Site Evaluation

Before you put your pencil to paper to make your garden plan, we suggest you take the time to evaluate your site properly. There's more to evaluating your garden site then just looking out your window. However, looking out your window is a great starting point! Seriously, there is a lot of data to collect, study, and analyze.

Each site has its own microcosm—unique features that make it different from all others even if they are on the same block in the same neighborhood. These factors are threefold 1) climate and weather 2) aspect and site; 3) and soil analysis.You should note these factors of your site over several months as seasonal variations may occur.

Climate and Weather

Climate and weather are the two most important factors that will define your garden and the plants you can grow.

In the Untied States, the Department of Agriculture has divided the country into hardiness zones based on the average minimum temperatures, the intensity, and length of its winters. Here in New York City, we are in USDA Zone 6 which means the average annual minimum temperature is -10° to 0°F.

The Rain and the Wind

The two weather factors that affect a garden are the rain and the wind. Water is the basis of all life on this planet. Evaporation, condensation, flow, and precipitation makes up the earth's water flow.

Plants Need Water

Just like you, plants need water. There must be a constant supply because plants are like giant wicks. Water is sucked from the soil by the roots, drawn up the stem and lost through the leaves. The amount of water in the soil is influenced by:

• Local rainfall
• Time of year
• Aspect (exposure)
• The water table (the point in the soil at which water drains away)

Shady or north facing corners often have damp soil. Much of the rainfall tends to come from the south west. Easterly aspects, protected by the house, tend to be dry. South-facing beds, or those in the "rain shadow" of a wall, tend to be dry.

Plants have evolved to take advantage of variation in moisture content. So on wet soil you can plant a bog garden and grow moisture-loving plants; on free-draining soil you can create a gravel garden full of drought-tolerant species.

Drainage

Check soil drainage and storm runoff. Does the existing paved surface drainage work or are there wet areas and puddles that could cause slick spots during rainy or winter conditions?

Areas that stay wet can be lethal to many plants, and damaging to structures. Either re-grade or install drain tiles to improve drainage, or plant that area only with water-tolerant plants. The type of soil in your yard will also affect drainage rates and the types of plants that will thrive.

Damp or dry areas should be noted. Bear in mind that damp areas are not always at the bottom of slopes; nor dry areas at the top.

Wind Worries

Are there any wind tunnels or channels? Note the direction of prevailing winds. Are any natural windbreaks in existence or do you need to provide some? Bear in mind that the windiest months are from October to March. On the positive side, note any tranquil areas in the garden. Long term, winds "deform" plants—think of sideways-growing trees in coastal areas. Sudden gales snap branches and stems. An unexpected cold wind may "scorch" tender new growth, leaving it crispy brown. Even gentle winds can scorch plants that naturally live in sheltered woodland, for example.

Aspect and Site

Where is your garden?

Unless you are an avid gardener, you probably moved into your house or apartment without considering whether its location would be suitable to creating a garden. We usually have to either adapt what we have inherited whether it is an already established garden or a new one just cleared of the contractor's rubble.

Once you have documented and studied not only the regional climate but the microclimate of your site, now it's time to go to that favorite window and look out.

Views

What do you see? Do you see a tree in your neighbor's yard that is overhanging slightly into yours? You'll need to include that tree in your survey as its canopy will dictate what you will be able to grow near or under it.

Do you see the unsightly mess of the non-gardener neighbor next door? Will you want to block that view somehow with a fence, hedge, or other well-placed plantings?

How about the neighbor on the other side with the beautiful garden? Not only do you want to seek out that neighbor for gardening advice and possible plant propagations, but perhaps you would like to incorporate that garden's beauty into your plan. You may decide to leave that side open or use a hedge or a "neighbor friendly" fence that may even have a gate, arbor or be short in stature.

Note the terrain and land form. Is your site level? Sloping? Or both?

Many gardeners don't take the time to stop, breathe, and just look at their gardens without stooping to pull a weed or deadhead a plant. Think about where you want to pause in the garden and "take it all in". What are the best views across the property? Are there paths that lead to a focal point—an important highlight in the garden? Don't forget to consider views from inside the house—from upstairs and at ground levels, if appropriate. Also consider the things you don't want to see—a nearby road, for example.

Existing Site and Conditions

Measure the perimeter and total square footage (or acreage). How much of that area is already covered in "hardscape" (patio, paths, pond, etc.)? Note condition of the existing paving elements, such as driveways, walks, patios, decks. Do the travel paths control the traffic flow logically?

Note the condition of the house, siding, trim, windows, doors, shutters, etc. Is the house made out of any additional materials than those in the garden? What are the materials and colors of both? Note any structural features (fences, walls, shade trellis, arbor, deck, etc.) and condition of them. Measure elements you want to keep.

