Assess Your Garden Conditions

Plants have evolved all over the world, adapting over the course of time to local conditions, whether temperate or tropical, wet or dry, loamy or rocky, sunny or shady. Plants that failed to find a niche became extinct and vanished. These days, we bring plants from diverse climates and communities into our gardens. Even when we try to design with native plants, we know that they, too, have diversity in their history. Their seeds may well have been brought to the region hundreds of years ago by animals, water, wind, and native people. Each plant species has a range of conditions under which it will thrive, other conditions under which it will merely survive, and unique limitations that will cause its death in hostile conditions.

Temperature

Heat and cold influence plant survival. Understanding temperature in your garden will help you find the varieties of plants that can thrive for you, especially those plants that normally live for more than a year. Conditions in your garden are influenced by your region's climate, including frost dates, and your garden's unique exposure. Plants can be grown outside their natural climate if you provide warmth to tropical plants in winter (for example, growing a lemon tree in a greenhouse in Massachusetts) or cold to plants from temperate climates in winter (for instance, treating tulip bulbs with weeks of refrigeration before planting them in Georgia). Consider both heat tolerance and cold tolerance before your select your plantings.

Seasons

Some regions, such as the Midwest, are hot in summer but icy cold in winter; some are either hot or cold all the time; and others are mild or moderate most of the year. In some regions, summers are very dry but winters are wet. Others are changeable from year to year. Even though we cannot do much about local weather, we can observe its patterns and choose plants that are naturally suited.

Microclimate

Within every garden, you can find areas with different kinds of exposure to the elements. These are called microclimates. Even a small deck will usually have several microclimates. The part closest to the house may get more reflected light if it faces west or more shade if it faces north compared to other parts of the same deck. In larger areas, differences are even more pronounced.

Within these special niches, some plants may bloom earlier or longer into the season or be more likely to freeze or overheat. South-facing slopes or sides of buildings tend to have a longer growing season than nearby areas. Spring flowers there may bloom a week or two earlier than those in a cooler part of the garden. Although a south-facing area may be warm on sunny winter days, the rapid drop in temperature from a bright winter day to a cold night may be too extreme for some plants. The cooler, shadier, north-facing exposure is better for marginally hardy plants and those that are prone to drying out in winter.

Wind

How windy is your garden? Strong winds can snap off branches and cause plants to dry out faster than they can take up water to replace its loss. When selecting plants for windy areas, try varieties that originated in windy climates because they have developed resistance through strength and flexibility. Leathery, stringy, or waxy leaves are another adaptation. Protection from wind may be needed for other garden plants. Windbreaks, walls, buildings, and berms (raised mounds of earth) help alter wind patterns in your garden.

The USDA's hardiness zone map shows the hardiness zones for the United States and Canada, which will help you chose the right plants for your climate. Go to the next page to see the hardiness zone map.

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The United States Department of Agriculture Plant Hardiness Zone Map divides North America into 11 zones based on average minimum winter temperatures, with Zone 1 being the coldest and Zone 11 the warmest. Each zone is further divided into sections that represent five-degree differences within each ten-degree zone.

 

This map should only be used as a general guideline, since the lines of separation between zones are not as clear-cut as they appear. Plants recommended for one zone might do well in the southern part of the adjoining colder zone, as well as in the neighboring warmer zone. Factors such as altitude, exposure to wind, proximity to a large body of water, and amount of available sunlight also contribute to a plant's winter hardiness. Because snow cover insulates plants, winters with little or no snow tend to be more damaging to marginally hardy varieties. Also note that the indicated temperatures are average minimums -- some winters will be colder and others warmer.

Your zone is just one factor you must consider when choosing plants for your garden. You must also determine the light conditions of your garden, taking into consideration the position of buildings or large trees and shrubs. Keep reading to learn more about assessing garden light conditions.

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Sunlight plays an essential role in your garden. Sunshine powers the process of photosynthesis, which allows plants to make their own food using air and water. As they grow, plants provide food for grazing animals, who in turn provide sustenance for higher levels of the food chain. Sun provides the start for the whole food pyramid, so it's vital to give it the respect it deserves in the garden.

Many plants, especially lawn grass, flowers, roses, conifers (needle-leaved evergreens), vegetables, and fruit trees thrive in bright sun, which provides abundant energy for growth, flowering, and fruiting. Six to eight hours of direct sun a day is sufficient for most plants that need full sun. The term "full sun" doesn't actually mean plants must be in bright light every moment of the day, only most of the day. However, the six- to eight-hour minimum must be met for perennials, trees, and shrubs even during the shorter days of spring and fall.

