Organic Fertilizers Boost Nutrients in Garden Soil
Organic fertilizers generally come from plants, animals, or minerals. Some gardeners add organic material that improves soil structure and supports soil microorganisms, which helps make nutrients available more quickly, especially in warm weather.

What to Feed and When

Before you buy or use fertilizer, read the instructions on the packet to make sure it is what you want. Plants can only take up nutrients in a solution, so always water after feeding.

  • Vegetables need a general fertilizer, such as blood, fish, and bone, applied before planting or sowing.
  • Fruiting crops, such as tomatoes, zucchini, pumpkins, and peppers, appreciate an application of liquid tomato fertilizer about once every two or three weeks.
  • Permanent plants, especially fruit trees or bushes, benefit from a general fertilizer, such as blood, fish, and bone, in early spring after weeding and before mulching.
  • Roses should be treated with a special rose fertilizer in spring right after pruning.
  • Temporary plantings in containers and hanging baskets soon use up the limited nutrients in the potting mix, so use a general-purpose liquid fertilizer every ten days in summer. For permanent plantings in containers, such as shrubs, push controlled-release fertilizer tablets or pellets into the potting mix in spring.
  • Lawns need a fertilizer with a high nitrogen content in spring for lush leaf growth, and one that encourages root development in fall.
  • Shrubs should be fertilized with a general-purpose fertilizer in spring. Sprinkle it around the plant, rake it in, then water.

Correct Fertilizer Levels

When fertilizing, resist the temptation to add a little extra fertilizer for good measure; more plants are lost through overfeeding than underfeeding. Always follow recommended application rates and dilute liquid fertilizer accurately. If in doubt, err on the side of caution, since too much fertilizer promotes lush growth that is more vulnerable to pest and disease attack, and summer bedding tends to flower better if slightly underfed. Overfeeding can also cause “reverse osmosis,” where plants lose, rather than absorb, nutrients.

Yellowing between the leaf veins is a common sign of malnutrition. It may indicate a lack of magnesium in acidic soil or crops given potassium-rich tomato fertilizer; the leaves may also be tinted brown or red. Apply Epsom salts (magnesium sulfate) in fall to replenish nutrients. Potassium deficiency also causes yellowing, purple or brown tints, and poor flowering, although a lack of flowers may indicate too much nitrogen. Regular application of organic matter promotes healthy plants. Beware of overfertilizing, though—this may actually reduce the number of flowers produced by some annuals and perennials.

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Dorling Kindersley Limited

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