Garden Doctors: Caring for ornamental grass

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Deb W. of Santa Rosa asks: I have quite a few ornamental grasses in my landscape and could use a few tips to keep them looking their best. I have both deciduous and evergreen varieties.

Grasses have the same basic requirements as many other garden plants, such as adequate light, well-draining soil, water, and occasional pruning. They should be planted the same way you would plant any perennial or shrub. Choose a location with adequate light for the needs of the plant, loosen the soil, don’t bury the crown, and water well.

These following tips should help you keep your grasses thriving in your garden:

Amendments and fertilizers are not usually necessary because they may stimulate the grass to grow too fast and the plant will then fall over.

Grasses that are native to Mediterranean climates (such as autumn moor grass, giant needle grass, ruby grass, and all of the California native grasses) need extra watering only during their first year to help them get established. Then, once they are established, occasional watering during dry periods of winter is all that is needed.

Grasses from other regions (such as Calamagrostis, Miscanthus and Muhlenbergia) will benefit from the occasional watering, especially during hot, dry summers, for their entire life. When watering such grasses, water thoroughly and infrequently, and probably not more than once a week.

Mulch should be spread out about 1-2 inches, around the grasses, to help conserve water and prevent weed growth. As the organic mulch decomposes, it will release an adequate supply of nutrients for most grasses.

Many ornamental grasses produce flower stalks that go dormant in winter, and these plants would benefit from a yearly trim. Trimming can be done anytime, but wait until the flower stalks become unsightly, break apart or fall over, and then remove them. In spring, cut back the grasses just before, or as soon as the new growth appears. The plants should be cut back to within 4-6 inches of the soil level.

Those grasses and grass-like plants that remain green year-round (evergreen), usually don’t need to be cut back except to remove any old, dead foliage.

If plant clumps become too large, you can dig up the whole plant and divide it into smaller, more manageable clumps and then replant. If the center of a clump dies out, dig up the clump, divide it and only replant the healthy portions.

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