Szechuan Pepper, Zanthoxylum simulans

Jeremy Bartlett's LET IT GROW blog Posted on by
Szechuan Pepper, Zanthoxylum simulans

Szechuan Pepper, Zanthoxylum simulans

Our Szechuan Pepper bush, Zanthoxylum simulans, is producing fruit for the first time.

I first read about Szechuan Pepper ten years ago, when I bought Mark Diacono’s book “A Taste Of The Unexpected”  (note 1). I wasn’t able to source a plant for Grapes Hill Community Garden in 2011 but when we replaced the big raised bed in our front garden in autumn 2016 I had another look online and bought a small plant from Jurassic Plants. It had clearly been grown with love and care, and came with an A4 printed sheet of care instructions. I kept it in an unheated greenhouse and planted it out in early spring 2017. (In the UK, plants are available from other sources too, such as Burncoose Nurseries and Pennard Plants. Seeds are available from Chiltern Seeds.)

Two years later, the Szechuan Pepper is doing well and has reached about four feet (1.2 metres) high, with a similar spread. Without pruning, it could ultimately reach seven metres (23 feet) tall but I will intervene long before that – and, if space is really limited, it is apparently a good bonsai plant (note 2). It is very hardy and seems tolerant of drought and likes the sunny, south-facing spot where it is growing. (It will also grow in light dappled shade.)

Zanthoxylum simulans is a member of family Rutaceae, the Citrus family, along with well-known fruits such as Oranges, Lemons and Grapefruit. There are about 250 species of Zanthoxylum worldwide, trees or shrubs native to warm temperate and subtropical areas. Zanthoxylum simulans is native to eastern China and Taiwan. The genus Zanthoxylum is so-called because some species have yellow heartwood (Ancient Greek xanthos (yellow) and xylon (wood)).

So why am I growing Zanthoxylum simulans?

It is an interesting and quite attractive plant, with rather formidable spines on its stems and ash-like leaves, which turn an attractive reddish-yellow in autumn. The shape of the leaves gives the plant its alternative English names of Prickly Ash, Chinese Prickly-ash and Flatspine Prickly-ash.

The flowers appear in spring and are rather tiny – I missed them altogether this year but they are described as tiny, cup-shaped flowers in cymes 5 cm (2 inches) across. (Mark Diacono says that they resemble small elderflower florets.) By July or August the plant has clusters of small pinky-red fruits. These are ornamental, but also contain the plant’s finest and strangest secret.

Known as Szechuan peppercorns, each berry is about the size of a black peppercorn (an unrelated, tropical vine, Piper nigrum). The seed is black and is revealed when the berry splits open in the autumn. The seed itself is tasteless but its pink coating (the pericarp) gives a fizzing and numbing sensation in the mouth and on the tongue.

Szechuan (Sichuan) peppercorns are used to make Chinese five spice powder, along with star anise, fennel, clove, and cinnamon. The powder is readily available, but Mark Diacono gives a recipe for making your own in his book and 2010 Guardian article. The Spruce Eats website lists a number of recipes using the powder (including Bang Bang Chicken, Dan Dan Noodles and Szechuan Beef) and Mark Diacono suggests Five Spice Pork Rillettes. The Vegetarian Times website lists several vegetarian and vegan recipes that use five spice mix, such as Garlic Ginger Vegetable Stir-fry and Spicy Peanut Noodles. Other culinary uses include flavoured salt or as additives in beer or in flavoured oils.

The experience of tasting a Szechuan Pepper is described by Mark Diacono as “like all peppers… much more an experience than a flavour”. He separates out two contrasting elements of flavour: “ma” and “la”. First comes “ma”, a numbing pungency that sets the tongue and lips tingling, followed by “la”, a spicy heat, which is (slightly) similar to the heat from a chilli. In my own experience, the “ma” is much more obvious. It doesn’t last long, but it is strangely addictive. I often pick a single berry when I walk to the allotment, carefully suck the pericarp and discard the seed. Full fizzing numbness starts several yards down the road, but has worn off after two or three minutes.