Decide What to Keep

Are there natural features that you love, or permanent features that aren't changeable? Moving the garage may not be an option! Figure out what you can live with, and what you can't. Be conservative when making your decisions, especially with removing things you can't replace in your own lifetime—you may regret it. For example, once you get rid of a fully grown tree, chances are you won't be able to replace it—and it may have provided needed shade to a particular area of your home in summer.

Sun Patterns

As everyone knows, sun is extraordinarily important to plants. This factor will determine the type of plantings you make in particular areas of your garden—where you'll grow vegetables, and where you'll grow shade plants.

Ideal aspect in the northern hemisphere is southwestern exposure as it can get the full benefit of the long summer days. Remember if you get great light in the front of your house or apartment, say in your living room, your garden may be in the shade. If you will want to sit in the sun in your garden, you may have to have the sitting area be further from the house than you imagined originally.

We recommend starting with either a compass or a street map of your area to determine the aspect. Then, determine sun and shade patterns for all areas. Does the area receive different light at different times of day or in different seasons? Some plants do well with full morning sun but cannot handle the hotter afternoon sun. Other plants that can handle full sun in summer are subject to sunburn in winter. You will also want to locate patios, shade trees and arbors according to sun patterns.

Sunshine and shade should be noted - through all seasons. A low winter sun at about 15° above the horizon, will give considerably more solar heat to a facing slope that it will to an adjoining flat area. Winter sun will also cause long shadow areas which could prevent some areas from warming—even on a bright winter day. Winter sun may also filter through leaf-bare branches to areas which could be shaded in the summer by a full foliage canopy of large trees.

Generally speaking, the following deductions on aspect can be applied:

• North-facing gardens get the least light and can be damp
• South-facing gardens get the most light
• East-facing gardens get morning light
• West-facing gardens get afternoon and evening light

Remember though, there are very few aspects or exposures that cannot be dealt with, but frequently too little consideration is paid to it.

Utilities

Don't do any digging until you have noted both underground and overhead utilities (Including sewage). Note water bib and storm drain. Note any outdoor lighting fixtures and electrical outlets.

Soil Analysis

Once you have gathered the data on the climate and weather and studied the aspect exposure of your site, the last item on the site survey is soil analysis. Like climate and weather, soil analysis is a complicated and scientific area to be sure, but one of vital importance to a gardener. Because we live in the Eastern Deciduous forest and many of us live in New York City, our soil is basically clay-based with a neutral pH. What do we mean by that?

First, let's take a look what soil is made of. Soil has been formed over millions of years by the breaking up of the rocks of the earth's crust. It is made up of different kinds of particles.

Definition of Particle Types

Sand

Sand is composed of many different sizes of particles. You should be able to see individual particles without the aid of a magnifying glass. If you water sand, the water runs through very quickly. Try squeezing it into a ball. Notice that sand does not hold its shape. Sand may be tan, white, or even black depending on what minerals are mixed in it. Most sand is white or tan-colored quartz.

Clay

You cannot see individual clay particles without a strong magnifying glass. Pour water through clay. Note that it does not easily drain. Clay feels sticky and forms a compact ball when squeezed. The color of clay depends on the minerals mixed with it.

Gravel

Gravel may come in several sizes. Look to see if the gravel consists of the same size rocks or if the rocks vary in size and shape. Look at the rocks. Are the edges smooth or rough? Generally, smooth rocks have come from riverbeds where they were smoothed out by the action of water. Rough edged rocks have always been on dry land or are freshly chipped from larger boulders.

Organic Matter

Organic matter is anything coming from a live plant or animal. This includes manure, dead leaves, plant stems, and chopped pieces of wood. Organic matter makes dark colored soil. It also helps the soil hold water and nutrients. If the soil is light colored, indicating it is low in organic matter, it will have difficulty holding adequate moisture and nutrients for proper plant growth.

Look over your garden site. Does the soil appear the same throughout the site? If so, take a cup of soil and study the particles in the soil. Try to estimate what percentage of the particles are clay, sand, gravel, and organic material. Write your estimates down so you can remember them. If you have more than one type of soil, do the same analyses for each type. See JAR AND WATER TEST and SOIL TEXTURE TRIANGLE DIAGRAM.

Soil Type Definitions

Now that you have noted percentages of the different soil ingredients, determine which soil type you have.

Loam

Loam is the best possible soil. Loam consists of various particle sizes. It contains sand, clay and organic matter. Loam crumbles easily when you try to make a ball.

Sandy Loam

Sandy loam has more sand than clay particles. If you try to make a ball with it, it will fall apart easily. Sandy loam drains easily.

Clay Loam

Clay loam is just the opposite of sandy loam. It has more clay than sand and does not drain easily. Clay loam soil holds together when you try to make a ball.

