The names of these animals and plants may be more familiar to conservationists than culinary gourmets, but this unusual and perhaps unappealing menu featuring species which have invaded Scotland is to be cooked up for dinner next month.
The “Eating Aliens” Feast has been concocted by Dr Ian Edwards, a botanist at the Royal Botanic Garden Edinburgh (RBGE), who regularly forages for unusual ingredients to cook with at home.
The aim is for diners to discuss whether the best way to deal with invasive species – another is Sitka spruce – is to cook them.
Edwards, who is co-hosting the RBGE event as part of the city’s International Science Festival, said: “We are using things which people have tended to dismiss in the past. Japanese knotweed, for example, is a terribly pernicious weed which is also edible and apparently tastes a bit like rhubarb.
We don’t have a native spruce in Scotland and although Sitka spruce has become a wonderful, iconic tree it’s a timebomb really, because it spreads so fast when trees become mature. I use spruce all the time for things when I cook at home, like salads.
“It’s funny that people buy wild rocket at the supermarket, which has probably been grown in polytunnels in Spain and flown across, when there are alternatives literally growing in cracks in the street. A lot of tree leaves are good in salads, like lime and elm. I once made a meal for friends using ten types of tree to show how many you can eat.”
Before the dishes are prepared at home, however, the experts warned that some of the ingredients may be hard to obtain. The lobster-like American signal crayfish is illegal to catch unless trappers have a licence to prevent it spreading.
It was introduced into the UK in the 1970s by restaurateurs who prized its rich and tender pink meat. But after some escaped they bred prolifically in the wild and have infested some lochs and rivers in Scotland. They pass on a fungal disease which destroys native freshwater crayfish, and their burrows undermine river banks.
It is also illegal to plant or spread Japanese knotweed, which was introduced in the mid-19th century as an ornamental plant but soon spread widely after outcompeting native plants. It is becoming increasingly common in Scotland’s towns and cities with a prolific growth rate of 40mm per day.
Edwards added: “You have got to be very careful. I am gathering Japanese knotweed from a place near the Botanics, but it will be sent in a sealed bag to another restaurant to be cooked before it is allowed into the Botanics. Any shoots which are not eaten must be incinerated. We are getting the crayfish from England where they are more widespread and some people have licences to harvest them.”
The spotted sika deer are native to the Far East but were imported into wildlife parks in the UK because of their ornamental value. They too have established colonies in the wild and are regarded as a serious pest in new forestry plantations where they eat tender young shoots. Sika deer meat is regarded as the most strongly flavoured of venisons.
Spruce needles are now gaining favour with some of the best chefs in Scotland. Michelin-starred Andrew Fairlie began using them at his restaurant in Gleneagles two years ago and he has become a keen convert to foraging.
Fairlie said: “I haven’t used Japanese knotweed yet but that’s more because we are still not used to using these things. I went out with a forager last autumn and I was amazed by all the things that you can eat.
“The reason that many things aren’t eaten is that they would taste awful, but things like spruce are delicious. We use it a lot, in chocolate petit fours, infused with cream and milk, in salads, and to garnish fish. We don’t tend to make a big deal about it but diners ask what it is when they see it on their plate. People have been eating these things forever, but as a hobby rather than getting it commercially into the food chain. Now chefs are looking at it more and more.”
Delicacy: Candied Japanese knotweed
1kg Japanese knotweed
1kg caster sugar, plus extra for rolling
½ litre water
100g stem ginger
2 star anise
2 whole oranges
First, take your Japanese knotweed stalks, trim and wash and cut into 3in (7½cm) pieces and place in the fridge.
Peel and slice the ginger. With a potato peeler, peel the outer skin of the orange into strips and squeeze the juice.
Place the sugar and water into a heavy-bottomed pan over a low heat and allow to reduce until sticky.
Next add the ginger, orange juice and zest and the star anise and allow the flavours to infuse for ten minutes off the heat.
Strain off all the ingredients from the stock and discard. Place the stock back on the heat and simmer for another ten minutes. Then add the Japanese knotweed and allow to cook until translucent. Remove gently from the stock syrup and drain. Retain the stock syrup for later use.
When cool, roll the knotweed in the extra caster sugar, then place on a wire tray in a cool area and allow to dry.
Repeat this process up to six times until you have the desired well-glazed finish.