Hello, UNDERSOW!
Maximizing your crop production and profits by undersowing.
Undersowing isn’t a type of farming. It’s a specific technique used in various farming practices. Let’s start at the beginning. MULTIPLE CROPPING (aka multicropping) is the growing of two or more crops — not necessarily cash crops — on the same piece of land during one growing season. This can be done successionally, one crop going into the ground after the other is harvested out. When multiple crops are grown simultaneously, this is specifically called “intercropping” or “interseeding.” Intercropping can be done with multiple cash crops or cash and beneficial crops.
COMPANION CROPPING (planting) refers to the joint growing of crops based on the benefits one will provide the other, which range from the suppression of weeds or suppling of nitrogen (via nitrogen fixation) to the attracting of pollinators or the disruption of insect pests. The companion crop is usually of little cash value or at least less than the primary crop.
Simultaneous crops aren’t always planted at the same time. Undersowing (sometimes called “overseeding”) is the planting of one crop into an established crop and can be done in many intercropping situations. You can overseed when companion planting or when inserting a green manure or cover crop into your rotation. However, it’s fundamental in relay cropping — when a cash crop (the relay crop) is planted into an established cash crop (which I call the initial crop). The two crops (again, each a source of revenue) are subsequently managed and harvested separately.
Undersowing does more than maximize the use of space. The close spacing and tight crop management leads to
better weed control, while the enhanced coverage of and increased concentration of roots in the soil decreases soil erosion and increases water infiltration. Additionally, effective undersowing plantings can lead to better crop productivity, reduced input costs, and better crop resiliency during adverse conditions.
HOW DOES YOUR VEGETABLE GARDEN GROW?
Though most associated with field crops, undersowing is being done in raised bed and other intensive vegetable gardening situations when space is at a premium. Different crops share space as they are sown, grow and harvested at overlapping times.
Plants will share space successfully when they: occupy complementary portions of the aboveground space and root zone (i.e., when you pair the large with slight or fruit and root crops), mature at different times and don’t compete for similar nutrients.
Corn, tomato, pepper, eggplant and summer squash have long seasons in the ground and require space be left for their future expansion at planting time; so do garden flowers such as globe amaranth, celosia, cosmos, statice and sunflower. Vining plants such as cucumber, melon, winter squash and sweet potato also require space be left for them to run.
All of this extra space (between and within rows) can be used for the production of rapidly grown, comparatively diminutive, somewhat shade tolerant crops such as heading lettuce, scallion, radish, beet and carrot (especially for baby production) and any favorite cut-andcome-again green such as arugula, leaf lettuce or spinach. These same crops can be planted in the fall garden; this time under the canopy of brassicas including broccoli, cabbage, cauliflower and kale.
Perhaps you are familiar with a well-known example of with extremely “companionable” components, namely the Three Sisters. In it, corn provides the physical support for vining beans, beans fix nitrogen to help feed the corn and a winter squash shades the ground, inhibiting weeds and water evaporation from the soil. It’s a long-established, excellent example of space maximization with all crops reaping the benefits of close quarters.
PARTNERS WITH POSSIBILITIES
Undersowing also offers the option to introduce crops other than vegetables and flowers into your garden beds, which bring with them a variety of different possibilities. Field crops grown on a small scale can serve many purposes. You can incorporate them into the soil as a soil-improving crop (i.e., cover crop or green manure). Undersowing is a particularly desirable practice with green manures as it allows you to utilize them without taking land out of production; the “manure” simply share growing time with the cash crop.
Additionally, legumes favored by bees — hairy vetch and crimson, red and white clover — can be allowed to flower and function as pollinator food sources; and grasses such as oat, winter wheat and rye can bear seed, which can be harvested for human or chicken consumption. And legumes and/or grasses can be left to stand as a hay field for cutting or pasture for animals to graze. Whether chickens or cattle, animal rotations onto vegetable production areas (during the offseason) creates a whole farm, integrated plant-and-animal system.
A major distinction for field crops is whether they are winter hardy or a winterkill (nonhardy). Winter-hardy crops will live in the ground through winter to resume growth in the spring, while those that won’t survive the cold die. Both types have their uses.
The winterkills can be planted amongst an overwintering crop to be in place in spring as soil protection; or they can be planted and then racked off an empty bed come spring, leaving the ground ready for early crops. A winterkill could be planted in a perennial produce bed (think rhubarb, asparagus, Egyptian walking onion, etc.) to compete with weeds through the summer and be a spring mulch. The winter hardy crops may offer an early pasture, honeybee food source, crop harvest or plow down (“till down”) for the spring.
