Dealing with Weeds, A Fact of Life In Farming

by Andrea Yoder

Cultivating Strawberry Plants using
the Kult cultivator

Weeds are a central theme to our year round conversations on the farm.  During the growing season Richard and Rafael have daily conversations and plans for eliminating and preventing weeds in our fields.  During the winter months they still think about how they can eliminate weeds as they research new implements and machinery to help with mechanical cultivation as well as brainstorming other techniques for decreasing weed pressure, etc.  If all the weed control they both do in their sleep at night could actually take place in our fields, we wouldn’t have a single weed to worry about!  I hope you get the point that weed control is a big deal to the overall success of our crops and we invest a considerable amount of energy, time and resources towards weed control.  In conventional agriculture, chemical herbicides are often the main form of weed control, but in organic farming systems chemicals are a very limited option.  The only herbicide we use on our farm is 30% vinegar that we spray on weeds that may grow in places where we are limited in options for eradicating them, such as around our irrigation headers that stay in place at the end of a field for the duration of the season.  Our use of this type of herbicide is very limited, and over the years we have developed many other ways of battling weeds.  But first, what is a weed?

A thick stand of a diverse cover crop blend
including mammoth clover, vetch & rye grass

I asked Richard how he defines what a weed is and he said “A weed is a plant that interferes with an intentionally planted crop.”  This is an important distinction because in some cases we may consider a plant to be the intentional crop while at other times we may consider that same type of plant to be a weed that needs to be removed.  An example of this is burdock.  We plant whole fields to burdock intentionally because we want to harvest the roots.  We also send our crew members out to dig wild burdock out of the areas surrounding our fields, in pastures, etc. to prevent it from making seed and spreading!  While we often don’t think of them in this way, weeds are actually Mother Nature’s gift to the soil because we know Mother Nature likes to keep the ground covered at all times!  Weed seeds can actually remain viable in the soil for 20-30 years.  They remain dormant until the conditions are right and then they germinate.  This is part of nature’s design to protect the soil and deal with extremes such as droughts or excess moisture.  This collection of seeds in the soil is called the “Seed Bank.”  Our goal in weed control is to deplete the Seed Bank by germinating weeds and then eliminating those plants, but we also want to make sure we are not depositing into the Seed Bank either by letting weeds mature to the point where they produce seeds.

So why do we work so hard to eliminate weeds from our fields?  Well obviously it’s because a weed-free field is much more beautiful than one filled with weeds!  Ok, while that’s a true statement, aesthetics are not the main objective in weed control.  Plants that we consider weeds are competition for the crop for sunlight, nutrients and water.  Many times weeds grow faster than the crop and diminish the crop’s access to sunlight.  Plants that we consider weeds also extract fertility and moisture, thereby depriving the crop of vital nutrients.  The result of this competition is that the crop is not able to achieve its maximum potential, yields may be decreased, efficiency in harvest is diminished, and if nutrients are lacking there may be impact on fruiting, growth and the ability of the plant to defend itself against pests and disease.  

Sunchokes, an excellent weed competitor!

Some crops we grow are pretty aggressive and we don’t worry so much about weed pressure.  A good example of this is sunchokes which can quickly grow a sizeable plant that creates a canopy which shades the ground under them and prevents weeds from growing.  Even though sunchokes have a very long growing season, we seldom ever have to weed them because we’re able to deal with any weeds early on using mechanical cultivation and then once the plant is big enough weeds just aren’t much of an issue.  There are other crops, however, that are very poor weed competitors.  Onions, carrots, beets and parsnips are good examples of crops that can be a challenge.  In many cases, weeds grow faster than these crops which gives the weeds the advantage.  The other reason is that these crops do not produce as much leaf or plant material above ground to overshadow the weeds, or do not produce the leaves fast enough.  One thing a farmer needs to consider is the weed history of a field.  We have a lot of fields, but Richard and Rafael are very familiar with the weeds that are present in the different locations and take this information into consideration when planning where a crop will be planted.  

