How to Grow Blue Flowers

Grow blue hydrangeas.

Many gardeners aspire to grow blue flowers and often end up growing lavender or purple ones instead. There are several flowers that grow blue or nearly blue flowers, such as hydrangeas and summer gentians. Like other plants, blue flowers have their own specific care needs and must be planted and grown with those individual needs in mind.

Instructions

1. Adjust the soil's pH level to 5.5 or lower in order to grow blue hydrangeas. Test the soil with a pH testing kit or take a soil sample to your county extension service office for testing. After testing you'll know what to add to produce the optimal pH. Add lime to raise your soil's pH or aluminum sulfate to lower it. How much depends on your initial soil test results.

2. Plant a blue passion flower vine (Passiflora caerulea) in USDA plant hardiness zones 8 to 11. Grow blue passion flower in full sun and on the south side of a structure in zones 8 and 9 to get the best warmth and sun. Plant in a similar fashion as other passion flowers, spacing them about 36 to 60 inches apart in soil that drains well.

3. Grow blue delphiniums, such as bellamosas. Plant them in full sun in USDA plant hardiness zones 2 to 7 and in soil that drains water well. Plant them about 3 feet apart. Insert a stake behind the tall varieties, which can grow up to 8 feet tall. Do this in the spring so you don't damage the roots. Loosely tie the plant to the stake in several spots as it grows.

4. Plant gentians, such as Gentiana septemfida, also known as summer gentians. They grow well across the United States, but they're easiest to grow in hardiness zones 4 to 7. Plant in a partially sunny location in well-draining soil, spaced about 15 inches apart.

5. Grow Himalayan blue poppies (Meconopsis grandis), which can grow to heights of 4 feet. In general, they are difficult plants to grow--but Himalayan blue poppies grow best in hardiness zones 5 and 6. Plant them about 15 inches apart. Grow them in partial shade and in moist soil--which, according to Penn State University, must be free of lime. Test your soil with a home testing kit or take a sample to a county extension office. Plant established plants after the last spring frost, or start them indoors from seeds about six weeks earlier.

References

• USDA: Hydrangea Questions and Answers
• Floridata: Passiflora caerulea
• The Florida Times Union: Passion Flower
• Reiman Gardens: Delphiniums
• Penn State University: The Poppy

Resources

• Wall Street Journal: Mad About Blue in the Garden
• Plant Delights: Gentiana septemfida
• University of Vermont: Delphinium