UNITED STATES—Old fashioned irrigation systems were quite thorough, and technically sustainable. They broadcast generous volumes of water over any vegetation that required it. Their systems were too simple to need much adjustment. Their metallic composition was very resilient. That is why so many old systems were in service for so long. Some continue to function.

However, such old fashioned irrigation systems were not perfect. Their consumption was not as sustainable as their plumbing. They wasted water on vegetation that needed less, and pavement. Some of the broadcast water evaporated before reaching any vegetation. Without automation, old irrigation systems operated when convenient for their operators.

Modern irrigation systems are typically more efficient. Automation allows them to operate prior to sunrise to limit evaporation. Most modern systems apply water directly to the soil. This leaves no irrigation water to evaporate from foliar or other surfaces. Also, it prevents evaporation from airborne broadcast irrigation water. Evaporation innately wastes water.

Newer is not necessarily better.

Of course, modern irrigation systems are no more perfect than old systems. Groundcover and lawns still rely on broadcast irrigation. Such systems still waste water on pavement. Automation can actually waste water if not adjusted manually for rain and other weather. Only the most modern automation adapts to weather. No system responds to vegetation.

Consequently, irrigation can become either deficient or excessive as vegetation matures. Many native species need regular irrigation only as they disperse roots after installation. They are likely to rot with the same irrigation as they mature. Many tropical species need more water as they grow. Some vegetation, as it grows, can obstruct broadcast irrigation.

The complexity of modern irrigation systems complicates their maintenance. Automation is merely one component of the infrastructure. Emitters of drip irrigation sometimes need relocation or replacement. They are sometimes difficult to find below healthy vegetation. Because components are plastic, they are not as durable as old fashioned components.

Highlight: Gaura

Although not native, gaura, Oenothera lindheimeri, can almost naturalize as if it were. All it needs is occasional watering through summer. It performs better with regular watering. Individual specimens live for only about four years. Some may last for only a single year. However, their abundant progeny are likely to replace and perhaps overwhelm them first.

Gaura prefers sunny and warm exposure. Shade causes sloppy form. Naturalized gaura has potential to become weedy or invade other vegetation. Seedlings relocate efficiently. Cutting back old growth as it deteriorates through winter promotes vibrant spring growth. Concurrent removal of the shabbiest old specimens favors vigorous younger specimens.

Collective growth is mostly less than five feet deep, with wispy and lightly foliated stems. Basal leaves are bigger than tiny upper leaves. Airy flowers are only about an inch wide. Floral color is mostly pale pink. Seedlings of cultivars with white or richer pink bloom are not necessarily true to type. Neither are seedlings of cultivars with richly bronzed foliage. Bloom continues from very early spring until cooler wintry weather.

Tony Tomeo can be contacted at tonytomeo.com.