If you happen to spend a few days in Tucson, Ariz., as I recently did, you will quickly develop an appreciation for drought-tolerant plants, since irrigation systems are utilized infrequently and hoses are seldom seen.
In the neighborhood where I stayed, it seemed that nearly every front yard was graced by a mesquite tree or two. Mesquite is a versatile desert denizen with the feathery, bipinnate foliage characteristic of leguminous, self-fertilizing trees. Mesquite (Prosopis spp.), naturally thorny but available in thornless hybrid varieties as well, has distinctive ornamental qualities.
Aside from its decorous light green leaves, it has single or multiple black trunks and bears yellow flowers in spring and summer. Although it can live without any water in 100-degree heat, it can also grow in a lawn.
Watered only by the rain, it grows rapidly to a height and spread of 30 feet and provides a modest amount of shade. In an irrigated landscape, it may reach 60 feet in height. Mesquite trees have the added benefit of requiring minimal, if any, pruning.
Poinciana (poin-see-AN-na) is a drought-tolerant leguminous shrub, widely planted in Tucson, that aptly complements mesquite. Yellow poinciana (Caesalpinia gilliesii) and red poinciana (Caesalpinia pulcherrima) are both encountered. They are commonly referred to as bird of paradise bushes or desert birds of paradise, in homage to their plumage of red stamens and their minimal water requirement.
Plant poincianas in well-drained soil if you want them to live for more than a few years. They should be pruned hard, just before spring, to half or less of their mature, 10- to 12-foot height. Otherwise, they will get leggy and produce progressively fewer flowers each year. Poinciana seeds and pods are highly toxic.
Mexican palo verde (Parkinsonia aculeata) is much in evidence in Tucson. This is a 15- to 30-foot leguminous tree whose multiple trunks are lime green to blue green in color. Its yellow flowers bloom throughout the year.
If you are looking for drama, you will want to plant an Ocotillo (Fouquieria splendens). This plant consists entirely of thin, thorny, Medusa-like appendages emanating up from the ground to a height of 10 feet or more. Flowers are orange. Octotillo, palo verde and mesquite may lose their leaves in the summer as a defense against desiccation.
Q. Our yard is full of wild onions and nothing seems to kill them. Please help!
– Dorlene Bailey, West Hills
A. Wild onions (Allium canadense), with flat leaves, and wild garlic (Allium veniale), with hollow leaves, are among the most difficult weeds to eradicate. They form clusters of underground bulbs that, unless every one is uprooted, will continue to send up shoots and form new bulblets of their own, spreading throughout the garden.
The plants are topped with small white to pinkish white flowers. Herbicides tend to slide off their slippery shoots, although some gardeners report control when, donning rubber gloves, a scouring sponge sprayed with glyphosate (Roundup) or 2,4-D (Trimec) makes chemical application more effective. The scouring sponge creates scratches in the waxy surface of the onion leaves, allowing the herbicide to penetrate.
Always read herbicide labels carefully prior to application. Incidentally, should you wish to get rid of ivy, the common ground cover, be aware that its slippery leaf surface makes it as difficult to eradicate with chemical sprays as wild onions.