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Glorious gardenias

These fragrant beauties can be demanding at times, but we're lucky: A local nursery has the last word on what it takes to help them grow.

Published May 5, 2007

Harmon Carroll, 82, founder of Carroll Brothers Nursery and his son, Richard Carroll, 52, co-owner of Carroll's, pose next to a Miami Supreme gardenia tree at their business in St. Petersburg. University of Florida horticulture experts refer to the Carrolls as the "gardenia gurus."
[Times photo: Scott Keeler]
[Carroll Nursery St. Petersburg]
The mary Ann is the largest of the blooms and has flat rather than upright petals. It blossoms later than the Miami Supreme and Belmont.

It's that time of year when the intense scent of gardenia floats in the air, spicing up the garden with its tantalizing perfume of vanilla, jasmine and nutmeg. The exotic beauty with the creamy white flowers has a mind of its own, releasing its sweet and spicy perfume now and then to lure pollinators that can't resist its seductive aroma.

If you'd like to add a gardenia shrub or tree to your landscape - or you want advice to care for this finicky flirt - you need look no further than a local family-owned nursery. Established as a small retail garden center in 1950, Carroll's Nursery in St. Petersburg has matured as one of the country's largest gardenia nurseries; it houses about 200,000 gardenia plants at its 10-acre wholesale nursery in Clearwater.

The horticulture experts at the University of Florida call the Carroll family, including patriarch Harmon Carroll and his sons Richard and Robert, the "gardenia gurus." "We are the largest grower of gardenia east of the Mississippi," Richard Carroll says.

"People think a gardenia is a gardenia, and it's not," says Carroll, 52, who operates the retail garden center in north St. Petersburg. "Discount stores sell some that are ungrafted; you put it in the ground and in nine months it's dead. Or they get one for Easter, but it only lasts a few months."

The root of gardenias

The problem with mass-produced seasonal gardenias is that they are grown from their own root system. If you plant one of these cultivars outdoors, it will most likely be ravaged by nematodes, those soil-borne microscopic root eaters that are rampant in Florida soils.

Gardenias grown for landscape use should be grafted from the rootstock of Gardenia thunbergia, a native of South Africa that is resistant to nematodes and produces more and larger flowers and healthier dark-green, glossy leaves. That's the only kind of gardenia grown by the Carroll family.

"It takes a lot of work to graft them. It's a lost art," says Carroll. Many nurseries don't want to devote the time required for grafting or establishing plants. By the time a 1-gallon gardenia makes it to the retail center, it has been growing for up to 14 months. A 3-gallon plant has been developing at the greenhouse for two years.

There are numerous varieties to choose from, but popular choices include Miami Supreme and Belmont (large blooms in spring), Veitchii (small blooms from spring to fall), and Mary Ann (later blooming to extend the season), Carroll says. Expect to pay about $7 for a 1-gallon plant and $16.99 for a 3-gallon one.

"Mix the varieties, and you have blooming all year long," he says.

Grow, grow, grow

Plant gardenias in well-drained soil amended with rich organic matter. Gardenias prefer full sun, partial shade or dappled shade. Too much shade during the day will reduce flowering, but direct, hot afternoon sun can scorch this temperamental tropical. Gardenias do best in acidic soil, which poses a problem in areas where soil alkalinity is high, especially coastal property.

You can test your soil's pH level for a nominal fee at your local county extension office, University of Florida horticulturist Joan Bradshaw says. "Knowing your conditions is probably the most proactive thing you can do before you get started. A lot of people think that by adding magical things to the soil they will make it better . . . but all the chemicals in the world won't help," she says.

Carroll's Nursery recommends a planting mix of equal parts coarse sand (such as builder's sand), sphagnum peat (such as Canadian peat) and dehydrated (not composted) cow manure. Mix well and amend the planting hole, which should be twice the diameter and as deep as the plant's container.

Gardenias should be fertilized two or three times each year (January, June and September) with an acid-rich fertilizer. Look for products with a nitrogen-phosphorous-potassium ratio of 15-5-10 or 15-5-15 and follow the label's instructions. Carroll's suggests Sunniland Azalea Gardenia Fertilizer, which includes minor elements such as sulfur and iron. For an organic acid boost, regularly toss coffee grounds on the soil around your plant.

Don't worry if some older leaves yellow a bit during winter months; that is typical of broadleaf evergreens. If leaves are yellowing at other times or buds are dropping before blooming, the plant might need more iron, which can be added with a foliar spray such as Ironite. Or the culprit could be insufficient light, overwatering or poor drainage, inconsistent watering, nematodes, disease (black sooty mold) or pests, including whiteflies, aphids, scale insects and spider mites. Regularly look at the underside of leaves for telltale spots, especially during hot, dry weather.

Pest control

Numerous products for controlling these common insects and disease are available. Carroll's uses Orthene and Cygon for pests and Malathion and oil for mold. Treatments are applied on the top and underside of foliage and only when the outdoor temperature is between 40 and 80 degrees. You can get detailed instructions and recommendations on chemical treatments from your local county extension office.

Despite your best efforts to keep your gardenia thriving, there's one more issue to contend with: water. Gardenias don't like salt from reclaimed water, water softener systems or wells where salt has leached in. You should use potable water or rainwater collected in a barrel.

Carroll's Nursery is at 4950 38th Ave. N, St. Petersburg. Call (727) 527-5418.

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

Gardenia lore

- Don't prune after the first week of October, or you'll reduce the number of blossoms in spring. The best time to prune is right after blooming.

- If you love gardenias but they don't love your soil, try growing one in a container. You can control the growing medium and keep root-ravenous nematodes at bay.


[Last modified May 4, 2007, 18:54:14]

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