Sulfur for Garden Plants

Sulfur weaves its way into garden plants and gardens in several complementary ways. Without sulfur, plants can't survive. One of the 16 nutrient elements essential for plant growth, sulfur is a valuable component in many fertilizers, pH-adjusting soil amendments and pesticides for fighting disease and insects. From plant tissues to fungal sprays, sulfur is an indispensable companion for garden plants.

Garden plants don't need sulfur in the same quantities they need carbon or nitrogen, but their life depends on sulfur's presence just the same. Known as a secondary macronutrient, sulfur comes to plants from soil or supplemental fertilizers. Without sulfur, plants can't produce chlorophyll needed to absorb sunlight, create plant energy and keep foliage healthy and green. Sulfur aids in seed production, root growth, respiration and overall plant growth and health. It also plays an important role in plants' ability to use other nutrients to full capacity. Plants that need high nitrogen levels rely on adequate sulfur to put nitrogen to use.

When soil sulfur runs short, sulfur-containing fertilizers recharge garden plants. Though not common, deficiencies occur in very sandy soils, areas with heavy rainfall and soils with low organic matter. Symptoms of sulfur deficiency look similar to other nutritional problems. A soil test or leaf analysis diagnoses the cause. Sulfur-deficient plants have yellowing foliage and take longer to mature. The youngest, upper leaves show signs first. In corn (Zea mays), yellow stripes run down the blades. Fertilizers often combine sulfur with other nutrients for specific results. Ammonium sulfate, a 21-0-0 fertilizer, teams high nitrogen with sulfur. Soil-test results recommend the best fertilizer for your garden plants.

Most garden plants do best when soil pH levels range between 6.0 and 7.0, where most plant nutrients are available. When soil pH gets too high or low, reactions tie up nutrients so plants can't absorb them. Plants vary in the amounts of certain nutrients they need. Acid-loving plants need nutrients that are most available at low pH. Amending soil with sulfur lowers pH and frees up those nutrients. Only amend your soil with sulfur when a soil test confirms the need. A one-point change in pH reflects a 10-fold change in actual acidity. Too much sulfur can render your soil inhospitable for garden plants.

History shows Mediterranean farmers used sulfur as a natural fungicide more than 2,000 years ago. It remains effective against powdery mildew, black spot, rusts and other fungal diseases. Sulfur works by preventing fungal spores from germinating. The key to effectiveness is spraying before disease starts. Once disease is active, sulfur helps reduce the spread. Sulfur dust helps treat spider mites. Never use sulfur when temperatures exceed 80 degrees Fahrenheit, and always check your product's label before using. Some plants and beneficial insects are sensitive to sulfur products. Whenever working with sulfur -- in any form or application -- wear gloves, protective clothing and protective eyewear.