This section is from the book "Nature's Garden", by Neltje Blanchan. Also available from Amazon: Nature's Garden; An Aid To Knowledge Of Our Wild Flowers And Their Insect Visitors.
Flowers - Yellow, sometimes reddish at centre, 2 to 3 in. across, solitary, mostly seated at the side of joints. Calyx tube not prolonged beyond ovary, its numerous lobes spreading. Petals numerous; stamens very numerous; ovary cylindric; the style longer than stamens, and with several stigmas. Stem: Prostrate or ascending, fleshy, juicy, branching, the thick, flattened joints oblong or rounded, 2 to 5 in. long. Leaves: Tiny, awl-shaped, dotting the joints, but usually falling early; tufts of yellowish bristles at their base. Plant unarmed, or with few solitary stout spines. Fruit: Pear-shaped, pulpy, red, nearly smooth, 1 in. long or over, edible.
Preferred Habitat - Sandy or dry or rocky places.
Flowering Season - June - August.
Distribution - Massachusetts to Florida.
Upwards of one hundred and fifty species of Opuntia, which elect to grow in parching sands, beneath a scorching sun, often prostrate on baking hot rocks, on glaring plains, beaches, and deserts, from Massachusetts to Peru - for all are natives of the New World - show so marvellous an adaptation to environment in each instance that no group of plants is more interesting to the botanist, more decorative in form and color from an artistic standpoint, more distinctively characteristic. Plants choosing such habitats as they have adopted, usually in tropical or semi-tropical regions, had to resort to various expedients to save loss of water through transpiration and evaporation. Now, as leaves are the natural outlets for moisture thrown off by any plant, manifestly the first thing to do was either to reduce the number of branches and leaves, or to modify them into sharp spines (not surface prickles like the rose's); to cultivate a low habit of growth, not to expose unnecessary surface to sun and air; to thicken the skin until little moisture could evaporate through the leathery coat; and, finally, to utilize the material thus saved in developing stems so large, fleshy, and juicy that they should become wells in a desert, with powers of sustenance great enough to support the plant through its fiery trials. A common expedient of plants in dry situations, even at the north, is to modify their leaves into spines, as the gorse and the barberry, for example, have done. That such an armor also serves to protect them against the ravages of grazing animals is an additional advantage, of course; but not their sole motive in wearing it. Popular to destruction would the cool juices of the cacti be in thirsty lands, if only they might be obtained without painful and often poisonous scratches. Given moist soil and greater humidity of atmosphere to grow in, spiny plants at once show a tendency to grow taller, to branch and become leafy. A covering of hairs which reflect the light, thus diminishing the amount that might reach the juicy interior area, has likewise been employed by many cacti, among other denizens of dry soil.
In this common prickly pear cactus of the Atlantic seaboard, where the air is laden with moisture from the ocean, few or no spines are produced; and dotted over the surface of its branching, fleshy, flattened joints we find tiny, awl-shaped leaves, whereas foliage is entirely wanting in the densely prickly, rounded, solid, unbranched, hairy cacti of the southwestern deserts, and the arid plains of Mexico.
In sunshine the beautiful yellow blossom of our prickly pear expands to welcome the bees, folding up its petals again for several successive nights. William Hamilton Gibson says it "encloses its buzzing visitor in a golden bower, from which he must emerge at the roof as dusty as a miller," only to enter another blossom and leave some pollen on its numerous stigmas.
But the cochineal, not the bee, is forever associated with cacti in the popular mind. Indeed, several species are extensively grown on plantations, known as Nopaleries, which furnish food to countless trillions of these tiny insects. Like its relative the aphis of rose bushes (see p. 99), the cochineal fastens itself to a cactus plant by its sucking tube, to live on the juices. The males are winged, and only the female, which yields the valuable dye, sticks tight to the plant. Three crops of insects a year are harvested on a Mexican plantation. After three months' sucking, the females are brushed off, dried in ovens, and sold for about two thousand dollars a ton. The annual yield of Mexico amounting to many thousands of tons, it is no wonder the cactus plant, which furnishes so valuable an industry, should appear on the coat-of-arms of the Mexican republic. Some cacti are planted for hedges, the fruit of others furnishes a refreshing drink in tropical climates, the juices are used as a water color, and to dye candies - in short, this genus Opuntia and allied clans have great commercial value.
The Western Prickly Pear (O. humifusa) - O. Rafinesquii of Gray - a variable species ranging from Minnesota to Texas, is similar to the preceding, but bears a larger flower, and longer, more rounded, deeper green joints, beset with not numerous spines, scattered chiefly near their margins. A few deflexed spines in a cluster leave the surface where a tiny awl-shaped leaf and a tuft of reddish brown hairs are likewise usually found.