UNITED STATES—Deciduous foliage gets colorful with autumn chill. Then, it gets messy. Then, with a bit of precipitation, it gets even messier! It seems like a waste as it all succumbs to rain and, in other climates, snow. It is sensible, though. Deciduous vegetation will be less vulnerable to stormy weather without it. Weather will be getting increasingly stormy through autumn.
This is how the Mediterranean climate here operates. The dry season that begins during spring continues until autumn. The relatively shorter rainy season centers around winter. Therefore, most precipitation occurs during winter. Spring and autumn are brief transition seasons that tend to favor the dry season. Almost no precipitation occurs during summer.
Spring and autumn transitions between rainy and dry seasons are innately variable. The rainy season tends to finish early during spring but may not. It sometimes pauses before resuming. It may do so more than once. Conversely, the rainy season tends to begin late during autumn but may begin earlier. Occasionally, precipitation begins disturbingly late.
Weather forecasts cannot apply to entire seasons.
Generally, the first significant storm with significant precipitation begins the rainy season. This may be difficult to believe with typically significant time between the first few storms. Yet, with cooler weather, elevated humidity, and shorter daylength, moisture lasts longer. Precipitation, even if merely drizzling fog, will likely dampen gardens before they get dry.
Irrigation obviously does not need to be as generous as it was during summer. Until next spring, some vegetation will require none at all. Not only will weather provide and retain more moisture, but vegetation uses much less. Refraining from manual irrigation is easy. Adjustment of automated irrigation systems actually requires more effort and awareness.
As deciduous species defoliate for winter, some other species might get more vivacious. Cacti, agave, and some yuccas that lack irrigation become more turgid with precipitation. Remaining palo verde foliage is likely to become greener and fresher prior to defoliation. Most xeric species utilize moisture from precipitation as it becomes available seasonally.
Highlight: Blue Palo Verde
If “verde” translates to “green,” then what color is blue palo verde, Parkinsonia florida? It is simply a bit more bluish green than other species that are a bit more yellowish. Its bark contains chlorophyll to photosynthesize without foliage. Blue palo verde is deciduous so defoliates for winter. Then, it defoliates in response to dryness through much of summer.
Blue palo verde in the wild may develop and retain foliage only during early spring. With landscape irrigation, it can retain some foliage through summer. It can also produce a bit more prior to late autumn defoliation. However, frequent irrigation promotes vigorous but structurally deficient growth. Few blue palo verdes thrive for a century within landscapes.
Blue palo verde can grow almost 40 feet tall, but typically grows only about half as tall. It naturally grows as large shrubbery. Removal of lower growth exposes sculptural trunks for small tree form. With staking, trees can develop single trunks. Light yellow flowers are tiny but profuse during spring bloom. Blue palo verde is the Official State Tree of Arizona.
Tony Tomeo can be contacted at tonytomeo.com.
