When you visit the farm, you see the vegetables and forage crops growing above ground, and it's easy to forget there's a whole world below the earth's surface that makes these plants what they are. Plant roots are the unsung heroes of organic farming systems. Their structures are just as diverse as the aerial plant parts we see and have come to appreciate. The intricacies of roots' interactions with the soil and the soil food web are the driving force of the food we eat. Let’s take a peek at what is going on down there.
A seed is said to germinate when the initial root—called a radicle—breaks through the protective coating of that seed. This baby root is feeding off the energy stored in the seed as it naturally turns downward in search of moisture and nutrients to feed the leaves that are soon to develop. As the spike-like root spears deeper into the ground, small root branches begin to spread laterally to begin anchoring the plant in preparation for the taller, leafy growth that will be exposed to the elements above the soil. As the plant matures, the root structure develops in a pattern unique to its genetic code.
Generally speaking, there are two basic types of root systems: tap and fibrous. Tap roots have a dominant shaft that dives deep into the soil, while fibrous root systems are a series of uniformly sized structures that fan out into the soil. Tap roots not only physically penetrate through denser sub-surface soils—even the tighter, clay soil profiles—but they are able to bring nutrients up to the surface that otherwise would not be available to the plant. Fibrous-type structures send their tentacles in all directions in search of nutrients and moisture. We use these differences to our advantage when planting cover crops and designing crop rotations. Water goes into the roots and out the leaves, called transpiration, which is akin to the chimney effect. The leaves then send down the nutrients they've accumulated through photosynthesis to feed the roots.
Building the Soil Food Web
Here is where plant roots get interesting. Whenever top growth of a plant is removed, such as when you cut the grass or when we harvest the outer leaves of kale from a plant, an equivalent amount of root growth dies, because there is not enough food available for all of them. When these roots decay, they provide nutrition to the soil microbes—bacteria and fungi—that feed on such plant material. The space where the now-dead root was also leaves a small void in the soil for air to move deeper into the ground, oxygenating those same microbes. There are tens of thousands of species of bacteria and fungi, each with unique growth and feeding requirements. Some like it hot, others cold, some wet, others dry, some high pH, others low. This cycle of new root growth and subsequent decay is how we build soil.
The interface between roots and the soil they live in is wildly intricate. The roots are not selfish with the nutrients they get from up top. They exude a nutrient-dense solution back into the soil, which further energizes the microbial flora and fauna around them. This symbiotic relationship is best seen with a class of fungi known as mycorrhizae. These filamentous-like fungi attach themselves to the roots, then form microscopic threads all through the soil profile, extracting specific nutrients, like calcium, phosphorus and magnesium. They then transfer the nutrients to the root, which sends them to the leaves or the fruits we eat. The roots cannot do this work on their own. Healthy soils are said to contain 20 miles of mycorrhizae fungi in a single teaspoon. When a plant has the balance of nutrients that match its genetic code, it can fend off disease and pestilence. This is the genesis of organic principles.
Within this complex, synergistic, nutrient sharing is a communication feedback loop that is a bit counterintuitive. For example, weeds that have a relatively higher concentration of zinc will grow in an area low in zinc. By doing so, the mycorrhizae and root systems mine the soil for zinc and send it to the top of the plant to be deposited on the surface of the soil at some point, therefore correcting the zinc deficiency in the soil. We manage the types of plants we grow to cycle those nutrients back into the working surface of the soil.
So, you see, the roots are much more than structural necessities. The wildly diverse and symbiotic jungle of plant tissue, microbes and insects cohabitate to create healthy plants. Please take a moment to consider that the produce you receive each week is just as nature intended. With a little help from us. —Mac Stone
In Your Share:
Fresh Herb: Oregano
Sugar Snap Peas
Red Russian Kale
Lettuce Soup, from Epicurious
1 c. chopped onions, scallions or shallots
1 garlic clove, chopped
3 T. unsalted butter
3/4 tsp. ground coriander
3/4 tsp. salt
1/4 tsp. black pepper
3/4 c. diced (1/3 in.), peeled potato
8 c. coarsely chopped lettuce leaves, including ribs
3 cups water or vegetable or chicken broth
Cook onion mixture and garlic in 2 tablespoons butter in a 4- to 5-quart heavy pot over moderately low heat, stirring, until softened, 3 to 5 minutes. Add coriander, salt and pepper and cook, stirring, 1 minute. Stir in potato, lettuce and water and bring to a boil, then reduce heat and simmer, covered, until potato is very tender, about 10 minutes.
Purée soup in batches in a blender (use caution when blending hot liquids) and transfer to a 2- to 3-quart saucepan. Bring soup to a simmer, then whisk in remaining tablespoon butter and salt and pepper to taste. Serves 4.
Strawberry-Avocado Salsa, adapted from Cooking Light
1 1/2 c. chopped strawberries
1/2 c. diced, peeled, ripe avocado
2 T. minced, seeded jalapeño pepper
2 T. chopped fresh cilantro
2 tsp. fresh lime juice
1/4 tsp. kosher salt
Combine all in a bowl. Serve over grilled chicken, alongside a Mexican-inspired meal or with vegetable chips as a snack.
Sugar Snap Peas with Onions and Bacon, adapted from FoodNetwork.com
3 slices bacon, cut into 1/2-inch pieces
1 small, yellow onion, peeled and chopped
1 lb. sugar snap peas
1/2 c. water
salt & pepper
In a medium skillet over medium-high heat, brown chopped bacon. Using a slotted spoon, remove bacon to a paper towel-lined plate. Add onion to the pan. Sauté onions 3 minutes or so, until they are just tender. Add peas and water to the pan. Cover and cook 5 minutes. Uncover and allow the liquid to cook almost out of the pan. Add bacon back to the skillet and remove pan from heat. Serves 4 as a side.
Raw Asparagus Caesar Salad, adapted from Serious Eats
You can also make this recipe with the sugar snap peas in place of or in addition to the asparagus called for here.
1 bunch asparagus, ends trimmed and chopped into 1/2-inch pieces
1 T. mayonnaise
1 1/2 T. red wine vinegar
2 T. freshly squeezed lemon juice, from 1 lemon
2 garlic cloves, roughly chopped
1 tsp. Dijon mustard
1 tsp. Worcestershire sauce
1 tsp. anchovy paste (or 1 anchovy filet)
6 T. extra virgin olive oil
salt & pepper
1/2 c. shaved Parmigiano-Reggiano
Combine mayonnaise, red wine vinegar, lemon juice, garlic, Dijon mustard, Worcestershire sauce and anchovy paste in a blender. Blend until smooth. Transfer to a medium bowl. Whisking constantly, add the olive oil in a thin, steady stream until incorporated. Season to taste with salt and pepper. In a medium bowl, toss the asparagus with the dressing. Transfer to a serving platter and top with the Parmigiano-Reggiano. Serves 4 as a side.