Roots, structural complexity in the garden and worries about the monarch butterfly
A couple of weeks ago I attended a brilliant symposium which has filled my mind with lots of ideas for the future. It was the biennial Beth Chatto Symposium held at the University of Essex in Colchester, entitled Beneath the Surface. Running over two days with an optional third day based at the Beth Chatto Gardens, it delved deep into soil, roots, resilience, boglands and much more. Just the type of event I thrive on.
Opening the symposium was the wonderful Merlin Sheldrake talking to Humaira Ikram about his best selling book, Entangled Life, which is mind blowing and if you haven’t read it yet, I encourage you to do so. Merlin talked about soil fungi and their role in plant health, the way that fungi can move around via their spores, and cutting edge science such as the use of viral therapy to deactivate pathogenic fungal resting structures, such as sclerotina, in the soil. It was interesting to learn how mycorrhizal fungi respond to the stresses of drought by producing spores, so they may be able to bounce back when conditions improve. He also stressed several times how glyphosate, fungicides and artificial fertilisers will disrupt fungal life in the soil.
During the two days, there were talks by Eddie Bailey of Rhizophilia on plants and the soil food web, Ellen Fry on how plants influence their surroundings, Alys Fowler on mosses and bogs, plus conversations with Richard Mabey and much more. And closing was a talk by Kevin Philip Williams and Michael Guidi, who gave a presentation about their new book Shrouded in Light that looks at diverse and inspiring ecosystems as models for future gardens.
My notebook was filled with notes by the end of the gathering. I can’t go into everything although I’ll find a way of weaving some of the knowledge in future posts, but today I am going to write about roots and creating complex spaces in your garden.
Roots
This is such a fascinating area and I have always thought about root diversity as much as above ground diversity, probably influenced by a brilliant advert from Cotswold Seeds running on the back cover of Organic Farming mag that I edited.
Noel Kingsbury (New Perennial Garden) took us underground and explored the world of roots and how root structure affects the longevity of a plant, the way it spreads and how competitive it can be. Lots of fascinating info and still much more to be researched. He wondered why so many perennials only had a short life span and how many gardeners would blame themselves for the ‘failure’ of their planting, while, in fact, it was more to do with root morphology.
Noel had been delving into the research of Jana Pasilova who wrote ‘A study of the root systems and root ecology of perennial herbs in the undergrowth of deciduous forests’ which was published in 1970. I found the paper online here This research was focused on three forest stands in NW Bohemia of the former Czechoslovakia.
By looking at roots you can predict the long term performance of the plant. For example, many short lived perennials have tap roots that are more like those of annuals. Noel suggested that it might be better to move away from the general classification of annuals, biennials and perennials to a system based on root type. He described three categories:
1. Rhizophytes, such as cerinthe and poppies, which have one point of contact between the shoot and root. These are mostly annuals, but occasionally the life of plant is extended by the production of offshoots. This made me consider the process of ‘perennialization’ in which some of the annual veg can actually be grown as short lived perennials, such as chard and runner bean. My 3-year old runner bean definitely has offshoots.
2. Rhizocaulophytes – in this category, the plants develop tap roots, and create a clump with a narrow base. Examples here include Veronicastrum virginicum which has huge roots, that support a resilient plant. Another is Aruncus dioicus, a plant that is slow spreading and you may get a fairy ring type growth. This group tends to be medium to long-lived, with deep tap roots and can cope with a stressed environment, such as a dry habitat.
3. Caulophytes – these plants don’t have a tap root, but rhizomes (underground stems) which spread. This results in clonal growth. Examples include geranium which creates a classic weed suppressing mat. With these roots, there can be an underground network of rhizomes, which may even be multi-layered. As a result, these are resilient, long lived plants typical of a high resource environment. They are competitive and dominant, low maintenance and self-repairing, and are not reliant on seed production.
Below is a screen shot of a piece of artwork in Pasilova’s research paper - look at how the root entwine and populate the soil. Its interesting that Pasilova subdivides these three categories further still.
Noel highlighted a few examples from the different categories:
Geranium phaeum - rhizomatous, single layer, clumping and good as gap fillers. It can also be split
Salvia nemorosa – clumping
Verbascum – rhizophyte, so is a seed producer and gap filler
Lysimachia ciliata – spreads and holds its space, but can’t penetrate other clumps, spreading, and able to look for new opportunities
Rudbeckia – produces annual shoots, but the roots hold few stores, so can be more vulnerable to stress
Noel has been studying some test beds, each 1.5 x 1.5m with a high density of 11 plants per square metre, and with no maintenance. Amongst his many observations, was one relating to Phlomis russeliana, a plant I use a lot and it can be quite thuggish. Noel found that in this dense planting with other competitive plants, it can lose space and become a gap filler, rather than a clump former.
There is much more to learn so Noel is interested in hearing from people who would be interested in carrying out test plantings
Structural complexity
John Little is a popular speaker at these events. He has a 4-acre site in Essex, Hilldrop, where he experiments with all sorts of waste materials – aggregates, rock, metals, dead wood and more. I have been following his work over the last five years or so, and in that time, his approaches have become more accepted and almost mainstream. If his name is new to you, do have a look at his work online. There is so much to inspire in his website.
