Watering

Watering

Water is as vital for plants as it is for other organisms. The pressure of water within the plant cells helps the plant’s leaves to remain firm. Water also is essential for most of the plant’s biochemical reactions. In addition, water stores essential dissolved nutrients. How often plants need water depends on how hot, dry, and windy the climate is, how well the plant tolerates dry conditions, and how deep the roots go into the soil. Plants can be watered at any time of day. However, to avoid plant diseases that thrive in cool, moist conditions and to reduce water lost through evaporation, gardeners water in the early morning, when the air is cool and still, but the sun will soon dry the leaves.

The best method for watering plants is to apply the water directly to the soil, rather than over the tops of the plants. The water should be applied at a rate no faster than it can percolate into the soil so that the excess will not run off and be wasted. This technique reduces water lost through evaporation and keeps leaves dry, which discourages diseases. A few tools for watering the soil efficiently include hoses with tiny holes all along their surface, called soaker hoses; plastic tubes with tiny holes punched in them at intervals for drip irrigation; and plastic jugs with small holes punched in the bottom, filled with water, and set beside a plant. Watering large, densely planted areas, such as a lawn, requires a sprinkler. Evaporation of water from the soil can be minimized by covering the soil with a protective layer known as mulch. Mulch acts as a barrier that slows evaporation by reducing the amount of air and heat that reaches the soil surface. Materials that can be used as mulch include leaves, bark chips, grass clippings, and cardboard.

Planting and Transplanting

Before planting seeds, gardeners prepare, or till, the soil using a variety of methods. Some turn over the soil with a spade, while others loosen it with a garden fork. Then, they rake it smooth before planting. Some gardeners prefer not to turn or loosen the soil because the oxygen that enters the soil when it is tilled by these methods hastens the breakdown of needed organic matter in the soil. Instead, they just dig a small hole for each seed or plant. To keep the soil loose so that roots can develop easily, they keep it covered with grass clippings, compost, or other organic matter. The presence of this organic matter encourages large populations of worms, whose tunneling breaks up the soil.

Gardeners plant seeds at different depths, depending on the seed’s size and its requirement for light. Seeds contain starch and oil, stored food that provides the energy needed for sprouting, or germination. Small seeds do not hold much food, so they are sown on or close to the soil surface, where they will not require a lot of energy to push through the soil. Larger seeds have enough food reserves to be planted deeper. This gives the root system more time to develop as the seedling, or young plant, grows up through the soil. As a general rule, a seed can be planted three times as deep as the seed is wide. Some seeds, such as lettuce, require light to germinate; these seeds must be sown on or very near the soil surface. Once the seeds are sown, the gardener gently presses down the soil to ensure that the seed touches soil, not air pockets—this soil contact helps keep the seeds moist.

Fertilizing

Fertilizing
Not all soils have enough nutrients or the right balance of nutrients. In addition, plants remove nutrients from the soil as they grow, so these nutrients must be replaced in order for the soil to remain productive. For these reasons, gardeners enhance soil by adding fertilizer, a material that contains one or more of the nutrients plants need.

Fertilizers are divided into two categories: synthetic and organic. Synthetic fertilizers are concentrated salts or minerals, some of which are produced as by-products of petroleum production. Organic fertilizers originate in plants, animals, or minerals and include compost, seaweed, and ground bone. (For advantages and disadvantages of synthetic and organic fertilizers, see Organic Farming.)

Fertilizers usually are sold in packages, on which the percentage by weight of the macronutrients nitrogen (N), phosphorus (P), and potassium (K) are listed on the label—always in the order N-P-K. For example, a fertilizer that is labeled 10-5-3 is 10 percent nitrogen, 5 percent phosphorus, and 3 percent potassium.

Understanding Soil

Healthy soil is indispensable for a healthy garden. Plants derive water, oxygen for their roots, and essential nutrients from the soil. Soil consists of two components: minerals from weathered rocks and organic matter from decayed organisms and animal wastes. The mineral content of the soil provides plants with nutrients, such as calcium, potassium, and phosphorus. Organic matter improves drainage and helps prevent waterlogged soils, reducing the occurrence of diseases such as root rot.

Soil texture, the size of the individual soil particles, affects how fast water drains and how well plants absorb nutrients. The largest soil particles are grains of sand. Sand grains fit loosely together with large gaps between them, resembling marbles in a jar. The large pores let water (and the nutrients dissolved in it) drain out too quickly for most plants to absorb it. Clay particles, on the other hand, are very tiny, and they pack closely together, resembling tiny beads in a jar. The pores between clay particles are so small that water drains very slowly. Slow drainage can lead to oxygen deprivation because the water takes the place of air in the pores. Another disadvantage of clay is that it binds water and some nutrients so tightly that most plants cannot absorb them. A third soil particle is silt, which is larger than clay but smaller than sand.

Most plants thrive in a soil type known as loam, which contains roughly 50 percent sand, 25 percent clay, and 25 percent silt. A loam soil drains water well, but not too quickly, and as a result, the plant can absorb nutrients more readily. Exceptions include desert plants, such as cacti, which do best in a sandy soil, and cottonwoods, which flourish in silty soils.

Selecting Plants

Selecting Plants

Plants differ in their tolerance for heat, cold, and moisture, so when selecting plants, gardeners must take into account the climate of their region. Gardeners also evaluate the soil type and how much sunlight falls on the proposed site, factors that affect the types of plants that can be grown in a particular area. They consider, too, the plant’s life cycle—how long it takes a plant to grow, flower, produce fruits or seeds, and die. Annuals such as petunias bloom and produce seed the same year they are planted, then die when cold temperatures set in. Biennials—hollyhocks, for example—live for two years, producing just leaves the first year. In the second year they produce flowers, and die when the weather turns cold. Perennials, which include shrubs and trees as well as flowers, are plants that live for three or more years.

A gardener can experiment with a stunning diversity of interesting garden styles and types. Herb gardens may feature culinary herbs, medicinal herbs, and fragrant herbs. Flower gardens may combine a variety of flowering plants or focus on just one type, such as roses, white-flowered plants, or flowers that bloom only at night. Specialized gardens include rock or alpine gardens, which display plants native to mountains, and water gardens, which host plants adapted to wet conditions. Botanical gardens are designed to display plants for scientific and educational purposes, and in these gardens, the plants are often labeled with their names and their optimal growing conditions.