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I live in San Diego, California, which is in the sunbelt in the southern part of the U.S. Here, deciduous trees drop their leaves in the fall and grow new ones in the spring, and have bare branches during the winter, even though it's warm enough here that they could grow new ones. They may start leafing out earlier than trees in the north. Leaves of California sycamore (platanus racemosa) trees turn a drab brown and then fall off.
We have a fig tree that is just now showing yellow on its leaves and they may drop soon. We have a redbud tree that will do the same shortly. The only tree in San Diego that gives any red or orange in the fall, as far as I know, is sweetgum (liquidambar styraciflua), which is not native here; it is native to the southeastern U.S. However it is widely planted here as it is one of the few, maybe even the only, tree that gives true fall colors here. Japanese Maple is sometime grown in highly protected locations here and it does provide fall colors but it is delicate and hard to grow here.
There are plenty of evergreen trees that stay green all year here, including conifers such as pines (the rare torrey pine is native to this county) and any other conifers that are planted such as redwoods, cedars, firs, etc. Coast Live Oak (quercus agrifolia) is a tree native to many areas in California, and it is evergreen. The leaves are small and curled on the edges like holly. There are also many tropical trees here such as palms, tropical fruits, and so forth, which also stay green all year here.
Eucalyptus trees, which were not originally native to California (they were imported from Australia entirely by seed) but are so widespread that one might assume they were native here, are evergreen trees but drop their leaves continuously all year, forming a carpet of dry, brown but still fragrant leaves around their bases. Citrus trees are very common in California and are tender to frost and cold, and are evergreen.
Citrus fruits ripen only on the tree, will not ripen after being picked, and have to be left on the tree for long periods. An orange may sit on a tree for a year before being picked. Ripe oranges may be on the tree at the same time as flowers for next year's fruit. Avocadoes are grown in huge numbers here, and have a shorter ripening period, but they are tender to cold and frost, and are usually grown on hillsides to keep them above "cold pockets" on valley floors. They are also evergreen.
I think in general, trees that are deciduous in their native habitat will also be deciduous here, if planted here, as the cooling temperatures and shorter amounts of daylight time in the fall may trigger them to drop their leaves. However, the period of time they are dormant may be shorter here than in their native habitat, depending on how cold or warm the winter is and how much rain falls or irrigation is applied. Roses can be grown all year long here, but almost everyone prunes their rose bushes back in January, so the period from New Year to about mid-March usually sees no roses on the bushes.
Plants that are native to southern California seem to have adapted to the long, dry summers by growing mostly during the cool, rainy months and going almost into a type of dormancy in the summer, with little growth.
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