Re: Sustainable Landscapes?

The topic of sustainable gardens is always an interesting one, and similar to the topic of fire safe landscape design, it gets more lip service than actual implementation.  The concept of abandoning a garden for a year and seeing what survives is certainly one end of the sectrum, and often abandoned gardens or those of owners who simply ignore them is illustrative of the various plants that can be used in any part of California and be left to fend for themselves.  On the other hand, it is also important to recognize that individual plants must also be given the room to grow if continual pruning to retain size is not practiced, and very few of my garden clients would be pleased with the initial installation if this was really factored in.  I try to strike a balance with spacing of plants for ultimate size versus initial appearance, and am certainly using far less fast growing more permanent shrubs and trees in too tight quarters anymore.  It does seem
 much more sustainable to space the big things out at proper distance one to another, and use annuals, short lived perennials, or fast growing and cheaply planted succulents and ground covers to fill the gaps, and count on them getting shaded out or overgrown and eventually removed as the more permanent things fill in.

It is also important to remember that while many drought tolerant plants can survive perfectly well without interference from us, regular grooming, deadheading, weeding, are all parts of keeping a garden looking like a garden, and not wilderness.  My personal preferences also tend toward a lusher summer look without the complete dormancy of an all California native garden, and more ground covering plantings than lots of bare earth.  I've found over the years that this is still easily attainable in my coastal influenced SF Bay Area climate, particularly if I provide at least some irrigation via drip systems every couple of weeks or at least once a month.  I find myself using more European, Chilean, Mexican, South African, Australian and New Zealand plants in particular to combine with natives, as these can still take the limited water regimen, but are not going into dormancy in mid to late summer.  

In particular, I love using succulent plants from all parts of the world in combination with some of our more colorful flowering natives, particularly those that are willing to keep blooming into the summer and water with proper siting or some additional water.  While these sorts of plants would probably require more supplemental water in hot, inland locations such as L.A.'s Simi Valley, our cooler conditions can keep them blooming happily on next to no additional water.  Amongst some of the natives that I have found particularly adapted to such use are our native Dudleya species, Sedum spathulifolium, Salvia clevelandii, Eriogonum grande var rubescens, Leymus condensatus 'Canyon Prince', Juncus patens and other Juncus species, Mimulus aurantiacus, various Clarkia species, Dichelopstemma species, Galvezia speciosa, etc.  Not to exclude the various more shrubby contenders that have dozens of species to choose from in the Ceanothus and Arctostaphylos
 genera.

Combining the natives with succulent plants from around the world such as Agaves, Aloes, Cotyledons, Beschornerias, Senecios, Calandrinias, Plectranthus such as P. neochilus, Aeoniums, Echeverias, Dyckias, Aechmeas, etc can easily be used here locally to give the year round color and lusher foliage effects with little to no water, and also have the advantage that they are not woody large shrubs or trees, and ongoing maintenance has more to do with the occasional thinning out and replanting to keep them fresh, than pruning and hauling away to the dump on a regular basis.

I also find myself paying a lot more attention to those plant species that actually can look good here locally with no irrigation at all.  These plants certainly exist, and will establish well enough if winter planted and given some minimal irrigation on occasion the first summer.  Amongst the local candidates for this category would include things like Lobelia laxiflora, Rosemaries and Lavenders and Phlomis, and even lawn grasses such as Kikuyu grass/Pennisetum clandestinum.  Some other plants that come to mind as they are blooming now, is the beautiful Aloe striatula in combination with Alstroemeria 'Ligtu Hybrids', soon to be followed by the Amaryllis belladonna.

It is possible to create colorful gardens that don't go completely dormant in summer, yet need little to no water.  To achieve such effects and not use irrigation at all, they can only be installed with the fall/winter rains and heavily mulched to conserve ground moisture.  It would greatly help if on-site water retention and recharge is considered the better way to handle roof run-off, by channeling downspouts to a system of perforated drain lines laid out to disperse water and recharge the water table.  Utilizing large boulders and rock mulches is also a very effective way to stretch the season of retained soil moisture, as well as giving some shade at the roots to plants that need the extra help to survive.

Strategies will obviously need to be tailored to the individual site and climate, and I know it is a whole other design dilemma to deal with hot dry winds and baking sun.  In such circumstances, creating windbreaks to moderate the drying out of plants is a much greater concern, and one I seldom need to address in our local conditions as our summer winds tend to be associated with cooling fog.  It was an eye opener to me to discover that South Africans in the Western Cape view exotic trees in watersheds as water thieves, rather than a source of capturing and retaining more rainfall to soak into the ground and provide more water.  In the Western Cape, such things as pines, cypresses and eucalyptus forests are seen as depleting the water resources rather than helping to conserve them.  It at first seemed counter-intuitive to me, bases on local circumstances where such trees capture fog drip and direct it to the ground, keeping it moister and shaded as
 opposed to the surrounding native chaparral vegetation.  I couldn't imagine the San Francisco Crystal Springs watershed behind the hills of the peninsula towns denuded of the vast planted pine/cypress forests, nor think of them as water thieves, and had never encountered this line of reasoning being applied to California circumstances in maximizing the capture of water for man's use in watersheds here in California.

The idea of cisterns as a source of landscape water is an appealing one except for the cost to install one of sufficient size for typical residential use, as our 6 to 8 month long dry season precludes this being useful when it is most needed.  It would seem more practical to install gray water systems at each residence that could use the wasted water in the garden, or install a secondary municipal water distribution system for treated waste water to be used for major landscape water users such as School ball fields, parks, parkway landscaping, golf courses and potentially urban vegetable gardens.  Such secondary water systems distributing treated waste water are already very much in use here in the SF Bay Area in larger developments that have been built in the last 10 to 15 years, and are mandated by law.  No doubt a sufficiently well fought for campaign would be necessary to implement this over the entire region, retrofitting existing older
 neighborhoods to re-use treated municipal waste water for outdoor landscaping, as the costs to do it seem prohibitive in this era of insufficient money for government based projects.  It may come to pass that desalination plants are more politically feasible, especially if the problems with energy supply needed to run them and intensified salinity discharge can be solved.
Other Mailing lists | Author Index | Date Index | Subject Index | Thread Index