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.
All organisms are fitted for the habitat in which they live. Some are sufficiently flexible in their requirements that they can withstand small shifts in their environment. Others are so well fitted that they cannot withstand habitat change and will eventually fail. The extent of seasonal changes varies with latitude. Plants in temperate and sub-arctic are fitted for changing weather patterns from hot and dry to cold and wet as the calendar moves from summer into winter. Deciduous plants start growing in spring with varying degrees of rapidity and move through flowering and fruiting in summer and early autumn. Finally, some produce a magnificent display of autumn colour, but all senesce and shut down with the return of winter. Evergreen plants frequently inhabit the higher latitudes and retain their foliage. This is an energy conservation measure as they can respond more quickly when winter ends and growth restarts.
Plants respond to seasonal change by sensing alterations in daylength, spectral composition and most importantly temperature. It is known as acclimatisation (acclimation in the American literature). Falling temperatures are the most potent triggers in preparation for winter dormancy. Cold and ultimately freezing weather will seriously damage plant growth where acclimatisation has not been completed. Without preparation freezing ruptures cell membranes in leaves and stems disrupting their normal functions. These effects are measurable and used as means of quantifying plant hardiness. Membrane leakiness correlates with increased ionic concentrations when damaged leaves are placed in water and the resultant pC measured. Changes in chlorophyll fluorescent indicated damaged photosynthetic apparatus and measurable. Similarly, in some species bonding in lipid molecules alters and can be traced by mass spectroscopy. Understanding these processes and their ultimate goal which is protective dormancy underpins more accurate understanding of the natural world. It also provides information useful for breeding cold tolerant crops and garden plants.
Cold Damaged Plant
The rapidity of climate change is such that the protective mechanisms of plants and other organisms cannot respond with sufficient speed. Autumn in cool temperate regions, for example, is now extending as an increasingly warm period. This means that plants are not receiving the triggers necessary for acclimatisation in preparation for severe cold. Buds are commencing growth earlier in spring and now frequently are badly damaged by short bursts of deep cold. These buds cannot be replaced and as a consequence deciduous trees and shrubs in particular are losing capacities for survival.
This tobacco (Nicotiana tabacum) relative was first planted in the SCIence Garden in the summer of 2018. It was grown from seed by Peter Grimbly, SCI Horticulture Group member. Although normally grown as an annual, some of the SCIence Garden plants have proven to be perennial. It is also gently self-seeding across the garden. It is native to the south and southeast of Brazil and the northeast of Argentina but both the species and many cultivars of it are now grown ornamentally across Europe. Flower colour is normally white, but variants with lime green and pink through to darker red flowers are available.
Like many Nicotiana this species has an attractive floral scent in the evening and through the night. The major component of the scent is 1.8-cineole. This constituent has been shown to be a chemical synapomorphy for the particular section of the genus Nicotiana that this species sits within (Raguso et al, Phytochemistry 67 (2006) 1931-1942). A synapomorphy is a shared derived character – one that all descendants and the shared single ancestor will have.
This ornamentally and olfactorily attractive plant was chosen for the SCIence Garden to represent two other (arguably less attractive) Nicotiana species.
Firstly, Nicotiana benthamiana, a tobacco species from northern Western Australia. It is widely used as a model organism in research and also for the “pharming” of monoclonal antibodies and other recombinant proteins.
In a very topical example of this technology, the North American biopharmaceutical company Medicago is currently undertaking Phase 1 clinical trials of a Covid-19 vaccine produced using their plant-based transient expression and manufacturing technology.
Secondly, Nicotiana tabacum, the cultivated tobacco which contains nicotine. This alkaloid is a potent insecticide and tobacco was formerly widely used as a pesticide.
This vivid extract from William Dallimore’s memoirs of working at Royal Botanic Gardens, Kew illustrate how tobacco was used in the late Victorian era.
