In the garden with Gerry Daly: outstanding hydrangeas

Few plants are as easy to grow and few shrubs flower for such a long period from mid-summer to late autumn. The hydrangea is especially suitable for country gardens where their natural looks are ideal and they can generally have the space they require. The common garden hydrangea is Hydrangea macrophylla, the second part meaning “large-leaved”. A native of Japan, it is thought to have arrived in Europe about 1790. In its wild state, its grows near the coast and on islands near Tokyo. The origin accounts for its remarkable performance as a seaside plant. Despite its large leaves – which in most plants are usually easily damaged – the bush can stand a good deal of wind exposure. The near absence of frost near the coast and reliable rainfall encourages luxuriant growth with large flower heads and rich colouring.

Any plant with large soft leaves and soft stem tissue needs to have a steady supply of moisture in soil that does not run dry in summer, and rich feeding. Contrast the hydrangeas of Cork and Kerry with those of the dry, limy soils of Dublin, and it is easy to understand the needs of the plant.

Dry soil stunts growth, resulting in smaller flowers of pale colouration, while the leaves often turn yellowish on very limy soil. Hydrangeas flower each year at the tips of the shoots made the previous year. Therefore, when pruning you should avoid removing these tips. While pruning for a late-flowering shrub should take place after flowering, this is not advisable with hydrangea because of the increased risk of frost damage. Therefore pruning is left until March, but be careful the flowering shoot tips are not removed before the flowering season.

Incorrect pruning is a common cause of the failure of hydrangeas to flower. Pruning should consist of the removal of some shoots close to ground level each year, a process of thinning that will keep the plant to size. Alternatively, let the plant grow as it wants for eight or 10 years and then cut it right back to soil level. One or two year’s flowering will be lost but this system might be more attractive to some people than regular pruning. The main reason for lack of flowering is the destruction of the flowering shoot tips by frost. This can happen year after year in cold localities, especially inland from the sea. Isolated plants in midland gardens will not flower reliably. It helps to have some overhead protection of trees. However, tree roots below ground can cause problems by soaking up moisture and creating overly dry conditions. Lacecap varieties are credited with greater hardiness than the mop-heads or hortonsias.

There are hundreds of hydrangea varieties, between the mop-heads and lacecap types. Practically all kinds will be pink on limy soils, blue on acid kinds and purplish on neutral soil. There is considerable variation of intensity of colour. Some kinds have pale flowers, either pale pink or pale blue, such as “Generale Vicomtesse de Vibraye” while others such as “Hamburg” are dark, changing from deep pink on limy soils to deep purple-blue or acid soil. The following are good varieties, and mostly available; Europa, Nigra, Westfalen, Altona, Bodensee, and Mme Emile Mouilliere – a white form. The best lacecaps are Blue Wave, Lilacina, Lanarth White and the Teller series of varieties.

Summer pruning of fruit trees – apples, pears and plums – is a way of reducing the vigour of these fruits, especially on trained trees on walls, such as espaliers but it can be used on free-standing trees too. Young trees are inclined naturally to be vigorous and summer pruning is a useful technique. Older trees that have been hard pruned to reduce their size often respond with vigorous growth of new shoots.

If for some reason such as frost, apple or pear trees have a small load of fruit, or no fruit at all, it is not surprising that the energy of the tree will go into shoot growth.

Summer pruning generally involves the shortening of the strong new shoots to three or four buds, or the complete removal of a proportion of them. The usual practice is to begin removing these shoots from mid-summer, generally between mid-July and the end of August.

It is important to remove the shoots in stages over a period of weeks. If they are all removed at one go, the pruned shoots will break bud and shoot out again, especially if it is done early.

Trees, shrubs and roses

Trees and shrubs are mostly in good condition after a summer of rain and sunshine. Rain fell when the dry spells were starting to pinch, but a check should be made just the same. Preparations for autumn and winter planting can be made now.

Flowers and containers

Bedding and container annuals will last longer if given some liquid feeding now. They still have two months in them but will tire long before that without feeding and regular watering. Spring bulbs are in the shops and it is a good time to make an assessment as to new locations for bulbs.

Lawns

Lawns have been growing strong since the arrival of heavy rain. Warm days kept the soil temperatures up and the result is that lawns are looking their very best. Little needs to be done except to keep the grass mown. Autumn lawn fertiliser could be applied if the grass is a bit slow.

Fruit, vegetables and herbs

The vegetable garden is well past its peak of early August with early cabbage and cauliflower, first carrots, French beans, broccoli and peas finished and second sowings ready. Sweet corn will still be coming in. Get rid of all old crops when they are finished and make sure not to let them get away.

Greenhouse and indoor plants

Keep picking greenhouse tomatoes, peppers and cucumbers as soon as they come ready – otherwise cropping tails off quickly. Stop feeding most greenhouse plants now because they will have enough in the pot to keep them going and they are better going into winter a little “harder”.

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