Notes from the Farm

Weeds Shall Overcome

To the beginning organic vegetable farmer, it seems that the weeds will overcome every crop that is planted, and often they do. In fact, weeds are the most difficult management problem, especially when planting on ground that has previously lain fallow. This is because the soil has had ample opportunity to store a huge reserve of weed seeds that will germinate over a number of years. It is often hard to find your new plants among the weeds that germinate even faster than your plants do.

Even if the planted beds are kept weed free for a few years, tilling will expose seeds that have been dormant below the soil, but over time the store of seeds in the soil will diminish making the organic farmer’s job somewhat easier, but never simple.

Managing weeds is definitely our most expensive operation and as such, we are always looking for ways to streamline the process. But even with our best efforts, we are often on our hands and knees pulling them out one at a time when they are mixed in with newly seeded plants. For the record, here are some of the ways we are manage weeds:

Planting Sets: Many types of plants are started in the greenhouse then transplanted into the soil partially grown to give them a jump start on the weeds that will inevitably germinate around them. This works well for lettuce, tomatoes, escarole, peppers and the like, but cannot be done for root crops like carrots, parsnips and others.

Drip Irrigating: By using drip irrigation, water is placed at the base of the plants instead of broadcast on top of the ground. This makes it difficult for weeds to germinate once the top layer of soil has dried out. Drip irrigation also conserves lots of water, using less than 1/4 of what would be required with overhead irrigation.

Mulching: Plants like garlic, tomatoes, strawberries and raspberries need to be in the soil for a long time and would require repeated weeding. This problem is solved by applying a heavy mat of rice straw mulch, which not only blocks weeds, but also conserves water. We use rice straw because, unlike wheat straw or field hay, the rice seeds in the straw will not germinate well in our area.

Cultivating: We have adapted one of our antique tractors to cultivate between rows of plants and between beds. For newly emerged seeds, we use a home-made “finger cultivator” that roughs up the soil between rows.

As plants grow in size, we use a “shoe” cultivator that slices weeds off under the ground and digs up the top few inches of soil.

This leaves the top layer of soil loose and friable, which cuts down on weed germination and holds in soil moisture. If cultivation is done properly, the soil is rolled up against the plants, burying the smaller weeds that have germinated in the plant row.

Hula Hoes: The hula hoe is used to slice off weeds under the soil and is an important tool in weed control although the labor to run it can become very expensive if weeds are allowed to grow too large. In fact, weeds are best hoed when they first emerge out of the soil and are still very small. If the soil is loose, a simple drag over the area with the hula hoe (or the finger cultivator) will get most of the weeds. Once they have developed strong roots, however, weeds will vigorously resist the most concerted efforts to remove them, so it is important to get them while they are young!

Hand Weeding: Hand weeding should always be a last resort because it is a slow and therefore expensive process—but at times there is simply no other way to get the weeds that grow within the rows. When resorting to hand weeding, it is best to water heavily beforehand. This makes it easy to pull out the roots along with the weeds. Otherwise many weeds will simply break off at ground level, wait until you go away and jump back with renewed vigor the next day.

Planting Cover Crops: Instead of letting beds revert to weeds when not in use, planting a cover crop that will grow tall enough to shadow out weeds (but will not reseed itself) will help reduce the seed load of the soil over time. Additionally, planting a legume cover crop will add nitrogen and organic matter to the soil. Our current favorite is fava beans which also produce a crop of delectable fresh favas.

In spite of all these efforts, the weeds still gain the upper hand. This spring, we plowed under some early crops that germinated with too many weeds because it would have been too time consuming to weed them. As I write this article, I know that lambs quarters, jimpson weed, johnson grass, crab grass, purslane, chickweed, dandelion and others are vigorously germinating, making more work for tomorrow.