Purple Toothwort, Lathraea clandestina

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Purple Toothwort - Lathraea clandestina

Purple Toothwort – Lathraea clandestina

A few weeks ago my friend Chris Lansdell asked me where he could find Moschatel in the local area and I gave him details of a couple of sites, including at Natural Surroundings at Bayfield. As a “thank you” he told me that the Purple Toothwort was in flower at Bowthorpe, on the western outskirts of Norwich. I was originally told about the plants a couple of years ago, but didn’t make the trip to see them. This time, I decided I would go and I’m glad I made the effort (just a fifteen minute cycle ride from home). The plants were growing on a bank in a shady spot underneath some Willow trees.

Purple Toothwort, Lathraea clandestina is a low growing, perennial plant that is parasitic on the roots of various trees, especially Poplar (Populus) and Willow (Salix). Other plants may be used too, including  Acer (Sycamore / Maples), Alder (Alnus), Box (Buxus), Hornbeam (Carpinus), Hazel (Corylus), Walnut (Juglans), Metasequoia, Rhododendron, Yew (Taxus) and Gunnera. The plant can be found in the damp shady places where its hosts grow.

Purple Toothwort is a member of the family Orobanchaceae, along with Broomrapes (such as Purple Broomrape and Ivy Broomrape), Eyebrights, Yellow Rattle and Red Bartsia. Like the Broomrapes, Purple Toothwort has no chlorophyll and relies on food taken from its host. It bears small, simple scale leaves on alternate sides of its stem and its very pretty purple flowers shoot upwards from the stems, appearing from March to May. These develop into explosive seed capsules later in the summer.

The plant is hardy but early flowers may sometimes be damaged by frost. It is a fairly recent introduction to the British Isles (a neophyte). It was brought into Britain as an attractive garden curiosity and was planted at Kew Gardens in 1888. It was first reported from the wild in 1908 at Coe Fen in Cambridgeshire, where it was probably deliberately planted. It can still be found there. Purple Toothwort is found in various parts of England and Wales, with a few outlying colonies in Scotland and Ireland. Its native home is across the English Channel in Belgium, France, Spain and Italy.

Purple Toothwort flowers are pollinated by bumblebees. I saw a single Tree Bumblebee (Bombus hypnorum) worker when I made my visit, but it was flying just above the flowers, rather than venturing inside. The flowers have very alkaline nectar, which tastes of ammonia, though I only found this out after my visit. The taste or alkalinity is thought to deter birds and ants from robbing the nectar from the flowers without pollinating them.

There are several other species of Lathraea in Europe, all parasitic and lacking chlorophyll. In Britain we have one native species, Toothwort, Lathraea squamaria. It usually uses Hazel (Corylus) as a host, but can sometimes be found on Elm (Ulmus), Ash (Fraxinus), Alder (Alnus), Walnut (Juglans) and Beech (Fagus). One grows at Kew Gardens, under a Black Walnut tree. Further afield Toothwort grows as an annual or perennial in lowland deciduous woodland, in hedgerows, and on the banks of rivers and streams. It has white or creamy to pinkish-purple flowers, produced from March to May. I have yet to see it, as it is more or less absent from East Anglia.

The generic name Lathraea comes from the Greek word lathraios, meaning hidden. Clandestina means secret (clandestine). Both words relate to Purple Toothwort’s habit of hiding in dark corners though, as I found on Tuesday, this beautiful vampire is well worth seeking out.

Purple Toothwort, Lathraea clandestina

A patch of Purple Toothwort, Lathraea clandestina.

Mimosa, Acacia dealbata

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Mimosa, Acacia dealbata

Our very mild late winter and spring has suited tender plants, such as Mimosa, Acacia dealbata. There are several Mimosa trees in Norwich and they have been flowering for weeks now, lighting up front gardens with the bright yellow puffs of their flowers. As I write, some of the flowers are beginning to turn brown with age, but from a distance the effect is still magnificent. Close up, the flowers have a delicious scent. The Fragantica website describes this as a “child-like, sweet, soft and hazy heliotrope-smelling note with sugar-spun tonalities”. Mary Keen describes the scent as the “smell of southern spring“.  They smell nice, anyway.

Acacia dealbata is a native of southeastern Australia (New South Wales, Victoria, Tasmania and the Australian Capital Territory). It was introduced into Southern France in 1820 and is now widely planted and naturalised in many parts of the world with a suitable climate, including other parts of Australia, the Mediterranean region from Portugal to Greece and Morocco to Israel, the Black Sea coast of Russia, Ukraine, California, Madagascar, South Africa, Zimbabwe, the highlands of southern India, south-western China and Chile. It can be a serious weed in New Zealand and parts of South Africa.

