Harvesting Sorghum: Judging Grain Ripeness, Cutting Heads by Hand and Pressing Cane

Judging a grain head

Grain sorghum ripens from the top of the head downward, so the seeds at the tip are hard while the seeds at the base are still soft. Judge the crop by the bottom of the head, not the top. Squeeze a seed from the lowest branch between thumbnail and finger: if it dents and stays dented, the crop is at hard dough and is close. If your nail slides off without marking it, the grain is at physiological maturity and can come off the plant.

The reliable confirmation is the black layer. Pull a few seeds and look at the point where each attached to the head; a dark spot forms there when the plant has finished moving sugars into that seed. Once the black layer is present, nothing more is going into the grain, and everything after that point is simply drying. You can cut then and finish the drying under cover, which is often the better plan if birds have found the block or if wet weather is forecast.

Left standing to dry fully, grain sorghum takes another one to three weeks past the black layer to come down to a moisture level safe for storage. The heads should rattle when you shake them and the seeds should shatter rather than squash when you bite one. That is the point at which you can thresh and store without the grain heating in the bin.

Cutting by hand, which sorghum makes easy

The great convenience of sorghum is that the seed head sits on a bare stalk well above the topmost leaf. There is no husk to strip and no working down inside the canopy. You cut the head with six to twelve inches (15-30 cm) of stem attached, drop it in a basket, and walk on. A modest garden block is an afternoon's work with a pair of pruners.

Cut in the morning after the dew has burned off but before the heat of the day, because dry heads shatter and you will lose seed onto the ground with every knock. If the crop is fully dry and shattering as you handle it, hold a bucket or an open sack directly under each head as you cut. Whatever falls is grain you have already grown.

Once cut, the heads need air more than anything. Spread them one layer deep on a rack or hang them in bunches of five or six, stem up, somewhere dry with moving air. Heads piled in a heap while still holding any moisture will mold within days, and moldy sorghum grain is not worth trying to salvage.

1. Cut heads with a handle of stem Take six to twelve inches (15-30 cm) of stalk with each head. That stem is what you tie bunches by and what you hold while threshing, and cutting the head off flush makes both jobs awkward.
2. Dry in a single layer or hanging bunches Two to three weeks in dry moving air brings a hard-dough head down to storage dryness. Never stack heads more than one deep while they still feel cool to the hand, which is the sign of moisture still leaving.
3. Thresh by rubbing or beating Rub heads between gloved hands over a tub, or put them in a sack and beat it against a wall. Sorghum threshes free far more readily than wheat because the grain is not held in a tight hull. Most of it comes off in the first minute.
4. Winnow in a breeze Pour the threshed mixture from one container to another in front of a fan or a steady wind. The chaff carries and the grain drops. Two or three passes gives you clean grain.
5. Store cool, dry and sealed Once the grain shatters cleanly under a bite, put it in airtight containers. Sorghum keeps well for years in that condition, and considerably worse than corn if it goes in even slightly damp.

Cutting syrup cane, which is a different judgement entirely

For syrup you are harvesting the stalk, not the seed, and the sugar in that stalk peaks when the seed in the head is at hard dough to early ripe. Cut before that and the juice is thin and weakly flavored; leave it much later and the plant starts converting stem sugar into starch and the syrup will not set properly. The seed head is your gauge even though you are not keeping it.

Strip the leaves off the standing cane a few days before cutting, running a gloved hand or a dull blade downward along the stalk. Leaves left on interfere with pressing and add green flavors to the juice. Then cut the head off, and cut the cane at ground level. Press the same day if you possibly can. Cut cane loses sugar quickly, and cane left lying for three days gives noticeably less and poorer juice than cane pressed within hours.

A frost changes the arithmetic. A light frost on standing cane is survivable if you cut and press immediately, but frozen stalks sour fast and a crop caught by a hard freeze is finished. If frost is forecast and the seed is anywhere near hard dough, cut the whole block rather than gambling on another week of sugar.

Broom sorghum is cut on yet another schedule. The heads are taken while the seed is still green and the fibers are flexible, because a head left to ripen fully goes brittle and the bristles snap when the broom is bound. Cut, strip the seed off with a coarse comb, and dry the bare heads flat under light weight.

What to record at harvest

Note the number of days from head emergence to the black layer for each block. That figure is far more portable between seasons than a calendar date, and once you have it for your own garden you can predict harvest from the moment the heads appear. Record the weight or volume of clean grain against the number of plants, since yield per plant tells you whether your spacing was right in a way that total yield never does.

Write down where you lost grain and how. Shattering during cutting, birds through the last fortnight, mold in the drying rack and grain left in poorly threshed heads are the four common losses, and they call for four different fixes. Noting which one actually cost you the most is worth more than a general resolution to be more careful next year.