How to grow Sorghum in Australia

Where to plant

Sorghum needs full sun, warm soil and a long, hot growing season of about four to five months. It is frost tender. Once established it tolerates dry spells and heat well and can recover after drought, which makes it a good choice where summers are hot and dry.

Plant it in a block of several short rows rather than a single line, so the plants support each other in wind, and on the south side of the garden so its height does not shade other crops.

• South East Queensland and the Northern Rivers: sow from October to December.
• North Queensland: sow from September to December. Darwin: sow from September to January, with the wet season.
• Adelaide and Perth: sow from October to December. The hot, dry summers suit it, though it still needs water to fill its heads.
• Sydney and Melbourne: sow in November and December only. Melbourne is marginal and needs a hot summer to ripen the grain.
• Hobart and Canberra: not suited, as summers are too cool or short.

Choosing a variety

• Grain sorghum has compact heads of white, red or brown seed that is dried and ground into flour or cooked whole.
• Sweet sorghum, such as Sugar Drip, has juicy, sugary stalks that can be pressed and boiled down into syrup, and it also makes grain.
• Broom corn is a type with long, stiff seed head fibres used for making brooms.

How to plant

1. Wait until the soil is warm and the risk of frost is well past. Sorghum seed is slow and patchy in cool soil.
2. Dig in compost and a little complete fertiliser.
3. Sow seed about 2 to 3 cm deep and about 15 cm apart, in a block of short rows about 50 to 75 cm apart.
4. Water in and keep the soil moist until the seedlings are up, usually within a week.

Watering and feeding

Water regularly while plants are young and again from flowering until the grain fills, which is when water matters most for yield. In between, established sorghum handles dry spells well.

Feed lightly with a nitrogen-rich fertiliser or compost tea as the plants grow tall.

Pruning and care through the year

• Keep weeds down while the plants are young. Once tall, they shade out most weeds.
• Hill a little soil around the base of tall plants in windy spots to help them stand.
• Bag the seed heads with paper or mesh bags once flowering ends if birds are a problem.

Harvesting

Grain is ready about four to five months after sowing, when the seed heads have dried and the grains are hard and resist being dented with a fingernail. Cut the heads with a short length of stalk, hang them in a dry, airy place to finish drying, then rub or thresh out the grain. Fully dried grain stores for years in a sealed container.

For syrup, sweet sorghum stalks are cut once the seed heads have formed, stripped of leaves and pressed, and the juice is boiled down the same day.

Using it

Sorghum grain is gluten free. Grind it into flour for flatbreads and baking or cook the whole grain like rice or barley. Sweet sorghum juice is boiled down slowly to a dark syrup.

Do not feed sorghum leaves or regrowth to livestock without advice. All sorghum plants can produce cyanide (prussic acid), especially young or stressed regrowth after drought, frost or trampling, and grain and sweet types are among the higher-risk sorghums. Cattle and sheep are most at risk.