Greenhouse Gardening

Nutritionally Speaking

Plants require certain nutrients in order to thrive and grow. These are not actually food, but chemical elements or minerals that are vital to helping a plant use the sugars (the real food) that it produces during photosynthesis. Nutrients are normally found in soil, in decomposed organic matter such as compost, and in commercial fertilizers. The "macro-nutrients"—those required in the greatest amount by plants—include nitrogen, phosphorus, and potassium. Micro-nutrients such as iron, sulfur, and zinc are also required by plants, but in smaller quantities.

Garden soil and organic matter in greenhouse beds provide some nutrients to the crops. You may want to side-dress plants with compost or other fertilizer from time to time as you would plants in an outdoor garden. Container-grown plants require more frequent fertilizing than those grown in greenhouse beds, particularly if you're using a soilless or nearly soilless potting mix. You can fertilize plants in containers with commercial liquid or water-soluble fertilizers, or slow-release pellets.

Whether using organic or synthetic fertilizers (you may want to compare different types), look for those containing micro-nutrients, and follow directions on containers. Because plant needs are so interconnected, plants tend to require more nutrients during the summer when they receive more light and heat, and fewer nutrients in the winter.

table of contents