Dealing With Weeds At Harmony Valley Farm

By:  Richard de Wilde

“What we call a weed is in fact merely a plant growing where we do not want it.”

 —E.J. Salisbury, The Living Garden, 1935

Leeks after cultivation using "The Lilliston"

As organic farmers we do our best to understand and work with the natural world.  Nature is wise and knows the value of keeping soil in place and covered with plants which maximize each day of sunshine, capturing carbon and nitrogen from the air while exhaling oxygen that we need to live.  In nature, soil is never left bare to be wasted or eroded by wind and water.  Weeds have a purpose, and it really is a good one!  So why are we so set on killing and eradicating them from our fields?  Weeds can be very aggressive and can inhibit the potential of a crop by competing for sunlight and nutrients.  They impede our harvest efficiency and produce thousands of seeds which will haunt us for years.  Most weeds have accompanied agriculture from its beginning.  They moved around the world as early settlers brought their grain seed along with some tag along weed seeds and today they hitchhike with the global grain trade and then further spread by way of wind, animals, equipment, etc.

Potato field cultivated with "The Lilliston" 

Weed plants are very adaptive.  They can lie dormant in soils for 10-30 years, just waiting for their time of need to germinate.  Some weed seeds  only germinate at certain times of the year, such as in cool spring or fall temperatures.  Others are triggered in times of excess moisture, while others only germinate in summer heat or extreme drought.  Weed seeds are also triggered to geminate by exposure to light, usually caused by tillage.  Tillage is any disruption of the soil, which in our case could be cultivation or other work to prepare the soil for planting.  As the soil is stirred and disrupted, even just a flash of sunlight is enough to trigger some weeds to germinate!  In fact, I’ve read that in Europe some farmers even started cultivating at night to avoid triggering weed seeds!  Weed seeds may also be triggered by fertility needs in the soil.  Some weeds have the ability to correct soil nutrient deficiencies.  For example, if soil is deficient in phosphorus, a seed for a plant that has the ability to scavenge phosphorus may be triggered to germinate and grow.  As we try to minimize weeds in our crop, one thing we do is to provide balanced nutritional needs for the soil to prevent the need for weeds to correct the deficiency.

Cilantro:  Cultivated with "Basket Weeder" with shields & Kult Kress Duo.

There are really only two kinds of weeds, annual or bi-annual weeds and perennial weeds.  Annual or bi-annual weeds grow rapidly from seed, but only under the right conditions.  In order to thrive once they germinate, they need to grow and develop their green structures above ground to capture sunlight and utilize photosynthesis for energy.  When these types of weeds die at the end of the season, they are dead and won’t grow again.   Thus their main way to propagate themselves is to produce seeds that drop back into the soil and are available for a future season.  In contrast, perennial weeds survive from year to year and their main strength and the key to their survival is their underground root storage system which holds nutrients and energy.  When a new year rolls around, they don’t have to wait for the right conditions to germinate a seed and start photosynthesizing, rather they draw their energy from their roots.  The key to eradicating these types of weeds is depleting their root reserves.  Up until the plant is six inches tall, it is drawing its energy from its root reserves.  When it is about six inches tall, it starts utilizing photosynthesis to put energy back into the roots and replete the reserve.  One way we can battle this type of weed is to repeatedly mow it off when it is about six inches tall. This takes persistence, but after time the root reserves will be depleted and the plant will die.

Rafael using disc cultivator in the cilantro field.

By now you may be wondering if there is a silver bullet for weed control.  Valid question and one farmers have been asking for years.  In a recent article in Acres U.S.A. written by Anneliese Abbott, she commented about the onset of agricultural herbicide use.  “It seemed so easy:  forget about plowing…and just spray chemicals to kill the weeds.  No tillage, no erosion and no weeds:  what could be better?  Unfortunately, herbicides caused as many problems as they solved. They polluted water, harmed non-target organisms and sometimes posed a threat to human health.  Worst of all, they only worked well for a short period of time.  Weeds quickly evolved resistance to every major type of herbicide, forcing farmers to spray more and more chemicals with less and less success every year.”   Sadly, as organic farmers there is no easy way to deal with weeds.  Rather we try to understand how weeds work, the conditions they thrive in, and then we utilize multiple methods to kill them and prevent their growth.  Aside from the occasional use of 30% vinegar, chemicals are not our answer.  So lets talk about the methods and tools we can use.

New weed control technique:
Low growing cover crops between rows of melons.

One of our weed control tools is planting cover crops of grains, grasses and clovers.  If we can satisfy the need to cover the soil, there’s no need for dormant weed seeds to germinate.  It helps that most grasses and cereal grains, such as rye, also exude chemicals to inhibit other seeds from germinating.  Historically we have planted most of our cover crops in the fall, which can serve to prevent the growth of bi-annual weeds.  Bi-annual weeds germinate in fall, but do their growing in the spring.  If we can inhibit germination with a fall cover crop planting, we won’t have those weeds in our spring planted crop.  We are also perfecting a new and exciting technique we’ve developed for controlling weeds that grow in the space between the beds where crops are planted.  Immediately after preparing the beds, we plant two very fast germinating cover crop plants, creeping red fescue and white Dutch clover.  Both grow fast and inhibit weeds.  They are also short in stature, only 6 inches tall at most, so they do not compete with our crop for sunshine.

