How to Grow Beans in Australia

Bean (Phaseolus vulgaris) is a frost-tender annual in the legume family, Fabaceae, grown for tender green pods and, left longer, for dried seed. It grows across Australia through the warm months, as a low bush or as a climber that repays a little vertical space. The commonest mistake is kindness: rich soil and heavy nitrogen give lush leaves and few pods, since beans supply much of their own nitrogen.

Three mistakes that matter

1. Sowing into cold, wet soil. Cold, wet soil rots bean seed, so an early sowing often leaves gaps rather than a head start. Wait for the soil to warm, and sow into moist, not soaked, ground.
2. Feeding for leaves instead of pods. Beans draw much of their own nitrogen, so rich manure and high-nitrogen feeds give soft, leafy plants that flower poorly and draw aphids. Feed lightly and lean on potassium once flowers open.
3. Leaving pods on too long. A pod left to fatten turns stringy and tough, and it signals the plant to stop making flowers. Pick young, while pods are pencil-thick and snap cleanly, and pick every few days.

When to plant

Beans are warm-season plants that germinate once the soil holds about 16°C and come up fast in warmer ground. Unlike broad beans (Vicia faba), which are an autumn and winter crop, the common bean waits for spring and the end of frost. Sow a short row every two to three weeks through the season for a steady supply rather than one flush.

At the cool end of the season, a sowing under cover gives a head start, but beans dislike disturbance, so move them out young. Check a variety's days to maturity where the season is short.

Site, soil and setup

An open, sunny bed with free-draining soil suits beans, which are not heavy feeders. Drainage and a near-neutral pH matter more than a barrowload of manure.

Beans host root bacteria that fix nitrogen (draw it from the air), and these work best in soil that is not already rich in nitrogen.

Container growing

Bush beans take happily to a large pot; climbing types can too, given a big container and a tepee. Give one bush plant a pot at least 30 cm across and about 15 L, in quality potting mix blended with compost. Compact bush varieties suit pots well: 'Provider', 'Jade', 'Royal Burgundy' and 'Goldrush' all stay low and crop over a few weeks.

• Water: keep the mix evenly moist and never bone dry; pots may need daily water in summer heat.
• Feed: lightly only, since beans make their own nitrogen. Seaweed solution at 30 mL per 9 L fortnightly, then liquid potash per label, fortnightly from first flowers.
• Position: full sun and out of strong wind, which rocks a laden tepee and bruises the pods.

Sowing Seeds

Beans are sown straight into the ground where they are to grow, because they resent having their roots disturbed.

Sowing direct

• Sow 25 to 30 mm deep, about three times the width of the seed, into warm, moist soil.
• Space bush beans 10 to 15 cm apart in rows 40 to 60 cm apart.
• Set climbing beans 15 to 20 cm apart at the foot of their support.
• Water in once, then keep the soil just moist until shoots break through, usually in 4 to 7 days in warm soil.
• Sow a few spare seeds at the row end to fill any gaps.

Starting under cover in cool zones

• Sow into deep cells or small pots three to four weeks before the last frost.
• Keep them warm and in strong light so they do not stretch and go leggy.
• Harden off (accustom seedlings to sun and wind over about a week) before planting.
• Plant out gently without breaking the root ball, once frost has passed.

Put a climbing bean's support in before you sow, so you do not spear the roots later.

Care by growth stage

Even moisture and light feeding carry a bean crop; the feed leans to potassium as flowers open, never to nitrogen. Weeks below count from sowing.

If growth stalls in poor soil, a light dose of all-purpose controlled release granular (NPK around 14-5-10) can help, though beans rarely need it.

Mulch with a few centimetres of straw once the soil is warm, to hold moisture through flowering and podding.

Companion planting

Grows well with

• Sweetcorn, which gives climbing beans a living frame and a little light shade.
• Carrot, beetroot and radish, low-rooted crops that use the ground without competing.
• Lettuce and spinach, quick leafy crops that finish before beans fill out.
• Summer savory, a low, traditional bean companion that shares the bed without crowding.

Keep apart

• Onions, garlic, leeks and chives, whose growth can check nearby beans and peas.
• Fennel, which releases compounds that slow many neighbouring crops.
• Sunflowers, tall competitors that shade a bean row and draw on the same soil.

Harvesting Pods

First pick comes about 7 to 10 weeks from sowing for bush beans, and a little later, up to 14 weeks, for climbers. Watch for pods that are firm, pencil-thick and snap cleanly, before the seeds swell and turn the pod lumpy.

• Pick every two or three days once pods start; regular picking keeps the flowers coming.
• Hold the stem and pull or snip each pod so you do not tear the plant.
• Pick in the cool of the morning, when the pods are crisp.
• Clear any over-mature pods, even onto the compost, to keep the plant productive.

Beans do not keep long once picked. Store them unwashed in a paper or perforated bag in the warmest part of the fridge for up to a week. Blanch and freeze any glut.

Steam or stir-fry young pods, or leave borlotti and other seed types on the plant to dry fully for the pantry. Dried beans are not safe eaten raw or lightly cooked. Soak them for at least five hours, then boil them briskly in fresh water for at least ten minutes. Do not rely on a slow cooker, which may not reach a high enough temperature to break down the natural toxins.

Common problems

Flowers and small pods dropping. Spells above about 32°C, hot drying winds or dry soil at flowering make beans shed their flowers and young pods.

Yellow leaves in wet ground. Beans in poorly drained, soggy soil yellow and stall because their roots need air, so raise the bed or improve drainage.

Powdery mildew. A white, dusty film on the leaves in humid weather or crowded, still air; space plants and keep water off the foliage. Read more

Mottled, puckered leaves. A yellow-green mosaic pattern with puckered new leaves suggests a mosaic virus, spread by aphids and in seed; pull badly affected plants. Read more

Pests and diseases

Bean fly (Ophiomyia phaseoli). Most common in the tropical and subtropical north, this small black fly lays in young leaves. Its maggots then tunnel the stem, and seedlings wilt or die.

Cowpea aphid (Aphis craccivora). Clusters of small dark aphids on shoot tips and pods suck sap and can carry bean mosaic viruses from plant to plant. Read more

Two-spotted mite (Tetranychus urticae). In hot, dry weather these tiny mites stipple the leaf undersides yellow and spin fine webbing, and their numbers explode after broad-spectrum sprays. Read more

Bean rust (Uromyces appendiculatus). Cool, damp weather with heavy dews suits it. Circular rusty pustules, 1 to 2 mm across with a yellow halo, appear on leaves and pods and later shed reddish-brown powder.

Common blight (Xanthomonas axonopodis pv. phaseoli). Warm, humid weather brings water-soaked, angular leaf spots and sunken pod lesions, with or without rain. It rides on seed, so clean seed and crop rotation matter most.

Prevention first

• Use fresh, healthy seed and rotate beans away from last year's bean bed.
• Space plants for airflow and water the soil, not the leaves, early in the day.
• Check shoot tips and leaf undersides weekly for aphids and mite stippling.
• Clear and bin spent plants and fallen pods, and keep the patch free of legume weeds.

Tips

1. In the subtropics and tropics, sow through the cooler, drier months to dodge bean fly and the humidity that peaks in the wet season.
2. Leave a few pods on an open-pollinated bush plant to dry fully, then save the plump seed for next season and label the variety.
3. At the crop's end, cut the plants off at ground level and leave the roots in the soil to feed the next leafy crop.