Ask a Master Gardener: From rose pruning to Zoysia grass weeds and Japanese beetles

Q. Can I prune my roses for the winter now? Mine are getting tall, and I'd like to cut them back.

A. We advise gardeners to wait until roses are going dormant to do pruning for the winter. This generally means November, once we've had some weather well below freezing. The height to cut them back is 24 inches or higher, but enough to get rid of lanky or floppy growth that is easily weighed down by snow or ice. This can cause damage lower on the cane. In the spring after the weather starts to warm (mid-March), a final pruning is done at about 18 inches or whatever is the desired height. Any winter damage can be removed at this time, and in a very harsh winter the canes may have to be cut even lower. If your roses are getting excessively long now (like mine are), go ahead and trim them back some so they aren't a nuisance. Then follow the above process.

If using rose cones to protect the plants, we advise pruning to place the rose cones on in November. That said, I have talked to "snow birds" who annually pruned in October, put the cones on and took off for the season. They said their plants were always fine.

Q. I have a Zoysia grass lawn I established about five years ago. It has always grown well, and I never had any weeds in it, until this year. I never did anything to the lawn - no fertilizer or herbicide because I have some poultry in the yard. What do I need to do?

A. Congratulations on getting along with your Zoysia lawn for so many years with no inputs. It is likely you can easily remedy your situation, and hopefully only need minimal herbicide.

Zoysia lawns need less nitrogen than cool-season or fescue-type lawns, but they still need some. Otherwise the canopy can thin out and the weeds start to grow. The rate advised is 2 pounds of actual nitrogen per 1,000 square feet applied May through August. Ideal would be -pound of nitrogen each month. If you have never had a soil test done, that would be good to do, to know if other major nutrients are needed, like phosphorus, potassium or calcium, or if the pH needs to be adjusted. Granular fertilizer should be safe to apply and let your birds back on the lawn after spreading.

So you wouldn't apply any fertilizer this fall. However, this fall check the lawn to make sure the thatch isn't too thick. I wouldn't expect it to be since you haven't fertilized, but if it is too thick, de-thatch early next summer just after it greens up. University of Missouri Extension has a useful publication titled "Establishment and Care of Zoysiagrass Lawns."

I would suggest you spray an herbicide this fall to kill broadleaf weeds. Fall is the better time to kill many perennial weeds, and you don't want them to grow more this fall and next spring, before your Zoysia competes better. There are a number of different products available that kill broadleaf weeds but not grass. Make sure the product expressly says something like that, e.g., "kills weeds, not lawns." You may have to mix the product up from a concentrate, or you can purchase "ready-to-use." The latter is a good option if you have a smaller area to treat. The label of the product will tell you when it is safe to reintroduce pets or children onto the treated area. Follow this for your poultry.

Q. I had Japanese beetles this past year for the first time, on knockout roses. Now that they have gone, is there anything I can do to permanently get rid of them?

A. No is the disappointing short answer. There are a few limited things you can do to reduce their number in your general area. You can treat their preferred habitat with a natural product or a synthetic insecticide. The bad news is their habitat is lawns, and that means not only yours but those every adjoining neighbor, if not even further. These beetles can easily fly mile.

There are several lawn insecticides that claim to control the grubs of Japanese beetles. They actually kill a wide variety of lawn grubs. Contact our office if you want to know these options. The most popular natural product to apply is "milky spore," which is quite selective to Japanese beetles. For best control, the label says to apply it for two years in spring, summer and fall (that's six times). I saw that a retailer had a 20-pound bag for $40, which treated 7,000 square feet. So, according to the label, this would cost $160. It is effective to the treated area after two years. A USDA publication says it works best if it can be a community-wide effort. Unfortunately, most of your neighbors probably won't want to spend that much money.