Our pampas grass has been beautiful for ten years, but this year it did not produce the feathery plumes. What could be the problem?
There are several possible reasons pampas grass (Cortaderia selloana) doesn’t produce the tall, graceful plumes that we look forward to in late summer. One of the most common seems to be overfertilization. If the grass is near a lawn that was heavily fertilized with nitrogen, it could have affected the plumes. Nitrogen fertilizer tends to grow a lot of greenery at the expense of flowers – or plumes, in the case of ornamental grass.
It may also be due to too little phosphorous in the soil. A soil test can provide the answer, and if it turns out to be a phosphorous deficiency, you can add bone meal to the planting bed. Some sources also say that young clumps of pampas grass may not plume for the first couple of years.
In general, pampas grass grows best in full sun and well-drained soil. It’s a good idea to cut the grass (and all ornamental grasses) back every year in late winter before new growth begins. Wear sturdy gloves (pampas grass’s sawtooth leaves can cut you!) and use hedge trimmers or shears to cut the clump to within about a foot of the ground. Over time, grass that is not cut may die out in the center – one more thing that might affect the formation of the tall, graceful plumes.