Using Flame Weeder to kill small weeds before crop emerges

We can also deplete the “weed seed bank” in the soil by triggering weeds to germinate, then killing them when they are small with very shallow cultivation or flaming.  We typically utilize this method before we plant the crop, but it requires us to prepare the beds one week ahead of planting.  Then, just before we plant, we “basket” the beds.  A “Basket Weeder” is an implement mounted on a small tractor.  It has horizontal wires that flip small weeds out as they roll across the surface of the bed.  We can also utilize a “Flame Weeder” to kill weeds that germinate and emerge after the crop has been planted, but before it comes up.  In order for this to work, the timing and conditions have to be just right.  The flame weeder is a tank of propane mounted on the back of the tractor with burners that carry just over the surface of the bed.  The flames burn the weeds off, thereby killing them.  If you flame too soon, you won’t maximize the number of weeds you kill.  If you wait too long, the crop may start to emerge and you risk burning off your crop.  We utilize flame weeding for crops such as cilantro and dill that we plant every week for over twenty weeks.  Typically we have to time the flaming about 4-8 days after the crop is planted, depending on temperature.  We also use this technique on carrots and parsnips and the difference between a crop that has been flamed and one that has not is dramatic!!  We have a significant reduction in weeds with timely flaming.  When we do get weeds in our field, it is critical that “bad” weeds to go to seed in the field or areas around our fields.  If they do, they’ll make a deposit into the “weed seed bank” that we’ll pay for in years to come!

Vicente using "The Lilliston" to "hill" sweet corn

We have a few more tools in our collection of things for weed control.  Sometimes we use a tool called “The Lilliston” which aggressively throws dirt in one direction and can be used to smother weeds by throwing dirt on them.  We use this to smother weeds within the rows of crops such as potatoes, leeks and sunchokes when the plants are big enough to get partially covered by dirt without damaging them.  Another tool we use is called a “Lely Tine Weeder.”  This tool has little tines that rake out very small weeds.  This is a more gentle tool and can be used on small transplants and fast growing crops that are direct seeded, as long as the crop is larger than the weeds.  The “Basket Weeder” is also extensively used with tunnel shields that we put on the implement to carry over the rows of crops to protect them from dirt flying into the row and smothering the crop when the crop is too small.  While this method preserves the crop and kills weeds in between the rows, it doesn’t do anything to remove weeds that are in the row.  Later, when the crop is bigger and can take a little more aggressive cultivation, we remove the shields.

Jaime and Felix G using "The Kult" in celeriac

In more recent years we’ve started using a steerable cultivator that we call “The Kult.”  It requires a team of two people to operate it.  One person drives the tractor and the other rides on the cultivator to steer the machine.  This tool is more effective at killing weeds within the rows of crops and it is indispensable at killing new weeds in larger, more established crops where we have to be careful not to disturb the crop’s root system or damage the plants.  It’s also adaptable and can be set up in a variety of ways to best meet our needs.  We have even more cultivating tools, but I think you can see we try to utilize mechanical options as they are our most efficient and cost-effective means of killing weeds.

Ascension using a hoe and his hands to remove weeds
in the strawberry field

We can also smother weeds by covering the soil with plastic or straw mulch.  Some of our crops are planted on plastic covered beds.  We use the plastic mulch for a variety of reasons, one being weed control.  As a last resort, when we’ve exhausted all other methods, we turn to old-fashioned hand weeding.  Yes, we do still do more than our fair share of hand weeding and this too is a skill.  We try to avoid weeding by hand because it is time consuming, but sometimes that’s the only option.

Will we ever kill all the weeds in our fields?  No, but the sum total of all our efforts will pay off this year and in years to come as we minimize the impact weeds have on our crops.

Managing Weeds at Harmony Valley Farm

How do you manage weeds? That is a great question we’re often asked and it has a variety of answers depending on the crop, the stage of growth of the crop, the weather conditions, etc.  While conventional farmers often use chemical forces in their battle against weeds, we turn to non-chemical methods including mechanical cultivation and flaming. Richard and Rafael keep a close watch over our fields. Richard referred to Rafael as the “Weed Manager”. His observations have been extremely helpful in deciding when to cultivate and which implement to use on each crop. The goal is to reduce the weed seed, also known as the ‘seed bank’ in the soil. Weed seeds can live for 10 – 30 years in the soil, just waiting for the perfect time and conditions to grow. Our job is to remove weeds and not let them produce any more seeds. Below I will summarize some of our equipment, crew and processes that take on the task of keeping the weeds at bay!

