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In Florida, vegetables need good earth

Retired horticulturist Allen Cordell of Largo recommends 25 percent organic matter in soil for a good vegetable garden. Florida’s soil usually comes up short.


Retired horticulturist Allen Cordell of Largo recommends 25 percent organic matter in soil for a good vegetable garden. Florida’s soil usually comes up short.

there's a veggie tale that should be told, but you won't find it on a package of Burpee seeds or on a bag of Miracle-Gro soil. It's not in the pages of thick manuals that give generic advice for growing food. You won't even hear it on HGTV, despite its picture-perfect gardens and celebrity garden hosts.

Only a Florida gardener with years of in-the-dirt experience can tell the story about raising food in Florida, where the soil and climate pose challenges you won't find in other parts of the country.

Retired horticulturist Allen Cordell of Largo, who spent 25 years at the Pinellas County Extension and oversaw the vegetable and herb garden at the Florida Botanical Gardens there, knows all about growing food in Florida. He is passionate about the topic and will tell you everything you need to know to grow a bumper crop of culinary herbs and vegetables galore, from arugula to zucchini.

But first, there's the real dirt about veggie gardening in Florida. "I really love to talk about soil," says Cordell, who can cite pH levels and micronutrient percentages faster than most of us can fathom. The bottom line is this: Natural Florida soils are, frankly, pretty rotten when it comes to growing vegetables and herbs. There's barely any organic matter present, and with the sand and high alkalinity, food crops don't stand a chance.

"We have less than 2 percent of organic matter in our natural soils, and we want a good 25 percent to grow a good vegetable garden. That's the standard practice," says Cordell.

The easiest way to provide good soil is by using containers or installing a raised bed (see Part 1 of this series, available online; check the box accompanying this story). Cordell recommends containers with adequate drainage, especially as you're getting started, because you can move them until you find just the right amount of sunlight and natural protection.

Never put soil from the ground into containers, or you'll likely introduce nematodes, those microscopic root eaters that are "Enemy No. 1" in the Florida vegetable garden. Instead, Cordell recommends making a mixture of 4 parts bagged topsoil, 1 part perlite and ½ part dolomite (available at most garden retail stores). When added to soil, perlite, which is a natural volcanic material, boosts moisture retention, improves drainage and encourages better root growth. Dolomite is finely ground hydrated lime that boosts calcium.

Don't use expensive bagged potting soil or premixed potting soil with fertilizer, which are formulated for houseplants, not food crops that need nutrients such as calcium for fruiting. Select topsoil instead, which will be less expensive. It should be loose and pliable to the touch, not heavy and mucky. Cordell also recommends skipping bagged cow manure, which provides inadequate nutrients. "The biggest farce out there" is bagged cow manure, he says. "It's like buying designer jeans."

Skip the expensive Canadian sphagnum peat moss, too. You're better off mixing in or top dressing (about 1 inch deep) with oak leaves, which provide tannic acid that will boost the soil's natural nutrients and minor trace elements, Cordell says.

A pH level between 6.2 and 6.8 is ideal, but bagged topsoil is rarely labeled for pH. Although it's not essential to test store-bought soil, you can have your soil mixture tested at nominal cost by some county extension services or use a do-it-yourself test at home (although they're not as reliable as professional testing).

You can use the same soil mixture for growing herbs, although the Mediterranean herbs, including rosemary and sage, do best with quick-draining soil preferred by cactus. Simply add a bit of builders sand to amend the soil.

Fill your containers or raised bed with the soil mixture at least 8 inches deep, which is about as deep as roots will grow. Some people like to line the bottom of containers with loose filler, including small rocks or lightweight packing peanuts, to conserve soil and promote good drainage. That's fine, but don't use concrete chunks, shells or marble chips, which can raise the soil's alkalinity.

After planting, you can sprinkle a handful of organic fertilizer on the soil's surface. Cordell recommends a complete formula that won't burn, such as "Black Hen" brand composted chicken manure manufactured by Black Gold Compost Co. in Oxford, Fla. (available at specialty nurseries or

Mulch is optional, but it will help the soil retain moisture and prevent weeds. A 1-inch layer of oak leaves, pine needles, recycled mulch and even coconut fiber are good choices, he says. Keep mulch at least 1 inch away from plant roots to prevent root rot.

Every month, you can sprinkle a handful of the chicken manure on the soil surface. Another good monthly organic is liquid fish emulsion, which is mixed with water and applied to plants. Most garden retailers sell bottled fish emulsion.

The only other product you'll likely need is a bottle of natural Neem horticultural oil to control both chewing and sucking pests such as whiteflies, aphids and scale, as well as fungal diseases. Follow the product directions for this all-natural product, which can be applied without affecting harvesting time, Cordell says.

Other pests, including caterpillars and beetles, can be removed by hand. Sometimes a strong spray of water from the hose will remove pests as well.

Yvonne Swanson is a freelance writer in St. Petersburg and a master gardener for Pinellas County.

. about the series

Four weeks to victory

• Aug. 30: Planning your garden. What to plant, where and what equipment you'll need. Available online at

• Today: Improving your soil. Delicious, nutritious vegetables begin with healthy soil. You'll learn how to prepare yours for planting and to care for crops from seed to harvest. Plus, a Florida gardener's guide to the perfect tomato.

• Sept. 13: Plant something different. Expand your harvest with citrus, banana, sugar cane, pineapple and other tropical produce.

• Sept. 20: Growing together. Community gardens and organic food co-ops are popular alternatives when you can't grow food at home.

In Florida, vegetables need good earth 09/05/08 [Last modified: Friday, September 5, 2008 4:30am]
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