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Ground Rules: Garden Basics

Martha Stewart Living, February 2009

The wealth of lore associated with gardening is one of the fascinations of this ancient craft. But for beginners, the basic terminology and principles can seem mystifying, even overwhelming.

Building a foundation of knowledge isn't hard, though. Master the following primer, and you'll be on your way to horticultural fluency.

Soil
Soil (no real gardener calls it dirt) is an infinitely varied blend of different-size mineral, or rock, particles -- ranging from coarse sands to finer silts and clays -- along with a portion of organic matter. The unique mix in your garden determines how readily moisture is absorbed and retained, how easily roots can penetrate, and whether there is a supply of vital plant nutrients.

Organic Matter
The portion of the soil that is derived exclusively from plant or animal remains is called organic matter. It occurs naturally in most soils, but you can supplement it with compost, manure, peat, or sphagnum. Adding organic matter generally makes the soil looser and airier, which enhances its ability to absorb water. As a result, the soil will retain necessary nutrients as well as moisture between waterings.

Mulch
Mulch is a porous layer of material, such as wood chips, straw, shredded bark, or gravel. Spread a couple of inches thick, mulch functions as insulation, keeping the soil cool and moist in warm weather. It also promotes root growth, reduces the need for watering, and protects against invasion by weed seeds.

Soil Testing
A soil test is available for less than $30 (in some areas, it's free) from cooperative extension offices; to find an office near you, go to csrees.usda.gov/Extension. The results provide a clear reading of your soil's pH and fertility. Often, for an additional fee, you can find out the percentage of organic matter in the soil and the levels of essential trace elements, such as iron and magnesium. The results also may include recommendations for attaining optimum soil pH and fertility.


The Optimum pH
The pH scale is used to measure soil acidity and alkalinity. The recommended pH for your soil depends on the plants you're growing. Most vegetables, flowers, and turfs prefer slightly acidic to neutral soils (pH 6 to 7). 

Rhododendrons, azaleas, hollies, and magnolias flourish in moderately acidic soil (pH 5 to 6). Soils in rainy areas tend to be acidic, while those in arid regions are sometimes more alkaline, or basic. Applying lime is one way to raise the pH (making the soil less acidic); applying sulfur lowers the pH. 

In the chart, the horizontal bars show how the availability of essential minerals (notably the three major ones at top) changes with the pH. The vertical bar marks the ideal pH range for most gardens.

Annuals
Annual plants, such as marigolds, sprout from seed, bloom, bear seed, and die within a single growing season. This is why deadheading -- pinching off blossoms as they fade -- is important with annuals: If allowed to set seed, they will stop flowering and soon expire.

Perennials
Perennials are plants that survive from year to year. Some, including phlox and daffodils, retreat underground during summer drought and winter. In warm regions, plants such as cacti grow and remain green year-round. There are also evergreen perennials, such as hellebores, that thrive in cold climates.

Tender Perennials
Some warm-climate plants, such as impatiens, are considered tender perennials. They are perennial in their native habitat but cannot tolerate winter cold. They are grown as annuals in chillier parts of North America.

The Role of Flowers
We commonly select plants because of their decorative blooms, but the biological purpose of these structures is seed production, and the blossoms of many plants, including most grasses and trees, are aesthetically unremarkable but no less useful. In some cases, understanding how a particular plant's reproductive cycle works can help you plan your garden: Holly bushes, for instance, are either female or male, producing only the corresponding flower type. If you want your winter garden to be bright with holly berries, you must plant a bush of each sex -- though only the female one will bear fruit.

Shrub Versus Tree
Shrubs and trees are distinguished by size and structure. Shrubs are typically less than 15 feet tall and have multiple stems, whereas trees have a single elongated trunk and may soar to towering heights. In their native environments, shrubs grow on the edges of woods or around trees and are more resilient. If one stem withers, the others can fill in. Trees, on the other hand, offer shade for animals and undergrowth.

Variety of Tree Fruits
Fruits are the ripened ovaries of a flowering plant and are not necessarily fleshy or edible. So, botanically speaking, the dry helicopter seeds of a maple are as much a fruit as a ripe apple is.

The Need for H2O
Not only is water essential for photosynthesis, it also dissolves nutrients in the soil so that plant roots can absorb them. Water taken in through the roots keeps plant tissues crisp, ensuring the rigidity of stems and leaves. In summer, plants sweat, or transpire, through their leaves to cool their surface. As many as 100 gallons of water may cycle through a large tree on a given day.

Fertilizer Basics
Plants produce their own energy; fertilizers simply add nutrients to aid in plant growth. A soil test is the most reliable guide to selecting the right fertilizer. Overfeeding or supplying the wrong balance of nutrients can be more harmful than not fertilizing at all. When shopping for fertilizers, check the three-number ratio on the label, such as 5-10-5 or 10-10-10. This describes the content by percentage of the three principal plant nutrients, nitrogen, phosphorus, and potassium (often abbreviated as NPK). Use liquid fertilizers for a quick boost; granular ones break down more slowly, providing a more gradual, long-lasting release.

A Sun-Based Diet
Solar energy is old hat to plants; they've been using the sun to fuel growth for three billion years. Sunlight drives photosynthesis, the process by which plants combine water and carbon dioxide to make carbohydrates, their basic food. Just as cars require a particular grade of fuel -- high-octane or regular -- each type of plant prefers a particular intensity of sunlight: full sun, filtered sunlight or partial shade, or shade.