While exploring ideas for wild plant based cocktails to serve at the end of a private foraging course, I came up with this recipe for a foraged tonic water that has the added bonus of being a great non-alcoholic drink on its own. Based on willow bark as a replacement for cinchona, it can be gathered and made in about an hour, and keeps well if you want to stock up on a batch.

For foragers, it is always an interesting challenge to look at a recipe that uses an imported ingredient and see what it can be replaced with from plants and fungi that you can find growing nearby. One area where this may seem particularly difficult is finding strong flavourings or spices, but if you look around there is a surprising range of intense tasting leaves, roots, flowers and seeds that can be foraged in the UK. Many of these possibilities are covered in this great blog and radio 4 programme with Mark Williams – Wild Spices of the UK. The quinine used in tonic water today is not really a spice, rather a flavouring, but strangely enough when it was first used people originally disliked it so much they tried to disguise its taste.

A Brief History of Tonic Water

When I start searching for foraged alternatives for well-known ingredients I like to first find out why a particular food or drink became so popular and why certain ingredients were used, as this can help direct where I look and how I prepare what I find. So, before I started experimenting with flavours for tonic water, I did some reading into the history of this ubiquitous mixer.

What we know today as tonic water is made from the bark of several species of Cinchona, a genus of trees and shrubs native to western parts of South America. These trees were traditionally used for treating fevers by indigenous populations in these areas, which is likely why cinchona became known as the ‘fever tree’ in English. In the 17^th century one of the most common causes of fever was malarial infection. After Europeans experimented with preparations they decided it was effective against ‘the ague’ and cinchona bark, and the quinine extracted from it, became the main anti-malarial drug worldwide for several hundred years. As with many medicinal plants, Europeans took advantage of traditional knowledge of indigenous people to support further colonisation. Securing supply of the bark became an imperative for supporting imperial expansion, as it was taken regularly by colonial troops and administrators as a preventative. So, as with many spirits and liqueurs, tonic water started life as medicine – because the taste of the powdered bark was unpleasant it was mixed in drinks to make it more palatable; most famously a splash of lemon or lime juice with simple syrup, and often a dash of gin for good measure.

A Local Replacement – Willow Bark

So where to start for a local tonic water? Most tree barks contain tannins, a large group of chemicals that usually taste bitter and are also astringent – this is the drying and slightly constricting sensation you will recognise from strong black tea or full bodied wines (aged, of course, in oak barrels). When considering a locally foraged alternative I chose to replace the cinchona with willow bark, as it was also traditionally used for fevers and has a similar bitter bark taste and astringent effect.

I’m not the first person to make this connection though – willow bark was investigated for possible use as a replacement for Cinchona spp. in the 18^th century in the hope of having a supply of anti-malarial medicine that could be grown in Britain, but a sufficient effect was not found. However, research into the chemistry of the bark did lead eventually to the drug aspirin, which was based on the chemical salicylic acid (from the genus name Salix).

Salicylic acid was isolated from willow and also from another plant traditionally used for fevers; meadowsweet (Filipendula ulmaria). It was the old scientific name for meadowsweet, Spiraea ulmaria, that was used to come up with the name aspirin, a synthetic chemical adapted from these plants. The anti-inflammatory effect of salicylic acid also helps explain why willow bark is widely used to treat musculoskeletal pain. Clinical trials have shown that extracts of willow bark can relieve chronic lower back pain, though it also found the doses required are much higher than those typically recommended.

Willow is very easy to find in the UK, in cities weeping willows are commonly planted in parks and along waterways. These are often varieties of the cultivar Salix × sepulcralis, which was bred by crossing Salix babylonica and Salix alba. Salix alba, known as white willow, is the species most commonly referred to when discussing medicinal use of willow bark, and is native to the UK. The name alba means white in Latin as this species was named for the soft white hairs that cover the back of the leaf, making it paler than other species. Other willow species you may come across are bay willow (Salix pentandra), goat willow (Saliz caprea), osier willow (Salix viminalis) and crack willow (Salix fragilis).

