- Full sun means at least six hours of direct sun. But not all sun is created equal: reflected light off a white wall or the heat-sink effect of nearby black asphalt can boost temperatures significantly.
- Half sun means at least four hours of direct sun. However, some plants will be fine in a half-day of cooler morning sun, but will look stressed with the equivalent hours of hotter afternoon sun.
- Filtered sun/bright shade means dappled light through a tree canopy, but light enough to read a book without straining.
- Full shade means no direct sun; typically found on the north side of a building (unless you’re in the southern hemisphere), or the canopy of a dense tree.
Soil type refers to both the chemical and textural properties of soil. Chemically speaking, we’re interested in whether a plant prefers an acidic, alkaline or neutral soil pH. Rather than bore you to tears with a treatise on soil chemistry (waaay beyond my pay grade, anyway), let’s just say that your best strategy for a hassle-free, sustainable, cheap-to-maintain garden is to stick with plants that are already adapted to the pH of your garden. Most local, in-tune nurseries will stock plants that are appropriate to the pH of nearby gardens, or at least warn you if that darling you’re bringing home might need special attention. When in doubt, look it up.
Soil texture (sometimes called tilth) is determined by the relative amounts of three primary ingredients: clay, silt and sand. The ideal soil type for most gardens is called loam, with more or less equal proportions of the following three:
- Clay soil is characterized by slow drainage (the kiss of death for many plants), high water-holding capacity, alkalinity, stickiness, high nutrient-holding capacity, and its nearly rock-hard, shovel-busting density when it dries.
- Silty soil drains better than clay and has some of its better nutrient-holding features, but compaction can be a problem, especially if the soil is worked when wet.
- Sandy soil is easy to cultivate, drains well and warms up quickly in spring. The trade-off is that it loses moisture quickly, meaning more frequent irrigation for many plants, and is not high in nutrients.
In addition, soil contains organic matter, air, and living organisms.
The good news is that if your soil runs toward either extreme, you can gradually improve its texture and fertility over time. It might sound like snake oil, but adding organic material works wonders for both clay and sand.
If you want to save some coin and your vertebrate, take the low-cost, sustainable approach and choose plants that are already adapted to your conditions, since making any significant change to your soil is very difficult.
Water management and your attitude toward irrigation should have a strong influence on the plants you choose for your yard. In arid regions, selecting plants that require dragging a hose around or turning on sprinklers comes at a financial as well as environmental cost. Water is essential for life and I think everyone with a garden and a bathtub needs to think responsibly about how we conserve or squander a limited and unreliable resource.
Like it or not, even the most sustainably conceived landscape will require some amount of supplemental irrigation to get established and make it through dry periods.
Of course, the most sustainable approach is to build your palette around local native plants that have evolved to survive on what the climate naturally provides. And since there are other parts of the world with similar climates to yours, you can include varieties from those regions as we’ll. Where I design, in coastal California’s Mediterranean Climate, we can use plants from regions of South Africa, Chile, Australia, Southern Europe and Northern Africa, as well as local natives. This doesn’t mean you need to feel guilty about tossing in a few special needs plants, but keeping these a t a minimum will make your life a lot simpler and hold your water bill down.