How to Plant and Grow Blue Oat Grass

Blue oat grass boasts one of nature's most elusive plant colors along with a graceful crown of straw-colored seed heads that reach far above the foliage each fall. The evergreen (or semi-evergreen) perennial is native to the grasslands of central and southwestern Europe and treasured for its showy fountains of blue-green blades and occasional flowering stems.

This tough ornamental grass is easy to grow and resistant to trouble from deer, drought, and even air pollution. For these reasons, it is frequently planted in curbside garden beds, at the edge of natural pools, or in desert gardens. It is also frequently used to add soft texture to rock gardens.

Where to Plant Blue Oat Grass

Add this elegant, ornamental specimen to a cottage garden to offer a cool contrast to warm green foliage and bright blossoms. Or, plant it in a rock garden and enjoy the soft blue hue among the browns and grays. You could also nestle it in a contemporary garden to gain its standout color and texture. Just be sure to choose a location with full sun and well-draining soil.

How and When to Plant Blue Oat Grass

In spring or fall, dig a hole twice as wide and just as deep as the plant's root ball. Set the plant in the center of the hole and ensure that the crown of your blue oat grass roots sits even with the surface of the hole. Backfill the hole, tamping down as you work, and water the plant thoroughly. While the plant is acclimating to the new space, continue to water it deeply and allow the soil to dry out slightly between waterings.

Blue Oat Grass Care Tips

Blue oat grass is an easy-to-grow ornamental grass that thrives in full sun and well-draining soil. It's a reliable and attractive addition to rock gardens, cottage gardens, or anywhere a soft texture is needed.

Light

Blue oat grass grows best in full sun (at least 6 hours per day). It can tolerate partial shade, but too much shade will increase the likelihood of foliar diseases like rust.

Soil and Water

Plant blue oat grass in well-drained average-to-dry soil (such as that found in rock gardens and curbside planting beds). Blue oat grass can also tolerate sandy and clay-based soils, but poorly drained soils often cause crown rot.

Water newly planted clumps of blue oat grass every week or so for the first growing season to encourage a strong root system. Supplemental watering is rarely necessary after the first year.

Temperature and Humidity

Blue oat grass prefers cool, dry climates with temperatures between 55˚ and 75˚ Fahrenheit. In these mild climates, the ornamental grass remains evergreen. In hotter or colder climates, the grass will likely brown between seasons, but it can be cut back in the winter to make way for new growth.

For the plant to produce flowering stems, it needs to spend about 8 to 10 weeks in temperatures below 40˚.

Fertilizer

Blue oat grass does not require fertilizer. However, if your plant is struggling in poor soil, feed it a single application of slow-release, balanced (10-10-10) fertilizer in early spring.

Pruning

Use a rake or your hands to remove old foliage at the beginning of every growing season before new foliage emerges. In the late winter, cut the foliage back to about 3 inches above ground level. Use sterile pruning shears or a powered hedge trimmer for quick and easy removal.

If you live in a mild climate (where blue oat grass remains evergreen) it may not be necessary to cut the plant back in the winter. Simply remove dead foliage as necessary to make room for new growth and improve air circulation.

Pests and Problems

Blue oat grass is resistant to most pests and diseases but is occasionally troubled by rust—especially if grown in overly wet or humid conditions. In poorly drained soils, crown rot can also occur.

How to Propagate Blue Oat Grass

The easiest way to propagate blue oat grass is via division. It can be divided every three or four years in spring. To divide yours, dig up the entire clump, then use a sharp spade or shears to slice the root ball into three or four pieces—each with a healthy section of roots. Replant the divisions and water them regularly to encourage strong root growth.

Blue oat grass can also be propagated from seed, but successful germination rates are low. If you wish to grow blue oat grass from seed, press the seeds partially into the soil in late summer. Protect the area with a cold frame over the winter. If successful, your seeds should germinate the following spring.

Types of Blue Oat Grass

Common Blue Oat Grass

Common blue oat grass (Helictotrichon sempervirens) is a semi-evergreen perennial that is hardy in zones 4-9. It grows 1 to 3 feet tall and features silvery, blue-green blades with tan, oat-like seed heads from summer to early fall.

‘Sapphire’ Blue Oat Grass

‘Sapphire’ blue oat grass (Helictotrichon sempervirens ‘Saphirsprudel’) is a semi-evergreen clumping ornamental grass with a pronounced silver-blue color. It grows approximately 2 to 3 feet tall in zones 4-9 and has a higher tolerance for heat and humidity than common blue oat grass.

Companion Plants for Blue Oat Grass

Plant blue oat grass alongside other blue-tinged plants for an intriguing garden display. Dwarf blue spruce and juniper offer evergreen blue foliage that complements bristling clumps of blue oat grass. Pink-flowering perennials, such as wandflower (Gaura), Japanese anemone, and turtlehead (Chelone obliqua), make pretty pastel partners for the spiky mounds of blue-gray leaves.

Agastache

Agastache is a group of hard-working perennials, most of which are heat and drought-tolerant. Like blue oat grass, they are showy garden additions with spikes of flowers atop tall, herbaceous stalks. What’s more, the blooms (which come in wonderful shades of blue, purple, pink, red, orange, and white) produce a fragrant nectar that is irresistible to hummingbirds and butterflies. Agastache is hearty in zones 4-10.

Ajuga

Ajuga is a low-maintenance groundcover that offers colorful, crinkled foliage in zones 3-10. It can handle both shade and sun (but most prefer at least partial shade). Ajuga grows best in well-drained, moist soil but is somewhat drought-tolerant.

Black-Eyed Susan

Black-eyed Susan (Rudbeckia) is a popular choice for cottage gardens, butterfly gardens, containers, and window boxes. These tough native plants bloom in midsummer and the tall varieties look especially appropriate among shrubs and ornamental grasses. Average soil that holds some moisture is sufficient for black-eyed Susans in zones 3-10. Once established, they are fairly drought-tolerant.

Globe Thistle

Globe thistle (Echinops) is a flowering perennial from the Asteraceae family, which includes daisies, sunflowers, cosmos, chrysanthemums, and other beloved garden ornamentals. When fully open, the large ball-shape blossoms are magnets for pollinators. They are also stunning in floral arrangements. Globe thistles are hardy in almost all climates (Zones 3-10) and tolerate poor soil conditions.

Russian Sage

Russian sage is an herbaceous perennial that is hardy in zones 4-9. Like blue oat grass, it offers a soft, wispy texture with silvery, blue-green foliage and lavender flowers that bloom from midsummer into fall. Russian sage prefers full sun (the hotter the better) and medium to dry, well-drained soil.