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Ask Dr. Hort: exotic plants, sweet viburnum and caterpillars

Exotics like bat flower require special care

Q: Please advise me on how to pot and care for some exotics. I had a lovely black tacca a few years back, but it went into a slow decline and belly-upped. I am getting three new ones, a large-growing variety, in white, green and black. Please tell me about potting soil mixes, degree of wetness and light requirements. I have researched them on the Internet, but need to know about local conditions.

Also, I recently bought giant farfugiums at the USF sale. Please tell me how to care for them. I have put them into larger pots with 50 percent bark, 50 percent sphagnum. Some plants like to be a bit root-bound; are farfugiums like this? Are taccas like this?

Robbi Garrison, Dunedin

A: You certainly do have a flair for the exotic. Your bat flower (Tacca spp.) is a member of the aroid family along with philodendrons, peace lilies, dumbcanes, Chinese evergreens and pothos, to name a few. They prefer shade and an organic mix, like Promix, which is a peat-based mix with some perlite and wetting agents thrown in. Don't overwater your bat flower or it will succumb to fungus in a heartbeat. Keep the light level consistent and the media moist, but not wet. On your giant leopard plant (farfugium), keep it moist all of the time (do not let it dry out between waterings). Your bark/peat mix may dry out too quickly. The Promix might be better for this application. The plant also requires shade, especially in the summer. You've chosen some plants that are quite challenging. Good luck!

Take care with pruning sweet viburnum

Q: I planted some sweet viburnums for a privacy hedge early last year. They are growing fast, but many times when I trim a branch to encourage lower shoots, that branch tends to die off. Because of this, some of the bushes are really leggy and don't really produce new shoots from the bottom. They get partial sun this time of the year, full sun in the summer. I also feed them. I don't know if my pruners are too dull and should be washed with alcohol and sharpened? Also, I was told that if you cut some of the white flowering blooms it will help them grow faster. Is that true?

And one more question: There are new shoots that look like suckers growing out of the inside bottom part of the shrub. I don't know if I should cut them in half to produce more middle branches or let them grow.

Anna Ramsey, St. Petersburg

A: Sweet viburnum (Viburnum odoratissimum) grows plenty fast whether it has flowers or you prune them. Take advantage of the fragrant blossoms, then prune. Cutting the internal suckers back halfway is a great way to help fill in the plant. And last but not least, when you prune shoots, always cut back to a leaf. Where there is a leaf there is a bud, this is called a node. It is from this node that a new branch will appear. The distance between nodes (leaves) is called an internode, where no buds appear, therefore no branches. It is this area that dies back when improperly pruned, so always prune back to a node, not an internode.

Milkweed will draw caterpillars away

Q: Finally I found the right spot for my gardenia bush. It only took years of trying. However, it is starting to bloom now and it is next to a milkweed plant. I see holes in my gardenia leaves. Is this due to the caterpillars? Or do I have an issue? Should I move the milkweed away?

Barbara Turchiarelli, St. Petersburg

A: Not to worry! 'Tis the season for everything to get a hole here and there, for growth is abounding and the critters are happy. However, your milkweed is a whole lot more attractive and tasty to the monarchs than your gardenia. Just sit back and watch nature take its course.

Fertilizer math

When applying fertilizers, most recommendations suggest 1 pound of actual nitrogen per 1,000 square feet. To obtain this number, divide your percent of nitrogen into 100. For example, for a 6-2-6 fertilizer divide 6 into 100, which results in 16.7 pounds (round up to 17) for 1,000 square feet. Another example, using a 10-0-12 fertilizer: Divide 10 into 100 to figure out you would need 10 pounds of fertilizer to spread over 1,000 square feet. No need to waste fertilizer!

Need help? E-mail your questions to Greg "Dr. Hort" Charles at or to (put Dr. Hort in the subject line). Mail questions to HomeLink, Features Department, St. Petersburg Times, P.O. Box 1121, St. Petersburg, FL 33731. Describe your problem in full, and include your name, city and contact information. If possible, include a photo. We will print his advice on Saturdays in HomeLink.

Ask Dr. Hort: exotic plants, sweet viburnum and caterpillars 05/07/10 [Last modified: Thursday, May 6, 2010 2:35pm]
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