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Wednesday, 22 June 2016

Seed sowing at the Botanic Garden

By Helen Roberts

Last month I met up with Penny Harms, Glasshouse Co-ordinator at the University of Bristol Botanic Garden to explore the many different plants they grow from seed. At the end of May the garden staff were nearing the end of a mammoth seed sowing frenzy in preparation for the summer ahead, but Penny explained that seed is continuously sown throughout the year depending on a particular plant’s germination requirements. 

We entered the glasshouses via the potting house, which contains a whole range of pots, growing media and tools for propagation. There are different shaped tampers for firming down compost, and numerous dibbers and widgers to gently prick out seedlings. The growing substrate typically used for most seed germinated at the Botanic Garden is a neutral peat-free compost composed mainly of composted bark, coir and composted green material. 

Penny explained the finer details of the growing media used, “This compost can be altered by sieving out larger chunks for those seeds that require a finer grade tilth, such as poppy species. Fine and medium grades can be produced depending on the particular size of the sieve pores with perlite often added to help with drainage and aeration.”

Some seeds need constant warmer temperatures

Seed sowing occurs in a number of places within the gardens. Some seed needs a dose of warmth to get germination underway and are sown in propagators in the glasshouses to ensure a stable warm temperature of about 22°C. Others can be directly sown into prepared soil and include many of the ballast seed garden species like Calendula officinalis and Amaranthus caudatus, which form a display in the gardens. Those species destined for the grain barge are grown under glass and have recently been ferried across to the barge and planted. I spied seedlings destined to make the watery journey including Avena sativa (oats) and Eruca sativa (rocket). 

Some of the Amaranthus caudatus Helen has grown from seed
at home. Photo credit: Helen Roberts.
Back in the warmth of the propagation glasshouses, Penny pointed to a number of seedlings planted at the start of April including the beautiful but very poisonous half-hardy annual Ricinus communis var. gibsonii, otherwise known as the castor oil plant. This species is grown for its dark red metallic foliage and is planted out in the hot border once all risk of frost is past. A dark purple bronze variety of this species, equally as lovely, is ‘New Zealand Purple’. 

Penny explained how to grow Ricinus communis, “The species is easy to germinate from seed, but does require a temperature of 20-25°C, so it is best grown in a propagator case in a cool greenhouse where the temperature can be kept stable. Once big enough, it is carefully pricked out and hardened off to then be planted out in June.”

Growing steadily under cover of glass are a number of seedlings destined for the hot border that act as effective border fillers. They include the lovely canary creeper, Tropaeolum peregrinum, a half-hardy annual climber with pale green stems, leaves and yellow flowers, and Tropaeolum majus ‘Black Velvet’, another half-hardy annual with beautiful almost black flowers. Other climbers sown in the glasshouses are the common but wonderfully scented varieties of Lathyrus odoratus (sweet peas). The sunny yellow flowers of Tithonia rotundifolia ‘Yellow Torch’ and Helianthus ‘Mongolian Giant’ currently growing in the glasshouses are also useful border fillers. The latter species is a giant that grows up to four metres high, making it a favourite amongst children. More delicate looking blooms also need the warmth of the glasshouses for germination, such as Digitalis lanata (Woolley Foxglove), which has woolly spikes of fawn coloured flowers with a pearlized lower lip. 

Some seed is worth the wait

Some seed germinates very quickly if conditions are right - sometimes within a week - but other seed can be extremely difficult and requires a great deal of molly-coddling in order to get germination success. Penny carefully pointed to a seedling of Cardiocrinum giganteum var. yunnanense, the Giant Yunnan Lily, which as an adult is a beast of a plant and can grow up to 2.5 metres with huge fragrant nodding creamy inflorescences. This species is normally propagated from either seed or by bulbs and can take as long as 4 to 5 years before it flowers. It is a monocarpic species that will die after it flowers leaving offsets, which will then become subsequent plants. This is certainly a species for a patient gardener; it takes a long time to flower but it also takes a considerable time to germinate as Penny emphasised.

Blooms of the Cardiocrinum giganteum var yunnanense
- the Giant Yunnan Lily.
Photo credit: Col Ford and Natasha de Vere
[via Flicr CC licence 2.0]
“This species can be tricky to germinate,” explained Penny, “This one has taken over a year to germinate so it is quite special.”

