The chart above shows percent liverwort control 90 days after potting. Percent control was determined by measuring the % of the container surface which was not covered by liverwort. Rout, Broadstar, Regal O-O, and OH2 provided effective control. Snapshot provided poor control. The bar labeled 'Control' represents containers not treated with any herbicide, and thus serves as control or comparison to herbicide treatments.
Among all weed species that occur commonly in container production, liverwort is the most sensitive to cultural practices. Our plants were grown in full sun, outside, under overhead irrigation, using a coarse bark as a substrate, and with all fertilizers incorporated into the substrate (not topdressed). Under conditions with more shade, higher humidity, and finer substrates, liverwort control would not likely be as high as that observed in this experiment, regardless of the herbicide used.
Liverwort control requires strict management of environmental and cultural conditions. Liverwort thrive in environments with high fertility, excess substrate moisture, and high humidity. Avoid topdressing fertilizers. Incorporating or dibbling controlled release fertilizers reduces liverwort growth compared to topdressing. Irrigate plants according to plant need instead of fixed irrigation rates. If possible, use a mulch or coarser bark to reduce moisture levels on the container surface. Improve air circulation around the container surface to decrease localized relative humidity. The quicker the container surface dries, the less vigorous liverwort will be.
Ronstar and Goal have also been reported as effective herbicides for preemergence liverwort control. This, along with the research above, indicate that products containing at least one herbicide classified as a protox inhibitor (oxyfluorfen, oxadiazon, and flumioxazin) provide the most effective control.
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