“Real tobacco was used at Kew for fumigating plant houses. It was a very mixed lot that had been confiscated by excise officers, and it was said that it had been treated in some way to make it unfit for ordinary use before being issued to Kew. With the men working in the house ten men were employed on the job. After the first hour the atmosphere became unpleasant and after 1 ½ hours the first casualties occurred, some of the young gardeners had to leave the house. At the conclusion there were only the two labourers the stoker and one young gardener to leave the house, I was still about but very unhappy. Each man employed at the work, with the exception of the foreman, received one shilling extra on his week’s pay.“
After a second such fumigation event it was reported that there was a great reduction in insect pests, particularly of mealy bug and thrips, with a “good deal of mealy bug” falling to the ground dead.
Health and safety protocols have improved since the Victorian era, but the effectiveness of nicotine as an insecticide remains. From the 1980’s through the 1990’s a range of neo-nicotinoid plant protection agents were developed, with structures based on nicotine. Although extremely effective, these substances have also been shown to be harmful to beneficial insects and honey bees. Concerns over these adverse effects have led to the withdrawal of approval of outdoor use in the EU.
Imidacloprid – the first neo-nicotinoid developed
In early 2020, the European commission decided not to renew the European license for the use of Thiacloprid in plant protection, making it the fourth neo-nicotinoid excluded for use in Europe.
Where the next generation of pest control agents will come from is of vital importance to the horticulture and agriculture industries in the UK and beyond and the presence of these plants in the garden serves to highlight this.
Soil is a very precious asset whether it be in your garden or an allotment. Soil has physical and chemical properties that support its biological life. Like any asset understanding its properties is fundamental for its effective use and conservation.
Soils will contain, depending on their origin four constituents: sand, clay, silt and organic matter. Mineral soils, those derived by the weathering of rocks contain varying proportions of all four. But their organic matter content will be less than 5 percent. Above that figure and the soil is classed as organic and is derived from the deposition of decaying plants under very wet conditions forming bogs.
Essentially this anaerobic deposition produces peat which if drained yields highly fertile soils such as the Fenlands of East Anglia. Peat’s disadvantage is oxidation, steadily the organic matter breaks down, releases carbon dioxide and is lost revealing the subsoil which is probably a layer of clay.
Cracked clay soil
Mineral soils with a high sand content are free draining, warm quickly in spring and are ‘light’ land. This latter term originates from the small number of horses required for their cultivation. Consequently, sandy soils encourage early spring growth and the first crops. Their disadvantage is limited water retention and hence crops need regular watering in warm weather.
Clay soils are water retentive to the extent that they will become waterlogged during rainy periods. They are ‘heavy’ soils meaning that large teams of horses were required for their cultivation. These soils produce main season crops, especially those which are deeply rooting such as maize. But in dry weather they crack open rupturing root systems and reducing yields.
Silt soils contain very fine particles and may have originated in geological time by sedimentation in lakes and river systems. They can be highly fertile and are particularly useful for high quality field vegetable and salad crops. Because of their preponderance of fine particles silt soils ‘cap’ easily in dry weather. The sealed surface is not easily penetrated by germinating seedlings causing erratic and patchy emergence.
Soil finger test
Soil composition can be determined by two very simple tests. A finger test will identify the relative content of sand, clay and silt. Roll a small sample of moist soil between your thumb and fingers and feel the sharpness of sand particles and the relative slipperiness of clay or the very fine almost imperceptible particles of silt. For a floatation test, place a small soil sample onto the top of a jam jar filled with water. Over 24 to 48 hours the particles will sediment with the heavier sand forming the lower layer with clay and silt deposited on top. Organic matter will float on the surface of the water.
Soil floatation test
Elderflowers are in full bloom this month, both in hedgerows as well as gardens across the country. Whether they are the wild Sambucus nigra or a cultivated variety with green or black leaves they are all beautiful and useful plants.
The black leaved cultivar growing in the SCIence Garden has pink blooms, whereas the wild species has white flowers. It was purchased as ‘Black Beauty’, but is also sold as ‘Gerda’.
Sambucus nigra f. porphyrophylla ‘Black Beauty’ growing in the SCIence Garden
This cultivar, along with ‘Black Lace’ (Eva) was developed by Ken Tobutt and Jacqui Prevette at the Horticulture Research International research station at East Malling in Kent and released for sale in the horticulture trade in 2000. The leaves stay a dark purple throughout the year and the flowers have a good fragrance.
