Weather and Environmental Factors in Green Landscape Design
I used to get really frustrated when I would buy attractive plants, plant them carefully, and they would die within a few months. Even now I feel frustrated when caring for someone's landscape, if they have azaleas and English roses planted in a desert area. These non-native plants take so much extra water that I can't empathize when the homeowner complains about expenses. Happily, more and more designers are recognizing the essential role that local weather plays in determining which plants will thrive, and they're planting accordingly.
Although the best adjusted and easiest to grow plants are those that are native to the area, there are many non-native plants that can be adapted to grow in a garden without supplementation, as long as they're from similar climates. Understanding your local weather patterns and other climate factors will help you choose those plants most likely to succeed where you live.
After reading this article, it might be a good idea to start watching and keeping notes about each of the following elements. That will give you a good basis from which to select the next thing you plant.
You also might want to look for microclimates in your landscape that are different from the main weather patterns. In a shady area down the hill from your lawn, for example, where lawn drainage stays longer than normal, you might be able to plant a water hungry bush like hydrangea and have it grow successfully.
Sunlight is needed by some plants and not so much by others.
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 burning up. A designer needs to pay close attention to how much sun a shaded area actually gets during the day, and what time of day it is that the sun penetrates that area, then choose plants according to how the sun/shade balance meets the plants' needs.
Where are your shady areas? How much sun do they actually get and when? Hot sun in the middle of the day has a different effect than morning or late afternoon sun.
Wind affects plants in surprising ways.
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. If the wind is strong enough and the tree is weak enough, the wind 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. If the wind blows half the spray away, which is common in the desert, a pine tree grown in the middle of a grassy area won't be able to send its roots down deep enough to stand upright when the wind gets strong.
How strong is the wind where you live? Which part of your landscape does it cross at what time of day? It may a good idea not to use sprinklers for irrigation in that area.
Rain is needed in greater or lesser amounts by different 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 sinks down into the earth (where there is access), making the soil 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.
Plants with slick 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, either in the soil or the air.
In 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 top of 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.
Which is the wettest part of your landscape? That's where you'll want to put plants that like more water than the others.
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 as 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 ten 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 the northwestern US and the river canyons of California it grows wild.
How hot does it get where you live? Do you start sweating when temperatures reach the eighties (F) or not until they reach the nineties? If the latter, you won't want to have plants in your landscape that need moist air to thrive.
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, looking for whatever climate zone predominates where you live. Find a plant hardiness zone map online and click on your region. Most good landscaping books also have hardiness zone charts, along with listings of plants that show in which zone that plant grows best.
Once you know your zone, then start looking at websites that show plants native to your area. Be sure to include hybrids of native plants, most often bred for showier flowers.
How Seasons Affect Plants
The passing of seasons gives plants a predictable sequence by which they can grow and produce. New growth starts in spring. Plants weed out and push their growth during the summer (in most areas). They transform with the glorious fruit of their labors in fall or flower again. Then they rest and recuperate in winter, until the beginning of the next cycle. Each season requires its own type of landscaping work.
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 go into dormancy, when they 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 calendars used to say.
In February 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, especially in areas devoted to annual flowers and crops. Lots of weeding is required here too.
Summer - This season starts around the first few weeks of May (May Day) when the temperature begins to really warm up. Weaker plants die, leaving the bigger, stronger ones to explode with growth. Citrus and seed fruit trees ripen their fruits for eating.
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 or to shade-loving flowers for hot weather.
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, Desert Willow, and Hollyleaf Cherry are summer flowering natives.
Pay special attention to watering during this season. In most places in the Northern Hemisphere it doesn't rain during the summer, so plants will need more water, if they're not native. Sprinkler heads break and underground pipes leak with constant use. It's also good to deadhead flowers, encouraging them to grow until the weather gets too hot.
Fall - This season starts around the first week of August. In Southern California, that's when the temperature 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, like apples and persimmons, also add color and interest.
This is the time to start pruning trees and bushes (as soon as they've dropped their fruits), readying them for dormancy in winter. You'll also have a lot of ground cleanup with dead leaves and fruits dropping.
Winter - In this season in most countries everything seems to go dead. 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, lilacs and poppies will begin to bloom during late winter and early spring.
This is also a great time to plan next steps in developing your landscape. Get out your landscaping books, explore design sites on the Internet, look for replacements for plants that don't really thrive in your landscape.
Climate and weather conditions need to be considered together.
Now ask yourself several questions:
- What kinds of plants grow naturally in my area?
- What are the most prevalent weather conditions here? Strong seasons or weak ones? Humid air or dry? Strong winds or mild breezes? Rain or drought?
- What hybrids of native plants are available for planting here?
- What other countries have climates similar to mine and what kinds of plants are native there?
All of these elements and considerations together create a complexity that a homeowner concerned with finances and appearance would do well to understand, even if it takes time. If you plan carefully ahead, taking the time to observe and do your research, you will save lots of effort and money later on. The resulting beautiful and interesting landscape will generate compliments from the neighbors and food for the local critters, as well as providing many hours of deep, personal satisfaction.
The landscaping books I use are out of print now, but one of my all-time favorite publishers is Better Homes and Gardens. This is a newer edition than the one I have. It includes hardiness zone charts, lots of great photos, and good instructions for new and middle level gardeners.