Gardening: Low-key potentilla

If you want an easy-to-grow shrub that will fill some space in a border while contributing flowers over a long season, then potentilla is worthy of consideration.

It is not a star plant in the way that rhododendron, roses and cistus are. It simply does not have the large showy flowers of those plants. Instead, after an initial burst of flowering in May and early June, it carries on flowering in its way with a good scatter of small flowers usually well into mid-autumn, longer after a sunny summer makes for good vigorous growth.

It certainly carries on long after once-flowering rhododendrons and cistus and indeed some all-in-a-rush roses are just a memory.

Potentilla is part of the rose family and it has the typical flat, five-petalled, simple rose-type flowers. Both the most-used common name and the botanical name are potentilla because it is an easy name to remember, and the not-so-common common name of shrubby cinquefoil is much less amenable.

Informative

The cinquefoil name is informative though, because, derived from French, it means five leaflets on each palm-shaped small leaf, which most potentillas do have.

The leaves are divided to the base of the leaf, or near it, and look like a background of small narrow leaves.

The shrubby part of the name was ascribed to it to mark its having woody stems to overwinter while the non-herbaceous kinds die back for the colder months.

The shrubby potentilla is a native shrub, appearing in parts of the western counties. It does not appear elsewhere but it is widely grown as a garden shrub.

The wild plant makes a small bush to about waist-high, though often less, with bright yellow flowers. It usually appears in rocky places with good drainage, though it might be temporally flooded.

The garden forms of this plant are very reliable and easy to grow. There has been much selection and breeding of this shrub, and many new kinds have been produced in recent decades.

The native species itself has flowers of bright yellow but there are now white, pink, orange and red kinds among the named varieties and these are hybrids and all the more reliable as a result.

One of the most popular, ‘Abbotswood’ is a lovely white-flowered kind, large flowers and good growth habit.

‘Princess’ is a good pink variety with a hint of yellow. ‘Daydawn’ also has a yellow touch to its pink flowers. ‘Elizabeth’ has large, bright yellow flowers.

Hugely popular, ‘Primrose Beauty’ has soft primrose yellow flowers. ‘Red Ace’ has bright red flowers.

‘Tangerine’ has yellow flowers, flushed with orange-red. ‘Sunset’ has orange-red flowers that fade as they age.

‘Tilford Cream’ is a spreading dense bush with creamy-white flowers. ‘Vilmoriniana’ is an old French variety with grey-green leaves and pale creamy yellow flowers. It is very distinctive and more vigorous than most.

More lively

The non-woody potentillas are more lively than the shrubs. Again, they fit the role of fillers, good background and a good foil for larger, more impressive flowers.

One of the best-known of the numerous named varieties is ‘Gibson’s Scarlet’, a bright scarlet red that really warms up a border and is a perfect filler for a hot border.

‘Gloire de Nancy’ has orange-red double flowers. The doubles have more flower effect but a tendency to hang under the weight of rain.

‘Monsieur Rouillard’ is another double kind with deep-red flower, yellow marked. ‘Flamenco’ is bright red with single flowers.

‘Yellow Queen’ has double or semi-double flowers of bright yellow. ‘Etna’ has single, deep-red maroon flowers.

The herbaceous potentillas are relatively early to flower, beginning in late spring in some cases, or in early summer, and flowering through summer.

Many apple and plum trees and some pear trees set too many fruits to ripen, the fruit remains tasteless or just rots.

Plums should be thinned when the fruits are the size of an olive, reducing the number of fruit to an average of one per 5cm of fruiting branches.

So a 60cm branch should have 12 fruits maximum to achieve sweetness and good flavour without breaking the branches, which is common and often leads to severe diseases of the tree.

June drop

Apple trees and, to a lesser extent, pear trees make an effort to rid themselves of excess fruits. This is called the “June drop”, which usually takes place in early July.

Sometimes the tree sheds just the right amount of fruit. Sometimes it sheds too many, even the entire crop, but this is a sign that the tree was struggling, or that pollination was inadequate.

When the June drop has taken place, leave one fruit for each 15cm of branch on average.

Trees, shrubs and roses

The swing from cold spring to pleasant summer days was remarkable and was followed by dry conditions that could affect young trees and shrubs, planted since last autumn.

Horse chestnut scale insect is damaging horse chestnuts, lime and maple, especially Japanese maple. If you see it, apply a garden insecticide.

Lawns

After a burst of rapid growth, many lawns began to suffer drought at the edges. The main growth period for grass is coming to an end.

It should now be easier to keep lawns mowed, but regular mowing should be kept up. Lawns look neater and are easier to mow. Feeding should be avoided if the ground is dry, as it is damaging.

Fruit, vegetables and herbs

Repeat-sow lettuce, beetroot, white turnips and peas. Thin out and transplant vegetables that have reached suitable size, and control weeds early.

Plant out Savoy cabbage and other winter varieties. Vegetables may be in need of watering because the winds have been drying the ground. There has been some blight weather too.

Flowers

It is still worthwhile to plant up pots and containers and bedding in beds and borders.

Control weeds among bedding plants after rain, as weeds will take away from the planting if they are allowed to make growth.

Water regularly and feed container plants. Stake border dahlias that have grown strongly and might topple.

Greenhouse and house plants

Make sure to water and feed all greenhouse plants well during the coming weeks to maintain vigorous growth during the longest days.

Use a greenhouse shading material if the house is inclined to get too hot.

Ventilate well during damp weather. Watch for red spider build-up on peach and whitefly on fuchsia and solanum.

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