Herb & floral syrup
Butterfly Pea Flower Syrup
A deep blue syrup that turns violet, then pink, the moment citrus hits it. Natural color, no dye.
- 17 min total
- 1½ cups350 ml
- Keeps 2 weeks
Quick answer
Butterfly pea flower syrup is simple syrup steeped with dried butterfly pea flowers, which turn it a vivid natural blue. Dissolve 1 cup sugar in 1 cup water, steep 2 tablespoons of dried flowers off the heat for 10 minutes and strain. Add lemon or lime only in the glass, where it turns the drink from blue to violet to pink.
Butterfly pea flowers are a Southeast Asian tea flower with a party trick: their blue pigment is a natural pH indicator. In the bottle the syrup is deep sapphire. Squeeze in lemon or lime and it swirls through violet to bright pink, right in the glass.
The flavor is very mild, faintly earthy and tea-like, so this syrup is really about color. Keep all acid out of the bottle and add it at serving, so the change happens in front of your guests.
Tastesmildearthytea-like
The recipe
Butterfly Pea Flower Syrup
Ingredients for 1½ cups350 ml
You’ll need: small saucepan, butterfly pea flowers, fine-mesh strainer, citrus press, ice cube tray, Glass Beverage Dispenser with Spigotsmall saucepan, butterfly pea flowers, fine-mesh strainer, citrus press, ice cube tray, Glass Beverage Dispenser with Spigot
Method
-
Dissolve
Warm the sugar and water in a small saucepan over medium heat, stirring, until clear and just starting to steam, about 3 minutes.
1 cup200 g granulated sugar1 cup240 ml water
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Steep
Take the pan off the heat and stir in the butterfly pea flowers. Cover and steep for 10 minutes, until the syrup is a deep, inky blue.
2 tbsp2.5 g dried butterfly pea flowers
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Strain
Strain through a fine-mesh strainer, pressing the flowers lightly. Don't add any lemon or other acid to the syrup itself.
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Bottle
Let it cool, then bottle and refrigerate, ideally in a dark or amber bottle, since light slowly fades the blue.
Storage. Keeps about 2 weeks sealed in the fridge. The blue fades gradually with light and time, so keep it in a dark bottle or at the back of the fridge. Freeze it in ice-cube trays for up to 3 months; the color holds well, and blue cubes turn lemonade purple as they melt. Toss it if it turns cloudy or smells sour.
Per 1 tbsp (15 ml): about 33 kcal, 8.6 g sugar (estimate).
How to use it
Color-changing lemonade
Stir 1 oz (30 ml) syrup into 4 oz (120 ml) cold water over ice, then pour in 1 oz (30 ml) fresh lemon juice at the table and watch it turn violet.
Color-changing gin and tonic
½ oz (15 ml) syrup with 2 oz (60 ml) gin over ice. Top with 4 oz (120 ml) tonic water, which turns it lavender, then squeeze in a lime wedge for a pinker finish.
Magic mocktail
1 oz (30 ml) syrup in 5 oz (150 ml) sparkling water over ice, served with a lime wedge for each guest to squeeze in.
Blue latte
1–2 tbsp (15–30 ml) in 8 oz (240 ml) steamed milk. Milk isn't acidic, so it stays sky blue.
Violet margarita
2 oz (60 ml) blanco tequila, 1 oz (30 ml) lime juice and ¾ oz (22 ml) syrup, shaken and strained over ice. The lime turns it a vivid violet-pink.
Gear for this recipe
Glass Beverage Dispenser with Spigot (2 gal)
For parties: a big batch of lemonade or punch sweetened with your syrup, self-serve. Glass shows off colorful fruit syrups.
Best for Parties and showers
Zulay Kitchen 2-in-1 Metal Lemon & Lime Squeezer
Best for Fresh citrus for sours and lemonade
W&P Peak Silicone Ice Cube Tray
Best for Freezing syrup portions
Amber Glass Swing-Top Bottles, 16 oz (6-pack)
Best for Light-sensitive, naturally coloured syrups
More gear for this recipe (3)
Cuisinart Fine Mesh Stainless Strainers (set of 3)
Best for Every infused or fruit syrup
Dried Butterfly Pea Flowers (culinary, 1.7 oz)
Best for Colour-changing lemonade and cocktails
Cuisinart Chef's Classic 1.5 qt Stainless Saucepan with Lid
Best for Every stovetop syrup
Tips for the best batch
- Keep the acid on the side. Lemon, lime, tonic water and many sodas turn the syrup purple-pink, so add them in the glass, not the bottle.
- Stir the syrup into water or soda before adding citrus. Neat syrup is dense and sinks, but diluted syrup changes color evenly and dramatically.
- Whole flowers strain cleanly. If you only have butterfly pea powder, use just ¼–½ tsp, since it's far more concentrated, and strain through a coffee filter.
- A teal or greenish syrup means your water is alkaline. Use filtered water for the next batch.
- The flavor is mild, so pair it with ingredients that have plenty of their own: lemon, lavender, ginger, lemongrass or vanilla.
Variations
Blue lavender
Steep 1 tsp dried culinary lavender with the flowers for a floral syrup that turns lilac with lemon.
Lemongrass ginger
Simmer 1 bruised lemongrass stalk and 3 slices of fresh ginger in the syrup for 5 minutes before adding the flowers. Fragrant and Thai-inspired.
Vanilla blue
Stir ½ tsp vanilla extract into the cooled syrup. Made for blue lattes and steamers.
Questions people ask
Why does butterfly pea flower syrup change color?
Its blue pigments (anthocyanins) react to acidity. In neutral liquid they're blue; a little acid turns them violet and a lot turns them pink-magenta. Alkaline water pushes them toward teal.
What does butterfly pea flower taste like?
Very little. It's mildly earthy and woody, a bit like a light green tea. Most of the flavor in your drink comes from whatever you mix it with.
Can I add lemon to the syrup bottle?
You can, but the syrup turns permanently purple-pink and you lose the color change. Add acid in the glass instead.
Is butterfly pea flower safe to drink?
It's a traditional tea and food coloring in Southeast Asia, and the U.S. FDA approved butterfly pea flower extract as a color additive in 2021. Research on large amounts is limited, so if you're pregnant, nursing or on medication, check with your doctor first.
How long does butterfly pea flower syrup last?
About 2 weeks in the fridge, though the blue slowly fades. Freeze it in cubes for up to 3 months.