The ingredient in Szechuan Pepper that causes the tingling numbness is the compound hydroxy-alpha-sanshool. Rather like the capsaicin in chillies, the chemical interacts with nerve cell receptors in the lips and mouth. In his book “On Food And Cooking: The Science And Lore Of The Kitchen“, the American author Harold McGee describes the chemical’s effects in the mouth:  “they produce a strange, tingling, buzzing, numbing sensation that is something like the effect of carbonated drinks or of a mild electric current (touching the terminals of a nine-volt battery to the tongue). Sanshools appear to act on several different kinds of nerve endings at once, induce sensitivity to touch and cold in nerves that are ordinarily nonsensitive, and so perhaps cause a kind of general neurological confusion.” (note 3).

The import of Szechuan peppercorns into the United States was banned in 1968 (along with all other citrus products) because Zanthoxylum plants act as hosts for a type of canker that attacks citrus trees. However, the ban was lifted in 2005 for peppercorns that had been heat-treated to kill off any potential pathogens, much to the relief of Chinese communities in particular.

My single Szechuan Pepper has set plenty of fruit by itself, but even more fruit can be set if you have more than one plant.

If you can’t get hold of Zanthoxylum simulans, Mark Diacono suggests Zanthoxylum schinifolium. (“I prefer its lighter touch – it’s more “ma” than “la”.“) UK suppliers include Van Den Berk Nurseries (who have some good photos and information on their website) and (for seeds) the Agroforestry Research Trust.

The wonderful Chelsea Physic Garden in London has a big specimen of the related North American species, the Toothache Tree (aka Common Prickly-ash)  Zanthoxylum americanum, “with spines and knobs along its trunk and branches – the small, round, fleshy fruits smell strongly of cloves when crushed“.

It is also worth rubbing the leaves of a Szechuan Pepper plant to release a heady hit of spice and citrus. In the words of Mark Diacono once more: “Like a tea break, it provides a perfect punctuation to the day, and is up there with popping fresh peas into your mouth as one of the finest kitchen-garden treats.”

Notes

Note 1 – Mark Diacono, “A taste of the unexpected : growing your own remarkable fruit, vegetables, nuts, herbs, spices and flowers”, Quadrille Publishing 2010.

The book appears to be out of print, but you may be able to buy a secondhand copy or borrow it from a library.

Mark also wrote about Szechuan Pepper in a 2010 article in The Guardian, “How to grow Szechuan pepper and make Chinese five spice“.

Note 2 – Many Zanthoxylum species make excellent bonsai specimens and can be grown successfully indoors in temperate climates. According to Wikipedia, Zanthoxylum beecheyanum and Zanthoxylum piperitum are two species commonly grown as bonsai.

Note 3 – A revised second edition of the book (published by Hodder & Stoughton in 2004)  was reviewed in The Guardian in 2004 by Tom Jaine.

Nodding Bur-Marigold, Bidens cernua

Jeremy Bartlett's LET IT GROW blog Posted on by
Nodding Bur-Marigold, Bidens cernua

Nodding Bur-Marigold, Bidens cernua. Rayed form (var. radiata), 2nd September 2019.

At the beginning of September Carl, my older brother-in-law, told me about an interesting plant he had seen at Whitlingham Country Park, on the outskirts of Norwich. It was the rayed form of Nodding Bur-Marigold, Bidens cernua (var. radiata), a plant I hadn’t seen, so the next day I cycled out to take a look. I found the plants very easily, just off the path on the southern edge of the Great Broad (a former gravel pit).

Nodding Bur-Marigold, Bidens cernua, is a member of the Asteraceae, the Daisy family, and I have already written about some other members of the family on this blog, including Oxeye Daisy, Pineapple Weed, Gallant Soldier, Dandelion, Mexican Fleabane, and Bristly Oxtongue. The Asteraceae is probably the largest family of flowering plants, with more than 32,000 species worldwide (note 1).

