LARRY WILLIAMS | Don’t use herbicides in compost pile

Q. I have a lot of compost from lawn cuttings, limb shredding, etc. A lot of weed seeds are in this and it does not get hot enough to kill the seeds. Is there a treatment to kill the seeds? Can I use a preemergence lawn herbicide in my compost pile to prevent the weeds from coming up? If so, will the compost be safe to use in my vegetable garden?

A. Compost is a great idea to help improve garden soil. The best way to handle the weeds in a compost pile is to frequently turn the pile. This allows thorough mixing and uniform heating of the entire pile. It’s the heat that’s produced during decomposition of the raw materials in a compost pile that kills the weed seeds. Turning and mixing the material also introduces oxygen throughout the material aiding decomposition. If turning and mixing the pile is ignored, the material on the surface of the pile never gets hot enough to kill the seeds. The compost pile also should be kept evenly moist. If it gets too dry or stays too wet decomposition will slow down or stop altogether. Never use any weed killer (herbicide) including weed and feed or preemergence products in a compost pile. If you do, you may not only kill plants growing in the compost but you also may have growth problems with your plants for a long time. Listed below is a University of Florida Web Page on composting.

http://edis.ifas.ufl.edu/ep323

Q. All the leaves on my tree suddenly turned brown but are still hanging on the tree and are firmly attached. What caused this and can I save the tree?

A. This is an indication of severe root injury. Usually a combination of factors over a long period of time caused extensive root injury. The tree had been functioning with a weakened, smaller root system. Some common causes for lethal root injury in trees include construction damage (particularly soil grade changes), floods, drought, hurricanes and herbicide injury (many trees are damaged by “weed and feed” products). There is nothing that can be done to correct this kind of injury. These types of problems are prevented, not cured. The initial damage could have been caused years prior to the tree’s leaves suddenly turning brown. Based on my experience, trees in this category usually do not recover.

Larry Williams, UF/IFAS Extension Agent, Okaloosa County, May 30, 2014