The shrub will tolerate hard pruning so is useful for smaller spaces and provides a long season of interest. The plant is also a forager’s delight, both in early summer (for the flowers) and in the autumn (for the berries).
Most commonly one may think of elderflower cordial, or perhaps even elderflower champagne, but an excellent alternative to the rose flavoured traditional “Turkish Delight” can be made - https://www.rivercottage.net/recipes/elderflower-delight. I can highly recommend it!
The chemistry of the elderflower aroma is complex. Analyses such as that in the reference below* have identified many different terpene and terpenoid components including nerol oxide, hotrienol and nonanal.
* Olfactory and Quantitative Analysis of Aroma Compounds in Elder Flower (Sambucus nigra L.) Drink Processed from Five Cultivars. Ulla Jørgensen, Merete Hansen, Lars P. Christensen, Karina Jensen, and Karl Kaack. Journal of Agricultural and Food Chemistry 2000 48 (6), 2376-2383. DOI: 10.1021/jf000005f
March in the SCIence Garden
Narcissus was the classical Greek name of a beautiful youth who became so entranced with his own reflection that he killed himself and all that was left was a flower – a Narcissus. The word is possibly derived from an ancient Iranian language. But the floral narcissi are not so self-obsessed. As a member of the Amaryllidaceae, a family known for containing biologically active alkaloids, it is no surprise to learn that they contain a potent medicinal agent.
Narcissus (and in particular this cultivar) are an excellent source of galanthamine, a drug more commonly associated with snowdrops (Galanthus spp.). Galanthamine is currently recommended for the treatment of moderate Alzheimer’s disease by the National Institute of Health and Clinical Excellence (NICE) but is very effective in earlier stages of the disease too.
Today, part of the commercial supply of this molecule comes from chemical synthesis, itself an amazing chemical achievement due to the structural complexity of the molecule, and partly from the natural product isolated from different sources across the globe. In China, Lycoris radiata is grown as a crop, in Bulgaria, Leucojum aestivum is farmed and in the UK the humble daffodil, Narcissus ‘Carlton’ is the provider.
Narcissus ‘Carlton’ growing on large scale
Agroceutical Products, was established in 2012 to commercialise the research of Trevor Walker and colleagues who developed a cost effective, reliable and scalable method for producing galanthamine by extraction from Narcissus. They discovered the “Black Mountains Effect” – the increased production of galanthamine in the narcissus when they are grown under stress conditions at 1,200 feet. With support from Innovate UK and other organisations, the process is still being developed. Whilst not a full scale commercial production process just yet, the work is ongoing. As well as providing a supply of the much needed drug, this company may be showing the Welsh farming community how to secure additional income from their land. They continue to look for partners who have suitable land over 1000 ft in elevation.
The estimated global patient population for Alzheimer’s in 2010 was 30 million. It is expected to reach 120 million by 2050. The global market for Alzheimer’s disease drugs for 2019 was US$ 2870 million.
Transferring plants between countries was a profitable source for novel commercial and garden plants until quite recently.
Potato crop: Geoff Dixon
Potatoes and tomatoes are classic examples arriving in Europe from South America during the 16th century. Substantial numbers of new plants fuelled empire expansion founding new industries such as rubber and coffee. One of the earliest functions of European botanic gardens was finding potentially valuable new crops for colonial businesses. At home selecting orchids and other exotics from imported plants brought fame and fortune for head gardeners managing the large 19th century estates such as Chatsworth. Commercially seed merchants selected by eye and feel new and improved vegetables, fruit and flowers.
The rediscovery of Mendel’s laws of inheritance brought systematic science and formalised breeding new crops and garden plants. Analysing the effects of transferring physical, chemical and biological characters identified gene numbers and their functions.
Colour range in Gladioli: Geoff Dixon
As a result, varieties with improved colourfulness, fruitfulness, yield and pest and pathogen tolerance fill seedsmen’s catalogues. Breeding increased food supplies and added colour into the gardens springing up in suburban areas as affluence increased.
Greater plant reliability and uniformity arrived with the discovery of F1 hybrids.