Members of the Asteraceae have composite flowers – what appears to be a single flower is actually a composite flowerhead known as a capitulum (note 2). Taking just three examples:

  • Dandelion flowerheads are made up only of ray florets.
  • Thistle and cornflower flowerheads are made up of only disc florets.
  • Flowerheads of the Oxeye Daisy consist of an inner cluster of yellow disc florets, surrounded by a ring of white ray florets which look like petals.

The rayed form of Nodding Bur-Marigold (var. radiata) has flowers structured rather like an Oxeye Daisy. The inner disc florets are a dull yellow, and these are surrounded by a ring of bright yellow, petal-like ray florets. But this very attractive form of Nodding Bur-Marigold is not particularly common and you are far more likely to see plants that only have disc florets. Both forms were growing by Whitlingham Great Broad.

In contrast to the rayed form of Nodding Bur-Marigold, the rayless form of the plant is not very spectacular, and it blends into its surroundings. However, both forms of the plant have characteristic undivided leaves with saw-tooth edges.

Nodding Bur-Marigold, Bidens cernua

Nodding Bur-Marigold, Bidens cernua. (Rayless form.) 2nd September 2019.

Bidens cernua is an annual, and when I visited the site again later in September the plants were already running to seed and many were developing mildew and looking past their best.

Nodding Bur-Marigold grows in damp places, such as on the margins of slow-flowing rivers and streams, in ditches and marshes and by broads, ponds and meres. The sites where it grows are often places subject to flooding in winter. It is widely distributed in the British Isles, particularly in England, Wales and Ireland. However, it is declining in the south-east of England as its habitats are destroyed. It is also found through many temperate parts of Europe, Asia and North America. There are good pictures of the plant on the Wild Flower Finder (rayless form only) and Illinois Wildflowers websites. (The latter lists some of the insects that are attracted to the plant in the United States.)

Bidens cernua contains the compound Phenylheptatriyne (PHT). This chemical, a type of polyacetylene, is phototoxic to bacteria and also acts as a fungicide. PHT may also have allelopathic properties: it appears to inhibit the growth of seedlings from other plants. Quantities of the chemical in Bidens cernua vary throughout the year, reaching their highest levels in October.

The closely related Trifid Bur-Marigold (Bidens tripartita) was growing alongside (and amongst) the Nodding Bur-Marigold at Whitlingham. Its flowers were similar to the rayless form of Bidens cernua but the leaves were distinctively divided into threes – hence trifid (but not triffid) (note 3). Although Trifid Bur-Marigold grows in similar areas to Nodding Bur-Marigold, it prefers slightly drier ground. It is also an annual. The leaves can be eaten when cooked and the plant has various possible uses in herbal medicine and was used medicinally to used to staunch blood flow.

Trifid Bur-Marigold, Bidens tripartita

Trifid Bur-Marigold, Bidens tripartita, growing next to Nodding Bur-Marigold at Whitlingham Great Broad (22nd September 2019).

The teeth on Bur-Marigold seeds attach to passing animals, including plant photographers and canoeists, and this aids the plant’s spread. This is known as zoochorous seed dispersal. (The Wild Flower Finder website has some good pictures of the seeds.) They also give the plant its generic name: Bidens comes from the Latin bis (“two”) and dens (“tooth”).

Notes

Note 1 – With around 32,000 species, the Asteraceae is usually considered to be the largest family of flowering plants. The next largest is the Orchid family (Orchidaceae), which has around 28,000 species. The exact numbers are difficult to determine as new species are discovered or reclassified, hence the “probably”.

Note 2 – The Asteraceae is also known as the Compositae, because of its composite flowerheads.

There is a useful glossary on the Kew Gardens ‘Compositae of Bolivia’ web pages.

Strictly, there are six possible kinds of florets, as explained in the Flowers of Asteraceae. (on the website of the South African National Biodiversity Institute).

Note 3 – Bidens tripartita can be quite variable, and there is rare form, var. integra, that doesn’t have trifid leaves. The Wildflower Finder website gives more details.