Mimosa is a member of the Fabaceae, the Pea family. Other English names include Silver Wattle and Blue Wattle. In its native land Acacia dealbata is a pioneer species that colonises after a bush fire. The roots have nitrogen-fixing bacteria in their nodules, and can bind together soils to prevent erosion. Mimosa grows rapidly to about 30 metres (100 feet) tall but seldom lives longer than thirty to forty years. In the UK, it is more likely to reach 8 – 12 metres (26 – 40 feet) tall and frost, rather than natural causes or fire, is likely to end its life.

In the UK, growing Mimosa is often a bit of a gamble and “probably not something to try out of doors north of the Trent“. It can survive brief cold spells down to -10°C, but it is officially given a hardiness rating of H3 by the RHS: Hardy in coastal and relatively mild parts of the UK (-5 to 1°C).  It would probably not survive a cold winter like 2009 and 2010, though most winters are now milder in the south of England.

Shrubs such as Leptospermum are equally tender but small enough to cover in the winter, whereas Mimosa can become too tall to wrap up against the chill. It is most likely to survive in a sunny, sheltered spot in well-drained soil. If cut down by frost, it may regrow as a multi-stemmed shrub. If you need to prune your Mimosa, follow the RHS instructions for Early flowering evergreen shrubs (pruning group 8) – prune after flowering.

Acacia dealbata subspecies ‘Subalpina’, which grows at higher altitudes, is a bit hardier than the wild type and said to be worth seeking out: at the time of writing it is stocked by Shoot. James Wong mentions a related dwarf form, Acacia nanodealbata (sometimes spelt nono-dealbata). Anna McKane describes some other hardy (ish) Acacia species in her 1996 article in The Independent, “On the trail of hardy mimosas“.

Mimosa trees can be raised from semi-hardwood cuttings or from seed, though the seeds need to be treated with boiling water and then left to soak for a day. The boiling water mimics the heat of a fire that would trigger germination in the wild.

The Plants for a Future website tells us that Mimosa gum (which exudes from the trunk) is edible, and can be used as a substitute for gum arabic. The real thing comes from two close relatives: Senegalia senegal (Gum Acacia) and Vachellia seyal (Red Acacia).

Mimosa flowers are often sold by florists. The flowers are edible when cooked and according to Plants for a Future can be made into fritters, although the recipes I found when searching for “Acacia flower fritters” used the white flowers of the related Black Locust tree,  Robinia pseudoacacia.  Mimosa can be used as a dye plant, either for yellow (the flowers) or green (the seed pods).

Mimosa Salad sounds appetising, but no Mimosa was harmed (or used) in making it. A festive salad in the former USSR, its main ingredients are cheese, eggs, canned fish, onion, and mayonnaise. If boiled egg yolk is crumbled and scattered on its surface, it is said to resemble mimosa flowers scattered on snow.

Mimosa, Acacia dealbata

Mimosa against a blue March sky.

Why You Should Ditch Peat

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Large Heath butterfly

The Large Heath butterfly – a species that has seriously declined following destruction of peat bogs. (The plant in the background is Bilberry, Vaccinium myrtillus.)

This morning we walked to our local garden centre. It was good to stretch our legs, but the experience was rather disappointing. Like many such places, it has become more gift shop and cafe than a place to buy plants. The only Hollyhocks on sale were double-flowered and therefore useless to pollinators and the trays of mixed blowsy-flowered Primulas made me feel a little bilious. We came away empty handed (note 1).

Saddest of all were the huge piles of bags of compost by the entrance, most of which contained peat.

In the United Kingdom, the industrial scale extraction of peat has destroyed or damaged more than 95% of lowland bogs. In Ireland, the Irish Peatland Conservation Council (IPCC) estimate that 90% of its raised bogs have been lost (note 2). As the IPCC say: “Peat may be dirt cheap, but it costs the earth.”

Peat is composed of waterlogged, partially-decomposed plant material (including sphagnum moss and other acid-loving plants), which builds up in wetland habitats such as fens, bogs and moorland. The process is slow: about 1 millimetre of peat forms in a year, and deposits in the British Isles have gradually built up over 10,000 years. In contrast, average annual extraction from a peat bog removes 20cm (8 inches) of peat in a year, which represents 200 years of peat formation (note 3). It’s actually worse than that because bogs are drained before extraction takes place, to allow machinery to work on the site. This kills off large tracts of peat and its unique plant and animal community. Industrial scale peat extraction is no more sustainable than clear-felling rainforest to create palm oil plantations.

Peat bogs are wonderful places, full of interesting plants, including beauties such as Bog Asphodel and Grass of Parnassus, which I have previously written about. Insect life abounds there too, such as the Black Darter dragonfly and, pictured above, the Large Heath butterfly. More recently, we have realised that peat bogs are great carbon sinks, capturing carbon dioxide from the atmosphere. It has been estimated 5% of the carbon currently locked up in the UK’s peatlands is equivalent to the UK’s annual greenhouse gas emissions (note 4). Peat bogs also store vast amounts of water and slow its release into rivers, preventing catastrophic flooding (note 5).