Utilizing an old-fashioned method of weed
control....hand weeding 

We have many methods of controlling weeds and are always considering what is going to be both most effective as well as cost effective.  The first objective we set is to prevent weeds from going to seed.  This is an underlying goal in all of our efforts because we do not want to contribute to that Seed Bank or we’ll pay for it for the next 20-30 years!  This is why timely weed control is so very important and must be a priority.  In wet years this can be a challenge as many of our weed control efforts are not possible when the field is too wet to take equipment into without getting stuck.  In these cases we can sometimes do hand weeding, however that can be counterproductive at times unless you actually carry the weeds out of the field.  If you just pull the weed and put it on the ground between the beds, it will often have enough moisture to take root and keep growing.  We do a lot of hand weeding, but weeding by hand is not easy work!  It’s hard on the body, very time consuming and consequently very expensive.  So, we try as much to use machinery and other methods which are more cost effective and faster.

Wet, but dry enough to not get stuck!

I consider Richard and Rafael to be masters of mechanical weed control and together they have developed quite an arsenal of machinery and implements to combat weeds on our farm.  If a piece of machinery doesn’t exist on the market, they design it and we build it!  There are many factors they consider when choosing which mechanical cultivation technique they are going to employ.  How big is the crop?  Are the weeds in the row, in between the rows or in the wheel tracks?  How aggressive can we be with a plant?  Is the plant well established and tough enough to take a little impact or is it delicate and cannot be disturbed?  How big are the weeds?  They also do weed control at all stages of the crop.  Before a crop is planted, the ground is prepared and, ideally, we wait at least two weeks to plant the crop.  During this two weeks we can germinate the weed seeds in the top layer of soil and get a nice flush of weeds.  Just before we plant the crop, they can “clean up” the bed using the basket cultivator that passes over the bed and flicks the little weeds out with shallow tillage.  This technique is called “stale bedding” and it’s a noticeable difference when we are able to accomplish this versus planting into freshly prepared soil.  We will do another article to explore the topic of tillage versus no-till farming methods, but I want to make a comment about tillage as it relates to weed control.  We do use tillage in our crop systems, but only when deemed necessary and we try to limit it to shallow tillage because deep tillage stirs up weed seeds and brings them to the surface where they are more likely to germinate.  We have enough weed issues on the surface already, so it behooves us to not create more issues we have to then deal with!  

Rafael operating the flame weeder

We also utilize pre-emergent flame weeding.  With this technique we use a machine called “The Flamer” which is basically a big propane tank set on a frame with burners that passes over the width of the bed very close to the surface of the soil.  The flames from the burners will kill any plant on the bed.  For this method to be effective, it has to be timed properly.  We want to kill the maximum amount of weeds, but we don’t want to kill our crop.  Thus, we have to time the flaming just ahead of when the crop emerges.  We utilize pre-emergent flame weeding for parsnips, carrots, cilantro and dill.  Luis has been doing most of the flame weeding this year and has been doing an excellent job of tracking the crops that need to be flamed and checking them regularly.  A crop can emerge from the soil literally overnight, so he has to be very timely in his efforts or he’ll miss a critical opportunity and the resultant weed pressure in the crop is noticeable.

Freshly mulched field in preparation
for planting peppers

I mentioned earlier that Mother Nature does not like to have the surface of the soil barren.  With this in mind, we have a few other tactics we can use to stay ahead of the weeds.  One tactic we use for some crops is mulch.  We mostly use rye straw for mulching crops such as strawberries, garlic, peppers and tomatoes.  Having straw mulch in place functions as a cover for the soil to discourage weed growth or smother any weeds that try to emerge.  We also use cover crops extensively, especially in the fall.  As soon as we take the last crop off a field for the year, we plant a diverse mix of cover crop seeds so we can establish a nice blanket of green to cover the soil.  There are some types of weeds that actually germinate and become established in the fall and then become a problem for us the following spring.  If we can get a cover crop growing quickly and shade the ground, we can discourage the growth of these weeds and reap the benefits of our efforts in the spring!

Freshly cultivated, weed-free 
field of potatoes

This is just a very little glimpse into the topic of weed control on a vegetable farm, but if we were to cover all there is to share we would have a book!  I hope you can appreciate the level of mastery of your farmers and have confidence that, while the battle against weeds is never ending, your team of farmers is doing their very best to continue to innovate and learn in an effort to manage weeds on our farm.  The result as it relates to you is that you will continue to receive wholesome, nutrient dense, flavorful and beautiful vegetables!