Flame weeding and beating the weeds on small farms

This is a field of beans.  Beans do not have yellow flowers, but brassica weed species do! Photo credit: Claire Collie

This is a field of beans.  Beans do not have yellow flowers, but brassica weed species do! Photo credit: Claire Collie

In my last post on plastic use in organic farms I said:

weeds are one of the biggest problems on small (organically practicing) farms.

When we find weeds in our garden we can pull them out individually, or we are told by herbicide companies to blast weeds with a sprayable concoction that will make them shrivel up.  But what do you do when there are weeds on acres and acres of fields and you don’t want to use herbicides?


Broccoli and weeds competing for space and resources in the field. Photo credit: Claire Collie

First, we have to know what a weed really is.  From an ecological standpoint:

weeds are any plant that is objectionable or interferes with activity of the welfare of humans.  

Weeds are competition for crop plants.  They suck up resources like nutrients, water, light and space that crop plants could be using.

Usually weeds are plants that are adapted to disturbed environments.  In Alena’s post a few weeks ago she defined disturbance as ‘an event that changes the ecosystem in some way.’  While farming doesn’t seem particularly devastating it can cause a lot of disturbance to the growing environment and weed seeds take advantage of that by being ready to sprout and grow as soon as the opportunity presents itself.  

The weed seed bank, or how many seeds are in the ground waiting to germinate, is huge.  So vast, that trying to kill all the weeds is not possible.  It is possible to manage weeds, and that is one of the biggest tasks a farmer has.


Managing weeds on the farm

There are lots of ways to manage weeds on a farm on both a long term (many years) and short term (help there are weeds everywhere!) scale. 

Long term management includes concepts like cover cropping, interplanting, and not tilling seed beds.  I might discuss some of these ideas in the future, but until then the UNH Agroecology blog is a good place to see current research on long term weed management projects. 

Short term weed management is about getting rid of the weeds that are competing with current crops by disturbing the environment of the weed without disturbing the crop plant.  


Flame weeding is the most exciting sounding method.  Here’s how you do it:

  1. Till your soil.
  2. Wait a bit then plant crop seeds.
  3. Wait a bit until weeds have sprouted but crops haven’t. 
  4. Blast weeds with heat! (In the video all the little bursts of flame are weeds exploding.)

In comparison soil cultivation is really mild.  There are many implements (equipment that attaches onto the back of a tractor) that disturb the soil around crops.  There are impliments that dig, that roll, that scratch.  These tools are getting more and more precise, and can even get weeds between plants without disturbing the crop.  For some crops you can’t get too close without harming them.  Then you’re stuck with old fashioned hand weeding. 

Like I mentioned in my last post, black plastic mulch is a well-used method of weed suppression directly around plants.  The idea is simple - if you cover up the area around a crop weed seeds won’t get any light to grow.  Of course, weeds can still grow in the pathways between crops, so this method isn’t perfect on it’s own.

A professor I had stressed the use of a 'many little hammers' approach to weed management.  Since getting rid of weeds completely isn't a plausible solution the best way to manage the weed population in a field or on a farm is by using lots of smaller tools and practices.  All the 'little hammers' will add up and crops will not have to compete for resources.  Hopefully, then your field would look like the one below - full of crop plants and not much else.


Flame weeding on raised beds that have carrots planted in them. The flame doesn't hurt the carrots because you flame prior to the carrots seeds emerging.  Video from New Sprouts Farm

Mechanical weeding of spring onions. Video from Agro Christiaens.

Cultivated salad greens in the early morning.  Photo credit: Claire Collie