Thursday, May 12, 2005
How, when to trim pampas grass
John Arbogast
Landscape consultant John Arbogast answers your questions every Thursday. Send questions about your lawn, garden, plants, or insects to:
Dear John
5102 Greenfield St. SW
Roanoke, Va. 24018
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Q: I got my husband to trim our pampas grass back to about eight inches above the ground four weeks ago to get rid of the dry dead part. My husband says that we should not have done that because the plants might die, and that no one else in the neighborhood has trimmed theirs. Should this type of grass be trimmed, and if so, when is the best time to trim it?
A: It’s a good idea to cut pampas grass blades to about eight inches above the ground to remove all brown blades of this big ornamental grass sometime from right after the green turns to brown in the fall on up until mid winter. T
he reason for this is to make room and allow more sunshine to reach the new spring’s shoots. Removing brown blades also makes the landscape area look neat and eliminates the fire hazard from dry grass.
As you have seen in your neighborhood, some folks don’t do this suggested job or might wait until the brown mess takes away from the tidiness of their landscape.
This trimming will not remove the dried dead naturally occurring inner mass of old pampas grass basal stems in the center of the ornamental grass base. Pampas grass produces its annual new shoots on the outside of the clump, thereby increasing the diameter of the ornamental grass and leaves the old brown inner stems. This cutting does not kill the plant.
The potential damage due to cutting back old pampas grass growth occurs when that trimming work is done after new shoots begin to grow and the tips of new blades are accidentally clipped along with the old. The cut ends of new shoots will remain as brown tips all during the growing season. New blade growth occurs as elongation of new green tissue beneath the clipped ends. These brown tips are an aesthetics problem, not a life-threatening dilemma.
Q: I have five Bradford Pear and four Cleveland pear trees in my yard. Most of them have these round black spots on the under side of the leaves. It was on them last year also. Can you tell me what is causing these spots and what I can do to stop them?
A: I don’t know of any disease that causes this kind of spotting on ornamental pears. Those round black spots on the underside of ornamental pear leaves are likely the result of some kind of non-disease stressor.
The damage and thus the necessity of applying controls should be based on knowing the extent of lost photosynthesis as the result of (A.) defoliation of spotted leaves and/or (B) from spotting at this early part of the 2005 food-production season.
If the spots cover only a small portion of the trees' total leaf "crop" or if defoliation is only minor, I would not spend any time or money on searching for what the stress is or what can be done. You want to be sure that a sufficient amount of food (plants make sugars) is being produced.
Q: I have dug some daffodils to make room for other plants. They have their green foliage intact. I wish to replant some of them. Should I do that now or can I wait until the fall? If the latter, how should I preserve them until I plant them?
A: The daffodil is one the few spring flowering bulbs that can be dug up while they are in their foliage stage and be immediately replanted with foliage in permanent new locations. Other spring bulbs must be left undisturbed until their foliage turns brown, followed by bulb drying, storage in a dry place, and then replanting in the fall.
Dig holes to replant daffodils with foliage at least 6 inches deep so these disturbed plants will not bothered for at least another 2 years. It will be helpful to mix 1 cup of bone meal organic fertilizer into the bottom of each transplanted daffodil hole. This fertilizer is a good source of phosphorus, which is very important for new root development.
Q: I’d like your comments about planting some cranberry bushes like a friend suggested that I do for a spring flowering hedge.
A: Actually, there are two viburnmums that carry the name of cranberrybush: the American cranberrybush viburnum and the European cranberrybush viburnum. Both can grow to be 8 to 12 feet in height with a very broad width.
The first selection would be a better choice for the Roanoke area, since it is hardier that the European.
To enjoy the handsome flowers as a hedge in a sunny or only partly shaded location, pruning should be minimized. I understand that there is at least 1 kind of dwarf American cranberrybush viburnum variety named ‘Compactum.’ The botanic name to look for if you have limited room is Viburnum trilobum variety ‘Compactum.’ This will grow to be about half the size of the standard.
