Thursday, August 07, 2008
Maintaining boxwoods, killing locusts
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
Or send an e-mail. Answers will be given only in this column. Please don't send pictures or samples.
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Q: I have 12 old and large English Boxwoods in Falls Church, Va., that have had little maintenance in the past 10 years. These plants are about 6 feet high and 6 feet in diameter. Some are individual specimens and some are in clumps of three forming 15-foot diameter circles around lamp posts at least 70 years old! I have sheared these plants a few times in the past, attempting to keep the nice round shape. I have mulched them with shredded hardwood and shredded hardwood bark a few times in the past 10 years. All these plants live under large oak trees and have neighboring plants (azaleas, hollies). They all have English ivy encroaching upon them. What should I be doing to keep these incredible plants going? They all look good, although very dense growth on only the outer 8 inches or so. Some are losing a bit of their round shape.
A: Boxwoods don’t respond well to mulch and fertilizer, so don’t waste time and energy on these.
Do the following jobs now and repeat as needed.
Keep the ivy 6-8 inches out from under each boxwood’s drip line. Breezes and fresh air help keep the boxwoods’ trunks healthy. Use a power weed whacker -- carefully -- to make this job faster.
Pull out and remove by hand all plant debris that has dropped or blown into each boxwood’s “inside area,” especially against boxwood trunks. Repeat in the fall and as needed later on.
Soak the boxwoods once per dry week during mild and hot weather, occasionally when the ground is not frozen during the winter.
Thin the boxwoods’ greenery occasionally during the growing season. Use sharp hand pruners and reach into your boxwoods’ dense outer greenery to snip out 6 inch pieces of stem and leaves. Do the same several inches away for the next thinning spot. The purpose of this job is to assist breezes and sunshine passing through.
Wait until new growth is starting but well before hot weather to shear each boxwood to maintain a desired shape. That is the only time of year that job can be done.
Q: I had a multitude of beautiful primroses bloom in the spring and early summer. If I had cut them back after blooming, would I have gotten a second blooming?
A: No. They require a certain combination of temperatures and day length plus time for flower buds to form and open.
Q: I have a real problem with black locust trees. I have heard that after you cut down the tree you should pour a mixture of diesel fuel and salt on the stump. This mixture will work itself down to the roots and destroy them. I have heard several others but I have not tried any homemade concoctions as of this date. I have cut them down, and cleaned up around the area but they just keep coming back like a bad dream. What can I do to get rid of them once and for all?
A: Nature has made them one of the fastest “re-greeners” in the natural process of reforestation. But try one of the “brush killer” herbicides.
Just know that the stumps are hearty and robust. The chemical may just not work.
