Tea, thatch and early spring

Crocus appearing in the Garden.

Today as I write this the sun is shining, the birds are in full voice singing, cawing and screeching around the Garden. Bulbs are popping up, crocus are the first with daffodils a week away from carpeting the ground with yellow. Primroses are dotting grassy areas and bees are beginning to forage in the middle of the day; the minimum temperature that a bee can fly is said to be 13 degrees, so when you see one out and about you know the season is changing. (more…)

The resilient plants of the western Mediterranean

By Helen Roberts

A recent talk to the Friends by Dr Chris Thorogood on the flora of the western Mediterranean was tonic for those of us longing for warmer weather. For Chris, the western Mediterranean has always had great appeal having spent many summers teaching field courses to undergraduate students at the University of Bristol and the last five years conducting fieldwork for his new book, a field guide to the area.

“The flora of the Western Mediterranean is really special. The plants are able to grow in some fascinating but really harsh places,” explains Chris. “Because of these severe conditions, plants have evolved numerous coping mechanisms in order to survive.”

The region is extremely rich botanically, with over 10,000 different species, all of which are specially adapted to particularly taxing conditions. The area covers a huge geographical expanse incorporating the westerly Portuguese Algarve, to Italy in the east, the islands (Balearic Islands, Corsica and Sardinia) and North Africa from Morocco to Tunisia (see my post last week, which discusses these regions in more detail).

A bounty of habitats: scrubby landscapes

There is a diverse range of floral habitats in the region from the scrubby maquis to forests with wonderful understories of orchids. The bare and arid habitats are home to ‘experts’ in drought tolerance; and at the other end of the watery spectrum are the seasonal lakes where deadly predatory plants reside. Humans have shaped the flora as well through thousands of years of agriculture, which has produced a visually evocative landscape throughout the whole Mediterranean basin.

Cistus ladanifer, the common gum cistus.
Photo credit: Henry Bush [via Flickr, CC]

A habitat that we so often associate with the Mediterranean landscape is maquis, which is specific to the Mediterranean area. It is comprised of spiny sclerophyllous  (a fancy word for hard-leafed) tough vegetation, which is specially adapted to cope with severe drought. There are often small trees and shrubs dotted about, often with beautiful understories of bulbs and short-lived annuals. Many of the species are aromatic. Typical species include prickly juniper (Juniperus oxycedrus) and common gum cistus (Cistus ladanifer), both highly pungent plants that are used by the cosmetic industry for their oils.

“The smells that exude from maquis vegetation are wonderful,” exclaims Chris, “and the scent from these aromatic plants just seems to hang on your clothes long afterwards.”

Garrigue vegetation is similar to that of maquis. It differs slightly in that it is low growing in form, occurs closer to the coasts and grows on shallower soils. Due to its close proximity to the coast it is battered by winter storms and winds. The low stature of the garrigue evergreen scrub means that perennials and bulbs are highly visible. The flowering displays in spring are visually spectacular and include wild tulips, crocuses, thymes, mints, helichrysums and lavenders.

Into the woods

The native forests of the western Mediterranean form prominent landscapes occupying quite different terrain than the shrubland regions. The oak woodlands are dominated by the holm and cork oak, with a spectacular understory that offers a refuge for many animals, including the endangered Iberian lynx.

The pine forests of Pinus halepensis and Pinus pinaster occupy coasts and cliffs. Healthy habitats have a particularly distinctive flora and fauna with rarities such as the semi-parasitic Violet Limadore orchid found in the maritime pine forest of Landes in France.

Ceratonia siliqua, commonly known as the carob tree.
Photo credit: Jesus Cabrera [via Flickr, CC]  

Humans have also shaped the forest landscapes of the region to a certain degree. Traditional farming practices in the Mediterranean have created unique assemblages of plants. Olive, carob, fig and almond groves represent landscapes people often associate with the Mediterranean. No other landscape denotes the true essence of the Mediterranean like a grove of olives. The olive is engrained in the lives and culture of the people of the region. Carob groves are also stunning in their composition with the gnarly dark trunks contrasting brilliantly against the green understory. The carob, Ceratonia siliqua, is a member of the ‘peas’ (Fabaceae), the most speciose family in the Mediterranean.

