Notes from the Field: Weeds

July morning in front of the Swiss chard

This is the time of year when the weeds on our farm make themselves well known. In the heat of July, amaranth, lambs' quarter, galinsoga, purslane, and assorted grasses grow at seemingly impossible rates, trying to go to flower and set seed like the rest of the natural world. Seeing this phenomenon, a Korean friend of ours once shook her head, grabbed Erinn by the arm, and demonstrated weeding to her, nodding vigorously. If we would just weed, she was saying, everything would be OK. 

The truth is, of course, we do weed. A lot. Waltham Fields is blessed with a particularly abundant weed seed bank. Our fields were essentially abandoned for a few years in the early 1990s as the University of Massachusetts, who owns our land, transferred most of its agricultural research to Amherst. During this time, weeds grew crazily in the fertile soil, dropping their seeds to the ground to germinate and grow over the next decade. When Oakes Plimpton, WFCF's founder, took over the fields, he initially farmed with only a small crew of volunteers, making it challenging to keep up with all those weeds -- more weeds, more weed seed. I came to WFCF from a farm where we used hoes to try to keep up with our weeds, so my knowledge of weed control methods was less than subtle, and less than effective -- more weeds, more weed seed. The old adage "one year of seed, seven years of weeds" is a very rough estimate, but given our history, we're looking at about 70 years of pretty intense weeds on our farm.

Lambs' quarter

These days, we control weeds in a number of different ways. Our first line of defense is creating what's called a "stale seedbed". We make a bed a week or two before we plan to plant a crop and kill the weeds that sprout there, hopefully a couple of times, before we plant seeds or transplants. If we do a good job killing the weeds without disturbing the soil enough to bring up new weed seeds, this technique ensures that our crop is slightly ahead of the weeds when it sprouts or when we put it into the ground as a transplant. This helps, but it's not enough on our farm. We are fortunate enough to have three cultivating tractors, two Farmall Super As from the late 1940s and a Kubota 245H, a relative spring chicken from the mid 1980s. These tractors have attachments that kill weeds (each sold separately, and some assembly required). The construction of the tractor chassis on a cultivating tractor means that the attachments can either mount just below the driver's seat where you can see the work that you're doing, or behind the driver where you can look forward and have faith. Both types of attachments could warrant their own field notes -- our basket weeders are good for killing weeds in between the rows of crops when the crops are very small, while the tine weeder can actually weed around the crop that's already in the bed once it's established. Ominous sounding pieces of steel like the flex-tine cultivators, torsion weeders, and rolling spiders all have their places in our toolbox of tractor-mounted weed control equipment. The I & J pathway cultivator, new to the farm this year, is a major improvement in helping control weeds in the pathways of the crops we grow on plastic. Killing weeds with a tractor is called "cultivation" -- it's the step before what most people traditionally think of as weeding, the quick and dirty, and sometimes extremely effective, method of moving the soil just enough to dislodge tiny weeds, almost before you can see them, and expose them to the sun and wind while (hopefully) not affecting the crop you plan to grow.

Purslane

We also cultivate with a strange-looking tool called a flame weeder, a propane tank mounted on a backpack frame that delivers a blast of heat to just-sprouted weeds, exploding their cell walls. This technique, called "flame weeding" is essentially a kind of stale seed bedding that we can do after we have planted seeds in the bed already. Ideally, for example we seed carrots, wait a week, and flame to kill any weeds that are germinating in the bed the day before the carrot plants break through the soil (some of us think the heat helps the carrots sprout, too). We might kill a few early-sprouting carrots, but it is so worth that small loss in terms of time saving later that flame weeding has become an essential part of our carrot-growing regimen at WFCF.

Tangy wood sorrel works well as a garnish or as an addition to salads

After all this equipment rolls through the field, we still have weeds. They are either weeds we missed, or new ones that germinated after the crop was too large to cultivate with the tractor. Some of these weeds are easily controlled with hoes (we like both colinear and scuffle hoes on our farm, depending on the job and the person), but some need the ultimate treatment -- the weed crew. The 2012 weed crew consists of four women, 20 hours per week, often joined by additional drop-in volunteers. On Mondays, they tackle whatever is most urgent in the pick-your-own field. Tuesday through Friday, they work on the rest of the farm. Not every crop needs to be hand-weeded; if we're lucky, we can usually get lettuce to the harvest stage with just a quick hoeing. Every planting of carrots, however, needs one hand weeding pass through in order to clean up the weeds that are right in the row and don't get killed by the cultivator; our parsnips, which are in the ground from May through mid-October, may actually need more than one. The weed crew makes their way around the whole farm over the course of the 12 weeks, from June through August, that they spend with us. The work that they do is some of the most important work that gets done here, hands down. The other person who does invaluable -- and unsung -- work to keep our weed population down these days is Fred, who mows and weed whacks our field edges once a week. Not only does this bring us incredible peace of mind and add to the beauty and tranquility of the fields, but it also keeps the weeds on the field edge from going to seed, adding to that tremendous weed seed bank of old.

Young lambs' quarter (identifiable by its "goosefoot" leaves and powdery white or lavender center)

We know that many of the weeds on the farm are not only edible, but very nutritious. Purslane is a rare plant source of omega-3 fatty acids, while lambs' quarters, a relative of spinach, packs all of that favorite green's nutritional punch. Vegetable amaranth is a favorite food of Jamaicans, who steam it and eat it with white rice and fish. They're all delicious -- you should take some home and try them. How about a car full? 

Infamous: dandelion greens

And we also know that there are folks who say that changing the mineral or biological balance in our soil may also change the weed population. While we continue to work on this from year to year, particularly through the addition of micronutrient blends and humates, we're definitely not there yet, and it's possible that our giant historic weed seed bank is simply too large for us to really see the effects of the fertility changes we've been making. Amaranth, for example, really seems to like to grow right where all of our vegetable crops grow, and it seems like it is encouraged -- not deterred --  as we increase the fertility of the soil. Of course, our crops are also growing better too, and with the help of some institutional knowledge, improved cultivation equipment, better fertility, and the weed crew, our farm is slowly growing more productive and less weedy. It's an uphill climb, but we are making progress each year. So yes, we do weed. All the time. 

Enjoy the harvest,

Amanda, for the farm crew

Images by Rebekah Carter (2012).