Water Mint, Mentha aquatica

Jeremy Bartlett's LET IT GROW blog Posted on by
Water Mint, Mentha aquatica

Water Mint, Mentha aquatica, on Beeston Common, Norfolk (August 2019).

One of my favourite smells is Water Mint, Mentha aquatica. The plant has a clear, pure minty freshness that soothes and clears the nose at the same time. I can’t resist touching Water Mint leaves when I walk past, but earlier in the season the scent can come as a pleasant surprise, when you tread on it in short, damp turf near a stream and unwittingly bruise its stems and leaves (note 1).

Last Thursday we made a brief visit to Beeston Common near Sheringham in North Norfolk. The wetter areas are a mass of flowers at the moment, and stands of Wild Angelica (Angelica sylvestris), Common Fleabane (Pulicaria dysenterica) , Tansy (Tanacetum vulgare) and Water Mint (Mentha aquatica) were attracting lots of insects, including butterflies, hoverflies and solitary bees. The dense stands of Water Mint were especially spectacular, with the plants growing over 30 centimetres (one foot) tall, topped by dense heads of small lilac-pink flowers with one or two further whorls of flowers beneath.

Water Mint is in flower somewhere in the UK from July to October, but the peak of flowering will depend on the year’s weather and where the plant is growing: late August to mid September is usually best here in Norfolk. To help you recognise the plant, there are great photos of Water Mint on the Wild Flower Finder, Nature Gate, Nature Spot and First Nature websites.

The plant’s scientific name, Mentha aquatica, literally means “Water Mint” (note 2). It is a hardy perennial plant (note 3) which spreads by rhizomes, which sometimes break off to create new plants. It grows in wet places such as marshes, fens, ditches, ponds and the edges of rivers, in dune-slacks and wet woods. Water Mint is a British native and is very widely distributed, so in most of the British Isles you won’t need to travel far to find your nearest patch. Mine is only yards away from there I am writing this, in a pond in the back garden.

Like other mints and many culinary herbs (such as Sage, Marjoram, Thyme and Hyssop) Water Mint is a member of the Lamiaceae, a family of plants with a cosmopolitan distribution and around 7,000 species in over 230 genera. The genus Mentha is distributed across Europe, Africa, Asia, Australia and North America and there are between 13 and 24 species, plus many hybrids (note 4).

As well as the British Isles, Water Mint is native to much of Europe and parts of north-west Africa and western Asia. It has been introduced (deliberately) to North and South America, Australia and some Atlantic islands. 

Mints are useful plants and the Plants For A Future website gives a number of uses for Water Mint. The leaves are edible raw or cooked but are very pungent, so a little goes a long way. They can be used, sparingly, in salads or cooked dishes, though “the leaves are too pungent for most people to use as a flavouring“.

One of the best uses of Water Mint is to make a mint tea from the leaves. Mint tea is very refreshing and a pleasant caffeine-free drink. The tea also has a number of possible medicinal properties and it has traditionally been used in the treatment of fevers, headaches, digestive disorders and various minor ailments. On his blog, Paul Kirtley suggests using Water Mint to calm digestive disorders, flatulence and nausea and he found that eating some eased his stomach cramps after a bout of food poisoning.

The Gardening Know How website suggests using Water Mint externally as a balm for sore muscles or to help clean wounds. Water Mint contain menthol, which has known antibacterial properties and triggers cooling receptors when applied to the skin.

Other volatile compounds in Water Mint include menthone, carvone, limonene, linalool, menthyl acetate, piperitone, and pulegone (note 5). Some of these, including pulegone (also found in Catmint) and menthol are toxic in large quantities but eating a bit of Water Mint now and then is not going to cause you any harm.

The Plants For a Future website has includes a warning: “Although no records of toxicity have been seen for this species, large quantities of some members of this genus, especially when taken in the form of the extracted essential oil, can cause abortions so some caution is advised”. The warning applies particularly to Pennyroyal, Mentha pulegium (note 6). Pennyroyal oil contains very high levels of pulegone (80% to 92%), whereas Water Mint oil has much lower levels (around 15%, note 5).

