Hydrangeas will bloom beautifully blue if watered with 1 natural item

Summer is a glorious time of year for gardens as the flowers come into full bloom, meaning it's full of vibrant colours and life.

Hydrangeas are a great choice for adding a big pop of colour to gardens as they bloom in lovely shades of blue, pink, purple and white and their striking ball and cone shaped flowerheads means they will stand out from the crowd. The flowers tend to come into bloom from mid-spring until late summer, although this can depend on the variety and the growing conditions and if you get the Hydrangea macrophylla variety - also known as a bigleaf hydrangea - these have the unique ability to change colour.

The flowers on bigleaf hydrangeas change colour due to the pH levels of the soil. The Royal Horticultural Society (RHS) says if the soil in your garden is acidic (with a pH of 5.5 or lower) then this should produce striking blue or purple flowers due to the availability of aluminium, whereas alkaline soils (with a pH of 6.5 or higher) encourage more pink or red blooms. So if you're a fan of the blue variety there is a very easy way to help maintain that striking bright colour throughout the summer, and that's simply by watering the plant with rainwater.

While hydrangeas can be watered with tap water, gardening experts say it is actually best to water them using rainwater instead, particularly if you want beautiful blue flowers.

Tap water - especially in hard water areas - can be alkaline and this can cause blue-flowered hydrangeas to turn pink. But rainwater, by comparison, is naturally more acidic and it is this acidity that helps hydrangeas to produce blue flowers.

Gardeners' World explains: "Water regularly, even weekly if necessary, throughout the plant's first growing season to help the roots establish.

"Water hydrangeas with rainwater to help keep the flowerheads blue. Hydrangeas do best in moist soil and can wilt in hot weather, so be ready to give extra water during hot spells in summer, especially if they are in full sun."

The type of soil you plant hydrangeas in can also affect their colour, so if you want a bloom colour you'll need an acidic soil with a pH of 5.5 or lower.

Scotland Grows adds: "To encourage blue hydrangea flowers, grow the plant in soil that has a pH of 5.2-5.5. If the pH of your soil is naturally higher and therefore alkaline, it will be very difficult to get blue flowers. You can, however, lower the pH of the soil by applying an acidic organic mulch, such as pine needles, pine bark, sawdust, or oak leaves.

"Coffee grounds are also slightly acidic if your local coffee shop lets you collect them. Alternatively, you can buy a commercial soil acidifier at your local garden centre or nursery.

"Another tip is to use rainwater to water your hydrangeas, since water from a mains tap can affect the flower colour, turning blue flowers mauve or pink.

"Remember though that even if you purchase a blue hydrangea in bloom, you cannot be sure that the plant will produce the same colour of flowers once it is growing in your garden if your garden soil pH is too alkaline."