Hybrid Sunflowers: Geoff Dixon
Selected parental lines each with very desirable characters such as fruit colour are in-breed for several generations. Then they are crossed bringing an explosion of vigour, uniformity and reliability (known as heterosis). Saving seed from the hybrid lines does not however, perpetuate these characters; new generations come only from remaking the original cross. That is a major boon for the breeder as competitors cannot pirate their intellectual property.
Knowledge at the molecular level has unravelled still further gene structure and functioning. Tagging or marking specific genes with known properties shortens the breeding cycle adding reliability and accuracy for the breeder. Simplifying the volume of genetic material used in crosses by halving the number of chromosomes involved adds further precision and control (known as haploidisation).
Opportunities for breeding new plants increases many-fold when advantageous genes are transferred between species. Recent developments of gene-editing where tailored enzymes very precisely snip out unwanted characters and insert advantageous ones is now offering huge opportunities as a non-transgenic technology. Breeding science makes possible mitigation of climate change, reducing for example the impact of soil degradation brought about by flooding.
Flood degraded land: Geoff Dixon
One of the most beloved flowers in China (and elsewhere) this small tree was planted here in the SCIence garden to represent the Chinese UK group. It is in bloom from late winter and the bright pink flowers have a strong perfume. It is growing in the centre at the back of the main area of the garden.
There are 309 accepted species in the genus Prunus listed on the Plants of the World Online database (plantsoftheworldonline.org). The genus is distributed mainly across the Northern temperate zones but there are some tropical species.
The genus Prunus is generally defined based on a combination of characteristics which include: a solitary carpel (the structure enclosing the ovules – a combination of the ovary, style and stigma) with a terminal style, a fleshy drupe (fruit), five sepals and five petals and solid branch pith. The drupe contains a single, relatively large, hard coated seed (stone) – familiar to us in cherries, apricots, nectarines, peaches etc
This particular species, Prunus mume, originates from southern China in the area around the Yangtze River. The ‘Beni-chidori’ cultivar has been given an Award of Garden Merit by the Royal Horticultural Society.
Over 300 different cultivars of this species have been recorded in China, perhaps not surprisingly for a plant that has been domesticated for thousands of years due to its floral beauty. A recent study on the genetic architecture of floral traits across the cultivars of this species was published in Nature Communications.1
Prunus mume was introduced from China into Japan, Korea, Taiwan and Vietnam and it is now fully integrated into the cuisines of all these countries. In addition to its uses in many foodstuffs and drinks, extracts from the fruit are also widely used in traditional Chinese medicine and in the traditional medicines in Korea and Japan. Anti-bacterial, anti-oxidative, anti-inflammatory and anti-cancer properties have all been ascribed to the extract which has been used to treat tiredness, headaches, constipation and stomach disorders amongst other things. A recent review published in the Journal of Ethnopharmacology2 gathers together information from literature reports on the anti-cancer activity of Prunus mume fruit extract.
One standardised extract in particular (MK615) has shown antitumour activity against most common cancer types.
The anti-cancer activity has not been ascribed to a particular component. Compounds isolated from the extract include ursolic acid, amygdalin, prunasin, chlorogenic acid, mumefural and syringaresinol.
Like all the plants in the SCIence garden – there’s a lot more to this one than just its ornamental beauty.
1. Zhang, Q., Zhang, H., Sun, L. et al. The genetic architecture of floral traits in the woody plant Prunus mume. Nat Commun 9, 1702 (2018). https://doi.org/10.1038/s41467-018-04093-z
2. Bailly, C. Anti-cancer properties of Prunus mume extracts. J Ethnopharmacology 246, 2020, 112215. https://doi.org/10.1016/j.jep.2019.112215
Holly berries are emblematic of Christmas. Decorative wreaths containing sprays of holly boughs, bright red with berries, or sprigs set on cakes and puddings help bring seasonal cheer.
Holly is a problem for horticulturists! Male and female flowers develop separately requiring cross-pollination before fertilised berries develop. Dutch nurserymen got around this by selecting a self-fertile variety ‘J. C Van Tol’ which sets copious berries. Adding further colour in the winter garden is the variety ‘Golden King’ producing mixtures of creamy-white and green foliage. Most hollies in Great Britain are Ilex aquifolium which is a native of Northern Europe and is still found wild in the Welsh Marches. It is a flexible and valuable garden evergreen, very suitable for hedges as they form tough, prickly, impenetrable barriers.
