Answer: The large leafed hydrangeas (macrophylla types) will be blue with an acid pH soil and pink with a higher or alkaline pH soil. A pH range of about 5.0 to 5.5 should produce blue flowers. If your soil is naturally acid you may not need to worry about this at all. An annual application of compost and/or a complete granular fertilizer such as 10-10-10 according to the package instructions should keep the plant healthy. Pruning is usually limited to removing any winter damage or possibly thinning older less productive branches. The plants bloom on the previous year's growth so pruning is usually kept to a minimum. Ongoing care would include using several layers of mulch to keep the soil cool and moist in the summer and possibly providing wind protection in the winter if the plant is in a particularly windy spot.
Q&A Library Searching Tips