Marin Master Gardeners
University of California
Marin Master Gardeners

Trees: not just nice to look at

"The best time to plant a tree was 20 years ago. The next best time is now," or so goes the Chinese proverb.

If you've ever basked under the cathedral-like canopy of a magnificent old shade tree on a warm summer day and reveled in the serenity and tranquility it creates, you're enjoying just one of the myriad benefits of a stately, mature tree. And while you may not have the space for such a tree in your garden, it's easy to find a tree that can add stunning dimensions to your landscape.
They're so much more than just a big, pretty plant.

"The best friend of earth and of man is the tree," reflected renowned architect Frank Lloyd Wright. "When we use the tree respectfully and economically, we have one of the greatest resources on the earth."

In addition to gracing our homes with shade and beauty, trees provide environmental and economic benefits. They purify the air by intercepting airborne particles, act as carbon sinks by absorbing and locking away carbon dioxide in their wood, roots and leaves, and they produce valuable oxygen for all of us to breathe. Their roots bind the soil, reducing erosion and slowing storm water runoff, and trees create a habitat for birds and other wildlife. From an economic point of view, trees can increase the value of your property. Shade trees can decrease the need for air conditioning in summer and lower winter's heating costs by breaking the force of winds.

Mating for life: choose the right tree, because it might outlive you

Considering that most trees have the potential to outlive the people who plant them, selecting the right tree for the right location can result in a lifetime of satisfaction – or many years of headaches. The function of the tree, its form and size at maturity, its growth rate and longevity, the planting site conditions and the desired plant characteristics are key things to evaluate before choosing a tree.

Fall is a great time to plant a tree. You'll give it a chance to settle in while the soil is warm and the rains are (hopefully) forthcoming, and be ready for active growth come spring. You may not be able to hang up your hammock in it for a few years, but if you make some careful choices and plant one now, you'll have a tree to cherish for your lifetime and for those that follow.

Function first: what do you want your tree to do?

Start by deciding what your tree must accomplish. Even the most beautiful specimen will disappoint if it fails to meet the needs of the owner. Will it serve as an ornamental focal point in your landscape? Act as a windbreak or privacy screen? Provide fruit for the owner and some for birds and wildlife? Should it cast shade that reduces summer heat around the perimeter of the house or provide a fun climbing structure for children?

Form and size: make it work for your space

Like people, trees come in all shapes and sizes: rounded domes, upright columns, broadly conical, umbrella-shaped canopies, weeping, and more. Choosing a tree that is cloaked in foliage year round (evergreen) or drops its leaves all at one time (deciduous) will narrow your range of choices. Size matters, too. Find out the size and shape of the tree at its maturity. What might be a reasonably sized tree in 10 years may be an outsized behemoth in twenty or more.

How fast a tree grows can have an impact its stability and longevity. Some eucalyptus trees grow at a rampant rate, though are reputed to be "widow makers" as they can drop enormous branches for no apparent reason. Many common landscape trees have a relatively short lifespan - 20 to 30 years. Slow growing trees may not give you that optimum shade in a few short years, but they're likely to have a long lifetime.

Assess your site: are the conditions right?

When assessing your planting site, evaluate the exposure to sun and wind over multiple seasons if possible. What might seem to be the perfect spot for that evergreen in summer may result in unwanted shade during the rest of year.

When choosing your planting location, look up and down. If there are power lines overhead, assess whether they could be impacted by a full-sized tree. Similarly, if there are underground utility lines in the vicinity, trees with aggressive root systems may interfere and cause significant damage. The site should have adequate drainage and space around the perimeter of the tree to avoid soil compaction by pavement, vehicles, active people, and pets.

Depending on your microclimate, you may need a tree that can handle intense summer heat, winter frost, windy afternoons, and/or lots of fog. Know that your tree can withstand your conditions before you take the plunge. If water is either costly or scarce, don't go for a water hog - some varieties can easily absorb hundreds of gallons of the precious liquid in a single day.

Pests or disease can decimate your investment; avoid varieties known to be susceptible to killer pests.

Finally, the fun part: what’s it going to look like?

In addition to flowers and fruit, you can extend seasonal interest by selecting trees with vivid foliage like the brilliant lemon-lime locust (Robinia pseudoacacia ‘Frisia’). Unusual seed pods are another fun characteristic that’s often overlooked, such as those that dangle from the castor-bean, catalpa, or golden rain tree, Koelreuteria paniculata.
Blazing fall color provides a pronounced punch to autumn gardens, as does uniquely colored or textured bark. Plant hardiness (their tolerance to hot and cold temperatures), water consumption, resistance to pests and diseases, and even health concerns like allergy and toxicity, are all important considerations.

One attribute often overlooked is the season, duration, and amount of litter from a tree. The fernlike foliage of the silk oak (Grevillea robusta) looks great much of the year except in spring when the space around the base of tree is ankle-deep in leaf litter. Evergreen conifers can produce a long season of leaf drop early summer through fall. Trees with small berries for the birds may result in your patio being pelted with fruit-laden bird droppings.

TREE RESOURCES
SelecTree: An interactive program to help match tree species to desired characteristics
Trees Are Good: A website that contains a wealth of information on selecting, planting and caring for trees
The National Arbor Day Foundation: A website that includes a tree selector tool as well as care information


Original article by Nanette Londeree
Edited for The Leaflet by Marie Narlock and Anne Wick 

Webmaster Email: banielsen@ucanr.edu