Rafael flaming the cilantro
field before the crop sprouted.

If you have ever been to our farm or seen field pictures, you have seen our raised bed fields. Our first line of defense is to reduce the weed seed in the top 2 inches of soil before planting a crop. We try, but do not always have the perfect weather conditions or enough time, to make the beds 2 weeks prior to planting, thus giving the weeds time to sprout. If that happens, we can use the ‘Flamer’ to burn off the weeds that have sprouted prior to planting. Juan or Rafael have been Richard’s go to guys when it comes to flaming our fields. The ‘Flamer’ is a piece of equipment that takes the propane from the large tank mounted on the implement and through the pipes to create, in essence a flame thrower.  Sounds pretty cool right!  No, there is no big ball of flames; it is really just enough heat/flames close to the ground to burn the weeds that are already growing, but can save a huge amount of time and manpower.  We can also use the ‘Flamer’ after the crop is                                                          planted but before the plants push through the ground to                                                                  burn the weeds that are already growing.

Rafael cultivating the cilantro field
with the 5 Row Basket Weeder

A closer look at Rafael basketing the
cilantro field!

Once the crop is out of the ground we lose the option to flame. Now we have to turn to a variety of different cultivating implements for help. This will depend on the crop and how big it is in the field. A good example is our cilantro. It is planted on raised beds in rows of 5 on top of each raised bed.  We use the 5 row ‘basket weeder’ to loosen the soil and pull out any small weeds that are already growing in the top inch of soil. Rafael has done an excellent job with perfecting his basketing procedures.  Rogelio, Ramon and Jose Manuel have also done a great job with the basket weeder.

Oscar (driving the tractor) and Luis operating 'The Kult'
to take care of those pesky weeds in our beautiful parsnip field.

A closer look at the fingers of 'The Kult' working!

Last year we purchased an awesome German made K.U.L.T. Kress Cultivator. We refer to this as ‘The Kult’. Rafael learned how to operate this implement and has now taught Oscar and Luis how to use it. Weeds growing in the row are a huge problem as they are hard to get to without damaging the crop. This implement, when conditions are good, will help to reduce those pesky weeds in the row. There is one person (Oscar) driving the tractor and another (Luis) steering the implement to make sure the crop does not get pulled out. The Kult has little fingers that come close to weaving together near the base of the crop loosening the soil and ‘stirring’ out the small weeds. We use this machine with our transplanted brassicas (broccoli, cauliflower, etc). We transplant our brassicas to give them a head start on the weeds, giving them the advantage of being larger than the sprouting weeds.  It is way easier to get rid of smaller weeds when our crop is larger and easier to see in the row and the Kult works very well with these crops.    

Vicente using the 2 row Lilliston
cultivator in the corn field.

Vicente using the disc Lilliston
to bury the weeds in the potato field.

For other larger crops, it makes more sense to bury the weeds with dirt. This is a great option for crops like potatoes or corn.
 Vicente has learned how to use the Lilliston cultivator with ease. The open steel fingers on this implement pull up the soil between each crop row and push the loose soil around the plant, essentially burying the weeds.
       

Corn row before (top) and
after (bottom) the Lilliston.

When all mechanical attempts have been applied,
we have one more tool: our hands to do hand weeding. This is very time consuming but also necessary in some cases.  With carrots or parsnips, both of which have longer germination rates, the weeds generally pop up before the crop. After the field is flamed with the flame weeder and the crop starts coming up, we need to make sure the hand weeding gets started soon.  This takes very good eye-hand coordination as well as knowing the difference between the crop and a weed.
I can’t stress this enough, but extreme precision while using any of these implements makes the difference between a well weeded crop and not having any crop at all because it was all pulled out or buried.   You have to watch the front of the tractor to see where you are going, but also the back to make sure you are not pulling up any plants.  Even the hand weeders need to be careful.

Picture of the tool room where we
store the hand weeding tools.

Here are some parting thoughts on weeds.  Richard estimates that we kill 90 -95% of the weeds in our fields with the mechanical weeding techniques, leaving only a smaller amount for the hand weeders. Did you know that 1 weed that has gone to seed can produce up to 20,000 seeds and that these seeds can and will be carried by birds, water and the wind? This means that even though we remove most of the weeds, we will always have some weeds to deal with on the farm. Did you also know that Mother Nature does not like bare ground? Turns out she doesn’t like to be naked!  We use cover crops to help with the weeds (and other reasons) since if we don’t cover it, she will use the weed seeds in her seed bank to cover herself up. I know we have only touched briefly on the weed subject and there is a lot of information out there we didn’t discuss.  Rest assured that Richard and Rafael are on top of the weed battle. Discussing when to cultivate, which crops, upcoming weather, which implements to use, should they use fingers, discs, knives or how deep to go when cultivating are just some of the conversions that they have on a daily basis. In the end, we are grateful to all of our cultivating crew for their attention to detail, which allows us to have healthy crops to harvest and eat!