Despite the heat of the past few days the summer weather has generally been disappointing so far but it has not been awful for all plants. While my zinnias are a disaster and the legions of snails have demolished my cabbages the cool and moist weather has suited the hydrangeas well.
Hydrangeas are among the most popular of garden shrubs and they provide lots of colour for many months. We usually mean the ‘bigleaf’ or ‘hortensia’ hydrangeas (Hydrangea macrophylla), commonly called mopheads or lace caps when we say ‘hydrangea’. But there are many more kinds and they all need different treatment.
Of course, apart from pruning, the most puzzling question is about why pink hydrangeas turn blue and vice versa. If you want to know about this in detail, pop over to my own blog and read about it here.
Hydrangea macrophylla is the common hydrangea with colourful flowers. In recent years lots of new varieties have been introduced that have unusual flower shapes and colours.
One of the most popular is Schloss Wackerbarth, sometimes sold as ‘Glam Rock’, though it is properly called ‘Horwack’ (PBR). The long-lasting flowers are maroon and green, everchanging as the develop and lots more ‘green and pink’ types are coming onto the market. A feature of many of these new kinds is that they are compact and very suitable for small gardens and pots.
Another unusual kind is ‘Ayesha’ which has flowers with curved ‘petals’ making it look like a lilac. It is often said that it is scented but I have never detected any fragrance. It is an old variety and a large shrub. New kinds with curly flowers are being introduced that are better for restricted spaces.
Hydrangeas are great for pots and you can control the flower colour easily. Always use a loam-based compost – John Innes No 3 for pink blooms and lime-free John Innes for blue. You can also easily apply hydrangea colourant to plants in pots. I have struggled getting these hydrangeas to establish in my garden but have found that if I grew them in a pot for a few years, the bigger plants then grew well when planted out.
These hydrangeas are frequently sold in spring, forced to flower early n greenhouses. They can be planted in the garden after the flowers fade but these have been bred and selected for pot sales and may not be as hardy as the kinds for sale now in the shrub section at Nags Hall.
These hydrangeas like a sunny or part-shaded spot. They cope well with coastal areas but do not like cold winds and prolonged frost. Ideally the soil should be enriched with plenty of organic matter and they dislike dry soils and summer drought.
The closely related Hydrangea serrata is rather smaller in size and generally tougher so a good option if you struggle with the usual hydrangeas. It was the first of my hydrangeas to really do well despite being is less than ideal conditions. ‘Bluebird’ is a popular, typical lace cap kind.
The kinds with masses of sterile florets, making a ‘blob’ of flowers, are called mopheads and those with a ring of large, sterile florets around a centre of small, fertile florets are called lace caps and this pattern applies to most kinds of hydrangeas. The lace caps are less showy but are more valuable for pollinators.
Hydrangea aspera is a very different shrub but with the typical lace cap flower style. It has a rather course habit with attractive flaky bark and soft, downy leaves. ‘Hot Chocolate’ is one to look out for with attractive purple foliage.
Of course there is also Hydrangea anomola (H. petiolaris), the climbing hydrangea. It is often recommended for north-facing walls and it is self-clinging so will stick to walls and also to tree trunks. It loses its leaves in autumn but the foliage does turn bright yellow before it falls. I always think that people expect ‘the climbing hydrangea’ to have large heads of pink or blue and are bitterly disappointed with the white lace cap flowers.
In recent years a lot of attention has been given to two other hydrangea species, both of which are hardy and simple to prune – just cut back hard in spring – and the will withstand cold winters and hot, dry summers.
‘Annabelle’ is the most common form of the American Hydrangea arborescens. The flowerhead are crowded with sterile florets and the flowers start lime green and mature to ivory white. I find that snails love the new growth and an added problem is that, if pruned hard, the impressive flowerhead are so large that, after rain, the stems collapse under the weight.
There are variations in foliage but there was no variation in flower colour until recently when ‘Invincibelle’ was introduced. I like this but the flowers do fade rather quickly to a rather dirty pink and new ‘improvements’ are being introduced every year.
It is definitely worth a try where other hydrangeas might struggle.
The other group are forms of Hydrangea paniculata. The species is rather dull but the first form with all-sterile florets called ‘Grandiflora’ is still worth growing. It is such a good plant that in the USA they are generally called simply PGs (Paniculata Grandiflora).
These days there are lots of similar kinds and the smallest, such as ‘Bobo’ only reach about 1m high. The flowers are usually lime green at first and turn cream, becoming tinged with pink as they age but some have been bred to be bright pink while others are predominantly lime green. All are wonderful shrubs for late summer display.
There are hydrangeas for every kind of garden and few shrubs bloom so reliably or for so long. Now is an ideal time to add one or two to your garden.
Weekly reminders
Continue to feed and water tomatoes. Remove a few of the lower leaves if they are turning yellow but do not strip the plants. The plants need the leaves to feed the plants and fruit
Gently lift onions that are starting to mature, breaking the roots to stop growth and encourage ripening
Deadhead summer flowers to prevent seed foratkon
Water and feed summer pots and baskets