Q: I have a plot of cannas in my backyard that is crowded, overgrown and just not pretty any more. I want to get rid of the cannas and replace them with gardenias but without a lot of digging. J. G. Humphries, Henry County
A: Cannas aren't terribly tenacious but I think you're too late to do much damage with herbicides this fall. Go ahead and cut the brown leaves down and spray the cut stumps with glyphosate (KillZall, Roundup, etc). Till the plot in winter to expose the roots to freezing weather. Spot spray the new leaves in spring and plant your gardenias in their midst.
Q: My lavender is lying down and it's become woody and not pretty. Should I trim it back for winter? Elaine Sharp, email
A: My experience with lavender is that it lasts a few years but eventually develops woody stems and sparse foliage. I think this could be avoided by removing a few interior branches every spring to promote vigorous new growth. That's what I'd do in your case: wait until late March and cut a few of the older stems back to three inches long.
Q: We are getting ready to plant fescue sod. When we were taking core samples we discovered a couple of white grubs. What should we do? Elaine Russell, email
A: The right answer is: do nothing. It's true that high numbers of grubs can damage grass roots, but finding just a few is no reason for concern. Fescue can tolerate eight grubs per square foot with no visible effect. The ones left in your lawn will likely die this winter. I my opinion, grub-control products are vastly oversold and overused.
Q: Would I be wasting my money applying pre-emergent now? I missed the September date you talk about. Bobby Holcomb, email
A: Winter weeds don't all germinate in early October. Some wait until later, even sprouting in the warm days of late November. That said, most are already up. You might get a bit of control if you use a pre-emergent now but I think you'll get better results by spot-spraying lawn weeds as you see them emerge.
Q: I've been raking the leaves out of my flower beds. After raking the beds over and over, I thought maybe it would be just as good to cover my perennials with leaves for the winter. Ellen Anderson, Gwinnett County
A: It all depends on how deep the mulch cover is. If your perennials have green leaf rosettes at ground level, like foxglove or Shasta daisy, you should put a couple of inches of mulch around the plant but not cover the leaves. For plants like hosta or daylily, which die completely to the ground, covering them with a light layer of leaves or straw is fine for winter. You can gently rake off the mulch when things warm up in March.