One of the most common problems encountered by the backyard grower, community gardener and urban farmer is how to effectively deal with weeds in the growing space. Weeds propagate in two general ways, either through vegetative growth such as rhizomes and lateral root growth or through the production of seeds. There are several ways of controlling weeds available to the grower including herbicides, mowing, mulching, cover crops and tillage. Understanding weed life cycles is critical in the fight for weed control. A combination of methods using Integrated Pest Management strategies has the greatest chance for success.
Weed numbers can reach severe levels when control measures are not implemented. Noted in this picture are cocklebur, thistle, morning glory, smartweed, pigweed, comfrey, lambs quarters and bindweed.
A seedbed was produced by mowing and then tillage of the residue into the soil after a few days of decomposition.
Cereal rye (Secale cereal) was chosen due to its ability to rapidly germinate and tolerate occasional mowing. While normally used as an over-wintered cover crop, it is ideal for this usage as it allows germination of weed seed and will regrow after several mowing passes allowing larger numbers of annual weeds to be eliminated.
The seed bank for weeds in this community garden plot is vast. Quick germination of many species of weeds including pigweed and smartweed were noted among the rye.
Mowing is one of the easiest and most effective strategies for weed control. When an annual weed is mown as it matures but prior to setting seed, that plant has been killed. When a perennial is mowed prior to seed set the plant is weakened and valuable root reserves must be used to produce new top growth.
Passes with a lawn mower were made when the growth reached about 12 – 16″ tall, but before any weeds were allowed to go to seed. A mulching mower was used to keep the organic matter present in the plot. Weeds can bring large amounts of nutrients from the subsoil and their organic matter should be kept in the soil profile unless they are invasive root fragments or have gone to seed.
After several mowing passes a large amount of annual weeds were removed from the weed seed bank. While some perennial weeds remain, the repeated mowing has weakened the plants allowing for easier control via herbicide if desired.
The winter rye being cold hardy will be able to persist over the winter. It will control erosion and use its profuse root system to hold on to the nitrogen and other nutrients that were scavenged by the weeds and mulched as green manure from mowing during the season.
Rye also has the effect of suppressing weeds allelopathically similar to a natural herbicide and has noted effects on both dandelions and canada thistle, two very common and difficult weeds to control in vegetable gardens.
With or without a cover crop added, mowing is a simple and effective strategy to assist in control of weeds for the backyard grower, community gardener or urban farmer. It will kill annual weeds and weaken perennial weeds and prevents them from adding more weed seed into the soil seed bank.
SAVE THE DATE!!: Tuesday September 11th, 6:30 pm
Over-Wintered Cover Crops
Details TBD.