Wednesday, 3 November 2010

How to grow broad beans

  • Broad bean plants comprise square sectioned hollow stems with leaves divided into 2-7 leaflets. 
  • These leaves are bluish-grey or green in colour. 
  • The plants usually stand 90-120cm (3 to 4ft) tall.
  • Leathery bean pods are produced once the white-and-black coloured flowers are spent. 
  • The 15 to 20cm (6 to 8 inch) long pods can be expected to contain upwards of four slightly kidney-shaped beans, light green in colour.
  • Broad beans are nitrogen fixing plants that enrich the soil in which they are planted.

How to grow Broad Beans - Varieties

  • Commonly cultivated broad beans mainly fall into two classes. 
  • Longpod broad beans feature eight beans per pod and are more durable to different climatic conditions. 
  • Windsor broad bean varieties have four or five beans per pod and are considered by some to have a finer flavour.

How to grow Broad Beans - Crop Rotation

  • Broad beans are a member of the Bean Family, and it is wise not to grow a new crop in soil that has grown a family member in the last three years.
  • Potatoes, cucumbers, corn, strawberries, celery, and summer savory all make good companion plantings. 
  • Do not plant broad beans with onions or garlic.

How to grow Broad Beans - Site and Soil

  • Broad beans grow best in a sunny spot.
  • Shelter is also beneficial. 
  • Avoid soil that waterlogs or conversely dries out rapidly
  • Broad beans don’t grow very well in a strongly acid soil preferring instead neutral to slightly alkaline soils (6.0 - 7.5 approx). 
  • If the pH (relative acidity or alkalinity) of your soil is not suited to the vegetable, then soil nutrients such as Nitrogen, Phosphorus, Potassium, iron, boron, copper, manganese and zinc start to become unavailable, leading to poor crops.
  • You can use a home soil test available in most garden centres to determine your soils ph. By taking account of the test results you can then decide how much if any amendments are required to bring the to pH of your vegetable garden soil in line.
  • The application of ground lime will be helpful in countering the acidity. Consult the pack for the application rates, as that varies between commercial products.

How to grow Broad Beans - Soil Preparation

  • For long term feeding of your crop, every 10m2 of growing area should have one wheelbarrow load of well-rotted homemade compost or farmyard animal manure spread over its surface sometime during the autumn/early winter before planting/sowing. 
  • Dig this in to a spades depth all over the proposed growing area to enrich it for your crop. 
  • Whilst digging, remove any stones and other obstacles that might obstruct roots.
  • As a rule of thumb, well-rotted manure/compost will be over six months old, and tend to be dark brown will little if any smell. You should not be able to distinguish individual pieces of straw, hay, vegetable peelings, grass etc., as it will all be rotted down.
  • A week or so before sowing the seed add a nitrogen feed to the soil. Although Broad Beans produce their own nitrogen in little nodules along the roots, this does not happen until the plants begin to grow strongly. So a little extra nitrogen at the beginning will get them off to a good start.

How to grow Broad Beans - Sowing Seed

Sowing broad bean seed directly in the soil

  • Broad beans are very frost hardy and will germinate in a soil temperature as low as 2°C (35°F). 
  • Sowing time is around late March in England. 
  • However if your soil is free draining they can also sow in early autumn when the weather is cooling down. This will give a crop about three weeks earlier than a spring sowing, but a winter-hardy variety must be used.
  • Dig out a drill in the soil to a depth of 6cm (2in) and 20cm (8in) wide. 
  • Sow the seed in two rows, one row down one side of the drill, the other row down the other side. 
  • Each bean in a row should be spaced 25cm (10in) apart from the next bean.
  • Close the drill with soil, then water well and label.
  • Create as many double rows as you like at 24in (60cm) intervals. 
  • If you haven’t much space you can always sow single rows if you like, but the double rows do provide each other with support and also improve germination. 
  • A helpful tip is to sow a few extra bean seeds at the end of some rows to be used as transplants if gaps appear.
  • Another tip to prevent gaps is to discard all seeds which display small, round holes, as these seldom germinate of if they do they produce weak plants. The small, round holes are created by seed beetle grubs
  • The expected seed germination time approx is 7-14 days. 
  • Any seed not required for sowing that year should be kept dry as it has a life expectancy of 2 years.