This is a species that appeals partly due to the fantastic inflorescences, but it has freaky (and rather scary) looking seedpods that resemble vegetative heads with fangs. In my opinion, the lengthy germination and time to flowering is worth the wait. 

Tropical and subtropical plants that only survive as mature specimens in the glasshouses can be even trickier to propagate by seed. The seed from Passiflora, a large genus of mostly vines needs to be sown quickly when fresh as dried seed takes much longer to germinate. The subtropical vines of the Aristolochia species, aptly named Dutchman’s pipe, require similar treatment. Species grown at the gardens are A. labiata and A. trilobata, and have beautiful ornate blooms of about 15cm. A. labiata flowers resemble the mottling and coloration of a rooster’s comb. Although tropical and sub tropical species can be a bit trickier to grow up from seed, most species can be sown throughout the year. 

Some species do not need the cosseting of warmth and will happily germinate outside although some seedlings, like borecole (kale), are protected with wire mesh to prevent bird damage particularly from pigeons. Species that have germinated and are growing happily outside at the Garden include the mixed colours of Salvia viridus, more commonly known as the Clary Sage. This produces small spires of lovely flowering bracts loved by pollinators. These are intended for the Mediterranean beds along with the tall spires of Echium italicum, the Pale Bugloss, a beautiful pyramidal plant belonging to the Borage family and Viola arborescens, a pretty violet with large lavender coloured flowers. 

Other plants need to be sown at different times of the year and some species have enough flexibility in this that you can sow depending on when you want a plant to flower in the subsequent year. For most gardeners, autumn and spring sowing are the busy sowing months. At the Botanic Garden, for example the open faced flowers of Papaver somniferum, (Opium Poppy), are sown in the autumn.

“These poppies are treated differently to other poppy species,” said Penny, “in that they have been sown in September and will be good strong plants by the time they are planted out the following year, producing flowers earlier than if seed had been sown in the spring.”

Helen Roberts is a trained landscape architect with a background in plant sciences. She is a probationary member of the Garden Media Guild and a regular contributor to the University of Bristol Botanic Garden blog.


Wednesday, 15 June 2016

Plants and war

By Helen Roberts

For centuries plants have been closely entangled in the complexities of wars and hostilities. Shortages of food during periods of conflict are one of the most pronounced impacts on humans. Conflict can impede our ability to grow and harvest crops as well as distribute food. Restricting the movement of food is a tactic that is used to control territories and ultimately bring down enemies. 

In the 1990s, in sub-Saharan Africa, many countries suffered famine as a result of conflict and this was primarily due to the different sides using food and hunger as political tools. As well as immediate famine in those areas of active war, there were indirect impacts as people were displaced by war and could not return home to plant their crops. Even more recent examples include the siege warfare occurring in many parts of Syria where the act of starvation is used to make opposing sides submit. The devastation and suffering as a result of food shortages to humans is untold during conflict, but the ultimate survival of certain plants can be threatened too.  

Saving seeds in Svalbard

Svalbard Global Seed Vault, Norway.
Photo credit: Amber Case [via Flickr CC licence]
Seed banks - facilities that specialise in collecting and storing seeds that society has deemed worthy of cultivation - are critical in preserving and potentially restoring the plants lost as a result of war. In 2015, researchers made the first ever withdrawal of 38,000 seed samples from such a bank in order to rebuild a seed collection to replace one lost to the conflict in Syria. 

In 2012, when war reached Aleppo, Syria, researchers from the International Center for Agriculture Research in the Dry Areas (ICARDA) shipped seeds representing 87% of their collection to the Svalbard Global Seed Vault in Norway (a subsequent blog will follow on this unique seed bank facility). The remaining seed was shipped out to other international seed banks. The ICARDA facility in Aleppo hosted seed from 150,000 specimens of significant agricultural importance from the Fertile Crescent - the birthplace of agriculture. Many of the plant varieties do not exist in the wild any more, including unique landraces and wild relatives of cereals, legumes and forages and are only represented in seed banks. 

Having fled Aleppo, ICARDA researchers, now in Terbol, Lebanon, have withdrawn some of this seed from Svalbard in order to recreate the collection lost in the war torn city of Aleppo. Seed was also sent to another ICARDA facility in Morocco. The seeds will be planted and allowed to germinate, grown up and seed collected and sent back to Svalbard to continue the loop of important seed conversation and diversity. At the facilities in Lebanon and Morocco, agricultural research will continue on the seed samples with germplasm being distributed worldwide to plant breeders. 

