Pampas Grass not Flowering

Gardening expert Conway Lum reveals how to keep your pampas grass flowering.

Q: I have two ‘Pampas grass’ plants in the same flower bed that are separated by another shrub. The first pampas to be planted has had 12 to 15 flower heads each year since year one. It was doing so nicely I decided to purchase another, which had on arrival two flowers. The next year, I got another Pampas grass plant, and for the last three years it has stubbornly refused to produce flower heads, but the greenery is very much taller than the other plants. I can’t imagine why it won’t flower.

I live in Northern Ireland. The climate is cold and damp, and we have a lot of rain!

The name ‘Pampas grass’ (Cortaderia selloana) means “level plain.” The plant must have full sun most of the day with few obstructions, e.g. the shrub next to the Pampas. Since the plant in question was purchased in flower indicates age is not a factor. I will also assume you are not over-fertilizing the plant (for example, adding rich compost to mulch the shrub next to the grass), which could lead to excessive growth.

The problem is most likely a combination of cultural and environmental factors. It is mentioned the plant in question is taller so it’s getting enough light without stretching. Pampas grass, once established, are very drought tolerant but dislike poorly drained soils, which freezes. This grass is at home with warm, humid conditions where there is constant wind with summer temperatures being very hot.

Applying a complete fertilizer early in the growing season with periodic watering during dry stretches is all this plant needs.