Hydrangeas are native to southern and eastern Asia and America. Hydrangeas thrive this year as they enjoy all the rain and cooler temperatures. There are so many different species, subspecies and cultivars available today that even experienced horticulturalist could not say the exact number. Most varieties are from the species Hydrangea macrophylla, paniculata and quercifolia. The most well know hydrangeas are the mopheads, which change colour on different pH soil and have a full, mop like flower head. Lacecaps have two types of flowers, big sterile flowers surrounding small fertile florets.
Cultivation
They grow well in most type of soil, although I found that heavy clay will affect their growing in a negative way. They are the happiest on fertile, well drained soil. Hydrangeas like their water a lot so make sure that you avoid dry spots when planting. Also a semi shady location is the best to grow these plants in. Dig in lots and lots of well rotted compost as this will provide food for your plants for years. Don’t plant the hydrangeas deeper than they were in the pots you bought them in as too deep planting could reduce new stem growth. Allow plenty of space for the plants as they can spread 6 metres wide and grow 2 metres tall.
Changing Colours
The colour of the flowers ranges from pale pink to blue, white to green and all shades of pinks, blues can be found. The well know colour changing is due to the amount of aluminium and iron the plant can take up from the soil and it is determined by the acidity of the soil, with other words pH. You will need to achieve a soil pH of 6.5 and lower if you want blue hydrangeas and a pH 7.0 and higher for pink blooms. The ability of changing colour vary between varieties, some will change colour during the growing season turning green then later blue. The age of the plants affects the colour of the flowers too; a small plant will need 2-4 years to establish its final colour sometimes. You can add lime to the soil around the base of the plants to get pink flowers or aluminium phosphate to get blue flowers. In garden centres you can buy ericaceous compost if you have blue flowering plants, as it has a pH of less than 7.0. White and green flowered cultivars keep their colour regardless of the soil pH.
Cut and Dry
Hydrangeas make excellent, long lasting cut flowers and they also can be dried out. Cut the flowers later in the season if you would like to dry them and just hang them upside down in a cool, airy room out of direct sunlight.
Propagation
Hydrangeas can be propagated very easily. The best is to take cuttings from young, non flowering stems in July – August. Make sure that your cuttings have 2 – 3 pairs of leaves. Place them in light, sandy compost in a shady area. Also you can try to root the cuttings in a glass of water; roots will form in about 3 weeks. I don’t like this method as the roots are very delicate and easily damaged when potted in compost.
Pruning
Most hydrangeas don’t need any pruning, except dead heading. If you expect cold winter than leave the dead flower heads on the plants, they will make some protection against the frost. The first 3 – 4 years of the young plants will not need any pruning for sure. Later if the shrubs get out of shape or take up too much space you can prune them lightly. The best time is late winter – early spring to cut back hydrangeas. Remove the dead flower heads by cutting back to the first strong, healthy pair of buds lower down the stem. Also on older plants you can remove the middle, woody stems, cutting them back completely by the base of the plant. Cut any damaged stem down to the base of the shrub if it shows no sign of rejuvenation. This severe pruning often results in a proliferation of new shoots from the base of the plant. This will encourage the plant to grow more young shoots and also will allow more sunlight into the middle of a big, established shrub.
