One of the most frequent reasonings I hear to use toxic herbicides like Round-Up, is that “there is no other way to control perennial grasses”. That is not true. The primary reason for herbicide use is allowing profit to take precedence over ecology and environment. Once we allow that to happen, we are shooting ourselves in the foot, compromising the very same environment we rely on to produce salable crops. Not only can we control weeds organically, but we can produce higher quality crops that will allow us to charge higher prices which account for the increased cost of production.

That said, it is not necessarily easy to control rhizomatic perennial grasses! These weeds have the unfortunate capability to regrow from tiny pieces. When cultivated the result can often be that they return with increased vigor. Cover crops can play a key role in avoiding their return however, by outcompeting them for sunlight , nutrients, and water. In addition, these same cover crops are turned back into the soil, improving the soil in the process.

Late summer and early autumn provide us with a great opportunity to use a couple of inexpensive, readily available cover crops to achieve the goal of reducing or eliminating pressure from perennial grasses.

Oats and Peas, when combined together, will create a cover crop stand that is thick, vigorous, tall, and rich in both Nitrogen and Organic Matter. For northern growers the stand will winter kill, leaving a thick mat of organic matter that protects from erosion and conserves soil. For more souther growers, a late summer / early autumn sowing will leave plenty of time to incorporate the cover crop and follow it with winter rye. These cover crops are so beneficial to the soil, farmers can often access both state and federal funding to plant them.

One great trick to help reduce weed pressure of all types, is to precede a cover crop planting by a period of “bare fallow”. This is a time when the soil is well cultivated and left bare for a period of time before being cultivated again. Responsible agricultural practices dictate “an eye to the sky”, and not utilizing a bare fallow technique when an obvious period of heavy rain is on the horizon. Of course, we can not know the weather 10 days ahead of time with certainty, but we can quite easily have a grasp on the general weather pattern. If a major frontal passage is anticipated, or a large complex Low pressure system will be crossing your region, then it’s not a good time to bare fallow. These types of weather are easy to see in advance on 10 day weather maps. Another weather feature easy to see on long term weather maps, is a large strong H pressure system. This creates ideal bare fallow conditions, since the warm dry weather will help to dry out and kill many of the rhizome pieces of perennial grass.

In an ideal timeline, we would cultivate the soil (using a rotary tiller, disc harrows, or similar) and then leave this bare ground for a period of around 10 days. Then, as wetter weather approaches, cultivate again and seed a mix of 50/50 oats and peas. These can be seeded by either broadcast or drilling. If broadcast, then the seed should be incorporated after with a shallow tilling or disc harrowing. On a micro scale, the seed can simply be raked in.

In Vermont in Zone 3/4, Aug 15th is the target date for establishment of the cover crop before adverse weather will set in. The further south you go, the later the date can be pushed back. Ask local farmers or state ag extension specialists for regional specific info.

In most grain and feed stores, you will find oats and peas. It is ok use the oats marketed for horse food, they are the same thing. For peas, be sure to search for “field peas”.

When following a bare fallow period with a quick to establish dense cover crop like this, you will not only make a huge dent in the weed pressure, but you will dramatically improve the nutrient profile and soil structure of the land. Clay soils can be aerated and have their drainage improved by incorporating cover crops. Sandy soils will have their water retention and nutrients increased.

For further reading on the subject, search for the SARE publication “Managing Cover Crops”.

As always , trial and error is the best way to learn. Allow me to encourage you to start now. You will see immediate benefits in your next case crop, and in the soil itself.

Best of luck in the busy times ahead! - Walt 

About the Author: Walt Krukowski started Mountain Flower Farm in 1998, and has been growing peonies on a hillside farm in Warren, VT ever since. Mountain Flower Farm specializes in shipping seasonal cut flowers and woody branches to discerning floral designers nationwide. The farm also produces peony root divisions and provides them at wholesale prices to growers throughout the USA. You can visit online:www.mountainflowerfarm.com