Gardening: How to grow and prune hydrangea

Phyl Boyce

Reporter:

Phyl Boyce

Gardening: How to grow and prune hydrangea

Hydrangeas from Phyl's garden: The flowering shrub is one of the most commonly grown plants in Irish gardens

Hydrangeas have large blooms, which bring flamboyant colour to the garden in late summer and autumn. This year they are flowering very well with very large flower heads due to recent rain.

Hydrangeas like lots of moisture. They are easy to grow, dependable and they improve with age. Hydrangeas can be seen growing in the vast majority of gardens. They are true survivors and can be seen flowering in overgrown or neglected gardens. With a small amount of care they will really do well.

Grow hydrangeas in fertile, moist but well-drained soil with compost added. Hydrangeas prefer dapple shade against a north or west-facing wall with some protection from cold winds, which burns the new foliage in spring. The flowers are likely to scorch if exposed to full sun. They need plenty of moisture during the summer.

The flowers come in a range of colours that include red, white, blue and various shades of pink. The flower colour depends on the cultivar and on the availability of aluminium in the soil, which is determined by the pH of the soil.

On acid soils (pH 4.5-5.5) flowers may achieve intense deep blue colour; this changes to shades of pink as the soil pH increases. The blue colour flowers may be enhanced by a weekly application of blueing compound (aluminium sulphate). It may take a few years before the flower colour changes. Nurseries can grow perfectly blue hydrangeas in lime-free compost but many of these will change to pink when planted in garden soil with some lime in it.

Pruning is not essential but may be done each spring as new shoots emerge. Since most hydrangeas flower on the previous years growth do not remove all of these shoots. Remove about a third of the older, less productive stems, cutting them back to ground level to encourage new shoots to grow from the ground. Leave old flowers heads on the shoots during the winter to give frost protection to the new delicate growth in spring. The old flower heads look fantastic when their brown papery domes are covered in frost. The flowers heads can be dried and sprayed with colour for winter decoration.

There are many cultivars of Hydrangea macrophylla (common hydrangea) producing red, pink and blue flowers that are either mophead or lacecap. Hydrangea paniculata produces beautiful cone-shaped flowers that are mostly white. There are several varieties of this shrub or small tree that can grow up to 20 feet tall. If pruned hard in spring it never gets out of hand and is ideal for the small garden.

Peaches

This week we picked the peaches from our peach tree. We grow our peach tree outside on a south-facing wall, where it gets maximum sun. Peach trees like a deep, fertile, slightly acid soil. Plant new trees before the middle of winter because they start growth very early in spring. They produce blossoms early in spring when few insects and bees are around. They can be pollinated by hand, using a soft brush to transfer pollen from one flower to another.

Cut back each stem that has produced fruit after the fruit has been picked. Peach-leaf curl is a common problem, spray the plant with Dithane or any traditional copper fungicide. Spray the leaves before they fall and again from January to February.

Make sure the spray runs down the bark and fills the crevices where the spores hide.

Jobs for the week

In the greenhouse, plants like tomatoes, peppers, chillies and cucumbers will continue to produce a plentiful supply of fruit. Removing the ripe fruit will encourage the green fruit to ripen.

To help lawns recover after the summer, apply an autumn lawn fertiliser to give the grass a boost before winter starts. This fertiliser is low in nitrogen and will help to produce a good root system to the grass. Apply the fertiliser when the grass is dry and there is no wind.