One of the most interesting habits of some hydrangeas is the ability of the flowers to change color. This is not true of all hydrangeas, but most often seen in the mophead and lacecap cultivars of hydrangea macrophylla.
This color change is due to the soil pH. Those with blue or pink flowers tend to be blue in acid soil conditions and pink in alkaline conditions. To get the best flower color, choose cultivars that give the best colors for the pH in question. White flowers will remain white regardless of soil pH.
Hydrangea with blue flowers can be kept blue by growing the plants in acidic soil, or by acidifying soils. In soils where hydrangeas are not reliably blue add aluminum sulfate. If the soil is very alkaline, this treatment may not work but can be very effective for container-grown plants. Use rainwater to water hydrangeas, since hard water can affect the flower color, turning blue flowers pink. Boost red or pink flowers, by applying granular lime in winter.
Hydrangeas flower from mid to late summer. Not all hydrangea are the same, different types have different flowering habits. Panicle and smooth hydrangeas flower, such as the white Annabelle and Incrediball® along with the pink Invincibelle-Spirit® bloom on new wood growth. Oakleaf hydrangeas, such as Snow Queen and Alice, flower on old wood growth.
Re-blooming hydrangeas are types that have the unique ability to flower on both old and new wood. Even if the buds are damaged by winter weather, the plant can still flower on wood it produces that season. Re-blooming hydrangea varieties include the Let’s Dance®, City Line®, and Endless Summer series. These mophead and lacecap varieties, such as Twist and Shout®hydrangeas will bloom with little attention, but regular pruning encourages new growth, that can produce a better display.
Hydrangeas thrive in a moist, but well-drained soil, in a cool, shady part of the garden. Avoid planting in dry, sunny spots and exposed areas, where cold winds may damage young spring growth.
Add Uncle’s Max Mix, landscapers mix, into the soil before planting to add plenty of organic matter and after planting use Black Magic peat compost as mulch.
Fertilizer hydrangeas with Uncle’s Root Accelerator, low nitrogen plant starter, at planting. Avoid feeding too often, with high nitrogen fertilizers which can encourage excessive leaf growth, with plants less likely to develop flower buds and more at risk from winter damage.