Michigan State University Extension
Ornamental Plants plus Version 3.0 - 00001797
11/12/99
Controlling Weeds
Weeds can make ornamental plantings look unsightly. Weeds
also may harbor insects and diseases that may cause
problems on more desirable ornamental plants. The weeds
will also compete for light or use water and nutrients
that ornamental plants could use for growth. Successful
weed control depends on preventive methods, proper weed
identification, and the timely use of cultivation or
chemicals.
Perennial weeds come up every year from the same roots.
These are the most difficult weeds to remove. Many
hard-to-control perennial weeds are brought into the
landscape as perennial flowers or as ground covers. The
plants then escape and become weeds (plants out of place).
Chemicals that kill these plants will also kill ornamental
plants.
Annual weeds come up from seed each year. These can be
somewhat easier to control because the pre-emergence
herbicides will kill the seedlings before they emerge from
the ground. Mulching and cultivating are other options
that control annual weeds. Annuals vary in the time of
year when the seed germinates, so some can become problems
at the end of the growing season.
Herbicides can be used effectively to control weeds.
Unfortunately, these useful chemical tools are often
misused. Weed control chemicals are designed to kill
plants. Many chemical controls do not differentiate
between weeds and ornamental plants. If they are applied
improperly, they can injure ornamentals. The most serious
problems occur when total vegetation killers are used to
kill grass around trees and shrubs. Once they reach the
roots, these chemicals will also injure the trees and
shrubs.
Timing of herbicide applications is important. Pre-
emergence herbicides will not control weed seedlings if
they are applied after the seedlings have begun to grow
vigorously. Young weeds are easier to kill than old,
established weeds. Post-emergence herbicides are used on
existing weeds.
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to commercial products or trade names does not imply
endorsement by MSU Extension or bias against those not
mentioned. This information becomes public property upon
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This file was generated from data base ZZ on 01/19/00.
Data base ZZ was last revised on 11/12/99.
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