Butterfly Pea (Sangu Poo): How to Grow It and Make Your Own Blue Tea

Few plants are as beautiful and useful as the butterfly pea, or sangu poo (சங்கு பூ). Its vivid blue flowers transform a plain balcony into something magical — and those same blooms make a stunning, caffeine-free blue tea that changes colour when you add lemon. It's a hardy climber that flowers for months with very little care. Here's how to grow it and turn the harvest into a gorgeous drink.

Why Grow Butterfly Pea?

Butterfly pea is a triple win: ornamental, edible and low-maintenance. The vine covers trellises and railings in deep blue flowers, attracts pollinators, and as a legume it gently enriches your soil. The flowers are prized for blue tea, as a natural food colour, and in traditional hair and skin care. Once established, it keeps blooming with almost no effort.

Step 1: Sowing the Seeds

Soak the seeds in water overnight to soften their hard coat. Sow them about 1.5 cm deep in a pot at least 10 inches deep, filled with a free-draining mix of garden soil, compost and sand. Keep the soil lightly moist and seeds will sprout in 5–10 days. You can sow directly in the final pot — no transplanting needed.

Step 2: Give It Something to Climb

Butterfly pea is a vigorous climber, so set up support early: a trellis, balcony grille, fence or string lines all work. As the vine grows, guide the young tendrils onto the support and it will take over from there, quickly creating a green, flowering screen.

Step 3: Sunlight and Watering

For the most flowers, give it full sun — at least 5–6 hours daily. Water when the top inch of soil dries out. It is fairly drought-tolerant once established, so avoid overwatering, which reduces flowering. The plant rewards warmth and light with continuous blooms.

Step 4: Feeding and Pruning

As a legume, it needs little feeding — a monthly handful of compost is plenty, and too much nitrogen gives leaves instead of flowers. Pinch the growing tips occasionally to encourage bushier growth and more flowering branches. Light pruning after a heavy flush keeps the vine tidy and productive.

Step 5: Harvesting the Flowers

Pick flowers in the morning when they are fully open and freshly bloomed. Harvest regularly — the more you pick, the more the plant produces. Use them fresh, or dry them in the shade on a clean cloth for a few days and store in an airtight jar for year-round blue tea.

How to Make Butterfly Pea Blue Tea

Steep 5–6 fresh or 8–10 dried flowers in a cup of hot water for 3–5 minutes. The water turns a deep, jewel-like blue. Strain, then sweeten with a little honey if you like. For a fun trick, squeeze in some lemon — the acidity turns the tea from blue to purple-pink before your eyes. Serve it hot or over ice.

Common Problems and Fixes

Lots of leaves but few flowers usually means too little sun or too much nitrogen — move it to brighter light and ease off feeding. Yellowing leaves often point to overwatering. Butterfly pea rarely suffers serious pests, though aphids may appear; a neem oil spray handles them easily.

Frequently Asked Questions

How long until it flowers? Usually 6–8 weeks from sowing, then continuously.

Does it need a trellis? Yes — it's a climber and performs best with support.

Is butterfly pea tea caffeine-free? Yes, it's a naturally caffeine-free herbal tea.

Can I grow it in a balcony pot? Absolutely, with a sunny spot and something to climb.

Final Thoughts

Butterfly pea gives you beauty, blooms and a colour-changing tea all from one easy vine. Sow it in full sun, give it a trellis, and within a couple of months you'll be brewing your own blue tea from flowers you grew yourself.