Although palms are trees, they are more closely related to grass. Their roots increase in length but not width, and are continually being replaced. Their trunks have no branches and, except for basal swelling of some types, trunks do not get wider as they get taller. A few produce "pups," which are secondary basal shoots that develop into additional trunks, but each trunk is limited to only one apical bud. Yuccas and dracaenas (two lily relatives) as well as sago palms are not really palms, which is why they are able to form branches.

Palms spend their first few years maturing at ground level. When their apical buds get large enough, they "launch," which means they begin to develop trunk height. After this, the buds do not get larger, but merely replace themselves, leaving old dead leaves and newly developed portions of trunk below as new leaves develop above.

All palms are either "feather" palms or "fan" palms. Feather palms have pinnately compound leaves, composed of small leaflets on single long rachis. Fan palms have pleated round leaves on long bare petioles (leaf stems). The various date palms, queen palm, king palm and pindo palm are feather palms. Mexican and California fan palms, Mediterranean fan palm and windmill palm are, obviously, fan palms.

Lower leaves of feather palms should be pruned off as they begin to turn brown. Otherwise, they eventually break off and fall. Fronds falling from tall trees can be damaging and dangerous. Petiole bases left on the trunk when leaves are pruned away are permanent fixtures on the trunks of most date palms, but eventually fall away cleanly from trunks of other feather palms.

Many fan palms accumulate "beards" of dead fronds if they are not pruned away. Large and possibly heavy portions of the beards of some fan palms, particularly California fan palm, may peel away from their trunks and fall. If pruned away, remaining "stubble" (petiole bases) leaves distinctive lattice patterns on Mexican and California fan palms and dark fur on windmill palms.

"Shaven" trunks of fan palms have had their stubble removed. Stubble may peel away easily from California fan palms, but typically needs to be cut away from young Mexican fan palms. Windmill and Mediterranean palms are very rarely shaven because their stubble is so dense, coarse and tough.

Palms may generally seem soft and lush, but some bite. Date palms, particularly the most common Canary Island date palm, have dangerously sharp and stout spines at the base of each petiole. The petioles of some fan palms, particularly Mediterranean and Mexican fan palms, have sharp inward curved teeth. Queen palms do not bite, but instead clobber their victims with very heavy bunches of hard fruit.

Tree of the Week: windmill palm

"Harry" is a windmill palm, Trachycarpus fortunei, in my back garden. Before getting shaven, Harry's formerly hairy trunk was covered with dense, shaggy, black fur. The fur coat was originally wider and much denser near the top, and narrower at the base. However, the now clean-shaven trunk is rather uniformly narrow from top to bottom.

Windmill palms grow as tall as 30 feet. Leaves are as wide as three feet and are held on petioles as long as two feet. Growth rate is variable. Happy trees can grow quite rapidly, but distressed trees can grow very slowly with stunted leaves. Windmill palm is so resilient to cold winters that it can be grown throughout Oregon and Washington. It is even grown in Oklahoma and central Pennsylvania. It just does not look so good if leaves get tattered by wind.

Windmill palm is one of the most common palms. It is often mislabeled in nurseries as Chamaerops excelsa. Unfortunately, the very different Mediterranean fan palm is often sold as windmill palm.

Horticulturist Tony Tomeo can be contacted at 408.358.2574 or at LGHORTICULTURE@aol.com.