Planting hydrangeas in the right location is extremely important. It can make the difference between growing a lush, lavishly blooming shrub and one that struggles and produces scrawny blooms.
All hydrangeas will bloom and grow well in morning sun and afternoon shade. This is especially true of the most commonly grown hydrangeas, the macrophyllas. These are the blue and pink mopheads and lacecaps.
In hot areas Hydrangeas need a lot of water. In fact the word "Hydrangea" comes from the Greek for "water tub". They grow best in rich soil, so dig in compost or other organic matter when you plant them, and mulch well. No hydrangea will do well in heavy shade.
Choose a location where your hydrangea can reach its full size without pruning. For normal sized hydrangeas, expect the plant to reach about 1 - 1.5 m. Look for our lovely dwarf varieties as well – these will grow 60-90cm.
Hydrangeas grow best if they are fertilised once or twice a year in spring and summer. Use organic additions to the soil, such as manure and compost, or a slow-release, balanced fertiliser. Apply ¼ cup around the base of a very small plant, and 1-2 cups around a very large plant. Spread out to drip line, but don't get it next to the trunk.
In Spring, prune back old or damaged growth and old flower stems. Don't cut new shoots - they are where the new blooms will be. In late summer, after blooming, prune to just above the next outward facing bud. For larger flower clusters, thin plant down to half the number of stems.
You can change the colour of the blossoms by changing the acidity of the soil. Add Aluminium Sulphate to make the soil acid for Blue flowers. Or add Lime to make the soil alkaline for Pink flowers. You will need to repeat the process 2 or 3 times over the growing season and continue it as long as you want the change to continue. It may take a year or two to see the results you want. This doesn't usually work on the white varieties on Hydrangeas.