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Ask Dr. Hort: Euphorb, a relative of the poinsettia, likes sand

This relative of the poinsettia likes sand

Q: Attached is a photo of a plant I've had for 25 years (seriously) that took a hit this winter. I trimmed out the dead, and in the process, ended up with a large stalk I would like to transplant. For years, I thought this was a "brain cactus," but after checking the Internet, I see that it is not. First, do you know the name of this plant, and second, do I just put this in a pot of soil?

Pat Bernitt, Lutz

A: Well, guess what, it's not a cactus at all! It's a member of the Euphorb family, and believe it or not, the poinsettia is a cousin as is crown-of-thorns and croton. Euphorbia lactea cristata is its scientific name. Any media high in sand is good for repotting, even straight builders sand. A shovel of soil out of the back yard would suffice. Use a heavy mix that will support the cutting but also drain well.

Too much attention hinders azalea blooms

Q: I have 10 very large azalea plants; they are 8 feet tall and seem healthy, getting both shade and sun. However, they probably are 15 to 20 years old and were here long before we moved in. They were blooming beautifully when we came. We cut them back to try to make them fuller. Even after fertilizing them four times that year and every year after that, they have had few blooms. I have experimented cutting them back various lengths from the top and I always trim them after blooming in May or June. Could the length of the cut cause them not to bloom?

Sandra Wittman, Dunedin

A: It appears that you are pruning at the right time and correctly, just a few inches now that you have re-established their height. Azaleas pruned in late summer or fall don't bloom as well or at all. Let's investigate the other cultural practices. Have you changed the watering practices? Azaleas of that age should only need irrigation during our hottest, driest time of year (now). They won't bloom if they have wet feet. The amount of sunlight is also key. Azaleas need filtered light, but not dense shade. Last, but not least, is fertilization. I think that's your problem. Azaleas of that age need no fertilization. Just kick back and give your azaleas a rest!

Blanket flower thrives in hot, dry, sandy soil

Q: The May 22 "Ask Dr. Hort" column pictured blanket flower. I have wanted to start some of these terrific flowers from seed in the area behind my house in Bayonet Point. The soil is almost entirely sand, but I would love to see a mass of these flowers at the edge of a woodsy area just this side of a small pond. Could blanket flower grow in such poor soil? I do not have a source for the seeds and also wonder if you know of a source for them.

Joan Van Tilburg, Bayonet Point

A: You have chosen a durable plant. Go online and type in Gaillardia seed. You can buy 1/4 pound of seed for $10. A pound contains 200,000 seeds. That ought to give you one heck of a meadow. Blanket flower feels at home in a hot, dry, sandy soil. Spread during the rainy season and watch your wildflowers grow.

Tomatoes rotting from bottom need calcium

Q: I am growing tomatoes in an Earthbox. The plants are large and healthy, with loads of tomatoes. However, as each tomato has grown larger and begun to turn red, it has rotted from the bottom. I am guessing blossom end rot based on Internet research. Does this sound correct? And if so, what can be done?

Vicki Wilson, St. Petersburg

A: Blossom end rot was a great diagnosis. This is common with tomatos and peppers, which are actually cousins. It is a nutritional problem caused by a lack of calcium. Add calcium chloride or, better yet, calcium nitrate to your nutrient solution and your problem should subside.

'Kent' mango very susceptible to fungus

Q: I have a large "Kent" mango tree. For the past few years, it has had lots of blossoms. I have sprayed with a copper-based spray all through blossoming time, but the blossoms just turn black and few become fruit. After the freeze, the whole tree abundantly blossomed again. Then many of the small fruit fell off. What can we do?

Sally Selfors, Largo

A: Unfortunately your "Kent" mango is very susceptible to anthracnose, the fungus wiping out your flowers. Copper sprays are recommended, based on its low cost, but mancozeb is a good alternative and may give you better control next year. If you want to go organic, neem oil 70 percent has been tried. Remember to start spraying at bud set and continue through fruit set. The panicle of mango flowers is 90 percent male (no fruit), so the 10 percent you get, you want to keep.

Need help? Enter Greg "Dr. Hort" Charles, who for more than 30 years educated gardeners through the Pinellas Technical Education Centers. He answers questions about landscape and garden pests. E-mail your questions to 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: Euphorb, a relative of the poinsettia, likes sand 06/11/10 [Last modified: Friday, June 11, 2010 7:14am]
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