Weeds in Deciduous Fruit Crops

Weeds compete with fruit plants for water and nutrients, and an overabundant weed population can severely stunt the growth of desired plants. Many common orchard weeds may also serve as reservoirs of important plant viruses. Weeds can be classified into three broad categories: annuals, perennials, and biennials. An annual plant is one that completes its life cycle in one year. It grows from seed, produces seed, and then dies. Summer annuals germinate in the spring or summer, while winter annuals germinate in the fall. A perennial plant grows and produces seed year after year. Herbaceous perennials, such as quackgrass and Canada thistle, die back to the ground each year. Woody perennials may drop their leaves, but they do not die back to the ground. The longer that perennial weeds are allowed to grow uncontrolled, the larger their root system becomes, the more they spread, and the harder they are to control.

A biennial plant, such as marestail, wild carrot, and dandelion, requires two growing seasons to complete its life cycle. During the first season after the seed germinates, the plant develops an extensive root system and a dense cluster of leaves, and generally dies back to ground level at the growing season's end. The next year the plant regrows from the root system, produces seed, and dies. Ways of managing these various types of weeds are discussed in Part III.