Gravel

Gravel is a combination of any of the loam types with a substantial amount of gravel. Unless you are a rock gardener, you won't want to garden in this site. Large size gravel may cause problems when working the soil by damaging rototillers and other equipment.

The best combinations contain 30 to 50 percent sand, 30 to 50 percent silt, 20 to 30 percent clay and 5 to 10 percent organic matter. Gardeners long for this type of soil because it's easy to work and warms up early in the spring, thanks to the sand. And it holds moisture and nutrients, courtesy of the silt and clay.

What is pH?

Soil pH or soil reaction is an indication of the acidity (sourness) or alkalinity (sweetness) of a soil and is measured in pH units. The acidity or alkalinity of the soil is measured by pH (potential Hydrogen ions). Basically it is a measure of the amount of lime (Calcium) contained in your soil, and the type of soil that you have.

Generally, soils in moist climates tend to be acid and those in dry climates are alkaline. A soil with a pH lower than 7.0 is an acid soil and one with a pH higher than 7.0 is alkaline. The soil must be adjusted to suit the plant which will occupy that area if it is not already within that plants requirement range.

We suggest, however, you try to use plants that fit the soil rather than change the soil to fit the plants. Plants that are already growing in a certain area can give an indication as to what kind of soil you have. For example, if you have Rhododendrons growing successfully, your soil is probably acidic. Viburnums, on the other hand, like an alkaline, chalky soil. Pine trees generally grow in sand.

Soil Testing

It's always a good idea when starting a garden or inheriting a garden to get your soil tested by a professional laboratory, particularly if you a re planning on growing food. You can also buy an inexpensive pH test kit at most garden centers or hardware stores.

These test kits generally consist of a test tube, some testing solution and a color chart. You put a sample of your soil in the tube, add a few drops of test solution, shake it up and leave it for an hour or so to settle. The solution in the tube changes color according to the pH of your soil. Compare the color of the sample with the color chart that came with the kit. Matching colors will tell you the pH of your sample. The better kits will also include advisory booklets about how to interpret your results. The following is a list of the top three laboratories we recommend.

Soil Testing Laboratories

University of Massachusetts

West Experiment Station Soil Testing Laboratory
Amherst, MA 01003-8020
(413) 545-2311

Rutgers Soil Testing Laboratory

P.O. Box 902
Milltown, NJ 08850
(732) 932-9295

Cornell Nutrient Analysis Laboratory

Department of Soil, Crop, and Atmosphere Sciences
Cornell University
804 Bradfield Hall
Ithaca, NY 14853
(607) 255-4540

If your garden is growing fine, you may be asking yourself, "Why do I need a soil test?" You might not, but you may just want to know more about your garden and how it grows. If you're starting a new garden or you've moved to a new area, your best bet is to test the soil before investing in new plants.

Topsoil

When you look at a border, all you see is topsoil. Dig down 1 foot to 2 feet and things change. You'll see a clear boundary between the topsoil and subsoil—stuff that plants won't grow in.

In some new gardens, especially ones built on heavy soil, that clay subsoil from footings, etc. has been spread over the natural topsoil and then covered with a few inches of indifferent topsoil and then turfed.

It's worth checking because if the topsoil layer is only a few inches thick, subsoil can cause problems. If it's clay—water logging in winter. If it's sandy or chalky—dehydration in summer.

Check the depth and quality of your topsoil. What are the subsurface materials underlying layers of hardpan clay, sand and gravel, or bedrock. This information is available as part of a soils survey done by the NRCS, National Resources Conservation Service or from the U.S. Geological Survey maps of your area.

But don't despair. You can amend your soil to improve things greatly (see Soil Amendment)

Nutrients—What Are They?

Nutrients are chemical elements needed by plants during their life cycles. Nutrients are present in water, the air, and in soils. Six nutrients are required by plants in large amounts. These nutrients are known as macronutrients.

Three of these macronutrients are the most common elements in plants: carbon, hydrogen and oxygen. These elements are obtained through the water and air. The other three macronutrients: nitrogen, phosphorus and potassium are naturally present in soil in inorganic forms, as the result of the weathering of soil minerals.

Nitrogen (N)

Green, leafy growth and proteins, including the food proteins found in corn, beans and other vegetables are made possible by nitrogen. It's one of the main components of chlorophyll. Nitrogen comes from many organic sources, such as urea, or it can be man-made.

Phosphorus (P)

This nutrient promotes root growth and the development of flowers and fruit. It strengthens stems and improves disease resistance. Two common sources of phosphorus are bone meal and rock phosphate. All forms release into the soil slowly.

