Gadenin日本語Get the appThe crop that stops and waits
The thing that separates sorghum from every other cereal in a home garden is what it does when water runs out. Corn in the same conditions rolls its leaves, aborts kernels and is finished. Sorghum rolls its leaves too, shuts its stomata, effectively halts growth, and sits. It can hold that state for two or three weeks. When rain comes it resumes from where it stopped, pushes new leaf, and goes on to head. This is not damage you are watching, it is a strategy, and the single most common mistake with sorghum is treating a drought pause as an emergency and drowning the crop in response.
The practical rule that follows: if the leaves are rolled in the afternoon heat but flat again by morning, the plant is fine and needs nothing. If the leaves are still rolled at dawn, the crop has genuinely run out and it is time to water. That morning check takes ten seconds and will save you most of the water you would otherwise put on this crop.
The one point in the season where the waiting strategy costs you is the two or three weeks around heading and flowering. Water stress there directly reduces how much grain sets, and the plant cannot make it up afterwards. If you can only water sorghum once all summer, do it when the heads are emerging from the boot.
| What you see | When you see it | What to do |
|---|---|---|
| Leaves rolled tight | Afternoon only, flat by dawn | Nothing. This is normal heat response |
| Leaves rolled at dawn | Any stage | Water deeply, 1 in (2.5 cm) or more |
| Lower leaves firing off brown | Mid-season, dry spell | Normal shedding. Do not feed |
| Growth stalled, color good | Dry spell | Wait. It will resume with rain |
| Heads emerging from the boot | Late summer | Water now regardless of leaf signs |
Nitrogen: enough to fill a head, not enough to fell the stalk
Sorghum responds well to nitrogen and then, past a point, responds badly. Overfed plants put the extra into height and soft stem tissue rather than into grain, and a tall soft stalk is a stalk that goes over in the first summer storm. Grain types are the ones to be careful with. Syrup cane can take a little more, because there you are actively growing stem, but even there a stand that has been pushed hard produces watery juice rather than sweet juice.
Split the feeding rather than giving it all at sowing. A moderate dose worked into the bed before sowing carries the crop to knee height, and a side-dressing at that point is what fills the head. After the heads have emerged, stop feeding entirely; nitrogen applied late delays maturity and leaves you with a crop still green when the frost arrives.
Watch the color of the lower leaves as your gauge. A crop that is genuinely short of nitrogen yellows from the bottom up, and the yellowing runs up the midrib in a V. That is worth correcting. Lower leaves that simply dry off and go brown during a dry spell are the plant deliberately shedding them to save water, and feeding in response to that does nothing useful.
| Stage | Feeding | Reason |
|---|---|---|
| Before sowing | Moderate balanced feed worked in | Carries the crop to knee height |
| Knee high, 18-24 in (45-60 cm) | Side-dress nitrogen along the row | This is what fills the seed head |
| Boot stage, head still enclosed | Water only, no feed | Late nitrogen delays maturity |
| After heading | Nothing | Feeding now softens stalks and invites lodging |
Tillers, suckers and whether to remove them
Sorghum tillers freely, sending up extra shoots from the base, and how you treat them depends on what you want. In a grain crop, tillers are usually welcome: they head a little later than the main stalk but they do head, and in a thin stand they are the plant filling in the space you failed to. Leave them. The only reason to remove tillers from a grain block is if the stand is already thick and the tillers are producing small heads that ripen out of step with the rest, which makes harvesting a nuisance.
In a syrup crop, tillers are a straight loss and should be cut off at ground level as soon as you can identify them. Every tiller draws sugar that would otherwise go into the main cane, and a stool that has thrown three side shoots gives you four thin canes instead of one good one. Go through the block once at knee height and once again a fortnight later; after that the plant has stopped tillering and you can leave it alone.
Broom types sit in between. A modest number of tillers gives you more heads, which is the point, but heads from late tillers are shorter and softer and are not worth much. Remove anything that appears after the main stalk has reached chest height.
Keeping a tall stand upright
A twelve-foot (3.7 m) syrup cane carrying a wet head in a storm is a considerable lever, and sorghum lodging is usually a root-lodging problem rather than a snapped stem. The stalk itself is strong; the crown pivots in soft, wet ground. That means the defenses are all about the root zone and the block as a whole rather than about propping individual plants.
Hill soil up around the base of tall types twice, once at knee height and once at chest height, drawing two or three inches (5-8 cm) of soil into a ridge along the row. Sorghum will root into that ridge and it broadens the base considerably. Beyond that, grow tall types in a block rather than a row, keep the nitrogen restrained, and avoid heavy watering once the heads have filled, when the crop is at its top-heavy worst.
- Hill at knee height Draw soil from between the rows up against the stems to make a low ridge. Do not bury any leaves. This is the single most effective anti-lodging step and takes a few minutes per row.
- Hill again at chest height Repeat with another two inches (5 cm) of soil. By now the plant has thrown out crown roots into the first ridge and will root into this one too, giving it a much wider anchor.
- Run a line for the tallest types For syrup and broom stands over eight feet (2.4 m), drive a stake at each end of the row and run twine down both sides at chest height. It does not hold individual plants, it stops the whole row folding sideways as a unit.
- Stop watering once the grain is dented The crop no longer needs it and wet ground under a heavy head is precisely how a stand goes flat. Let the soil firm up through the ripening period.
What to record through the season
Write down the date the heads first pushed clear of the boot on each block. That date is the anchor for everything downstream: harvest for grain runs roughly 35 to 45 days after it, and it also tells you whether the season is running ahead or behind. Note the number of days between the first head emerging and the last, because a spread of more than a week means an uneven stand and points back at sowing conditions.
Record the dates you watered and, more usefully, the dates you decided not to water after a dawn leaf check. Over two seasons that record shows you how much drought this crop will genuinely absorb in your soil, which is knowledge that no general guide can give you. Note the height at which any lodging happened and which row it started in, since lodging almost always starts on the windward edge and tells you where a windbreak would pay.