Fertilizer spikes not best way to feed trees

By Audrey Post
MS. GROW-IT-ALL

Q: Our sandy soil does not retain nutrients so we must fertilize. I found the use of loose, bagged fertilizer that must be spread by hand burns the grass and other nearby plants. We are now using Palm Fertilizer Spikes (6-0-6), which is slow release. After reading several articles that suggest that calcium is a necessary nutrient I discovered these spikes are lacking calcium. Does anyone make a slow-release fertilizer spike that is 15-5-15?

A: My first reaction was that if your lawn is being burned, you’re using too much fertilizer or you’re not applying it according to manufacturer’s instructions. I consulted David Marshall, the University of Florida/IFAS horticultural agent for Leon County, and he agreed.

“If the granular fertilizer is burning the grass, it is either being put out at too high a rate, or is not being watered in properly with a quarter-inch of water after application. Tree roots are widely spread beneath a tree and can run out into the lawn and other areas as far as three to four times the branch spread of the tree. For example, a small tree with branches that extend out 10 feet from the trunk may easily have roots running out 30 feet from the trunk,” he said.

“Therefore, spreading the proper rate of granular fertilizer over 900 square feet, or a 30- by 30-foot area, would do a much better job of distributing the fertilizer to the tree roots than merely putting in a few fertilizer spikes,” he recommended.

As far as adding calcium, you might not need to. Test your soil first. Contact your county Extension Office for a soil-test kit, which comes with instructions on collecting the sample and mailing it to the lab for testing. The cost is minimal, and it can save you a lot of money by telling you what nutrients your soil needs, and what it doesn’t need.

Gardeners in Leon County, Fla., can visit the Extension Office at 615 Paul Russell Road, about a mile east of the fairgrounds. If you garden in another Florida county, go to http://solutionsforyourlife.ufl.edu/map/index.html for a list of county Extension Offices around the state.

Gardeners outside Florida should contact their county's Cooperative Extension Service.

Internet Radio Show: Ms. Grow-It-All’s Internet radio show on the Free World Radio Network will not be broadcast this week. Join us next Thursday, July 30, 2009, at 6:30 p.m. for a discussion on rain gardens: http://www.blogtalkradio.com/Ms_Grow-It-All.