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Weed control, vital to plant health

Weed killers can be harmful to your fruiting plants. Avoid using broadcast weed and feed lawn products within the root zone area of your fruit trees, which can be harmed by the herbicides. The typical spread of an established trees root system is 3-5 times the width of the canopy.

Spray drift from glyphosate (in Roundup and other products) can cause dieback, stress, or death when it lands on thin bark; or bark lesions in stone fruits if absorbed through the roots. Symptoms may not be present until the following year.

The pre-emergent dichlorbenil (in Casoron) leads to stunted yellow leaves and death if over-applied or used repeatedly.

A quick search on the internet for organic herbicides shows several products that could be useful substitutes for the standard chemicals usually available. I have not researched or tried any of them, but you may wish to.

Trees. Keep grass short and weeds under control. Regular shallow (2-4” deep) cultivation around newly planted trees will help keep weeds under control, keep a loose layer of soil on the surface that helps reduce moisture loss, and encourage the new roots from your tree to go deep. Don’t try this with shallow rooted plants like blueberry and other small shrubs though.

Weed barrier fabrics may seem to be a good solution for controlling weeds, but only if used for just a year or two, or only just near the trunk of the tree. Longer use in the active root zone area of the plant interferes with organic matter rebuilding in the soil, which can have a negative impact on the general health of your trees.

Berry Bushes & Vines. If your blueberries have a lot of weeds under them you might try cutting the weeds to the ground, putting down a ½-1” layer of peat moss, several layers of newspaper or a layer of cardboard, and then wood chips on top. Most weeds will be smothered. More persistent perennials that eventually come back through the mulch, can be repeatedly cut off (every 10-14 days) until their roots starve out.

Remember to dig or rototill around your raspberry rows to keep those vigorous spreaders where they belong.

Groundcovers. New plantings of ground covers, such as cranberry, lingonberry, or wintergreen, need regular weeding. Even after they have filled the space, some weeds may still come through. Putting down cardboard or layers of newspaper covered with mulch between the new plants will help reduce weeds, as well as contribute to building the soil organic matter.

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About Theresa Knutsen

Theresa Knutsen is a horticulturist and writes the Raintree Nursery newsletter "Growing Tips." Email: theresa@raintreenursery.com.

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