Sowing broad bean seed indoors

  • The other alternative is to sow the seeds in peat pots and initially grow them in a greenhouse, polytunnel or on the windowsill until all danger of frost has passed.
  • Then plant them, peat pots and all, directly into the ground, using the same spacings as described above.
  • Remember to soak the peat pots in water prior to planting so that they will quickly break down in the soil.
  • Before planting out, ensure that the soil is warm, and this is best done by covering the growing site with a sheet of clear polythene at the same time as sowing the seeds in their pots.
  • Starting the plants into growth before the frosts have finished will provide a crop earlier than sowing direct outdoors.

How to grow Broad Beans - Care and Cultivation

  • Keep the soil around the broad bean plant weed-free. Take care when weeding because the roots are easily damaged.
  • During a prolonged spell without rain (week or more) you should water gently but deeply once a week. As a rough rule of thumb apply approx 10 litres per metre squared of soil area. Carry out this watering in the morning and try to avoid splashing the leaves, watering the soil instead. Water reserves must be adequate once the bean pods start to form, or else they may end up empty.
  • At about the sixth or seventh week after seed germination and while plants are growing strongly you can apply a second application of a well balanced fertilizer. Although not essential, a further scattering of Growmore or fish blood and bone can increase the vegetables vigour and make the less susceptible to plant ills. Once scattered the fertiliser should be lightly scratched into the soils surface followed by gentle but deep watering of the soil.
  • As soon as young beans appear at the base of the plant it's time to 'pinch out' the growing tips. Go to the very top of the plant and remove the tip with two leaves attached, you can compost these or steam them as a leaf vegetable.
  • Spacing shouldn't be compromised as good airflow is essential for combating fungal disease.
  • As the plants grow you will need to stake them to prevent the fragile stems from bending or breaking and pods being damaged. 
  • Stake after the seedlings are up and use anything from pea sticks to bamboo with string to support the plant.
  • Dwarf varieties will need less space and less staking and are well worth considering especially on windy or small sites.

How to grow Broad Beans - Pests and Diseases

A bad attack of black aphids down the stem of a plant
  • Black bean aphids and green aphids are the main pests of broad beans. 
  • They are mainly attracted to the soft and succulent tips of the shoots, but will eventually roam all over the plant sucking sap and stunting growth.
  • To discourage them simply pinch off the growing tip of each plant by one inch as soon as the first aphids are spotted. Reducing this attractiveness reduces the number of green and black bean aphids that show up. Any stragglers remaining can be sprayed with the following soapy water solution….
    • 8ml of plain washing up liquid mixed into 1 litre of water.
    • Do not use detergent or any soap containing detergent as it will burn the plants and possibly leave a residue in the soil.
    • Apply liberally to the pest using a plant mister or spray bottle.
    • It is best to use a fresh soapy mix of this each time you spray.

How to grow Broad Beans - Harvesting

  • Pick broad beans for fresh use like snap beans when seeds are about the size of a pea. 
  • Commonly broad beans are grown to maturity and used as shelled beans. 
  • Time from spring planting to harvest is from 10 to 12 weeks. 
  • Pods are ready for picking once they have reached about 15-20cm (6-8in) in length. 
  • You can let them grow longer but realise the larger the pod the less palatable the swelled beans inside will be. 
  • Once the shape of the beans starts to show through the pod then you can harvest.
  • To harvest the pods, give them a sharp twist in a downward direction away from the plant. 
  • Check back and harvest every couple of days, as regular picking will force your plants to keep up production for about 6 weeks.
  • Pick from the bottom up when ripe and continue to harvest frequently. 
  • Finger-thick beans can be eaten whole or wait until the pod bursts open to harvest the fully ripe beans inside.
  • When finished, cut off stems for compost and dig roots back into the soil to make use of captured nitrogen.

How to grow Broad Beans - Storage and Preservation

  • For short-term storage (one week), place unshelled beans in the salad crisper compartment of your refrigerator.
  • Broad beans are great for storing. You can dry or freeze the beans, when they will keep for twelve months.
  • To freeze, pick fresh, pod, place in a plastic bag and freeze. 
  • To dry, pick, pod and lay out the beans in a dry place. Leave beans to completely dry and store in an air tight container. These can be sown next year or rehydrated for use in cooking.

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