UNITED STATES—The primary problem with autumn foliar color is that it eventually becomes quite a mess. Premature shedding started the process even before much of the foliar color developed. Evergreen foliage can contribute to the mess, but most debris now is deciduous. Autumn is, obviously, its season for defoliation. Falling leaves merely do what is natural for them.
Falling leaves fall at different rates. Just as some fall prematurely, some might linger into winter. Also, some that usually linger into winter may fall earlier or later for some winters. Unusually cool, windy or rainy weather accelerates defoliation. However, defoliation can be slower with milder weather. Prolonged foliar color is pretty, but prolonged mess is not.
Besides falling at different rates, falling leaves are quite diverse. Big leaves of sycamore and fruitless mulberry are easy to rake away. Small and abundant leaves of Chinese elm require a bit more effort. They tend to sift between rake tines. Sycamore leaves disperse tomentum that is irritating and perhaps dangerous to inhale. Oak leaves stain pavement.
Autumn is the best and worst time for defoliation.
In a few relevant regards, falling leaves are quite convenient. Their absence allows more warming sunshine through as the weather cools. Not very long ago, they provided shade during summer warmth. Defoliation also allows wintery wind to blow more safely through deciduous trees. Otherwise, such trees would be more susceptible to damage from wind.
Falling leaves are also quite inconvenient. They clog eavestroughs and gutters precisely when they should not. As rainy weather begins for winter, it dislodges even more foliage. Also, it dampens foliar detritus so that it stains concrete and decking more than while dry. Raking detritus is most important while it is most unpleasant because of wintery weather.
Some coarse groundcover, such as Algerian ivy, can absorb smaller falling leaves. Most groundcover or turf is not so accommodating, though. Bigger leaves can overwhelm and shade them, as well as low or dense shrubbery. Slugs and, where they do not hibernate, snails can proliferate within this damp shade. So can fungal pathogens that tolerate chill.
Highlight: Chinese Elm
Dutch elm disease became a serious problem for American elms in the 1930s. However, it did not reach California until half a century or so later. Chinese elm, Ulmus parvifolia, is not very susceptible to the disease, but is a vector. In other words, it can survive infection to share it with other species of elm. Consequently, it became unavailable by the 1980s.
Some mature specimens of formerly common Chinese elm still inhabit older landscapes. Younger specimens in newer landscapes are mostly ‘Drake’ Chinese elm. They are a bit more upright, with more symmetrical form. More importantly, they are not vectors of Dutch elm disease. Other cultivars that are also resistant are rarely available at local nurseries.
Classic and formerly common Chinese elm can eventually grow more than 50 feet high. Some can grow 30 feet wide to shade an entire urban front lawn. Some cultivars might grow nearly as high but are generally not quite as broad. Their blotchy gray and tan bark adorns curvaceous limbs. Their small deciduous leaves are not very colorful for autumn. They can be copious, messy and quite tedious to rake.
Tony Tomeo can be contacted at tonytomeo.com.
