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Ask Dr. Hort: Desert rose's problem likely started with potting mix, large containers

Problem could be rooted in potting mix

Q: We bought a couple of nice-sized plants (foot tall, 3 gallons) from Lowe's in the late summer. We put them is large pots at the edge of our east-northeast-facing patio. We added a thick layer of coarse stones for drainage and used a potting mix for the soil medium. At first they flourished lushly and bloomed like crazy. Then we had that near-weeklong period of high winds (we live off of the land side of the Intracoastal). After that the blooms fell off and the leaves yellowed and fell. Many looked damaged from rubbing on others. My wife then decided, against my advice, to trim the bare limbs up a bit "to add shape." We are starting to see some new sprouts where she trimmed, but that dark green lushness just isn't there. They get full sun until about 2 p.m. and the only water they get is dew and when it rains. The pots seem to drain well after a rain, which seems right as we understand they don't like too much water. I'm wondering if we should mix some sand into the potting medium. Should we fertilize them? Rick Franz

A: The problem on your desert rose, Adenium obesum, . probably started with the potting mix and the large containers. If it was a peat based mix such as Promix, or Miracle Gro potting mix, repot mixing the peat mix with sand (playsand), 40/60. If it was "potting soil," start over with 40/60 peat-based mix. The original rootball will probably still be intact (hasn't ventured out much), so transplanting shouldn't set your plant into a tailspin. Water biweekly with a bloom buster soluble fertilizer such as a 10-20-30, 11-35-15 or similar. The salty wind dehydrated the plant, causing the flower and leaf drop, but the deficient new growth would be because of the potting mix/fertilizer. Now to save the marriage. Pruning will add more character (branches) to a plant that doesn't like to branch, so not to worry!

Skip the shells in plant beds and try organic mulches

Q: Could you please advise on the pros and cons of using crushed shell in beds? I am thinking about using shell in several of our beds. I like the light color and I understand is will hold up for a long time. My wife is concerned about the calcium that will leach into the ground and possibly affect her annuals and perennials. Randy Maxson

A: Using crushed shell in plant beds is a disaster for the plants involved. Your wife is right, the calcium carbonate will be released, causing the soil pH (acidity or alkalinity) to rise. This will make the soil very alkaline, locking up the micronutrients such as iron, zinc, manganese and others, causing your plants to stunt and die. You were right in it holding up. It will forever. You are better off to leave the shell at the beach and use organic mulches around the home, unless you want to create a seaside landscape.

Gloriosa lily commands attention

Q: A friend of mine sent me this picture to identify. I have no idea what it is. Can you help? Buz Fyvolent

A: The way the leaves clasp the stem with a tendril at the end of the leaf (very unique for a tendril) in the photo that you sent leads me to believe that is a gloriosa lily, (Gloriosa superba or Gloriosa rothschildiana), in bud stage. Yours is probably G. rothschildiana, having the broader leaf. The flower will open upside down with the petals folding backward and the reproductive parts hanging down. If you want to produce seed, rub noses between two flowers to help spread the pollen. The vines sprout from an L-shaped tuber (storage organ) in the ground in the spring, bloom summer through fall, dying back in the winter. The striking colors of red, yellow and orange make this vine a showstopper, it also will last up to a week as a cut flower.

Need help? Dr. Hort (Greg Charles) answers questions about garden problems. Email him at drhort@tampabay.rr.com or mail questions to HomeLink, Features Department, Tampa Bay Times, P.O. Box 1121, St. Petersburg, FL 33731. Describe problem in full, and include your name, city of residence and contact information. If possible, include a good-quality photo. Fuzzy ones won't do. Photos cannot be returned.

Ask Dr. Hort: Desert rose's problem likely started with potting mix, large containers 03/03/12 [Last modified: Saturday, March 3, 2012 3:31am]

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