Sorghum: The Old-New Everything Crop

This resilient and versatile plant is experiencing a surge in demand and production as farmers and consumers rediscover its worth.

Sorghum stacks

At harvest, the leaves are allowed to dry before pressing. The canes are bundled and removed from the field, either directly to be pressed, or stored indoors in a frost-free location, where they may safely be held for several weeks.

Photo by Randel A. Agrella

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Sorghum is an old crop that is suddenly new again. A tall grass, looking similar to corn, reaching above 10 feet in height, sorghum is a botanical powerhouse that today's small farmers and gardeners are rediscovering. The plant yields grain, sweet syrup, forage for livestock, and is an emerging source for biofuel. Sorghum even tolerates drought and heat that send corn packing. What crop offers us more?

Sorghums comprise about 20 grass species, mostly hailing from sub-Saharan Africa. Sorghum bicolor is the predominant commercial species, coming in two main types: grain sorghum or milo, grown for human and livestock consumption, and sweet sorghum, whose sweet juice is extracted and boiled down into a thick syrup, variously called molasses or just “sorghum.”

In recent decades, a third category has been added: hybrid types, collectively referred to as Sudan grass, are grown for their green leaves and stems, which are used as pasture, hay and silage. Finally, broom corn has been grown for centuries for its finely-branched seed heads. These, when trimmed and the seeds removed, provide excellent raw material for making brooms.

A grain crop widely grown in the South and Midwest for many years, sorghum has been under-utilized elsewhere in the country. Worldwide, however, milo has never ceased to be a major human food, mainly in areas like Africa and India, where the weather is often too hot or too dry to grow corn. There, sorghum is the staple grain of about a half-billion people, who make it into couscous, use it as a cereal, grind and bake into unleavened bread, or ferment it into alcoholic beverages.

Sorghum used to be very widely produced in the days when most Americans lived on family farms. The crop, brought from Africa as early as the 1600s, only rose to prominence in the 1850s, when sorghum presses became available. At that time, Isaac Hedges called it “the Northern Sugar Plant,” because of its high content of sucrose and fructose. The first known named variety was ‘Black Amber’, introduced from China via France, and still available.

Though today sorghum is regarded as mainly a Southern crop, it first caught on in the Midwest. Annual production of syrup reached 24 million gallons by the 1880s. It was only in the 1890s that the South became the dominant sorghum-growing region. Production then slowly dwindled over the decades, with the syrup becoming mainly a regional crop. This despite the fact that the syrup is second only to honey as a wholesome sweetener that can be produced with practicality on the small farm.

Choosing Varieties

There are a few varieties that may be useful for both syrup and grain production, such as ‘White African’, but usually it's a matter of “either-or” when choosing a variety. That's because most of the sweet types have dark seeds, commonly ranging from red to almost black, which are usually loaded with tannin, rendering them unpalatable or worse. Grain types are usually light seeded or white.

Other considerations pertain to length of the growing season: Sorghums tend to be 90-120 day crops, meaning 90-120 days of heat, not just frost-free days. Sorghum needs warm conditions to germinate and to grow; it just sits in cool weather. Nevertheless it can be grown as far north as Wisconsin. Adventuresome northern growers should start out with ‘Red's Red Sweet’ or Cana Dulce (from higher elevations of the Southwest), before trying longer-season types. Would-be growers in the Southeast can count on pretty much any widely available variety. Finally, for forage use, Piper Sudan grass is a standard.

Growing Sorghum

Sorghum's needs are simple and few. It's a heat-loving plant, requiring warm soil to germinate promptly and to thrive. It does need water, but is very drought tolerant, far exceeding corn in this respect. Like any plant producing a lot of biomass, sorghum needs plenty of nitrogen. Finally, sorghum needs a fairly long season, at least for syrup or seed production.

Seeds are sown directly where they are to grow. Sowing should be delayed until a soil temperature of 65 degrees F is reached; emergence is rapid in soils above 70 degrees F. Clay soils in full sun are preferred; a somewhat alkaline soil is fine. Seed is sown from 3/4" deep in heavy soils to up to 2" deep in very light ones. Row spacing depends mainly upon how weeds are to be controlled; if mulched, up to 2-3 plants per square foot is workable. A typical spacing is 3-4 plants per foot of row, with rows spaced 2 feet apart.