Some three billion litres of peat are used every year in our gardens. We have known that harvesting peat is damaging and unsustainable for many years, but the majority of commercial composts still contain a large proportion of peat. Unless a bag of multi-purpose compost says it is peat free, it will contain peat. Some bags say that the peat doesn’t come from a SSSI (Site of Scientific Interest), but this is either because the extraction site is so degraded that it has no designation or if it comes from outside the United Kingdom, where the term SSSI isn’t used (note 6).

In December 2010 the British Government announced a plan to phase out the horticultural use of peat by gardeners by 2020. But as I write, peat extraction for gardening in the UK is still rising.

The following quote from Monty Don, which dates from March 2002, is still sadly true:

“Go to any garden centre and try and buy a non-peat based compost. It is certainly easier now than it was even five years ago, when you had more chance of scoring a bag of heroin over the counter at the local supermarket, but you still have to fight past the pallets of peat and peat-based composts to get to it.”

Alternatives to Peat

I stopped using peat in the 1980s.

For containers of shrubs and hardy perennials I use my home-made compost, which starts off as kitchen and garden waste. However, my own compost doesn’t rot at a high enough temperature to kill all weed seeds, so I use a commercial compost for the top inch or so of the pot, to stop light from triggering  germination of unwanted seedlings. (Peter Hill also suggests this in his February 2010 Guardian  article “Tips for a Peat Free Garden“.)

For raising seedlings and small plants, whether vegetables or wild flowers, I buy bags of peat-free compost.

The quality of composts can be variable, and I have learnt that some ones are better than others. Price can be an indicator, as you generally get what you pay for. I have had the occasional failure: about twenty years ago one (not cheap) brand of peat-free compost, whose formula has now changed, only gave me a crop of Common Inkcap fungi, rather than the potatoes I had hoped for.

If you’re switching to a peat-free compost, bear in mind that the compost may behave differently to a peat-based one. This is not necessarily a bad thing, but it’s best to check that plants really need watering. The surface of a coir or wood-chip based compost can dry out on the surface while the depths remain moist. Don’t rely on visual clues – poke a finger into the compost to check.

There is a lot of useful advice on peat-free composts online. One of the best articles I’ve found comes from the Telegraph just a couple days ago. There are also recommendations on the RHS and  Earth-Friendly Gardener websites. It includes some recommended brands. I’ve had success  New Horizon compost (a blend of coir, wood fibre and bark) and Fertile Fibre. The former is available in many garden centres, as well as DIY stores such as Homebase and Wickes. Buying online with home delivery makes sense if you don’t have a car, or a garden centre near where you live.

Peat is often used to lower soil pH, making it more suitable for growing lime-hating plants such as Blueberries and Rhododendrons. But peat-free ericaceous composts are available, including Ericaceous Wool Compost and Vital Earth Ericaceous Compost. I’ve had success growing Blueberries in a tub in a wool-based compost. On a larger scale, it is probably better to stop fighting nature and grow plants suited to your garden soil.

Notes

Note 1:  To be fair, they did have a smaller number of nice plants too, including some Cowslips and a couple of varieties of Lungwort.

Note 2: This loss has resulted from a combination of commercial peat extraction, turf cutting and forestry. See http://www.ipcc.ie/help-ipcc/be-a-peat-free-gardener/.

Note 3: Plantlife gives a higher figure: “Commercial extraction can remove over 500 years worth of ‘growth’ in a single year“.

Note 4: IUCN UK Peatland Programme (2011), Commission of Inquiry on Peatlands: Summary of Findings, October 2011. Quoted by Plantlife: https://www.plantlife.org.uk/uk/our-work/campaigning-change/why-we-need-to-keep-peat-in-the-ground-and-out-of-our-gardens.

Note 5: One inspiring story, reported in the Independent newspaper in January 2016, comes from Pickering in Yorkshire, which was flooded four times between 1999 and 2007. Rather than building an ugly and expensive flood wall in the town, local people, local councils, the Environment Agency, the Forestry Commission and DEFRA (the Department of the Environment, Food and Rural Affairs) worked together to slow water flow from surrounding moorland. The scheme worked well, the peat soaked up excess rainfall and the scheme cost only a tenth of building a flood wall.

Note 6: Even in Northern Ireland and the Isle of Man, the alternative term Area of Special Scientific Interest (ASSI) is used. Currently 32% of our peat comes from the UK, 60% from Ireland and 8% from Europe. (Plantlife: https://www.plantlife.org.uk/uk/our-work/campaigning-change/why-we-need-to-keep-peat-in-the-ground-and-out-of-our-gardens.)