Why plants use considerable energy to produce brightly coloured fruits is a puzzle for botanists. Co-evolution is an explanation. Bright berries attract birds which eat them, digesting the flesh and excreting the seeds. Wide seed distribution accompanied by a package of manure helps spread these plants increasing their geographical range.
Which came first, bright berries or vectoring birds? A combination is the answer. Plants with brighter berries attracted more birds spreading their seed more widely. Brighter berries are more nutritious and hence those birds which ate them were stronger and better fitted for the rigours of winter. Garden residents such as blackbirds and thrushes now thrive and survive on such natural food. Migratory species such as fieldfares travel from Scandinavia, attracted particularly by other berried treasures such as Cotoneaster.
Fleshy fruits such as those of holly or Cotoneaster are examples of some of the last energy sinks formed in the gardening year.
They draw products of photosynthesis from the manufacturing centres in leaves and accumulate sugars plus nutrients drawn up from the soil via root systems. That provides a rich diet for birds.
While digestive acids in the vector’s gut starts degrading the hard shell which surrounds the seed at the centre of the berry. Botanically that term is a misnomer since true berries, such as gooseberry fruits contain several seeds. Holly has one seed contained within a hard case encased in flesh and should be a drupe! Not a term which fits well for Christmas carols, decorations or cards!
Merry Christmas and a Prosperous New Year.
Gooseberries- true berry
At the SCI HQ in Belgrave Square, London, we have curated a beautiful garden filled with plants that represent our technical and regional interest groups. Each of these plants has a scientific significance. On World Wildlife Day, we take a look at how some of our plants are doing in March.
Cyclamen hederifolium - the ivy-leaved cyclamen. Image: SCI
Cyclamen hederifolium is included in the SCIence garden to represent the horticulture group. This beautiful pink flower has a mutualistic relationship with ants, in which the ants carry the seeds far away, ensuring no competition between young plants and the original.
Dichroa febrifuga - a hydrangea with anti-malarial properties. Image: SCI
Not yet flowering, D. febrifuga is a traditional Chinese herbal medicine that is used for treatment of malaria. It contains the alkaloids febrifugine and isofebrifugine which are thought to be responsible for it’s anti-malaria properties.
Fatsia japonica - the paper plant. Image: SCI
F. japonica is also known as the glossy-leaved paper plant and is native to Japan, southern Korea and Taiwan. This plant represents our materials group.
Rosmarinus officinalis aka rosemary - a herb with many uses from culinary to chemical. Image: SCI
Rosemary is a common herb that originates in the Mediterranean. It has many uses, including as a herb for cooking and fragrance. One of it’s more scientific uses is as a supply of lucrative useful phytochemicals such as camphor and rosemarinic acid.
Prunus mume ‘Beni-chidori’ - a Chinese ornamental flower. Image: SCI
The Prunus mume tree is a beautiful ornamental tree that has significance in East Asian culture. It has a wide variety of applications, from medicinal to beverages, and can been seen in many pieces of art. This plant is in the SCIence garden to represent our Chinese Group UK.
Pieris japonica - the Dwarf-Lilly-of-the-Valley-Shrub. Image: SCI
The Pieris japonica ree has Asian origins, and represents our Agrisciences group. The leaves contain diterpenoids which inhibit the activity of feeding pests, such as insects.
Pulmonaria ‘Blue Ensign’ - lungwort. Image: SCI
The lungwort has been used since the Middle Ages as a medicinal herb to treat chest or lung diseases. It is an example of the use of the doctrine of signatures - where doctors believed that if a plant resembled a body, it could be used to treat illness in that body part.
Euphorbia amygdaloides - the wood spruce. Image:SCI
Euphorbia amygdaloides is planted to represent our Materials Chemistry group. It has a waxy feel, and has potential to be used as an alternative to latex.
Erysimum ‘Bowles Mauve’ - a flowering plant in the cabbage family. Image: SCI
The Erysimum ‘Bowles Mauve’ is a member of the cabbage family (Brassicaceae). This plant was used to make the first synthetic dye, Mauvine, when SCI founding member William Perkin discovered in in 1858.