Consider differences in sun intensity when planting on the east and west side of shade-casting trees or buildings. Even if east- and west-facing sites receive equal hours of sun, they will not produce identical results. Gardens with an eastern exposure are illuminated with cool morning sun, then shaded in the afternoon. They are ideal locations for minimizing heat stress in southern climates or for plants such as rhododendrons that can burn in hot sun. Gardens with a western exposure are shaded in the morning and drenched in hot sun in the afternoon. Sunburn, bleaching, and sometimes death of delicate leaves can result, especially in warm climates and when growing sensitive young or shade-loving plants. Afternoon sun can also cause brightly colored flowers to fade. The west side of a building is the ideal place for sun-loving plants.

Shady gardens need different kinds of plants, but these gardens can still be successful. Keep reading to learn about assessing garden shade.

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Shade, from partial to full, has a big impact on the plants in your garden. Watch how shadows and sunlight hit the ground to determine how much shade exists during the growing season under deciduous trees (those that drop their leaves in fall). This test will determine which shade-loving plants will thrive there.

Limb up trees or remove smaller, scraggly, or unwanted saplings and brush to brighten a densely shaded spot. Prune the lowest rung of branches off young trees to raise the level of the canopy in the future. Tall, mature shade trees can have their lower limbs removed (a heavy job requiring a professional arborist) to produce light shade. For even more light, arborists can thin out overcrowded branches in the canopy, leaving some openings in the foliage for sun penetration.

Prune low-hanging branches on a sunny day so you can see how the light changes. This way you can watch the shade lighten. You can also keep an eye on the shadows, which will dance from one side of the tree to the other, changing with the time of day and position of the sun. Their silhouettes can be a beautiful part of the garden, especially in winter when the dark shadows stand out on the white snow.

Light Shade

Even in places where plants are in direct sun for a portion of the day, you also have light shade. This can be found in a garden under mature trees with long barren trunks. The sun shines in under the high leaf canopy. Light-shade conditions also exist on the east or west side of a wall or building. Here you can grow many shade-loving plants as well as shade-tolerant plants, which are sun lovers capable of growing moderately well in light shade.

Partial Shade

Filtered light, or partial shade, can be found under trees that allow sunlight to penetrate through the canopy and dapple the ground throughout the day. A garden grown beneath a lightly branched honey locust tree would fall into this category. More kinds of plants are capable of growing under these conditions than in deep shade.

Deep Shade

Full or deep shade is found under thickly branched trees or evergreens. A garden that's located here will receive little or no direct sun and remain gloomily lit. Only a limited number of plants are suitable for this situation, so choose carefully (flowers and ferns with evergreen leaves).

The length of the day changes depending on where you live, and long or short day lengths can have a big impact on your plants. Keep reading to learn about assessing day lenghts for your garden.

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Day length can play a big part in the success of your garden. We've all heard of the midnight sun, but we may not be aware of how our geographic position affects day length. At the equator, the length of the day stays the same through the year, but the closer you are to the North (or South) Pole, the more the light shifts with the season.

In practical terms, plants get more hours of sunlight during the summer in Boston than they do in Miami, but the reverse is true in the winter. Plants react to more hours of light per day with fast growth, which is why you'll find giant vegetable contests in northern areas such as Anchorage, Alaska. Changes in day length affect plants' growth cycles.

Water is another essential piece of the puzzle when it comes to growing healthy plants. On the next page, learn how to assess the rainfall that naturally waters your garden.

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At least 90 percent of every plant is water. No plant can live without some moisture, and certain plants use it in amazing ways. Orchids and bromeliads that live on tropical trees absorb rainwater through their foliage. Succulent plants and cacti store reservoirs of water in their swollen stem tissues so they can go for a month or more without rain. Prairie flowers such as butterfly weed store water in their fleshy taproots. And daffodils store water in their bulbs.

Without water, plants wilt and die. But too much water can be as bad for plants as not enough. If land plants are submerged in water for too long -- even if just their roots are submerged -- they may rot or drown from lack of oxygen.

Balancing plants' water needs is like having a healthful diet. Everything should be consumed in moderation. Provide your plants with enough water for good health, but don't flood them with it. Most plants prefer steady moisture in the soil, especially in spring, so they can grow without interruption.

