FNGLA IFAS University of Florida

Don’t Feed Your Weeds

Topdressing with fertilizer is a bad idea. Sub-dressing is superior.

This idea was demonstrated clearly at the Mid-Florida Research and Education Center this week. Dr. Chris Marble, weed specialist, showed us many trials with pre-emergent herbicides and how various mulches affected weed growth. He concluded by showing how fertilizer placement makes weed growth worse.

Various ways to apply slow release fertilizer to potted plants

The traditional way to apply slow release fertilizer is by sprinkling it on the surface of the soil. But some is lost by sunlight degradation and more can be lost by heavy rains. Another problem is that it feeds weeds and encourages their growth.

Fertilizer 3″ deep fed the crop but not the weeds.

So, a wiser way to apply fertilizer is to fill the pot about half way up with soil, apply fertilizer, then fill the pot the rest of the way, then plant the new plant. The new plants roots will come in contact with the fertile area but the nutrients are out of reach of any weed seedlings.


Fertilizer draws a crowd?

Who would show up for a lecture about fertilizer? At 10:00 on a Thursday morning no less.

My hat is off to the Collier County Master Gardeners and the educational programs they hold for the public. This year they created a series of talks, given by local experts, to teach about horticultural topics ranging from fruits, vegetables, flowering shrubs and vines, etc. They asked me to explain the dodgy subject of fertilizer.

At Unity Church auditorium, Naples

O.K. I made a nice Power Point presentation, brought along a ripe tomato and flowers from the garden to prove that the simple rules I suggest really work here. Then I printed out a page of general recommendations and made 30 copies. I expected an echo chamber. Instead, nearly 300 people showed up!

I guess all the Florida fertilizer laws and confusing/conflicting information out there has created a strong desire for clear, current, correct advice.

Many Florida counties and some cities restrict the nitrogen and phosphorus applied during rainy season. But much of the public think they hear “fertilizer ban!” and they are afraid of feeding their plants…often when they need it most.