Fall is here and all of those end-of-season projects are looming. If you’ve got questions, turn to Ask an Expert, an online question-and-answer tool from Oregon State University’s Extension Service. OSU Extension faculty and Master Gardeners reply to queries within two business days, usually less. To ask a question, simply go to the OSU Extension website and type in a question and the county where you live. Here are some questions asked by other gardeners. What’s yours?
Q: I have two beautiful Hinoki cypress trees in my front yard that are 27 years old. I don’t know what is killing them. They appear to have a disease that is causing the browning of the evergreen foliage. Can you help me figure out the cause and how to save them? – Marion County
A: The brown leaves appear in most cases to be those on the inside of the canopy, not at the tips of the shoots. This is common on conifers that have dense canopies, where the inner leaves become shaded, or on conifers that become drought stressed and then the inner leaves often turn brown first. Often the browning of the foliage due to drought is delayed from summer and appears in fall. If this plant is not irrigated and the brown leaves showed up recently it is most likely drought stress. – Neil Bell, OSU Extension horticulturist
Q: This week we were given two bags of crimson clover from two different people who know a lot about gardens. According to the packages we missed the prime window for broadcasting the seeds. Is it still fine to use them this fall, or should we wait until the spring? – Marion County
A: It is too late to seed crimson clover and, in any case, it is reportedly a bit tender as well. It would be best to wait until spring. I include a link to the OSU Extension publication on cover crops. Feel free to write with questions. – Neil Bell, OSU Extension horticulturist
Q: Can you get rid of oxalis growing in thick ground cover? My neighbor and I share a patch of brass buttons between our homes. It’s so thick I thought it would crowd out weeds, but oxalis has happily taken up residence and is spreading like mad. It’s very hard to even find the roots among the brass buttons, and then when you pull on it, it doesn’t all come out. I have two questions:
- Is there anything that will kill oxalis and not our ground cover, like some weed killers for grass or turf?
- Will a pre-emergent help if it’s spreading from the roots we can’t get out?
I put one down a few months ago on my side before oxalis showed up, and I seem to have way less of it than she does, but it’s rapidly spreading from her side. – Washington County
A: Short of pulling out the oxalis, there aren’t any other options for your situation.
Selective herbicide products for broadleaf plants will kill both the oxalis and your brass buttons.
Pre-emergent herbicides keep weed seeds from germinating in…