Sunday, October 21, 2018

Plant Story--More on Prickly Pear Cacti, Flowers and Fruits

prickly pear cactus

Prickly pear cacti, genus Opuntia, are easily-recognized members of the cactus family (Cactaceae) with a very wide native range across the Americas. There are more than 150 species, native from southern Canada to Argentina and Chile. They are also called nopales (singular nopal).

prickly pear cactus, northern Colorado
Prickly pears in desert grasslands, not flowering
Most of the time you see them in the grass, just a group of low cladodes (segments, pads). Or, in frost free climates, as taller shrub or even tree-like plants
large prickly pear in Arizona
prickly pear, Opuntia, seen in northern Argentina
tree prickly pear seen in Argentina
But when conditions are good, they produce beautiful flowers.

prickly pear flower seen in Argentina
Close up of flowers on "tree" prickly pear above
The flowers are generally larger than a quarter. Most open in the sunlight of midmorning and close at night to reopen the next day for a few days. Lots of the common species have yellow flowers but if you watch for prickly pears, you can find orange, magenta, white and two-toned flowers.

prickly pear in flower

orange prickly pear flower

They attract a variety of bees, flies, butterflies, beetles and other flower-visiting insects. Almost all prickly pears require insects to carry pollen between flowers for seed production.

bumble bee in prickly pear flower
Bumble bee in prickly pear flower
The fruits, often called tunas, are fleshy when ripe in some species and dry in others.  Some ripen to a red color, others are yellow or green when ripe.
Opuntia fruit
Prickly pear fruit. On bigroot prickly pear, Opuntia
, a northern speices, the fruit (tuna) is about 2" long
The seeds of fleshy fruits are clearly dispersed by animals who eat them. Native animals eating prickly pear fruits on the Americas range from deer, wild pigs, rabbits, foxes, coyotes, native mice and rats, a wide variety of birds to tortoises to ants.

Opuntia tunas
Prickly pear fruits (tunas)
Humans eat prickly pear tunas. Peel off the outside and eat the flesh around the seeds. They can be eaten raw, made into jam or used any place you use a fruit. Prickly pear juice can flavor everything from cocktails to icing. (link link ).

The one I cut up, from the bigroot prickly pear (Opuntia macrorhiza) in my yard, looked pretty innocent but I still got the tiny irritating hairs, glocids, in my fingers from picking them. There isn't much to eat on these either.  They tasted good but not wonderful.

Cut open Opuntia tuna
Here is the fruit cut open.
Blade of a small paring knife.
The fruits contain ten to over a hundred seeds, depending on the species. Taken directly out of the fruit, the seeds are notoriously slow to germinate. Passing through an animal improves germination, so treatment to breakdown the hard seed coat helps germination. Looking online, some of the websites used southwestern or Mexican desert prickly pears, likely cultivated varieties, and recommended solely to keep the conditions warm enough (SFGate) while others not only treated the seeds with acid but then refrigerated them for months (imitating winter) (link). If you gather tunas and want to germinate seeds--seedlings are very cute!--try to provide conditions similar to those the seed would experience where the adult plant was growing.

Opuntia seeds
prickly pear (Opuntia) seeds
Prickly pear cladodes (pads) also root fairly easily. When they break off, the cladode can live a long time wherever it landed, since it is photosynthetic and succulent (can make its own food and has stored water). It puts down roots and grows at the new location. (How to do it yourself: link link). This is important in nature because the isolated cladode has more resources than a seed so is more likely to survive if it does not rain, a common problem in the dry climates prickly pears like. The botanical concensus is that seeds are important because they are genetic recombinations, different from both parents, so may contain really advantageous new gene combinations, but that rooting of cladodes (vegetative reproduction, cloning) is a critical survival technique for the species in harsh climates where seedlings often do not survive.

Prickly pear cacti are widespread plants, avoided because of their spines but both the cladodes (see previous post link) and fruits are edible. The flowers are beautiful and pollinators love them.

And, you can put the spines to work for you. This very happy prickly pear was planted on the corner of a corner yard near me and it is very effective keeping pedestrians on the sidewalk.

bigroot prickly pear, Opuntia macrorhiza

Comments and corrections welcome.

Lots of information on particular prickly pear (Opuntia) species on U.S. Forest Service data base, for example:  link  (google genus and species, chose Forest Service FEIS options)
Reyes-AgĂșero, J. A., J.R. Aguirre R. and A. Valiente-Banuet. 2006. Reproductive biology of Opuntia: a review. Journal of Arid Environments. 64: 549-585.

Kathy Keeler, A Wandering Botanist

No comments:

Post a Comment