Potassium/Potash (K)

The flow of water in plant cells is regulated by potassium. It's necessary for flowering, fruiting and disease resistance. It also plays an important role in the formation of chlorophyll. Wood ash, crushed granite or sulfate of potash, a synthetic ash, are all good sources.

A proper nutrient balance is important to plant growth. Most soils supply enough trace elements but often need to be supplemented periodically with N, P and K. These three nutrients are the three numbers found on bags of fertilizer.

Soil Amendments

If your plants aren't performing or your soil test indicates it, you may need to amend your soil. Amending your soil can accomplish many things. It can improve the aeration, pH, drainage and friability (desirable texture of soil that allows it to crumble into small particles rather than large clods) of garden soils, and the moisture retaining ability, without water logging, of light, sandy varieties. Soil conditioners actually modify the structure and texture of soil to achieve these results.

Soil conditioners may be organic (such as peats and composts) or chemical (lime or gypsum). Organic and chemical conditioners function differently, but both help the soil particles combine and improve physical structure. Mineral conditioners modify soil texture (or the distribution of soil particle size) to improve aeration and drainage.

Organic materials are usually spread over the top of the soil and tilled or turned under to the depth of the root system—about 6 inches. In contrast, most fertilizers are not considered amendments since they do not contribute to the soil's tilth or improve the physical properties of the soil.

Likewise, mulches are not amendments either, since they are added to the top of the soil as a barrier to moisture loss, to help in controlling weeds and protect the plant from damaging low temperatures. Although many mulches also eventually work into the soil and improve its tilth, their purpose is related to the surface application and not to their incorporation.

Organic Matter

Organic matter, or humus, is the final component of good, rich soil. It makes up a small, but very important, part of soil. Its role is to coat the various-sized mineral particles, kind of like glue.

The following is a list of four organic materials to work into your soil that will improve its tilth, the textural quality of tilled soil:

Sand

Soil with a high percentage of clay benefits from sand. But always add more organic matter or you may end up with concrete. Coarse, round-grained sand, uniform in size, works best—sharp builder's sand packs together.

Topsoil

Topsoil may help your soil retain moisture. You can buy this silty amendment in bags from the garden center or by contacting local landscaping firms. Look for topsoil with a grainy texture.

Sphagnum peat moss

You'll find this form of organic matter in bales or bags at the garden center. Peat moss is a good way to improve the texture of soil that has lots of sand or clay. It breaks down over time, so you'll need to replace it periodically. It also acidifies soil. We recommend keeping the use of peat to a minimum as it is a natural resource that has been deleted to alarmingly levels.

Humus

Garden centers usually sell this form of organic matter in bags. It's a good texture-improving amendment for almost any soil, especially those with high percentages of sand or clay.

Compost is another good candidate. Organic matter breaks down over time and will need to be added to your soil yearly. This will help overcome too much or too little sand, clay or silt.

When organic matter attaches to clay or silt particles, it creates spaces that hold water and nutrients for the plant to absorb. These spaces also provide air and make it easier for the roots to penetrate the soil.

In sandy soil, organic matter holds the particles together so water and nutrients don't run through before the plant has a chance to absorb them. Too much clay? Add lots of organic matter and a little sand to hold the particles apart. Then you're on your way to that wonderful loam we all dream about.

So, the next time someone recommends planting in "good, rich soil," keep this in mind: "Good" refers to the texture of the soil and the amount of organic matter it contains. And "rich" is how much nutrition is available. Rich soil is the first step to a beautiful garden.

Moisture Content, Water Flow, Drainage and Irrigation

What do you think the moisture content of you soil? Dry? Moist? Wet? Like we mentioned before plants need water to live. Hopefully you have a water bib and drain in your garden. Do you? Locate both.

How is the water removed (roof, surface, and subsurface)? Does your drain work well? Does the water drain fast, moderate or slow? Do you know if the property has been graded for drainage?

Do you know the flow of your water? The gallons per minute (gpm) or gallons per hour (gph)? Look at the size of the line coming into and out of the water meter. A ¾" diameter meter supply delivers roughly 30 gpm and a 5/8" line, 20 gpm. To calculate, take a 5 gallon bucket and a stopwatch. Place the bucket under the faucet, turn it on full force, and time how long it takes to fill the bucket. Using simple math, calculate the gallons per minute. The average water flow is 15 to 30 gpm.

What is the pressure of your water or pounds per square inch (psi)? Call your local water department or borrow a plumber's water pressure gauge. Attach the gauge to an outdoor faucet or hose bib and turn on full force that faucet and at least one other faucet either inside or outside the house.

Is there an irrigation system? If so, what kind? If not, how is the garden watered? You may want to consider putting in an irrigation system now.

Once you have collected, studied and analyzed your data on climate and weather, aspect and site, and soil analysis, needs assessment, and design preference, it's time to begin your garden plan!