Within a very few days, the threadlike seedlings emerge. Underground, a primary root first develops, providing the seedling with support and moisture. This is followed by the finely-branched secondary roots, extending a yard from the plant and up to 6 feet in depth.

Growth is divided into vegetative and reproductive phases. For a mere 30 days or so, depending upon variety and weather conditions, the plant is doing nothing more than unfurling one flat, strap-shaped leaf after another. Each plant may initiate as few as 8 to as many as 22 of the waxy-surfaced leaves. At this stage the stem tends to be fairly short and the plant compact.

The reproductive cycle begins with initiation of flower buds. Suddenly the plant's appearance changes. Stems stretch out, and the compact seedling habit becomes open and rangy, as each leaf is fully deployed to catch the sun's life-giving energy. Finally at about 30-45 days the developing inflorescence becomes visible. This is known as “booting.” At the boot stage, a supplemental dose of nitrogen is often applied, at least for grain (seed) production. At around 60 days from planting, the flower stem has reached its maximum height and the small flower cluster begins blooming, a process which extends over a number of days. The grain is produced at the top of the plant, where a corn plant would have a tassel. Full maturity is reached, perhaps at 90 or so days, again depending upon weather and variety.

In much of the country, sorghum requires little to no supplemental irrigation; the enormous root system masterfully exploits whatever water and nutrient resources are available. But if the leaves curl up along their longitudinal axis, the plant is showing drought stress. Originating as sorghum does from semi-arid regions, the plants really can tolerate such stress quite well. However, little growth is made under such conditions, so, where the season is uncomfortably short, it's best to irrigate the plants if this point is reached.

Numerous pest species can affect sorghum; most are not host-specific and did not co-evolve with sorghum, meaning they tend to be only occasional or transient problems. The list of potential pests is nevertheless formidable: wire worms, corn ear worm, spider mites, army worms, midges, borers, aphids: all cause occasional damage. In my experience, over several years in the Ozarks, no pest caused significant harm, but that might not be the case in regions that grow a lot of sorghum, especially where it's grown as large monocultural stands.

Birds are the exception. They know when grain sorghum is ripe, they have nothing better to do than help themselves, and they have all day to do it. The usual remedies are worth trying: noisemakers, scarecrows, or netting. Prompt harvesting is probably the best approach, combined with planting extra to compensate. Unrestricted, I've seen birds purloin about a quarter of my harvest!

Against weeds, sorghum nearly looks after itself. I try to eliminate weeds by hoeing or hand-pulling when the plants are a few inches high; after that, rapid growth and the plants' production of sorgoleone, a weed suppressant, seems to eliminate any further need for weed control, at least in my often weedy Ozark gardens.

Lodging can be problematic with sorghum, and in my experience often is. Lodging simply means the plants tip over; it happens fairly often with corn as well. My sorghum is apt to lodge when prolonged wind comes in early fall frequently accompanied with rain; the combination often proves too much for sorghum's wiry stems and whole rows bend over. As with corn, the plants usually curl back upward and the actual crop isn't much affected, unless machine harvesting was in the program; then lodging can be a disaster.

Harvest

Whether grown for grain or syrup production, harvest comes at about the same stage of growth.

For grain production, the plants are left in place until the seeds reach full maturity. Individual kernels will be firm, not the least bit juicy when popped between finger and thumb. However, in much of the country, they may never quite dry-down on the plants — early autumn rains often begin and the plants just keep growing until frost kills them. It's best to harvest the mature seed heads before frost. Even in the Deep South, which has the longest growing season in the country, the seed heads or whole plants are harvested and dried under cover, sometimes with the addition of heat. Small amounts of grain are threshed by hand, usually fairly easily; for larger quantities machine threshing is preferred. I have threshed and winnowed 30 pounds in an hour or two by feeding whole, dried seed heads into a chipper-shredder and then winnowing away the chaff with a leaf-blower.

For syrup production, seed heads may be removed when in the “milk” stage (when the majority of seeds release milky — not clear — fluid when popped between finger and thumb). University sources recommend removal of the seed heads, with harvest of the stalks 2-3 week later, at which time the plants will have developed their highest sugar content. But the plants may simply be harvested when the seed is mature, and the seed heads removed immediately prior to pressing. This at least is the usual practice among Amish growers in our area of Missouri.

