Weed control options in the landscape include hand-weeding and cultivation, mowing, mulching, hot water treatments, and chemical control. All of these methods are used at one time or another in landscape maintenance operations. For instance, after elimination by hand-pulling, cultivation, or a postemergent herbicide application, the subsequent growth of annual weeds can be discouraged with mulches and/or preemergent herbicides.
Herbicides should not normally be needed by home gardeners. Mulching, removal by hand, and proper placement of irrigation water will be sufficient in most cases.
Densely shaded plantings reduce weeds. Preplant weed control is not as critical as in other types of plantings. It is often necessary to combine treatments for complete weed control.
Control perennial weeds before planting (although control may be possible after planting); use geotextile fabrics with a shallow layer of mulch or use a thick layer of mulch without a geotextile base; use a preemergent herbicide, if needed, and supplement with spot applications of postemergent herbicides and/or hand-weeding. Perennial weeds may be controlled by manual removal, spot applications of glyphosate or glufosinate, or, in some instances, dormant-season applications of preemergent herbicides. Escaped weeds may be controlled manually or with spot applications of postemergent herbicides.
Woody mature ground covers should exclude most weeds; however, weed encroachment during establishment is likely.
Control perennial weeds before planting, although perennial grasses may be selectively controlled after planting with fluazifop (Fusilade, Ornamec), clethodim (Envoy), sethoxydim (Grass-Getter), or other selective grass herbicides. (All of these except sethozydim are for use only by professional applicators.) Annual weeds may be controlled with mulch plus a preemergent herbicide, supplemented with some hand-weeding. Use geotextiles where possible but do not use them where ground covers are expected to root and spread. After planting, it is difficult to make spot applications of nonselective herbicides without injuring desirable plants. Postemergent control of most annual and perennial grasses is possible.
A closed canopy will help shade out many weeds. Periodic cultivations (at 3- to 4-week intervals and between display rotations) will suppress many weeds.
Control perennial weeds before planting and carefully select flower species for weed management compatibility. Annual weeds may be controlled with mulches, preemergent herbicides, frequent cultivation, and/or hand-weeding. Perennial grasses can be selectively controlled with clethodim or fluazifop, or other grass-selective herbicides, but other perennial weeds cannot be selectively controlled after planting. Geotextiles generally are not useful because of the short-term nature of the planting. Avoid nonselective herbicides after planting.
Weed management options in herbaceous perennial beds are similar to those for annual flowers, except (1) it is more important to eradicate perennial weeds as there will be no opportunity to cultivate or renovate the bed for several years; and (2) fewer species are included on herbicide labels.
Control perennial weeds before planting; use geotextiles where possible; use mulches with a preemergent herbicide; and supplement with hand-weeding.
Weed management is complex because of the diversity of species. Different areas of the bed could receive different treatments. Site preparation is critical because postplant herbicide choices are few.
Plant the woody species first; control perennial weeds in the first two growing seasons, then introduce the herbaceous species. Plant close together to shade the entire area. Another option may be to define use-areas within the bed that will receive similar weed management programs.