Mixers

Butterfly Pea Syrup

Butterfly pea syrup is plain 1:1 syrup in which dried butterfly pea flowers have steeped, which turn it deep blue; it has no alcohol and keeps for seven days in the fridge. Add acid and it shifts to violet and then pink, because the flower's blue anthocyanins change colour with pH. It tastes of very little, so its job in a drink is colour.

Quick Facts

ABV0% ABV

Legal categoryNon-alcoholic

Flavour Strengthlight

Our keeping timeHome-made: one week refrigerated.

Storage

Refrigerated in a dark bottle: light dulls the pigment before time does.

Allergens

None of the 14 listed allergens.

The ingredient

About Butterfly Pea Syrup

Flavour Profile

Primary Flavours

FloralGreen teaEarthy

Tasting Notes

Barely there by design: a light, tea-like earthiness under plain sweetness. The colour is the point.

Butterfly pea syrup is a dye as much as a sweetener

Butterfly pea, Clitoria ternatea, is a climbing legume whose flowers are a vivid deep blue. Steeped in hot simple syrup for about ten minutes, the dried flowers give up that colour and very little taste. In Southeast Asia the flower has long been used to colour rice and desserts, and in Thailand and Vietnam a tea of it is mixed with honey and lemon.

Acid moves it from blue to pink

The colour comes from anthocyanins, chiefly a group called ternatins, which change structure with acidity: near neutral they read blue, and as acid lowers the pH they move through violet towards pink. Lemon or lime juice is enough, and so is tonic water, which is why butterfly pea gins turn pink when tonic goes in.

Butterfly pea syrup against other ways to turn a drink blue

House butterfly pea syrup

Colour: Deep blue
Changes with acid: Yes, to violet and pink
Alcohol: None
Keeps: One week, refrigerated

Butterfly pea tea

Colour: Blue
Changes with acid: Yes
Alcohol: None
Keeps: Made as needed

Blue curaçao

Colour: Blue, from added colouring
Changes with acid: No
Alcohol: 20%
Keeps: A year or more once opened

Option	Colour	Changes with acid	Alcohol	Keeps
House butterfly pea syrup	Deep blue	Yes, to violet and pink	None	One week, refrigerated
Butterfly pea tea	Blue	Yes	None	Made as needed
Blue curaçao	Blue, from added colouring	No	20%	A year or more once opened

Small batches, kept dark

Heat 250g of water and dissolve the same weight of caster sugar in it, then steep about 2g of dried flowers off the heat for ten minutes and strain, for roughly 400ml. Refrigerate it and use it within a week, in a dark bottle if you have one: the pigment is not permanent, and light dulls it before the syrup spoils. Dried flowers keep far longer than the syrup, so make small batches as needed.

The Witch's Brew lands violet

The Witch's Brew shakes 20ml of the syrup with 45ml of gin, 15ml of elderflower liqueur and 20ml of lemon, so the drink reaches the glass violet rather than blue. Its recipe line makes its own syrup with a tablespoon of flowers in 200ml of hot syrup, a small batch on the same principle.

Using it

Using Butterfly Pea Syrup

Usage

Our Witch's Brew pours 20ml with gin, elderflower liqueur and 20ml of lemon, which turns the blue to violet. Where the colour change is the point, add the citrus last, in front of the drinker.

House Recipe

Ratio1:1 by weight, steeped with dried flowers

MakesAbout 400ml

Our keeping timeOne week refrigerated

Ingredients

250g caster sugar
250g water (250ml)
About 2g dried butterfly pea flowers, a small handful

Method

Warm the water and stir in the sugar until clear.
Take it off the heat, add the flowers and steep for about ten minutes.
Strain, cool and bottle, in a dark bottle if you have one.
Label with the date and refrigerate.

Food safety

Keep it cold and dark. Faded colour is light at work, not spoilage; cloudiness, fizz or mould is spoilage, and the batch goes.

Pro Tip

Tonic changes the colour too. Butterfly pea gins turn from blue to pink when tonic goes in, because tonic is acidic, so a highball built on this syrup will shift even without citrus.

Top Tips

Pour the acid last. Shaken in with the lemon, the drink arrives already violet; built in the glass, it changes as you watch.
Keep the bottle dark. The pigment fades in light before the syrup spoils.
Buy the dried flowers rather than a finished syrup: a batch takes ten minutes, and dry petals keep far longer than syrup.

Possible Substitutions

Simple Syrup: Plus a strong butterfly pea tea: the same colour change at short notice
Blue Curaçao: Blue that stays blue, with 20% alcohol and orange: a different drink

Production Method

Simple syrup steeped with dried butterfly pea flowers (Clitoria ternatea), then strained. The flowers release water-soluble anthocyanin pigments that carry the colour into the syrup.

History & Context

In Southeast Asia the flower has long coloured food and drink: it gives Kelantan's nasi kerabu its blue rice, and in Thailand and Vietnam a butterfly pea tea is mixed with honey and lemon, turning it pink-purple.

Go further

More to explore

Common Questions

What is butterfly pea syrup?

Simple syrup steeped with the dried flowers of Clitoria ternatea, the butterfly pea, a climbing legume from Southeast Asia. The flowers dye the syrup a deep blue and add almost no taste. In drinks it is used for its colour, and for the way that colour changes when acid arrives.

Why does butterfly pea change colour?

Its blue comes from anthocyanins, chiefly ternatins, pigments whose structure and colour change with acidity. In a near-neutral liquid they are blue; as lemon, lime or tonic lowers the pH they shift through violet to pink. Nothing is added: the same pigment simply reads differently in acid.

What does butterfly pea syrup taste of?

Mostly of sugar. The flower is usually described as mild and faintly earthy, and the syrup's sweetness covers most of that. Build the drink's flavour from its other ingredients, and when balancing the sweetness treat the syrup as plain 1:1 syrup with colour attached.

How do I make butterfly pea syrup?

Heat 250g of water, add the same weight of caster sugar and stir until clear, then, away from the heat, steep about 2g of dried flowers, a small handful, for ten minutes. Strain, cool and bottle, in a dark bottle if you have one, then date it and chill it. The batch comes to about 400ml.

How long does butterfly pea syrup keep?

Up to seven days, refrigerated. The colour fades sooner if the bottle sits in light, which is a loss of colour, not spoilage; cloudiness, fizzing or mould are spoilage, and that batch goes. Small batches stay bluest.

Can I use butterfly pea tea instead?

Yes, for one drink. Steep the dried flowers in a little hot water, strain, and add it alongside plain simple syrup: the colour change works the same way. The tea adds a little more water than the syrup would, so the drink comes out slightly longer.

Why is my butterfly pea drink purple, not blue?

Because the acid is already in it. Shaken with lemon or lime, the pigments shift before the drink reaches the glass. To serve it blue, build the syrup and spirit first and add the citrus or tonic at the table, or serve the acid on the side.

Make something

Made with Butterfly Pea Syrup

Featured In These Cocktails

Witch’s Brew

Often Used With

Simple Syrup

Guide by Jerry Can Spirits · Updated 11 October 2026

Back to Ingredients Guide