UNITED STATES—Recently wintry weather is a reminder that large trees require maintenance. Otherwise, some are likely to eventually drop limbs or blow over. Even some of the most stable and structurally sound trees benefit from maintenance. Otherwise, they can become shabby, overgrown or obtrusive. Such maintenance is what constitutes the basis of arboriculture.

Arboriculture is, most simply, the specialized horticulture of trees. Of course, it is not as simple as its definition. It is as complex as the diversity of the countless species of trees that it involves. In some gardens, particularly within rural regions, it may involve forestry. For small trees, such as citrus or Japanese maples, it may be comparable to gardening.

Garden enthusiasts are likely to maintain small trees within their gardens. Those who do not enjoy gardening may rely on maintenance gardeners to do so. Unfortunately though, very few maintenance gardeners are qualified for arboriculture. Many commonly damage or ruin trees by attempting to maintain them improperly. Arboriculture is very specialized!

Gardeners are not necessarily arborists!

Arborists are specialized horticulturists of trees who perform arboriculture. Most prefer to work with large trees that are beyond reach of garden enthusiasts. Many also work with small trees for those who do not enjoy gardening. Information about arborists is available at isa-arbor.com. This is the website of the International Society of Arboriculture, or ISA.

Garden enthusiasts who maintain their small trees may not be able to do so forever. Only a few of the smallest sorts of trees will never grow beyond their reach. Most trees that are manageable while young eventually mature. Taller types of palms grow too tall to groom within only a few years. It becomes more practical and much safer to rely on arborists.

Trees are the most substantial and permanent of vegetation within home gardens. They are not as temporary or disposable as annual bedding and vegetable plants. Some can survive for centuries. Within most municipalities nowadays, mature trees are protected by ordinance. Trees are commitments, which are certainly worthy of proper arboriculture.

Highlight: Arizona Cypress

Although not native, Arizona cypress, Hesperocyparis arizonica, behaves as if it is. It is native to deserts and chaparrals of Mexico, New Mexico and, of course, Arizona. Hence, new specimens only require irrigation until they disperse their roots. Afterwards, they are happy with seasonal rainfall. They are more resistant to pathogens than other cypress.

Most modern Arizona cypress cultivars are bluish gray with densely conical form. A few are yellowish, pendulous or columnar. ‘Blue Ice’ is a strikingly silvery bluish gray cultivar of smooth Arizona cypress. Most old Arizona cypress trees exhibit significant variation because they grew from seed. Some develop irregular form or more greenish drab color.

In the wild, Arizona cypress can grow taller than 60 feet. Locally, few get 40 feet tall, particularly since modern trees are compact cultivars. Most stay less than 20 feet tall, and some stay about half as wide as they are tall. They work well as informal evergreen hedges. Smooth Arizona cypress exfoliates rough outer bark to expose smooth red inner bark. It is Hesperocyparis arizonica variety glabra.

Tony Tomeo can be contacted at tonytomeo.com.