911±¬ÁÏ

Even under ideal conditions, sometimes more than half of runner bean flowers may fail to set bean pods. If significantly more than this fail to set pods, yield is noticeably reduced.

The following steps have been shown to help improve pod set in runner beans:

• Plant or sow runner beans into soil that has had plenty of organic matter – such as well-rotted manure – added the previous autumn, as this will aid moisture and nutrient retention around the roots
• Lime the soil before planting if the pH is below 6.5
• If sowing outdoors, wait until mid-May or June to sow when frosts have passed
• Apply a mulch of organic matter over the root area, to help conserve moisture
• Plant in a sheltered site, as this will encourage bees to visit and pollinate the plants
• Rotate the crop each year, never growing it in the same site for two years running. This will help avoid build-up of pest and disease problems
• Water in dry weather, giving 5-11 litres per sq m (1.1-2.2 gallons per 10 sq ft) twice a week throughout the cropping period
• Don’t mist or spray the flowers with water (as used to be advocated) as this has not been shown to help pod-set and may deter bees
• Take care when applying treatments for aphids or other insects on runner beans, pesticide
  A pesticide is a substance designed to kill or control the growth and behaviour of living organisms. It is also known as plant protection product and includes insecticides, fungicides, herbicides and molluscicides. The 911±¬ÁÏ doesn’t support the use of pesticides and recommends that gardeners use non-chemical control options whenever needed. will also kill bees and other pollinating insects.
• Where birds are a problem, try growing a variety with different colour flowers the following year, as this may deter them. If this does not work, consider growing a dwarf runner bean variety such as ‘Hestia’ or ‘Pickwick’, which can be netted against birds

The main causes of failure to set pods are:

• Lack of moisture at the roots
• Poor soil or growing conditions, such as acid soils below pH
  This describes how acid or alkaline soil is, and is expressed as a number between 0 and 14. Soil with a pH of 7 is neutral, an acid soil has a lower value, and an alkaline soil has a higher one. Most plants grow best in soil that’s within a specific pH range, so it’s useful to know your soil’s pH. Testing kits are easy to use and widely available in garden centres and online. 6.5, pest or disease problems, frost damage, lack of nutrients
  To grow well, plants need a wide range of nutrients in various amounts, depending on the individual plant and its stage of growth. The three key nutrients usually taken up from the soil are nitrogen, phosphorus and potassium. Plants also need carbon, oxygen and hydrogen to make carbohydrates — their main energy source. Carbon and oxygen come from the air as carbon dioxide, while hydrogen is drawn from water absorbed by the roots. Other important soil nutrients include magnesium, calcium and sulphur. Most garden soils contain enough of these nutrients to support healthy plant growth. or organic matter
• Lack of pollinating insects, perhaps because of cold, wet or windy weather
• Very hot weather, especially at night, which inhibits the germination
  Germination is the process by which a seed develops into a new plant. It starts with the seed coat absorbing water, expanding and splitting, which allows oxygen and water into the seed so its food reserves can be broken down and used by the embryo for growth. The first root (called the radicle) pushes into the soil to anchor the new plant in place and start absorbing water and nutrients. The first shoot (called the plumule) then grows upwards, out of the soil, towards the light. of pollen grains, interrupting the pollination and fruit-set process. Cropping should resume in September, once the nights start to cool down
• Nectar-robbing bumblebees. Some bumblebee species don’t have long enough tongues to reach the nectaries. They can rob the sweet nectar from the runner bean flowers by biting a hole at their base, without entering the mouth of the flower and coming into contact with the pollen-producing parts. There are usually plenty of pollinating insects that enter the flower in the normal way that this has a very limited effect on pollination and cropping
• Birds, especially house sparrows, which peck at the flowers, making them harder for insects to pollinate
• Infrequent harvesting: it is important to pick beans every two or three days, otherwise the pods will start to swell and set seed, which inhibits further pod production