Of course, crops aren’t only planted in autumn. There is really no time when you can’t undersow. A clover may be seeded into a cereal grass crop such as rye or winter wheat in late winter to early spring, ready to take over as a green manure after harvest. A spring vegetable crop can be undersown with oat or white clover, depending on your preference. And buckwheat can be sown almost anytime during the summer for a quick green manure.
KNOW YOUR OPTIONS
Common field crops used for soil improvement and/or harvesting include the following.
BUCKWHEAT: nonhardy rapid grower and fast decomposer, ideal when speed is needed
CRIMSON CLOVER: legume frequently used for weed control and easily eliminated with tillage
RED CLOVER: shade tolerant, hardy legume that partners well with large crops
DWARF WHITE CLOVER: low-growing, shade tolerant, hardy, and traffic resistant legume
SWEET CLOVER: tall legume that requires mowing
HAIRY VETCH: traffic resistant legume with rapid growth
SOYBEAN: nonhardy legume able to withstand foot traffic
OAT: nonhardy grass popular in the north as a winterkill
RYE (SECALE CEREALE): hardiest of the winter hardy (can be planted even after frost), most common winter cover crop
WINTER WHEAT: grass commonly used for production/harvesting rather than soil improvement
These crops and vegetable crops can come together in several combinations; the crops naturally dictate how you manage the undersow situation. Corn, for example, might be
undersown with oat to offer late autumn cattle grazing. Or clover for a pasture or hay production the following year. Or rye for a cover crop and a harvest next year. Or soybean for a nitrogen boost throughout its growing season, etc.
MANAGEMENT LEVEL DISCUSSIONS
Management is all-important to make undersowing successful. In all situations, weeding is important to keep the planting ground clean; remember, the undersow is a crop, too. Because the timing of growth is so important, you may need to supply both crops with moisture to keep on schedule.
Multicropping only with vegetable and flower crops is straight forward. The initial crops are planted at their normal spacing and time of year with the relays occupying the vacant space that isn’t needed until the initials increase in size, by which time the relays have been harvested out.
Field crop undersowing, however, requires more decisions be made and more observation. Are you to drill seed into the ground with a planter or broadcast it onto the soil surface? When broadcasting, increased seeding rates or racking seed in (as well as tamping for increased seed/soil contact) are often considered. The initial crop must be established prior to undersowing to minimize resource competition, so it’s often timed around four to five weeks after the first planting (or transplanting).
In a vegetable production situation, the undersown crop must be planted early enough so it’s established for survival of foot traffic related to the initial crop’s harvest. In fieldcrop-only situations, it must simply be planted before the initial’s canopy is closed.
Be sure to provide it enough time for growth for the crop to serve its purpose. Buckwheat and soybean (as a green manure) require planting about two months ahead of the first frost (which will winterkill them). On the other hand, rye, hairy vetch, winter wheat and red clover may be planted as late as 20 days before first frost day and will be ready to grow in the spring.
A final and important note about any field crop management is that crops must be tilled or mowed to prevent seed set if harvesting or self-seeding are not your objectives. Such seeds will become weeds in the future.
WINNING TEAMS
Compatibility between crops in proximity can occur in a number of ways. They could be partnered in terms of heavy and light water use, height and shade-tolerance, or heavy-feeding and nitrogen-fixing, for example. One might have a quick and relatively short life cycle, whereas the other is slower to establish and takes longer to finally mature. One might be harvested prior to winter, while the other overwinters for spring harvesting. So obviously some crops make better partners than others. Large winter squash plants can be paired with the lofty red clover and sweet clover, while root crops have a better option in dwarf white clover.
Some cash and field crop combinations are often repeated because of their success. Nightshades (peppers, tomatoes, eggplant) are often undersown with oat. Brassicas are frequently partnered with legumes, though rye is equally suitable depending on the situation. Undersowings for vining crops must be low-growing or mowable.
There can also be other benefits to plant pairings that make for good partnerships. For example, oat can be planted in spring as an undersown green manure for peas, keeping their surrounding ground cool as they prefer. And a grass such as rye that has been undersown in the autumn garden will save you from trudging (and sinking) in the rain-induced mud.
Just remember that undersowing is all about overlapping the life cycles of different plants — to everyone’s advantage!
Leah Smith is a freelance writer and home and market gardener. She works on her family’s farm in midMichigan called Nodding Thistle (certified organic 19842009, principally by Organic Growers of Michigan). A graduate of Michigan State University, she can be reached at noddingthistle@gmail.com.