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Ask Dr. Hort: Defining palms, desiring more desert cassia, getting orchid cactus to bloom

Avocado plant

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Avocado plant

Yes, technically palms are a big grass

Q: I recently returned from a visit in Arizona. While there I took a tour and was told a palm is not a tree (in your article under a picture it states that overpruning is bad for palm trees). Please verify. Ruth

A: You were told correctly. In the higher classification of flowering plants, botanically speaking, there is a division between monocotyledons (monocots) and dicotyledons (dicots). Monocots are characterized by having one seed leaf and fibrous stems. They lack a vascular cambium, the roots are also fibrous, the veins in the leaves are parallel, and the flower parts are in ones and threes. Examples are grasses, sedges, grains, bamboos, lilies, orchids and palms. Dicots, on the other hand, have two seed leaves, woody stems, a vascular cambium and a tap root system. Veins in the leaves are net or weblike, and the floral parts are in ones, fours and fives. Examples are sequoia, oak, citrus, elm, hibiscus, rose and juniper. So, botanically speaking, palms are big grass. However, when discussing plants in the landscape, many palms are rather tall so they are designated as trees to separate them from shrubs and ground covers.

What led to avocado sibling's demise?

Q: I have an avocado plant that is about 3 feet tall. I gave its "brother" to a friend a couple of years ago, and she planted it outside and it died within a few months. Thank you. Fredi Prager

A: It sounds like the death of the "brother" was from lack of water. It's best to purchase a grafted plant — or better yet, purchase two grafted and different varieties in the same pot. From seed, avocados take eight to 12 years to fruit. Plus they need a pollinator for best fruit set.

Getting a desert cassia to sprout, a cactus to bloom

Q: Several years ago I purchased a small tree called a desert cassia. It has tiny leaves and small yellow flowers and it always seems to be blooming. Last year, I made a garden on one side of my house and wanted to plant three of these small trees there as this side of my house gets sun all day and the tree does not grow very high. However, I have been unable to make the seedpods sprout; nor have I been able to locate a nursery that sells this tree. Do you know where I could find someplace that sells them? Or can you suggest a way to make the seedpods produce seedlings?

Also, several years ago, I purchased a plant named an orchid cactus, Epiphyllum hybrid, which I was told produced a flower that resembled an orchid. However, this plant has never produced a flower. I have even cut the top of it (and started other plants) to spur blooming, but neither the original nor the offshoots have ever bloomed. It is supposed to be kept in a shaded location, which I have done. Can you offer any suggestions?

Lorraine Parrino, Tampa

A: Desert cassia, Cassia polyphylla, has been reclassified as Senna polyphylla, like most of the cassias. It is a gorgeous small tree, growing to 10 feet, and blooms all year, unlike most of the other cassias (sennas). It doesn't propagate from cuttings, so seed is it. Wait for the tiny seedpods to turn hard and brown on the tree, remove, open the pod and drop the seeds into a cup of hot tap water and soak overnight. Place the seeds in small pots with a potting mix, half an inch deep. Place in full sun, keep watered and within two weeks you should have sprouts. Desert cassia is slow growing, so it is commonly not a mainstay in nurseries. Online is probably your best bet.

As for your orchid cactus, Epiphyllum spp, from a cutting it will bloom in two to four years with enough light. Epis need a couple of hours of morning sun to trigger flowering. An east exposure under some shade (30 percent) of a tree would be ideal. Keep it in the same pot and let it become rootbound. In year two or three, begin fertilizing with a bloom-booster-soluble fertilizer, especially on the stems, such as 5-50-17, 11-54-4 or 6-40-10, following label directions. Sometime between April and August you should see the spectacular blooms, but they open but one night like many other cacti.

Need help?

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

Ask Dr. Hort: Defining palms, desiring more desert cassia, getting orchid cactus to bloom 10/29/11 [Last modified: Tuesday, November 1, 2011 5:06pm]

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