Shade trees live for a century or more, and they are the most permanent plants one can grow. Builders and developers tend to remove all trees so their large equipment can move easily over the ground. Already open cropland is being gobbled up for housing developments. Consequently, owners of newly constructed homes and buildings typically find themselves with barren lots and no shade trees. Planting shade trees soon after construction is completed will help "settle" the landscaping and provide focus for future gardening and landscaping efforts.
Importance of Shade
The air temperature in shade is several degrees lower than the temperature in adjacent non-shade areas. The soil temperature in shade also stays lower, since the sun does not reach it. Without the sun to heat and dry the soil, shady areas sometimes retain moisture. However, large trees use a great deal of water, which can offset moisture retention.
Shade trees have extensive root systems that hold soil in place and prevent erosion.
A mature tree that shades a home will keep the sun's heat from striking portions of the house. This keeps the interior temperature of the home significantly lower, and will reduce cooling costs.
Usually when we think of shade trees, spreading deciduous trees come to mind. Oak, maple, walnut, chestnut and elm are native tree species that have adapted for most areas of the US. A tree is a long term investment, so make a selection based on as much local information as you can gather.
Check a tree's expected longevity before purchasing it. Recently, arborists and tree developers have bred new hybrid varieties of shade trees that are extremely fast-growing. Some hybrid poplars were developed for landscaping use and may live 50 years or more. Hybrid poplars developed for timber are more brittle; they reach maturity in about 30 years. Native tulip poplars will live for 100 to 150 years in areas of the country where they occur naturally.
Most trees that mature at least 30 feet in height are considered to be shade trees. Native trees with a mature height up to 60 feet are considered medium height, and tall trees are those that mature at 60 feet or taller. A 30 to 50 foot horizontal spread is common with medium and large trees.
A mature shade tree will canopy. A canopied tree has vigorously growing middle and upper branches, which provide shade. Lower branches do not receive as much light, and do not continue to grow. In natural woodlands, canopy trees thrive with a layer of saplings and undergrowth. A large specimen shade tree will also develop alone with no competition from undergrowth.
Fast-growing shade trees may also be short-lived trees, such as Mimosa Silk (Albizia julibrissin) or Golden Medallion (Cassia leptophylla). Although these examples grow up to three feet per year and can shade a two story house at maturity, they may decline well before 50 years of age. Fast growers are sometimes interplanted with slower growing shade trees, such as oak or maple. When the health of the quick growers declines, they can be removed. A remaining oak or maple can then take over and live an expected 100 to 150 years.
Shade trees can be grown successfully almost everywhere except deserts, beaches, high elevations and arctic areas. Specific varieties of shade trees will thrive in different areas of the US. Select shade trees by matching their characteristics with the growing conditions where they will be planted.