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Tuesday - May 27, 2008

From: Florence, TX
Region: Southwest
Topic: Cacti and Succulents
Title: Mystery cactus in Williamson County, Texas
Answered by: Nan Hampton

QUESTION:

We have a cactus plant on our place that I have not seen anywhere else in central Texas. The flowers are bright yellow with wine-red centers, but very sparse--only one flower blooms at a time. The pads are small; most to all spine clusters on the upper pads have no large spines, only small, wine-red, "hair spines." According to my field guide of Texas & Southwestern wildflowers, this would be red-eyed cactus, Opuntia violacea. But according to both that book and Correll & Johnston, O. violacea is confined to areas in far west Texas (and NM and Arizona. We live in northern Williamson County. This plant is less than 2 feet across and perhaps one foot to 18 inches tall, growing in a fencerow along with various grasses, greenbrier, wild grape, Mexican plum, etc. I haven't take a soil sample in this area, but it's probably a red-brown clay with some rock chips in it, over a chalky clay. The former owner at one time terraced and ditched the field it's on the edge of, so it's getting more water than out in the main field. This land, so far as I know, was never used for anything but agriculture; the original vegetation was tallgrass prairie and there are remnant patches of old tallgrass plants here and there. My questions are: 1)Is there any central Texas prickly pear with wine-red centers to yellow flowers, or is this really O. violacea a long way from its known range? (or, is the range reported in my two books wrong?) 2) Would it be a good idea to try to propagate this plant to have more than one individual, and if so would it be a good idea to put the young cacti up on the rocky knoll, which might feel more like "home"? 3) If propagation is a good idea, is this one of the prickly pears that will grow from a pad to form a new plant, or do I have to hope that nothing runs off with the fruits?

ANSWER:

1) There are, indeed, prickly pear cactus in Central Texas that have red centers to their blossoms. Please see Opuntia engelmannii (cactus apple), Opuntia engelmannii var. engelmannii (cactus apple), Opuntia engelmannii var. lindheimeri (Texas pricklypear), and Opuntia macrorhiza (plains pricklypear).

The new name for Opuntia violacea (purple pricklypear) is Opuntia macrocentra var. macrocentra (purple pricklypear) and its range is far West Texas, especially in the Big Bend National Park and the Guadalupe Mountains National Park areas, as well as New Mexico, Arizona, and northern Mexico. Although I can't be completely sure without examining the cactus firsthand, I suspect it is not purple pricklypear. From your description of its growth form it sounds as if it could be O. macrorhiza.

Here are some of the descriptions for O. macrocentra var. macrocentra (purple pricklypear):

Both Powell (Cacti of Texas: a field guide. Texas Tech University Press. 2008) and Correll and Johnston (Manual of the Vascular Plants of Texas. Texas Research Foundation. 1970) mention that the stems (pads) and/or their joints are noted for their purple color. You don't mention that your cactus is purple. Powell gives the size as "30-60 cm tall" and the pads "10-20 cm long, 10-20 cm in diameter, or slightly wider than long." Powell does say for that: "...spines produced in areoles on upper one-fourth to one-half of the pad, or only on the upper margin." He also says: "Reddish-brown to yellowish glochids abundant, especialy in upper areoles." "Flowers with sharply defined bright red centers...6-8 cm long, 5.5-8 cm wide, in general not opening as widely as most other opuntias. Filaments ca. 1.5 cm long, pale green proximally cream-colored distally. Anthers 1.8-2mm long, yellow. Cream-colored style 1.7-2 cm long. Stigma lobes ca. six, ca. 5 mm long, cream-colored or pale green."

Here are some of the descriptions for O. macrorhiza (plains pricklypear):

Powell"s description reads: "Low, sprawling plants, usually less than 30-40 cm high..." The size of the pads is given as "...7.5-13 cm long and 8-12 cm wide..." Correll and Johnson say: "...spines from mostly from the uppermost areoles". Powell says: "...1-3 main spines on the upper areoles". "Flowers...are typically yellow with sharply defined orange or red centers...6 cm long and 5-8 cm in diameter. Filaments cream distally and greenish basally, anthers yellow. Cream-colored style closely matches stigma. Stigma barely elevated above anthers, at least in some flowers."

Perhaps, some of this description will help you decide which your cactus is, but I suspect it is O. macrorhiza and not O. macrocentra var. macrocentra.

2) & 3) If you do want to propagate this cactus, you certainly could start another plant in the same area since it seems to grow well there, or you could move it to the rocky knoll, or do both. It should be relatively easy to do from the pads since at least, according to Powell, O. macrorhiza "Pads...tend to root where their edges touch the ground."