Thursday, September 16, 2004
Further details on beating wiregrass
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: You said to fertilize heavily in August and September to help kill wiregrass and not in the spring. If you do this, then what do you put down in the spring or fall to help kill the weeds? Is there anything that will really kill chickweed, which is coming back like mad? Also, I have three apple trees that don’t produce any apples, even though I get apples on the other trees. What is happening? Also, when is the best time to apply lime pellets so they don’t interfere with the fertilizer?
A: The goal of applying lawn fertilizer in the fall to combat wiregrass is to provide nutrients when a bluegrass or fescue lawn (cool season grass category) can use them to become vigorous rather in the spring when wiregrass (warm season grass category) benefits from nutrients to become vigorous. The overall objective is to do everything that we can in order to help our good grass to become denser and outgrow wiregrass. This recommendation has nothing specifically to do with the time to kill lawn weeds. Our goal there is to kill weeds at the time of year that those weeds are young and thus more tender. Chickweed is a winter annual weed that shows up in shady turf areas containing thin grass in early spring. It is tender in mid fall, so apply a three-ingredient turf weed killer that contains the ingredient dicamba as directed on the label directions in early November.
Age and overall condition are two major controlling factors on apple trees. As you mentioned getting apples on your other trees, I’m assuming that there is plenty of apple pollen that bees can carry from apple variety to other varieties. So, if these three barren apple trees are less than 7 years old, simply wait a few more years for them to become mature enough for that variety to bear. If those three trees are over 30 years old, they are probably too old to make apples and should be replaced. If the three barren trees are in poor soil or enduring any adversity, think what can be the stressor and act accordingly.
Q: My two pyracanthas have become much too large. Will they come back if I trim them back to the main trunks and when can I do that? Also, the two hollies that I planted 13 years ago have become so big that they are rubbing the house and are growing onto the roof and eaves. How much and when can they be trimmed?
A: Cut back both kinds of plants in early to mid spring when the days are starting to become warmer but prior to hot weather. It would be okay to trim the pyracanthas back to the main trunks, because there should be a new growth bud at the intersection of each side branch and trunk. Cut hollies back to about half of their current size. During the entire growing season following major spring pruning, be sure to provide weekly soakings to all landscape plants during all droughts.
Q: I want to start pine seedlings but need instructions. Do they grow from pine cones?
A: Seed germination is the most common method of pine propagation, but the procedure varies from pine variety to pine variety. Pine seeds develop at the base of each pinecone compartment following pollination. By nature, eventually the ripe seeds are dropped out of the open cone to the ground below where they try to germinate or are collected for sowing in prepared seedbeds. Seeds of some pine varieties must endure a number of days in a damp, chilly environment in a process called “stratification” before they will germinate. Mature seeds of other pine varieties do not require “stratification” in order to germinate. Contact your local Virginia Department of Forestry office for specific seedling information.
Q: What are the cause of and the solution to various swollen places and narrow bark cracks on the trunk of my old oak tree?
A: Those bark cracks might be peculiar to the species that you have and are therefore nothing to worry about or past winter sun injury that we can’t do much about.
The swelling symptoms sound like growth of callus tissue that is like a scab on a person’s wound that has grown by nature to cover places where side branches have either fallen or have been cut off. Or it could be a type of gall, which is extra growth triggered by either a pathogen or irritation from insects or mites. Generally, galls cause only cosmetic injury with little or no permanent injury. It is possible for some galls to weaken plants, though, so have a tree professional visit your oak tree to do an evaluation of the entire tree and site before you spend much time or money on the abnormalities.