John and ecologist and wildlife advocate Benny Hawksbee talked about structural complexity and disturbance to increase biodiversity in our growing spaces, an alternative approach to growing lots of different types of plants. Their talked focused on invertebrates, especially insects, rather than vertebrates.
They believe that structure, soil, topography and dead materials have just as much importance as plants, if not more. The more structural diversity, the more species that call the space home.
I have long been interested in brownfield sites and after completing my degree, I researched restoration ecology, specifically the establishment of woody plants on quarry faces. I visited many disused quarries, many of which had been designated nature reserves due to the diversity of species found living in them. John’s example of an abandoned industrial site was Canvey Wick in Essex, an old oil refinery site which now holds more biodiversity than an ancient woodland.
John likes to use rock filled gabions, and I have many on my site too. They are so beneficial to biodiversity as they can create refugia for many types of invertebrates as well as amphibians and reptiles. They can be heat sinks at night, offer shade during the day, and provide wonderful hiding places etc.
So what we need to do in our gardens is create complicated structures and mosaics with lots of different microclimates.
His recommendations:
· the inclusion of sand in which so many bees and wasps nest. This could be piles of bare sand, sand paths etc. Sand varies depending on origin and mix. So a good option is a relatively fine sand with a bit of clay mixed in. This means that it holds its shape when insects burrow into it and doesn’t collapse.
· Stagnant water is brilliant for attracting drone flies (Eristalis tenax), a type of hoverfly. They need water to compete their life cycle as their larvae are aquatic. The larva goes under the rather unattractive name of rat-tailed maggot, which is a shame as it doesn’t reflect the beneficial nature of this insect. John’s suggested stagnant water source is a length of downpipe, blocked at the bottom. The top is cut at an angle to create a slope that allows animals to crawl out. It’s supported in an upright position and filled with water and organic matter to creating a ‘stinky’ hole to attract hoverflies and mosquitoes.
· So many garden centres sell fancy bug hotels but there is no need to buy these. It is far better to have lots of different sources of nesting materials spread around your garden to attract a diverse mix of insects. Often you are recommended to clean out the tubes each year, but in nature this would never happen. Dead wood breaks down and new cavities form, so it is far better to keep adding lots of different type of cavities to your garden, such as bundles of short lengths of bamboo canes of differing diameters, which can be hung from trees etc.
· Pruning roses. Classic pruning advice is to neatly cut the shoot above a node so you don’t get dieback etc, but John has found that leaving a length of internode above the node can be really beneficial. The internode dies back leaving a hollow stem that will be used as a habitat for insects such as aphid-hunting wasps. And this is true of all manner of tidying up in the garden, leaving perennial growth through the winter will result in many more temporary cavities.
· Dead wood is vital for biodiversity gain and put simply, you cannot have enough. This could be in the form of log piles, lengths of branches in beds and under trees. You could even bring in a dead tree as use as a centrepiece in the garden.
A quick garden update
Back in in June I wrote about the lack of butterflies and other insects in my garden, something that was reported on across the country following the mild yet wet winter. Bees were slow too, but when I walked around the garden the other day, it was a buzz, especially around the beds full of borage, which was a great relief. Interestingly, I have seen a good diversity of insects this year, especially dragonflies and damselflies, but the numbers (frequency) wasn’t great.
And I was delighted to spot this under a brassica leaf …
Concerns for the monarch butterfly
It’s not been a great year for insects in other parts of the world too. And there is one story that I must report on, it’s depressing news but I can’t ignore it.
One of the great natural wonders of the world that I have always wanted to see but never managed to witness is the millions of monarch butterflies roosting in a forest in Mexico. They use a small area of forest in central Mexico that is designated as a Butterfly Biosphere Reserve.
This amazing butterfly overwinters in Mexico and then migrates north across North America where it breeds, before the new generations make the journey back. The migration of this iconic butterfly is well documented in books and films. But sadly, forest degradation, pesticide use, the loss of milkweed plants (larval plant) and extreme weather events have resulted in a decline in their numbers.
Recently, the WWF published the results of their annual survey which found the number of overwintering butterflies to be at its second lowest ever level, down 59% compared with the previous year. On their return journey last autumn the butterflies had to cross the southern USA where drought and heat had reduced the number of flowers, so there was less nectar available to fuel the monarchs’ flight. What can Americans do? To help they can plant more milkweed and ensure there are lots of nectar rich flowers in the garden.
There have been years when numbers fell and then recovered - lets hope they bounce back again. May be some of our North American readers can update us – I would love to hear from you.
Happy gardening
Sally
Talks
I am talking about Creating a Resilient Garden at Yeo Valley Organic Garden this Friday 13 Sept - there are a few tickets left if you fancy a day out in the garden. As well as my talk, your ticket gives you access to the wonderful garden where there is plenty to see plus there is a super cafe. Yeo Valley Garden is near Blagdon, just south of Bristol and tickets can be purchased via the Yeo Valley website
I am also this month’s speaker at the Somerset Hardy Plant Society’s meeting which takes place on Sat 21 September at 11.30 am at West Monkton near Taunton. There is a plant sale beforehand. My talk is on Controlling pests and diseases in the organic garden.
Next month I am talking at the Clevedon Gardeners’ Club on 2 October, Nynehead Gardening Club near Wellington on Monday 14 October and Dulverton Gardening Club on Thursday 17 Oct.