The Role of Climate in Landscape Design
Local climate is a major determiner of the types of plants that develop in an area naturally, and in those that can be adapted to grow in your garden without supplementation. Native plants are always the best adjusted and easiest to grow. However, understanding the factors below will help you choose plants from other, similar climates around the world, if you need them to add interest.
Many Plants Need Sunlight
The sun fuels and energizes plants. It awakens them in spring, as it combines with the pull of the moon to pull new life up from the earth. The tree loving Celts (early inhabitants of Europe) noticed that fruit trees started budding in February in response to the sun warming up the cold, winter earth, hence that became for them the start of spring. Because of its powerful role, the sun is a major factor in choosing where to place plants in a landscape.
The counterpart to sun is areas of shade. Areas of shade can protect more sensitive plants from too much sun. A designer needs to pay close attention to how much sun an area shaded by trees or buildings actually gets during the day, and when it is that the sun penetrates that area, then choose plants according to how the sun/shade balance meets their needs.
Lots of sun and little rain combine to create very dry air in Southern California where I live, except near the coast, which is moister. Some plants like dry air and others don't. There are ways of moistening the air to accommodate plants that need it, but it's much easier and cheaper just to choose the kind of plant that suits local conditions in the first place. Define the conditions first, then start looking at websites that show plants native to your area.
How Wind Affects Plants
The wind shakes up plants and prunes them. Dead leaves and weak branches get blown off. All lightweight debris is blown across the land until it reaches a rock or ravine or a blockage of some sort, where it collects into a compost pile. This is where fungi that like really rich soil grow naturally. They help to break debris down into components that feed their neighbors.
In ocean areas, wind brings in moist air as it blows across the ocean and then across the land. Plants like bougainvillea and ice plants, and trees like palm and bananas grow well by the coast where the temperature is warm and the air is moist.
Across deserts the wind blows heat and dries the air even more than the sun does. Moisture-retentive plants with thick skins grow well there, like saguaro and ocotillo cactus.
Wind bends trees, like the rows of coastal cyprus in Northern California, and if it's strong enough and the tree weak enough, can blow them down.
Wind also blows away irrigation water that is supposed to be watering the landscape, in areas where there are no bushes or buildings to block it. Most irrigation systems are set to water grass, not trees, and the wind blows half of that away, hence a pine tree grown in the middle of a grassy area in the desert cannot send its roots down deep enough to hold itself upright in a strong wind.
Effect of Rain on Plants
Rain waters and cleanses plants and the earth. It also cleans the air as it descends, taking particulates out of it that often become food for plants. It fills up the earth (where there is access), making it soft and spongy for roots to penetrate.
Water provides the medium by which plants suck up nutrients from the soil and distribute them to their cells. It washes toxins out from the cells, cleansing the insides of plants as well as the outsides. Water plays the same roles in our own bodies, which is why we need to drink a lot of it.
Plants with thin leaves generally like moister climates, whereas plants with thick trunks and/or leaves like drier climates. The thickness has grown to protect them against evaporation (called "transpiration" in plants), helping them to preserve water inside their bodies. These types of plants will rot when exposed to a lot of moisture.
In the jungles, where there is almost too much water, plants have thin, veiny leaves and slick coatings to let water slide off. Many plants grow on each other, and some have broad leaves that overlap to catch and hold the water they drink, instead of drinking through their roots. Two thirds of the world's plant species are found in jungles, including 90% of the world's vines.
Temperature and Humidity
Extremes of temperature challenge and make plants hardy. Citrus fruits grow firm and sweet in areas that have distinct cold and hot seasons, as long the cold stays above freezing. Mild temperature changes make plants soften. Mangoes and bananas thrive in the even temperatures of the tropics, whereas citrus fruits grown there are mushy and tasteless.
Different plants grow better or worse depending on the amount of moisture in the air as well (humidity). Oranges do well in California, because the air is dry. Ferns don't do well at all. They need high humidity, so they grow best in the tropics. Bougainvillea needs heat and humidity. It grows well in the tropics, and also on the coast of California where sea breezes keep the air moist.
In the West Indies plants like coleus, bamboo, and elephant ears grow naturally to be well over six feet tall. In most of the United States these plants are grown as indoor house plants, since they need moist air and mild temperatures in order to thrive. Maidenhair fern is a delicate-leaved plant that grows naturally by the sides of streams, where tumbling water keeps the air moist. This, also, is a houseplant in most of the United States, but in Oregon it grows wild.
Plant hardiness zones are mappings of extremes of temperature around the world. They are used to tell you what types of plants grow well within those extremes. If you look for a hardiness zone map, you can click on your region and usually find a list of good plants with which to design your landscape. Most good landscaping books also have hardiness zone charts you can refer to, and the listings of plants show in which zone that plant grows best.
For Europe see:
For the United States see:
How Seasons Affect Plants
Seasons give plants the same cycle they give us, with a chance to start new growth in spring, really push during the summer (in most areas), relax with the glorious fruit of their labors in fall, and then rest and recuperate in winter until the next cycle begins. Some locations, like Southern California, have a different sort of cycle that includes a rest period in the middle of its hot summers. During those times California native plants do not like to be watered, although California homeowners often try.
Spring - Once I started looking, I realized that wherever I go in Southern California, most trees start budding in early February, so I quietly acknowledged that the beginning of spring really does start with Groundhog Day, just as the old Celtic calendar said. I get out my camera and start taking photographs of landscapes waking up - showing new little leaves next to old dry ones, and little colored buds spotting dead-looking branches. The birds suddenly start singing more loudly and I know that the bees and butterflies will come out of hiding soon. This is the time to begin cultivating the earth, preparing it for planting in areas devoted to annual flowers and crops.
Summer - This season starts around the first few weeks of May (May Day) when the temperature begins to really warm up. This is the season where plants focus their growth and take off. Many of them have finished blooming and are bearing fruit. Most plants, even roses, begin to back off of flowering, saving their energy to flower again in fall. A good landscaper will design to have an area devoted to summer-flowering plants to keep interest going even during that season.
For summer It's a good idea to remember the flowering trees, like jacaranda (native to Central and South America) and crepe myrtle (native to India, SE Asia, and northern Australia). In Southern California, Pacific Dogwood and Hollyleaf Cherry are summer flowering natives.
Fall - This season starts around the first week of August when the temperature in Southern California is often at its hottest, but nights are starting to grow longer and days shorter. Slowly the nights start cooling down and then the days do also.
Roses and many other fall flowerers start their second blooming session and gardens seem to come alive again. This is a season that's easy to plan for, because there are so many plants that flower in fall. Fall fruits also add color and interest.
Winter - In this season everything seems to go dead (except in Southern California). To keep your landscape looking interesting, plant a section that focuses on shapes and textures. Add bark mulch and clean off the rocks and pavers that give your garden a little contrast. In a very short time, California lilacs and poppies will begin to bloom during late winter and early spring.
All of these elements and considerations together create a complexity that a homeowner concerned with economics and appearance will do well to commit time to understanding. Careful planning ahead will save lots of effort and money later on, and the resulting beautiful and interesting landscape will generate compliments from the neighbors, as well as providing many hours of deep satisfaction.