Rare aquatic habitats

Most of the western Mediterranean habitats are dry and parched, but surprisingly there are some wet ecosystems too. These unusual habitats are rare and include some curious species like the carnivorous bladderworts, found in seasonal lakes, which catch insect prey using sticky hairs and trap doors.

“The aquatic habitats of the western Mediterranean are interesting because they are pretty rare,” explained Chris. “Many are only seasonal but they support a wealth of interesting species from tiny forget-me-nots, tongue orchids and the carnivorous bladderworts.”

Tough but not invincible

While the native species of the western Mediterranean might be seen as tough and indestructible in the harsh landscapes they occupy, they are extremely susceptible to invasive alien species (IAS). Chris explained that the
two most invasive plants in the region include certain species of Eucalyptus and Acacia. People assume these species are native, probably because they fit into the landscape visually and they can tolerate harsh climatic conditions. However, both these trees can alter native ecosystems and have a negative impact on biodiversity. Unfortunately, many are still planted as ornamental shrubs despite measures drawn up to prohibit the cultivation of them.

Chris explains the danger of one such exotic: “Acacia cyclops is an invasive species that is likely to become the next big invasive in the western Mediterranean. This species forms a mass of vegetation in barren landscapes due to its ability to cope with extremely dry and saline conditions. Ultimately it outcompetes native species.”

These invasive pests steal native plants’ water and change the biochemistry and microbiology of the soil. The native flora is sensitive because the western Mediterranean is exceptionally biodiverse in a relatively small area, with high levels of endemism, particularly on some of the islands. As well as the threat from IAS, there is also intense pressures on these fragile native habitats from humans due to urbanisation, afforestation, and coastal and agricultural development. Effective and timely conservation measures are vital to ensure the survival of these beautiful and botanically rich habitats before it is too late and they go into decline.

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.

Plants that work together

By Helen Roberts

As we roll into spring, gardeners eagerly collect packets of flower and vegetable seed to plant in their gardens. I have my disorganised pile of seeds ready and waiting, nestled in their respective packets, overflowing out of a tin stored on my kitchen dresser. Random seed that I have gleaned from gardens over the course of the year can be found in bags and random pockets.

Companion planting.
Photo credit: Brian Pettinger courtesy of Flickr.

My vegetable garden at home is minuscule and consists of a number of pots in the front and rear garden. I don’t own a greenhouse but use an area in my parent’s and beg ground from a friend to grow larger vegetables. Space is limited and therefore my crop is valuable. I don’t want attacks by cabbage white or carrot fly, I need to grow at different levels to maximise space and grow a wide range of small crops to give a varied meal. This has made me think more about what I can do to increase my crop productivity. I never use pesticides or herbicides in my garden and my resolve in this has been reinforced by recent press coverage over the importance of urban gardens for pollinators. I actually quite like cabbage white butterflies – my children do anyway – and they would be horrified if they knew I sprayed to rid the garden of them. Instead, I have decided to use the art of companion planting.

What is companion planting?

Companion planting is an age-old agricultural technique used for centuries across the world. It involves the idea of planting crops that are mutually beneficial to each other in order to increase productivity.

Why should gardeners companion plant?

Companion planting has a very wide number of benefits and uses:

1. Mix it up

It is best not to put all of your eggs in one basket when growing crops – grow a mix of crops rather than a monoculture so if one crop fails you have other crops as a fall back option. Moreover, a mix of crops will make it more difficult for pests to find their host plants, a hypothesis known as the ‘disruptive-crop hypothesis’.

