Regional Gardening Reports :: National Gardening Association

In the Garden:
Southern California Coastal & Inland Valleys
March, 2009
Regional Report

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Citrus blossoms and fruit bespeak So Cal -- and only home gardeners can enjoy the glorious fragrance!

Trees, Nature's Air Filter

Trees and plants are as nature's filtering system. Each day, the average person uses 35 pounds of oxygen -- all of it coming from plants and trees. They literally filter the air by collecting dust and pollutants in the air before they reach our lungs. They make our life more peaceful by providing a sound barrier, filtering out noise. Trees mask unattractive sights, as well.

Trees cool homes in summer -- one tree can have the same cooling effect as ten room-size air conditioners. In the winter, deciduous trees let the sun shine through bare branches to warm our homes. Trees provide wood to burn for heat, lumber to build houses, and paper for books and newspapers. Tree roots lessen water runoff, and branches slow down wind. Commercial fruit and nut trees provide 26 million tons of food each year. Plant a tree!

Some trees do best when transplanted in the spring, when warm soil and air speed healthy root growth. These include Nootka cypress, golden-rain tree, hornbeam, magnolia, English and red and white oaks, poplar, tulip tree, tupelo, and zelkova.

Citrus and avocado trees do best when they're planted from now through May -- as the weather warms up. Choose a southwest exposure that is protected from the wind, for the best protection from cold weather and frost. Plant them on a mound or in a raised bed so water drains away from the roots. Rub suckers off trunks as they appear. Tape together or remove broken branches. Paint trunks and large limbs with a matte-finish, off-white interior latex paint mixed half and half with water to prevent sunscald.

Don't try to rush growth of nectarines, peaches, or plums by providing too much nitrogen. This contributes to generally poor fruit quality -- poor color development, delayed maturity, softness, and reduced storageability. Too much vegetative growth from excessive nitrogen can also result in poor fruit set for the following year. If the trees have good growth with dark green leaves in the spring, they have sufficient nitrogen.

Tree roots can extend almost four times the distance from the trunk to the dripline. The longest ones -- the "feeder" roots -- are near the soil surface. When planting the tree, dig the planting hole twice the size of the rootball, and turn over soil a foot deep for that distance again further out. Incorporate some compost and other organic matter to help keep soil uncompacted. Then, new roots can easily reach out into this native soil and become well established. In addition, keep walking, decks, and other heavy-traffic and construction at least five feet away from the trunk, so feeder roots won't be harmed.

Newly planted trees may need support for a year while they develop strong root systems and trunks. First, remove the stake that came from the nursery. Into the ground on either side of the trunk and a foot out from it, drive two sturdy 1-inch- or 2-inch-wide stakes about 16 inches deep. About two-thirds the way up the trunk, tie loops from each stake around the trunk; use "soft" material like stockings or rags or old garden hose pieces. Tie the loops loosely so the trunk can sway gently in the wind -- this strengthens the trunk and stimulates strong root growth. Remove the stakes after a year.

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