Hairy galinsoga is an annual weed that is native to Mexico and South America but is now found on the east, mid-west, and west coast of the United States. It prefers a sunny site with rich, moist, slightly acidic soil and commonly appears in gardens and other cultivated areas. It can be especially troublesome in vegetable gardens where it can significantly reduce yields by robbing the vegetable plants of nutrients and moisture. Hairy galinsoga can also be found in waste areas, along roadsides, and in fields.
Description: The common name, hairy galinsoga, is especially apt since both the leaves and stem have a dense covering of fine white hairs. In addition, the mature leaves are opposite, oval to triangular, and coarsely toothed. The plants have multiple, erect, branched stems and that are usually green but may have a touch of maroon. If the stems come in contact with the ground they may produce roots. From May to late fall plants produce small flower-heads less than a centimeter across. The flower-heads consist of numerous yellow disc flowers in the center surrounded by four to five, 3-lobed ray flowers that are usually white but are sometimes pink. Flowers are followed by tiny brown or black seeds with white appendages that form a crown on one end. The seeds are produced in flushes with some seed ripening before the last flowers have opened. A single plant can produce up to 7,500 seeds that are viable in the soil for only a few years. On the other hand, the seeds have no dormancy requirements and can germinates as soon as they are shed. The root system is fibrous and can be very strong and resilient when mature.
Control: Removing hairy galinsoga when young before seed-set and while the root system is undeveloped is the best approach to control. Seeds do not germinate if buried deeply so tillage or mulching may be used to inhibit germination. Mowing the plants is not recommended as it causes the plants to become bushier and produce more branches and flower-heads. Glyphosate is effective if herbicides are necessary.