2. Plants that give a helping hand

The other advantage is, if like me your garden is space constrained, you can plant on different levels. For example, a tall crop (such as corn) can provide a trellis support for a climbing crop (such as beans) and a ground crop (such as squash) provides shade and discourages weeds. You get three crops in a small amount of space and the companion plants provide physical advantages for the other crops.

3. Provide a home

Some plants provide shelter and shade for other plants; for example, the planting of corn can provide shade for lettuce or spinach (although most vegetable planting in this country requires as much sun as possible). Companion plants can also provide refuges for many beneficial insects.

4. Pest control

Marigolds are supposed to help keep aphids away from tomato
plants. Photo credit: Ruth Hartnup (on Flickr).

Companion planting is also supposedly helpful in pest suppression through the release of repellent chemicals. Numerous companion plants also attract beneficial insects, such as ladybirds and lacewings, which predate on crop pests and many of these insects also act as important pollinators. Some plant species are used as ‘trap-crops’ drawing the attention of pests away from the crop and acting as sacrificial plants. Companion plants also provide a visual distraction to pests. In a monoculture, pests move easily from one plant to another, but companion plants break up this assault.

Folklore or scientific fact?

It is hard to know whether some traditional planting combinations that have endured the decades are based on any sound evidence of benefits. Certainly there is plenty of information about companion planting in the popular press and gardening books, but most is not backed up by any rigorous scientific trials in the peer reviewed literature. In academic literature, experimental results investigating the use of certain companion plants are varied as to their effectiveness. Here are some examples that I have come across:

Odorous onions

I learned from my maternal grandfather to plant Allium species in amongst my carrot rows to help deter the pesky carrot fly, Psila rosae. This annoying pest feeds not only on the roots of carrots but also on other crops too including parsnip, celery, parsley and celeriac. The small 9 mm creamy white maggots cause scarring of the tap roots making them inedible and more prone to secondary rots. This year I plan to plant my carrots in amongst garlic chives, a plant similar to the onion chive and which also produces pretty white edible flowers.

It is generally thought that aromatic species deter pests by exuding repellent chemicals. Most relevant to the carrot-allium combination was a study that looked at mixed cropping of onion and carrots and the effects on pests of these crops. They found that there were reduced attacks by carrot fly compared to monocultures of both crops and that when the plants were planted together in high densities this also reduced plant pests and increased predators of carrot fly eggs. Stan Finch and his colleagues from Horticulture Research International in Warwick found no evidence that odours from aromatic plants repel or deter crop pests, suggesting that reduced attacks on host plants were a result of other mechanisms, such as simple disruptive effect.

Get a sniff of marigolds

I am not a big fan of Tagetes species, more c
ommonly known as marigolds. They just remind me of old fashioned bedding plants in staid Victorian parks, but if they ward off pests in the vegetable plot then I am willing to use them. Tagetes sp. exude a strong odour that is apparently not pleasant for plant pests. They are supposedly useful to plant with tomatoes to ward off greenfly but I have yet to find any scientific literature to support this planting combination. Again, Finch and his associates specifically found that it was not the odour of the marigolds that repelled the pests, but simply the fact that they acted as a diversion for the pests.

Setting a trap

I often grow pots of nasturtium (Tropaeolum majus) in my garden. I like the look of the flowers and especially the leaves, using them as salad garnishes and the seed to make capers. This plant is said to help attract black fly, aphids and other pests away from host plants acting as a crop trap and functioning as a sacrificial plant. There are mixed results as to whether nasturtiums really do this. One year in my garden I grew cabbage and nasturtium together and both crops were smothered in cabbage white caterpillars. The butterflies definitely did not show a preference for the Nasturtium and the caterpillars eventually obliterated both plants. Certainly there is not a wide range of recent academic literature investigating the use of nasturtiums as a companion plant. However, according to the Royal Horticultural Society (RHS), this plant is beneficial to pollinators and as I can also eat it, I plan to trial a variety known as Blue Pepe, known for its distinctive bluish leaves and bright red flowers.