Regional Rainfall Patterns

It is rare for nature to provide exactly the right amount of water, not too much nor too little, for garden plants. You'll probably have to water your plants during dry spells to keep them looking their best. You can also observe your region's normal rainfall patterns and choose plants that are appropriate. For instance, bulbs like tulips and daffodils come from regions with wet winters but dry summers. North American wildflowers such as Virginia bluebell tend to bloom early, during moist weather at a time when tree leaves are just emerging, and then go dormant, sitting out summer in dry shade. For this reason they are referred to as ephemerals. Subtropic areas, such as parts of Florida, have frequent storms in the summer rainy season, bringing floods of rain. During interruptions of the usual pattern, fast-growing plants may need extra water.

To monitor rainfall patterns, set a rain gauge in an open area of the garden. You can purchase one at a garden center or use a topless coffee can. After each rainfall, check the depth of the rain inside. A commercial rain gauge is calibrated and easy to read. To read rain levels in a coffee can, insert a ruler and note how high the water has risen. Then keep this information in mind as you choose your plantings.

Garden soil usually needs some work before it's ready to support plants. On the next page, learn about assessing your garden's soil.

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The garden soil in which your plants grow serves four basic purposes. It helps, through its structure, to hold the plant upright, and it supplies food, water, and air to the roots. Some soils are already capable of meeting these purposes and can be used with little amendment. Called loam soils, they contain a mixture of different-size soil particles and organic matter. Beneficial microorganisms help break organic matter into nutrient-rich soil with good texture. If you have a garden with rich, fertile soil, you won't need to treat it.

It is possible, however, that you'll need to improve one or more of the conditions of your soil. For example, soil with a significant proportion of clay (at or above 25 percent) is made up of rock particles so tiny and close together they allow little air circulation. Clay retains more moisture, so it takes longer to dry in spring and may need less watering in summer. It can be made richer and more likely to produce lush growth with just the addition of compost and, occasionally, a little fertilizer. The compost is important. It helps break up clay so the soil won't be too thick and poorly aerated.

Sandy soil contains larger rock particles. Air is present in abundance in sandy soil, but water runs straight through, sometimes carrying nutrients away too rapidly and drying out soon after a rain. This means that in rainy climates, the gardener may have to add everything the plants need.

The texture of your garden soil needs to be the right balance of sand, silt, and clay. Learn how to assess the texture of your garden soil on the next page.

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Garden soil consists of sand, silt, and clay, and for plants to grow well, it must have all three in the right proporitons. There are a few ways to determine which kind of soil you're dealing with. For a quick test, simply squeeze some slightly moist soil in your hand. Clay soils form a compact lump and retain their shape. Loam soils form a ball but fall apart if poked. Sandy soils won't hold their shape at all. 

You can also check the texture of your soil in a jar filled with water. Gather some soil from the garden, choosing a sample from near the surface and down to a depth of eight inches. Let it dry, pulverize it into fine granules, and mix well. Put a one-inch layer (a little over a cup) in a quart glass jar with 1/4 teaspoon of powdered dishwasher detergent. (Dishwasher detergent won't foam up.) Add enough water to fill the jar two-thirds full. Shake the jar for a minute, turning it upside down as needed to get all the soil off the bottom, then put the jar on a counter where it can sit undisturbed. One minute later, mark the level of settled particles on the jar with a crayon or wax pencil. This is sand. Set an alarm for four hours, and when it goes off, mark the next level, which is the amount of silt that has settled. Over the next day or two, the clay will slowly settle and allow you to take the final measurement. These measurements show the relative percentages of sand, silt, and clay in your soil. 

Organic matter provides nutrients to the plants in your garden. Keep reading to learn about assessing the organic content of your garden soil.

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In nature, topsoil is richer than subsoil. Topsoil is the dark brown layer of soil that is at the surface and is the product of years and years of breakdown of organic matter, whereas the subsoil below can be mainly clay or sand. Organic matter gives life to the soil.

Every soil needs organic matter for its texture and workability, as well as a supply of nutrients necessary for healthy plant growth. It is the material that comes from leaves, animal droppings, twigs, fallen logs, weeds, and many other once-living sources.

In the forest, leaves pile up, mixed with other organic matter, and decay into a dark, rich layer, which is where growing plants prefer to have their roots. Earthworms and beneficial microorganisms process the organic matter, turning it into simpler compounds that plants use to nurture themselves.

Where there is little organic matter, the necessary compounds can be added with packaged fertilizers, but they do not address soil texture, and it can be difficult to add every necessary trace mineral that natural organic matter will provide. Ensure good soil quality, texture, and quantity by adding plentiful organic matter in the form of chopped leaves, animal manures, wood chips and other mulches, and compost.

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