Gathering the Bark and Developing the Recipe

I haven’t got around to trying all of these species, though I imagine the flavour from the bark would be very similar, just stronger in some than others. The species I used was a weeping willow, with the distinctive long dangling branches, that I found growing along a canal. When picking the bark, I used a knife to cut pieces from the tips of branches, taking only a small amount from each tree. It is important to note that harvesting bark from the main trunk of any tree can cause long lasting damage, so I only gather from the branches. I then chopped up the soft tips into small pieces, and peeled the bark off the larger bits of branch. These pieces were then added to a pan, covered with water and boiled to make a decoction. The resulting liquid had the expected strong bitter taste and astringent sensation, that is quite intense to stomach alone, but that is exactly what I was looking for as it was the unpalatable taste of cinchona bark alone that led to other ingredients being added to make the original tonic water.

As I had started looking for alternative foraged ingredients, I also tried to replace the sour taste that was originally provided by lemon in the earliest recipes (and is now provided by just citric acid in commercial preparations). I added some rowan berries to the decoction. As anyone who has tasted rowan berries raw knows they are incredibly sour, and also very bitter, so it also added a different type of bitterness to the mix that I think really enhanced it.

However, after experimenting with a final drink I found it still needed some lemon juice to lift it and provide freshness. I then added sugar to completed the tonic water base, keeping close to the original preparation of bark, lemon juice and sugar. I found it needs a lot less sugar than is used in most syrups (50-60%), adding only about 25% sugar. This means it won’t have the preservative effect, so best to keep it in the fridge if you aren’t going to drink it all straight away (though the antibacterial action of the bark and preservative effect of the sorbic acid form the rowan berries may mean you don’t need to). The base can then be diluted with sparkling water, the best ratio I found was about 3 times the water to base. Though I will also be experimenting using it in cocktails undiluted in the same way bitters are used.

Recipe 

Ingredients

• 1 cup willow bark
• 1 cup rowan berries
• 3 cups water
• 150g sugar
• 100ml lemon juice

Method

1. Simmer the bark in the water for 10 mins with the lid on the pan.
2. Remove from the heat.
3. Add the rowan berries, squashing them with a large spoon to release their juice.
4. Leave for half an hour.
5. Strain through a muslin lined funnel into a measuring jug
6. For each 1 part of liquid add 1/4 parts  of sugar and dissolve then add 1/6 lemon juice. So for 600ml liquid I added 150g sugar and 100ml lemon juice.

For the gin and tonic, pour the following (ideally all chilled) ingredients into an ice filled glass:

• 30ml tonic base
• 100ml sparkling water
• 50ml gin

Garnish with a rowan berry, slice of lemon and willow leaf.

Adapting the Recipe 

I normally keep some rowan berries in the freezer as they are abundant in most towns and cities, because councils often plant them for the ornamental effect of their orange berries that persist in winter. If you don’t have any rowan berries knocking around, you can follow the recipe using 2 cups of willow instead. You could also have a go at experimenting with unripe fruit that is around at the moment as a replacement for the rowan berries, such as cherry plums or apples.

You could also experiment with other plants for the bitter element in place of the willow bark, such as the bark of oak (Quercus spp.) or wild cherry (Prunus avium). Meadowsweet leaves are relatively high in tannins, though not particularly bitter, and also have the historic link to treating fevers. Plants that will provide the bitterness but not the same strong astringency from high tannin content include: sea wormwood (Artemisia maritima) or other species of Artemisia (interestingly, sweet wormwood was where the newest anti-malarial drug artemisin was discovered), chicory (Chicorium intybus), yarrow flowers (Achillea millefolium) and I am sure many more!

An alternative to the decoction method for the base would be to use a tincture, which worked well for me with willow bark tincture that I added straight to sparkling water with lemon juice and some dissolved sugar. Finally, the amounts in the recipe can of course be increased equally to make a bigger batch.