Russian scientists protect seeds with their lives

It is not the first time that scientists have battled for seed survival. Russian scientists during the Second World War were so desperate in their unerring determination to protect an internationally important seed bank from devastation that lives were lost. The man in charge of the collection was Nikolai Vavilov, a Soviet botanist and geneticist most famous for his work on the evolution of domesticated plants. As a child, he had witnessed first hand the horror of food shortages and this spurred him on to a follow a career in the plant sciences concentrating on plant breeding in order to help combat famine in Russia. He has long been considered the founder of modern seed banks. 

Unfortunately, Stalin who foolishly sought short-term solutions to Russia’s problem of famine, did not support his work. Vavilov fell from favour and whilst on a plant collecting expedition in the Carpathian Mountains was taken and incarcerated, slowly dying in prison of starvation in 1943. Vavilov’s vast seed bank survived the 872-day Siege of Leningrad. Dedicated scientists bent on protecting this valuable collection, barricaded themselves into the seed bank building and guarded it against looting. Sadly, they succumbed to either starvation or disease. This was an ironic tragedy considering they refused to eat any of the seed they were so intent on protecting. 

Plant-based resources in short supply

Not only does conflict cause basic food shortages and threaten plant species survival but it can affect the availability of important plant-based resources. Commodities such as rubber, coal, paper, timber, drugs, cotton and hemp, all derived from plants, have played a key part in conflicts. Of course, control of these critical resources has also propelled countries into war, including tea, spices, salt, grain, flour, bread, sugar and rice. 

One of the many 'Dig for Victory' posters
of the Second World War.
War also pushes the agricultural and manufacturing boundaries in the production of food and plant materials. One major commodity during the Second World War of vital importance was rubber. Natural rubber supplies from the plantations of Southeast Asia were severed at the start of the war and American forces were faced with the loss of a hugely important resource even though rubber had been stockpiled in the years preceding the war. With the fall of Singapore and the Dutch East Indies in 1942, rubber exports came to a complete standstill. The Americans invested heavily into developing synthetic rubber, but one of the twentieth century’s greatest ethnobotanists, Professor Richard Evans Schultes, was sent into the remote Amazon basin to hunt for wild rubber. For Schultes, this resulted in 12 years of exploratory research deep within the rainforest. 

People in Britain were growing their own to combat food shortages during the Second World War - spurred by iconic posters emblazoned with the words ‘Dig for Victory’. A staggering 1.4 million people dug up their gardens and lawns to grow vegetables and fruit in Britain. It was similarly successful in the US - by May 1943, 100 acres of land in the Portland area of Oregon was being cultivated by just children!

Plants used to commemorate lives lost

During and after conflict, many plants can hold particular meanings for people. The flowers of certain plants are commonly seen as peaceful elements imbuing a sense of calm and many plants are closely associated with the recognition and commemoration of those who have fallen in wars. The red poppy is one of the most emotive and unforgettable flowers because of war. A symbol of remembrance and hope, and worn by millions of people to remember those who have fallen in battle. The idea of using the poppies stemmed from one of the world’s truly poignant poems, ‘In Flanders Fields’ and is now inextricably entwined with the memory or war. It represents a powerful symbol of our relationship with a plant during and after conflict.

Helen Roberts is a trained landscape architect with a background in plant sciences. She is a probationary member of the Garden Media Guild and a regular contributor to the University of Bristol Botanic Garden blog.


Sources:


  1. Seed bank aims to protect world's agricultural inheritance from Syria war. (2016). The Guardian. <http://www.theguardian.com/world/2016/feb/24/seed-bank-aims-to-protect-worlds-agricultural-inheritance-from-syria-war>
  2. ICARDA’s update on its seed retrival from Svalbard <http://www.icarda.org/update/icarda’s-seed-retrieval-mission-svalbard-seed-vault#sthash.5nrDjLb8.dpbs>
  3. Richard D. Bardgett. (2016). Earth Matters: How Soil Underlies Civilization.  Oxford: Oxford University Press.
  4. Wade Davis. (1996). One River: Science, Adventure and Hallucinogenics in the Amazon Basin. London: Simon & Schuster Ltd. 
  5. Kathy Willis & Carolyn Fry. (2014). Plants: From Roots to Riches. London: John Murray.