Digging is the best way to control smilax

Q: We have smilax vine growing up into a dogwood tree through large azaleas. What will kill it? Nancy Payne, Marietta

A: Smilax is very tough to kill with any method other than pulling it up or digging it out. If you excavate the roots, you'll see there are many swollen yellow nodes along each one. Each node can sprout into a new thorny smilax vine. No herbicide is able to move down the vine and into the length of the roots to kill all the nodes: some inevitably survive and become problematic again. It's easiest to dig a smilax when you have a helper. One person can pull and the other can operate a shovel or mattock to get every piece of root out of the ground.

Q: I need to identify my lawn grass so I can follow your lawn guides. In summer it's a pretty green color, it's dense and is not the softest grass. It's brown now. Brent Gorman, East Cobb

A: You've given me two important clues: the grass's lack of softness and the fact it's brown now. The brown color tells me it's not fescue. I'd bet you have zoysiagrass. It looks similar to bermudagrass when both are dormant in winter but in summer zoysiagrass is much "springier" to walk on. I have tips on identifying common lawn grasses at bit.ly/GAlawnID.

Q: I have used cottonseed meal for my boxwoods in the past. Is this still the best choice? Jan Richins, Birmingham

A: I think cottonseed meal works great! Commonly sold as livestock feed, cottonseed meal slowly decomposes over time and gradually releases nutrients to the boxwoods. In addition, it is an effective mulch as it prevents weeds and conserves water. Its appearance is not very attractive though. When I've used it in the past, I covered the cottonseed meal with pine straw or chips.

Q: Are ammonium sulfate and 21-0-0 the same thing? Janice Rowe, Monroe

A: They are identical! It's always good to remember in the back of your mind that fertilizers, whether organic or synthetic, are basically chemicals. Organic fertilizers are complex organic compounds; synthetic fertilizers, including 21-0-0, are sometimes simpler. Ammonium sulfate is a very simple chemical. The ammonium part provides nitrogen to plants when dissolved in water. The sulfur part provides sulfur and slightly acidifies the soil. If you have a bag of the chemical it will contain 21 percent nitrogen and nothing else but filler.

Q: I have a big dogwood tree under which the roots are exposed. Can I cover them with soil without harming the tree? David Emerson, Fayetteville

A: If the tree looks healthy, with plenty of green leaves each year, you can add enough soil to slightly cover the root system. Do not cover the roots with more than an inch or two of soil. An alternative is to simply spread mulch over the area.

Listen to Walter Reeves Saturday mornings on News 95.5 FM and AM750 WSB. Visit his website, www.walterreeves.com, follow him on Twitter @walterreeves, on Pinterest, or join his Facebook Fan Page at bit.ly/georgiagardener for more garden tips