The wild milkwort is a fairly unusual wild flower of old pasture, dry seaside grassland and rocky places.

It has deep blue flowers on a short stem, usually less than 30cm, often just half that. It is not well-known, appearing mainly on limestone areas.

The name milkwort is unusual and garners instant curiosity.

The word “wort” is an old English name for a plant. It was once credited with increasing milk production in dairy cattle.

There is no evidence of it being effective for that purpose but it is sometimes used in herbal cough preparations.

]South African species

The South African species, Polygala myrtifolia, is a shrub or small tree in its native land, sometimes reaching four metres.

It grows in a wide range of habitat, from coastal areas to rocky hillsides. It is an early coloniser of bare ground, much as broom does the same here.

It is an evergreen plant with small green or blue-green leaves. These are oval and quite like those of myrtle, hence the second part of the name, myrtifolia.

This shrubby species has purple and pink flowers and some white sorts pop up from time to time.

The flowers of polygala are quite like pea-flowers – two large petals and three smaller ones, one with a very distinctive pale pink fringe at the lip.

Native

The native milkwort is a non-woody perennial flower and it is hardy. The South African species, as might be expected, is not fully hardy, even if it has been grown successfully outdoors in mild coastal areas.

However, while it might survive a couple of winters outdoors, a hard frost can wither it.

It has been used as a flowering hedge in Cornwall, but that is a very mild area. More often, this polygala is grown in a large pot so it can be taken under cover in harsh weather.

Some books have it down as a tender plant that needs a minimum of 5°C, not even close to freezing, but it is not that tender and survives well in many unheated greenhouses and it is very happy in a conservatory attached to the house.

Soil

In a pot or in the open ground, perhaps with the protection of a wall, this shrub prefers acid to neutral soil, while its blue relative likes limy soil. Use plenty of leaf-mould to acidify limy soil.

Grown indoors, this polygala flowers year-round, most in late spring and early summer, but it is never without a few flowers on some part of it.

It produces a continuous array of small new shoots and these carry a group of flowers at the tips. It is a spreading, rather loose shrub with whippy shoots.

These take pruning readily and this makes the plants more rounded and bushy.

People are often reluctant to prune because there are flowers on some branches, but it is best to prune after the main show of flowers in early summer and it will soon re-sprout and flower again.

There is another polygala that appears on the sales bench from time to time, namely Polygala chamaebuxus, which means false buxus, because its small leaves are like those of box hedging.

This is a small evergreen shrub, an alpine species that makes a low spreading mound. It has pretty purple and yellow flowers that are large and plentiful for the size of the tiny bush.

It is hardy and can be grown on a rock garden or in a cool greenhouse in a broad pot when it will flower for months, mainly late spring. The chalk milkwort, Polygala calcarea, is also grown as alpine. It is small, with blue flowers like the common milkwort but carrying more flowers.

Frost damage

The frost recently was not as bad as the very severe freeze of the two winters at either end of 2010. That period of frost saw temperatures drop to -17°C in some parts and it was prolonged for many days. Killer frosts need a few unbroken days to freeze through bark and down into the soil.

The worst damage is not evident at first – cordyline, for instance, only showing signs of collapse weeks later.

Watch out for frost damage.

Surface damage can look worse but is not as deadly. Camellia flowers turn brown quickly with a touch of frost, especially if there are strong, cold, drying winds. Camellia buds can be killed, although they look fine, and fall off without opening.

Keep an eye on susceptible plants: phormium, fuchsia, pittosporum, tree ferns, leptospermum, euryops, African daisy and the like.

But luckily the chances of survival are better this time round, and a good fall of snow can act like a layer of insulation, limiting damage.

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