The scientific literature on many companion plant combinations is mixed, but what is clear is that there are no disadvantages to using companion planting. The physical advantages of companion planting will be evident even if the other benefits are less obvious, and many companion plants can be found in the RHS’s ‘Perfect for Pollinators plant list‘. Even if you don’t get increased crop productivity, then the garden will be diverse and look beautiful too.

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:

Associate Professor Jane Mt. Pleasant 

Uvah, I. I. I. and Coaker, T. H.  Effect of mixed cropping on some insect pests of carrots and onions. Entomologia Experimentalis et Applicata 1984; 36: 159-167

Finch, S., Billiald, H. and Collier, R. H. Companion planting-do aromatic plants disrupt host-plant finding by the cabbage root fly and the onion fly more effectively than non-aromatic plants? Entomologia Experimentalis et Applicata 2003; 109: 183-195

Saving our nation’s lost landscapes

By Helen Roberts

Historic gardens are an integral part of our cultural link with landscapes; a place where we can connect with nature. They represent a form of artistic expression and illustrate snapshots of past ages, cultures and societies. For that reason alone these garden masterpieces deserve recognition and preservation. 
Often the final level of protection for many of these gardens falls to English Heritage, a registered charity, independent of government since April 2015, which essentially acts as guardians for the upkeep of some 400 historic sites. English Heritage is often seen as the last resort of protection for these sites, some of which are so special that the government has stepped in to look after them and rescue them for the nation. 
Late last year the Friends’ Lecture was given by Christopher Wedell, a former trainee of The University of Bristol Botanic Garden (21 years ago) and now senior gardens advisor to English Heritage. 
Bridge in Sheffield Park Garden.
Photo credit: ReflectedSerendipity
courtesy Flickr [CC BY-SA 2.0], via Wikimedia Commons
Christopher’s horticultural career began early; as a teenager he already expressed a keen interest in the outdoors. A stint of work at Sheffield Park in Sussex fuelled his passion for horticulture and historic landscapes and led to a degree in Horticulture at Writtle College with a final year dissertation on historic gardens. After his work at the University of Bristol Botanic Garden and Tylney Hall, Christopher obtained his Kew Diploma in Horticulture and then spent 18 months working in the famous Palm House. From Kew he went to Wisley where he eventually became superintendent under curator. When a 6-month contract offered itself at English Heritage he applied and 7 years later he is looking after 23 historic and contemporary gardens ranging from Elizabethan to contemporary in design.  
Christopher spoke in detail about the gardens under the care of English Heritage, the complexities of restoration and the many challenges the team faces when completing historic garden works. 

The importance of authenticity

The restoration of historic gardens is a difficult task in itself when there is a lack of historical information in the form of maps, descriptions and documents. Often gardens are multi-layered over time, making it difficult to know at what particular point in time to restore the garden to. 
Belsay Hall, a thirteenth century site located just north of Newcastle has magnificent Grade I listed gardens and were primarily the work of Sir Charles Monck (1779-1867). He was influenced by the Picturesque movement, which sought to create landscapes less conventionally beautiful and more naturalistic in design. The restoration of the unique Quarry Garden, a dramatic place with a special microclimate with many exotic trees and shrubs, presented English Heritage with a challenge of maintaining the correct authenticity. To achieve this, the team used a number of photographs collected over the decades to aid in the restoration process.
“Photographic and historical documents are very important in the restoration process,” explained Christopher, “and it is vital that as much historical information is collated as possible, thereby restoring the landscape at the most significant point in historical time”. 
Osborne House from the road to Swiss Cottage.
Photo credit: By Loz Pycock from London, UK
[CC BY-SA 2.0 ], via Wikimedia Commons
Sometimes, as gardens change over time, plants become over-mature and cease to provide the effect for which they were first planted. English Heritage faces a number of challenges with such restoration projects because people often develop strong attachment to these mature trees. One such example includes Sovereign Avenue at Osborne House on the Isle of Wight – the private home of Queen Victoria. The avenue was planted in 1851-1854 with two lines of alternating deciduous and coniferous trees. Over time (as expected), these trees matured, but eventually became too large and made the avenue dark and oppressive. This was not the intention of the design when planted by Prince Albert. English Heritage then faced the challenge of how to visually present this avenue with the possibility of replanting every 50 years to maintain authenticity. 

