Broad beans are an undemanding and valuable crop for all gardens. Probably originating in the Eastern Mediterranean and grown domestically since about 6,000BC, this plant was brought to Great Britain by the Romans.
Header image: a rich harvest of succulent broad beans for the table
Capable of tolerating most soil types and temperatures they provide successional fresh pickings from June to September. Early crops are grown from over-wintered sowings of cv Aquadulce. They are traditionally sown on All Souls Day on 2 November but milder autumns now cause too rapid germination and extension growth. Sowing is best now delayed until well into December. Juicy young broad bean seedlings offer pigeons a tasty winter snack, consequently protection with cloches or netting is vital insurance.
From late February onwards dwarf cultivars such as The Sutton or the more vigorous longer podded Meteor Vroma are used. Early cropping is promoted by growing the first batches of seedlings under protection in a glasshouse. Germinate the seed in propagating compost and grow the resultant seedlings until they have formed three to four prominent leaflets. Plant out into fertile, well-cultivated soil and protect with string or netting frameworks supported with bamboo canes to discourage bird damage.
Young broad bean plants supported by string and bamboo canes
More supporting layers will be required as the plants grow and mature. Later sowings are made directly into the vegetable garden. As the plants begin flowering remove the apical buds and about two to three leaves. This deters invasions by the black bean aphid (Aphis fabae). Winged aphids detect the lighter green of upper foliage of broad beans and navigate towards them!
Allow the pods ample time for swelling and the development of bean seeds of up to 2cm diameter before picking. Beware, however, of over-mature beans since these are flavourless and lack succulence. Broad beans have multiple benefits in the garden and for our diets. They are legumes and hence the roots enter mutually beneficial relationships with nitrogen fixing bacteria. These bacteria are naturally present in most soils. They capture atmospheric nitrogen, converting it into nitrates which the plant utilises for growth. In return, the bacteria gain sources of carbohydrates from photosynthesis.
Broad bean root carrying nodules formed around colonies of nitrogen fixing bacteria
Broad beans are pollinated by bees and other beneficial insects. They are good sources of pollen and nectar, encouraging biodiversity in the garden. Nutritionally, beans are high in protein, fibre, folate, Vitamin B and minerals such as manganese, phosphorus, magnesium and iron, therefore cultivating healthy living. Finally, they form extensive roots, improving soil structure, drainage and reserves of organic nitrogen. Truly gardeners’ friends!
Professor Geoff Dixon, author of Garden practices and their science (ISBN 978-1-138-20906-0) published by Routledge 2019.
Gardens and parks provide visual evidence of climate change. Regular observation shows us that our flowering bulbous plants are emerging, growing and flowering. Great Britain is particularly rich in long term recordings of dates of budbreak, growth and flowering of trees, shrubs and perennial herbaceous plants. Until recently, this was dismissed as ‘stamp collecting by Victorian ladies and clerics’.
The science of phenology now provides vital evidence that quantifies the scale and rapidity of climate change. Serious scientific evidence of the impact of climate change comes, for example, from an analysis of 29,500 phenological datasets. This research shows that plants and animals are responding consistently to temperature change with earlier blooming, leaf unfurling, flowering and migration. This scale of change has not been seen on Earth for the past three quarters of a million years. And this time it is happening with increased rapidity and is caused by the activities of a single species – US – humans!
Iris unguicularis (stylosa).
Changing seasonal cycles seriously affects our gardens. Fruit trees bloom earlier than previously and are potentially out of synchrony with pollinators. That results in irregular, poor fruit set and low yields. Climate change is causing increased variability in weather events. This is particularly damaging when short, very sharp periods of freezing weather coincide with precious bud bursts and shoot growth. Many early flowering trees and shrubs are incapable of replacing damaged buds, as a result a whole season’s worth of growth is lost. Damaged buds and shoots are more easily invaded by fungi which cause diseases such as dieback and rotting. Eventually valuable feature plants fail, damaging the garden’s benefits for enjoyment and relaxation.
Plant diseases caused by fungi and bacteria benefit from our increasingly milder, damper winters. Previously, cooling temperatures in the autumn and winter frosts prevented these microbes from over-wintering. Now they are surviving and thriving in the warmer conditions. This is especially the case with soil borne microbes such as those which cause clubroot of brassicas and white rot, which affects a wide range of garden crops.
Hazel (Coryllus spp.) typical wind-pollinated yellow male catkins, which produce pollen.
Can gardeners help mitigate climate change? Of course! Grow flowering plants which are bee friendly; minimise using chemical controls; ban bonfires – which are excellent sources of CO2; establish wildlife-friendly areas filled with native plants and pieces of rotting wood, and it is amazing how quickly beneficial insects, slow worms and voles will populate your garden.
Professor Geoff Dixon is the author of Garden Practices and their Science, published by Routledge 2019.