Water Mint was sometimes strewn on floors to give a scent of mint and it can be used to scent a room in potpourri, in aromatherapy or added to herb pillows or used fresh or dried in herbal baths. The cut foliage is said repel mice and flies as well.

Water Mint is abundant enough to pick from the wild but also very easy to grow in the garden in damp soil or in a pond, though it spreads fast and it usually needs to be kept in control. I let mine grow in the open water of the pond and remove clumps of it from time to time to prevent it from taking over. It can be grown from seed but the easiest option is to find someone near you who already grows it and ask for some. If you have some Water Mint growing wild near where you live, you can cut a few stems and place them in a vase of water and they will root within a few weeks (note 7).

My own favourite use of Water Mint is in Watermint Sorbet. The recipe comes from John Wright’s book “Hedgerow” (River Cottage Handbook No. 7, Bloomsbury, 2010). For the original recipe, you’ll need to buy the book (and I suggest that you do, as it is very good) but the Noémie’s kitchen website gives a slightly modified version (called Lemon and watermint sorbet). I tend to use slightly less sugar than in the recipes. The result is a lemon sorbet with a refreshingly minty tang and often a slight pink colour.

I find the flavour of the Water Mint varies as summer progresses. Herbs, including Water Mint, have the best flavour when they are gathered just before flowering, but for the sorbet I quite like the added complexity of flavour once the plant has started to flower.

Notes

Note 1 – Unfortunately the limits of the internet prevent me from sharing the smell of Water Mint with you, so you will need to go and find your own patch to sniff.

People have tried to combine smells with pictures several times, not via the internet but by releasing smells (such as tobacco smoke) into cinemas at appropriate points during a film. This has been tried several times, but never very successfully, under the names “Smell-O-Vision”, “Smellorama”, “Scentovision” and “AromaRama”. I recommend Wikipedia’s “Smell-O-Vision” page if you want to know more. I don’t think Water Mint’s smell has ever been used in this way, which is a pity.

Note 2 – The genus Mentha is named after the naiad Minthe (also spelt Menthe, Mintha or Mentha) in Greek mythology. Minthe fancied the Greek god Hades and tried to seduce him but Persephone (daughter of Zeus and queen of the underworld) transformed her into a sweet-smelling mint plant. (Allegedly.)

Note 3 – The Gardening Know How website says it is hardy in USDA zones 8 to 11. In Finland, Water Mint is only native in the milder Åland Islands but it has escaped from cultivation elsewhere.

Note 4 – Water Mint is one of the parents of Peppermint (Mentha x piperita). This is a a hybrid mint formed by a natural cross between Mentha aquatica and Spearmint (Mentha spicata). Peppermint is grown as a commercial crop and the world production of peppermint in 2014 was 92,296 tonnes, largely in Morocco (92% of the total). Peppermint leaves are used to make herb teas and the plant’s essential oil is used to flavour confectionery and toothpaste.

Note 5 – For details of the compounds found in Water Mint in Tunisia, see Wissal Dhifi , Mariem Litaiem , Nahida Jelali , Naceur Hamdi and Wissem Mnif (2011) –  Identification of A New Chemotype of the Plant Mentha aquatica Grown in Tunisia: Chemical Composition, Antioxidant and Biological activities of its Essential Oil, Jeobp 14 (3) pp 320 – 328.

Note 6 – Pennyroyal, Mentha pulegium, is a low and spreading type of mint with pretty flowers and a very intense scent, which is sometimes grown as a garden herb. It was formerly used as a medicinal herb. Two of its main uses were as a contraceptive and to trigger abortions, but its use is very risky and large or concentrated doses of Pennyroyal have caused the deaths of several pregnant women over the years.

Note 7 – It is illegal to uproot wild flowers without the landowner’s permission (under the Wildlife and Countryside Act, 1981 in Britain and the Wildlife (Northern Ireland) Order, 1985, in Northern Ireland.) See the Wild Flower Society’s Code of Conduct for the conservation and enjoyment of wild plants.