Maintaining the fabric of the garden

The fabric of a historic garden represents the context in which a garden is situated. Gardens do not simply exist as islands on their own but connect and integrate with surrounding landscapes to create cohesion and robustness, both of which are sought after qualities in designed landscapes. Often it is difficult to maintain connectedness in historic landscapes due to the simple issue of land ownership. 
One such English Heritage example is that of Audley End House, a Jacobean Mansion landscaped by Lancelot ‘Capability’ Brown and set within the rolling cou
ntryside of Essex. English Heritage has in their care the mansion and grounds itself, but also a tower located outside of the boundary of the mansion grounds some distance away and the land in between is not under English Heritage ownership. Here, English Heritage faces the difficulty of maintaining a connected landscape, as the sites are geographically distant from one another, but sit within the same landscape. Belsay Hall also faces similar challenges as the existing car park is set within the historical landscape fabric, which disrupts the harmony of the site. 

The visitor experience

It can be difficult to maintain a good visitor experience all year round in many of the English Heritage gardens. Many of the gardens are very seasonal in nature as bedding schemes took precedence over year-round interest. At Kenilworth Castle (just north of Warwick) an Elizabethan garden was created by Robert Dudley, Earl of Leicester in order to seduce Queen Elizabeth I when she was staying at the property for a mere 19 days. This garden was restored in May 2009 using advances in garden archaeology and the survival of a fascinating eyewitness description from 1575. When the garden was originally designed for a short spell of interest, English Heritage now faces the difficult task of creating a garden that is attractive to visitors throughout the year. 
To attract visitors to the gardens, many English Heritage sites hold contemporary art exhibitions, such as the one held at Belsay Hall called ‘Extraordinary Measures’ with many of the installations located in the grounds of the Hall. 
Other attractions to entice families have recently been sensitively incorporated into some historic landscapes. An imaginative wooden play structure for children has proved very popular at Witley Court near Bromsgrove with a tree house in the form of a seed pod, outdoor musical instruments and wobbly bridges, scramble nets and slides. The opening of the beach at Osborne House on the Isle of Wight has been well received with people enjoying swimming, paddling, building sandcastles and looking inside a bathing machine. With the opening of access to the beach though, English Heritage was then faced with the challenge of incorporating essential utilities, such as power and water, into a historic landscape. Other interesting plans for enhancing the visitor experience described by Christopher included the potential restoration of the unique hard tennis court at Down House, home of Charles Darwin, which would provide a great play facility for adults and children alike when visiting this historically significant place. 
“It’s really important that sites do not simply stagnate in terms of a design sense and that the gardens are able to evolve and be used imaginatively,” explained Christopher. 
Many sites have successfully integrated contemporary spaces into the gardens adding a new vitality to these historic places. A new contemporary garden was added in 2000 to the kitchen garden of Osborne House by designer Rupert Golby as part of the contemporary heritage garden project. It includes many plants with names associated with Albert and Victoria. 

The future

Christopher’s message was clear throughout the talk. These gardens need to be brought to life for current and future visitors and be places that continually thrive for decades and centuries hereinafter. 
Christopher emphasised that, “English Heritage is playing a vitally important role in looking after these sites; we are the landscape custodians helping to safeguard some of England’s most treasured historic gardens.”
The next Friends’ Lecture will be given by Nick Wray, Curator, University of Bristol Botanic Garden on 21 January 2016, Frank Theatre, Wills Physics Laboratory from 7:30pm – 9:00pm. Nick will be speaking about the ballast seed garden project. Friends are free with presentation of membership card; non-Friends will be asked for a donation (suggested £5).