Recently, on a hot Sunday afternoon, I noticed a curious thing: On a comfortable chaise-lounge in the shade of my Tipu tree, I was reading a good book when I felt drops of water or some other liquid falling on me.  Was it raining? The drops were so tiny that I couldn’t even see them on my skin, but there was no doubt about what I was sensing. Wondering if I was experiencing aphid droplets falling out of the tree canopy, I examined the surrounding furniture on my deck, but there was nothing of that sticky substance that aphids exude and that is known as honeydew. What could these droplets be?
Knowing about how trees cool themselves, I imagine that it was the tree itself that sprayed on me: Evaporation (“transpirationâ€) of water from its foliage in the hot afternoon was extra fast and generous to form the minutest droplets that ‘rained’ on me.
A gentle spray to cool me off – how awesome!
Have you ever noticed how wonderful the shade under a tree feels, especially on a hot day? The lovely sensation on my skin made me think again about how important trees are in the sustainable landscape design, no matter which climate you live in. Consider the most obvious at this time of year: Beauty from bloom and form; shade and reduced energy cost, and an emotional connection that we all have to trees.
As I was lounging in the shade, I was wondering how big the temperature difference was that I felt there: In the full sun it was close to 100° F that afternoon; in the shade by contrast a comfortable 85° F! And the air that I was breathing under it was fresh and cool – the tiny droplets were just an added pleasure.
Numerous authors and organizations have made a valuable contribution to this subject and demonstrated to homeowners and planners alike, with hard numbers, the measurable payback of trees, even the increase in real estate value! There are many fun facts about the social, environmental, economic and communal benefits of trees at sites like these:
“Trees are Goodâ€,  by the International Society of Arboriculture; “Canopyâ€, a publication by a volunteer organization in Palo Alto that cares for trees; “Why Shade Streets? The Unexpected Benefit†by the Center of Urban Forest Research.
As gardener and landscape designer San Diego passionate about sustainable landscape design another benefit comes to mind that many gardeners have certainly noticed, too:
The canopy of an evergreen tree provides a perfect microclimate for cold-sensitive plants as well as for those that prefer the dappled shade over a sun-baked situation. This is particularly true of inland valley or desert situations where many plants, even the desert plant species, that tolerate full sun closer to the coast appreciate the reprieve that a tree canopy provides as too much sunlight creates problems with the plant’s ability to regulate photosynthesis (this is the chemical process by which plants convert water and carbon dioxide from the air into carbohydrates).
The shade also translates into lower water needs for everything growing beneath as well as prolonged growth and flowering:Â While many plants, even drought resistant plants, go limp or floppy in the mid-day heat of summer, the ones in the shade show more intense color and firmer foliage. (Some plants respond to the heat and drought by going dormant and dropping their leaves, such as California Buckeye, a California native plant.)
Drought resistant plants that actually prefer the dappled shade (or afternoon shade from a building) are many succulents, such as Aeoniums, Sedums and Echeverias, even Foxtail Agave Agave attenuata prefers this situation. Also many flowering perennials and soft-leaved plants such as Sundrops Calylophus drummondii, Copper Canyon Daisy (Mexican Marigold) Tagetes lemmonii, and Purple Sage Salvia leucophylla come to mind.
And then there are the strictly aesthetic-driven aspects of designing with trees, and I can’t even begin to consider a home landscape design without them, or any landscape design for that matter. (I wrote about it already in a previous post “Trees in my garden? No trees, please!â€). They are a garden’s upright support and beams; they are the main structural elements around which all other plants are arranged.  They feel to me like the “ceiling†and walls in the garden; shrubs and flowers are the furniture so to speak…
Trees also give a garden its mood: Compare the feel that a palm tree creates in a garden, with that of a deciduous Sycamore; or picture the branches of a pine tree and the “whoosh†of a breeze going through it, and compare it with the burning orange fall-foliage of a Crape Myrtle or Western Redbud!
Trees can mark a spot as focal point; they can denote a boundary; they can frame and enhance a view or screen out an unsightly one. Most important perhaps is the comforting, protected feeling that we experience: There’s something primordial about sitting under the canopy of a tree: It connects us with ancient, genetically anchored memories of our cave days, I imagine, and sitting in an open field has a very different, un-sheltered feel. A landscape without them is feels lifeless to me, depressing even; there’s not much shelter for birds so they stay away, and it doesn’t feel nurturing.
If all this makes you want to design your landscape and select the best tree for it, here are a few more resources specifically for San Diego homeowners:
San Diego Tree/Palm/Plant Pictures at http://www.geographylists.com/sandiegoplants.html
And perhaps the tree down the street that you have been interested in has already been identified and listed in our own San Diego Tree map?
This fun interactive map lets you search for a particular tree by neighborhood: Just locate your street, zero in on it and see whether the tree you are interested in has already been identified. Conversely, if you have identified a tree in your neighborhood and want to contribute to this database, just upload a photo and the information, and you’ll help your neighbors learn about it. This great resource also shows you some of those ‘hard numbers’ that I mentioned above as the trees’ “Yearly Eco Impactâ€.
To get a feel for the physical presence and characteristics of a tree, especially at maturity, nothing suits this better than a visit to any of the resources that we have here in San Diego: There’s the San Diego Zoo of which its founder, Dr. Harry Wegeforth said,  “A luxuriant growth of trees and foliage was one of the chief features of the Zoo as I planned it in my mind’s eye.†(Read also “San Diego Zoo Gardens”).
Then there’s the San Diego Botanic Garden in Encinitas, and the Water Conservation Garden in El Cajon. Or the San Diego Safari Park that is home to 4 ac of California nativescapes, with more than 1500 individual plants representing 500 species, all of which historically call SoCal home.  And then there’s their conifer forest with more than 1,000 plants representing 400 species of conifers..
And don’t forget San Diego’s Balboa Park!
Take a stroll one of these summer days and marvel at the beauty and cool comfort that the shade of the trees provide. Send me photos of our finds, share your landscape design ideas with me and let me know if there’s a resource that I didn’t think of!
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