Whether your plants are struggling to peek their heads over their pots or you just want the biggest, healthiest blooms you can grow, choosing the right fertilizer makes the difference. Plants need a plethora of nutrients to grow, but there are three major nutrients that all plants use more than any others. Providing your plants with a regular supply of nitrogen, potassium and phosphorus will help your plants fulfill their maximum growth potential.
Fertilizers fall into two main categories that you can use to promote rapid growth in your plants. Organic fertilizers are made from plant and animal byproducts that must break down in the soil before your plants can use them. These fertilizers usually contain low concentrations of nutrients and are not effective at producing quick flushes of growth. Inorganic fertilizer is a concentrated source of nutrients that can release nutrients over a period of weeks, or immediately, depending on the type you use. Inorganic fertilizers list the percentage of nitrogen, phosphorus and potassium they contain by weight on the package in a series of three numbers separated by dashes. Fertilizer marked 20-5-10 contains 20 percent nitrogen, 5 percent phosphorous and 10 percent potassium. Other nutrients such as iron or magnesium are often listed as a fourth number.
Granular vs. Liquid
Inorganic fertilizers are commonly available in granular and liquid form. Granular fertilizers are available in immediate and slow-release formulations while liquid fertilizers only provide a quick release of nutrients into the soil. Both granular and liquid fertilizers are an effective source of nutrients for plants, but liquid fertilizers penetrate the ground more rapidly and produce visible results quickly.
Plants use more nitrogen than any other nutrient when they are growing. Nitrogen regulates the growth of stems and leafy green foliage. Feeding your plants with a fertilizer high in nitrogen promotes rapid growth in leaves and stems. The plants that benefit the most from nitrogen are grasses, herbs and leafy vegetables. On lawns and in unplanted gardens you can spread nitrogen fertilizers evenly over the ground. You can use a technique known as side dressing to fertilize an established garden and keep fertilizer off your edible plants. Side dressing is the application of fertilizer in bands down the length of your garden rows or in a circle around the base of each plant, if you do not use rows.
Phosphorus and Potassium
Plants use phosphorus and potassium to regulate metabolic processes and to grow flowers and fruit. Fruiting garden vegetables such as tomatoes (Solanum lycopersicum) or summer squash (Cucurbita pepo) need phosphorus and potassium instead of nitrogen when they begin to develop flowers. In most cases fruiting plants and tubers -- such as potatoes (Solanum tuberosum) -- need more potassium than phosphorus. Adding a fertilizer heavy in nitrogen shortly before or after your plants begin flowering will force the plant to focus on growing leaves and stems to the detriment of flowers and fruit.
Timing Fertilizer Applications
Providing your plants with a constant supply of nutrients helps them grow quickly. Fertilizers that supply nitrogen and potassium can provide these nutrients for your plants relatively quickly and are best applied as your plants need them. Applying a combination of slow and fast acting fertilizers containing nitrogen and potassium prior to planting provides a quick boost of nutrients that will continue throughout your plant's initial stages of growth. You can split the amount of fertilizer your plants need evenly between the two types of fertilizers to provide a steady supply of nutrients. Phosphorus takes time to break down in the soil; the best time to apply phosphorus is usually early in the spring, before you plant your garden. Once your plants are ready to flower, applying fertilizer that contains potassium and a light dose of nitrogen ensures rapid growth and productive fruiting.
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