color of the plant’s foliage.
If you determine that the plant is faring poorly in the soil conditions, you could opt for an organic fertilizer that will be easily utilized by the plant—like compost, leaf mold, etc. If you decide to go with a conventional fertilizer, a 10-10-10 formula is typically recommended for ornamental grasses.
Anything with too much nitrogen can cause the plant to overproduce foliage and underproduce flowers, leading to a leggy, poorly flowering specimen.
Types of Blue Oat Grass
- Helictotrichon sempervirens ‘Saphirsprudel’: This variety is very similar in appearance to conventional blue oat grass. However, this cultivar has been developed to have a significantly more pronounced blue hue to its foliage, with slightly thicker grass shoots, and an increased tolerance for heat and humidity.
Blue oat grass is famously low maintenance, but it’s beneficial to occasionally clear dead growth from each plant. You can easily pull out dead, brown stalks of grass by hand or use a garden rake to comb through the clump and remove old growth.
When the plant goes into dormancy each winter, you can trim foliage down, leaving several inches above the crown of the plant. However, in some climates with mild winters, blue oat grass retains its characteristic blue-green color throughout the winter season. In such cases, it’s not necessary to cut back any growth and you can enjoy the foliage of the plant throughout the season.
Propagating Blue Oat Grass
The most popular way to propagate an ornamental grass like this one is by division; usually, this is done every three or four years in the spring before the growing season commences.
To propagate blue oat grass, do the following:
- Dig around the perimeter of the plant using a shovel or spade. Take the time to dig deep enough that you free the entire root ball, remembering that ornamental grasses can have a substantial root system.
- Using the shovel or spade, cut the plant from the crown into two or three pieces of roughly equal size. Depending on how dense the root ball is, it might take lots of muscle, a sharp tool, or a chainsaw to complete the task.
- Replace one section of the divided plant back into the original hole. The additional pieces can be planted in a new garden location or in a container.
How to Grow Blue Oat Grass From Seed
Blue oat grass can be propagated by seed, but many gardeners find this plant to have a low seed germination rate, so this method is not recommended. Instead, purchase plants and place them in desired locations around your landscape, then propagate per the instructions for division, above.
Potting and Repotting Blue Oat Grass
Blue oat grass can adapt to life in a container, but you’ll need to take steps to ensure that the soil has adequate drainage. In addition, some plants grown in containers lack the necessary nutrients for the sustained healthy growth of foliage in flowers.
While blue oat grass plants in the ground rarely need fertilizer, you may need to supplement soil nutrients when this plant is located in a container.
This hardy perennial grass does not require special care during the winter.
Common Pests and Plant Diseases
Pests and disease are generally not a problem for blue oat grass, though they can develop rust fungus in overly humid conditions. This condition can be identified by speckled, rust-colored masses on the surfaces of leaves. Simply reducing the amount you water your grass will deter this moisture-loving fungus.
Additionally, if you fail to space these plants far enough from each other (at least three feet is recommended), they may suffer from a lack of airflow and be subject to another fungal problem called tar spot. Thin your plants and keep watering to a minimum to discourage any fungal growth.
How tall does blue oat grass get?
This clumping grass can grow to be about 3 feet tall.
Is blue oat grass native?
Blue oat grass originated in Europe, so it is not native to the United States; however, it is not an invasive species.
What are native alternatives to blue oat grass?
An excellent native alternative to blue oat grass is big bluestem (Andropogon gerardi), a prairie grass that has a blue hue and can grow up to 8 feet tall. Its smaller cousin, little bluestem (Schizachyrium scoparium) is also a lovely grass option for native gardens that reaches approximately 5 feet in height.