Traditionally, the leaves, which grow in two parallel rows running the entire height of the plant, are removed by sharply whacking them with two hefty sticks — they are quite brittle where they join the stalk. However, more recent university recommendations indicate this time-consuming practice may be skipped, so long as the leaves are allowed to dry before pressing. (Green leaves fed into the press make the syrup bitter.) The canes in any case are bundled and removed from the field, either directly to be pressed, or stored indoors in a frost-free location, where they may safely be held for several weeks.

Pressing & Boiling

Once the canes are harvested, the sweet juice must be squeezed from them, collected, then boiled down for syrup.

The best tool for pressing the canes was and is the sorghum press. Today, in areas where the crop was once prominent, sorghum presses sometimes sell at farm auctions for next to nothing. Not many farmers use them anymore, although the principle is simple enough: Stripped canes are fed through the press, which thoroughly crushes them. The crushed stems, sometimes called bagasse, after an analogous by-product of sugar production in the tropics, can be fed to livestock, which relish them.

The dark-green juice is then collected in a bucket or barrel. Traditional boiling pans are also still to be found. These usually consist of a large vessel divided into sections, each section to accommodate a particular stage of the boiling process. The freshly-pressed juice would be fed into the first compartment and boiled while additional pressing was done. The boiled product would be moved down the line to accommodate a new batch of fresh juice. A separate compartment would be available for each of several stages, with the very concentrated syrup, by this stage a rich dark brown in color, collecting in the last compartment. But small quantities of juice can be batch-processed from start to finish in a single pot or kettle. Care must be taken toward the end of the process: if removed too soon, the syrup will be thin; too late, and it may have a strong flavor.

And what does cane syrup taste like? The golden- to dark-brown syrup is sweet, vaguely earthy, and complex. I’ll just say it's heavenly on biscuits, cornbread and pancakes. It's also used in place of molasses, honey, or sugar in baking.

Yield

For grain production, yields even in the far north (Wisconsin) have approached 5000 pounds per acre, which translates to a pound per 8-10 square feet. Yields are higher where average summer temperatures are warmer. For syrup, a ton of canes yields 10-15 gallons of syrup, or 200-300 gallons per acre. That translates to a gallon per 200 pounds of canes, which can be grown on 200-300 square feet of ground. Happily, such statistics put very small-scale syrup production within reach of many home gardeners. The drawback is that it might not be economical to press such a small amount. This problem could be overcome by cooperative ownership of a sorghum press, or simply by purchasing one cheaply and offering custom pressing for friends and neighbors.

Forage & Fodder

Besides feeding the bagasse to livestock, sorghum has been grown expressly for livestock feed; indeed in the United States, about 90 percent of all sorghum is grown for this purpose. Milo is often seen in prepared chicken scratch, sorghum plots may be grazed, and the plants may be cut for hay or silage. Sudan grass provides quick temporary pasture, and is very useful in hot weather, when cool-season grasses are dormant. It can be grazed in as little as 5-6 weeks after planting.

A note of caution: Sorghum must be handled carefully when used as livestock feed. Young shoots and damaged plants may contain elevated levels of prussic acid, a cyanide compound. Ensiling or field-drying for hay causes the substance to evaporate. Never feed merely wilted sorghum to stock, and learn more about correct handling of the crop before harvesting sorghum for feed.

Biofuel

The recent upsurge of interest in renewable crops for biofuel production has inevitably included sorghum. Paradoxically, the main thrust has been not so much toward ethanol production from the sweet sap, but rather the use of overall biomass production for synthetic gas and biodeisel. The crop produces 20-50 tons of biomass per acre. In drier and hotter areas, sorghum can exceed corn in biomass per acre of ground, and, since sorghum requires less nitrogen inputs, its efficiency can be higher than that of corn.

Brooms and biofuel aside, sorghum syrup is enjoying a resurgence. What used to be strictly a home-produced delicacy, rarely available commercially in the 1980s, is now gradually finding its way onto retail shelves. The increasing demand has fueled an increase in acreage planted to sweet sorghum. By 1975, the U.S. Agricultural Census reported a mere 2400 acres producing less than 400,000 gallons of syrup annually. But 25,000 to 30,000 acres are planted for syrup today, and the product is acquiring a new following. Sorghum, the old-new crop, is back!


Randel A. Agrella lives, works and gardens in central Connecticut, where he also manages historic Comstock, Ferre and Co. An heirloom seed saver since 1982, he offers heirloom plants in season on his website, www.abundantacres.net. His articles have appeared in Heirloom Gardener since 2005.