Hydrangeas are deciduous shrubs or vines that produce massive leaves and an abundance of showy blossoms grouped in clusters of various colours including whites, pinks, reds and blues. You can separate the Hydrangea genus into five main groups: big leaf (Hydrangea macrophylla), climbing (Hydrangea anomala), oak leaf (Hydrangea quercifolia), panicle (Hydrangea paniculata) and smooth hydrangea (Hydrangea arborescens). Select a hydrangea species suited for your location for the best results.
The best times to plant hydrangeas is after the chance of frost has long passed in late spring, in early summer or in the autumn. Hydrangeas grown in containers outside in nurseries or garden centres can be planted during any season, but midsummer plantings should be avoided, if possible. Plant hydrangeas on a cool and overcast day in the morning or wait until late afternoon to early evening on a sunny day.
Find a planting site for the hydrangea that is large enough for the expected full-grown size in both width and height, which varies depending on the variety grown. The climbing hydrangea needs strong supports, such as a trellis or walls, since this variety can reach more than 15 metres (50 feet) in length over many years. Most hydrangea varieties develop more flowers when planted in locations with sun in the mornings and shade during the afternoon. Hydrangeas prefer well-drained soil.
Water the hydrangeas well several hours and up to 24 hours before planting. Remove all foliage in the planting area selected and space the planting holes according to the plant's marker, if planting more than one hydrangea. Dig planting holes at depths that are equivalent to the containers or root ball of the hydrangeas, and at least double the width. Take the hydrangea out of the container, loosen the roots and place the plant in the centre of the hole.
Add soil to the hole until half-full; fill the hole with water to settle the hydrangea plant in place and to get rid of any air in the soil. Finish filling the hole and then water the area well. Cover the ground beneath the hydrangea's drip line with compost and 5 to 10 cm (2 to 4 inches) of mulch. Do not put any mulch against the stem of the plants. Supply 2.5 cm (1 inch) of water to the hydrangeas weekly any time rainfall is less through the summer.