The queen of the prairies is a common name for eupatorium and gives a strong indication of its origins in North America.

The name is accurate – this is indeed a plant of the western prairies – but at over two metres tall, it hardly fits with the usual picture of the prairies of short grass, grazed by bison and other animals.

Such prairie land did exist, but a great area of high prairie existed too, tall enough for a man on horseback to be just able to see over. Many of these meadows had low-lying areas with damp soil and it was in this kind of prairie that eupatorium thrived and, no doubt, it was a magnificent sight of purple colour in flowing swathes.

The botanical name is Eupatorium purpureum and another common name used is Joe Pye weed, apparently named after a healer who used it in herbal remedies. Little is known reliably about the man, but the name lives on as it is catchy and easily remembered. It is certainly known that native Americans used the plant as a remedy for various ailments, including gout.

The plant has tall stems with heads of small puffy purple flowers. Flowering lasts over a period of weeks from July into September. It is a magnet for butterflies that come to drink nectar from the flowers. If the area is reasonably sheltered, they visit in greater numbers. The pale purple-pink flowers, opening from purple-red buds, have white tips that give a fuzzy look and enhance the flowers.

Carried at the top of the tall stems, the flowers have the greatest visibility and every stem carries a head of small flowers, closely grouped.

The purple colour makes a lovely contrast with the many yellow, daisy-type flowers around at this time of year, such as the helianthus, heleniums, inula and echinacea. It is very vigorous, so this is not really a plant for a small garden, but it can look great in a rural garden, especially near a pond. It can be used in a flower border too as long as it is matched with strong perennials of similar vigour or shrubs of sufficient size to keep it in its place. If you have a damp spot near a boundary, this plant is a robust candidate to fill it.

There is a smaller form, aptly named Little Joe, that reaches only half the height.

It has the same foliage and flowers as the bigger variety, but the individual flower heads are not quite as large. There is a native eupatorium species, known by the common name of hemp agrimony, often seen in damp places by roadsides and in marshy ground over much of the country at this time of year, but especially in the southern half.

It is pinkish or white rather than purple. But it is much too vigorous for garden use, except possibly for semi-wild damp areas in a rural garden. It is also excellent for attracting butterflies.

There is also a shrubby form of eupatorium, evergreen. It is covered in late summer with airy clusters of small white flowers opening from pink buds. Native to Mexico, this is not completely hardy and can be damaged during prolonged spells of hard frost. But it survives in many gardens in mild areas.

It makes a broad bush up to three metres tall and wide. It is worth keeping it on the wanted list.

Cabbage root fly increase?

It would seem that there is a fair incidence of cabbage root fly in garden brassicas this year. There is always some level of cabbage root fly attack, but perhaps the damp weather and damp soil makes it easier for the grubs to go about their business of eating roots. The first signs are a leaf or two wilting and a slow-down of growth. This is due to the fine roots being eaten by the larvae about 2cm or 3cm below soil.

As they grow in size, the damage is more severe and the plant begins to collapse, growth halted and the older leaves yellowing. It affects all cabbage family plants to a greater or lesser extent, including radish and pak choi. Collars of plastic can be put around individual plants to prevent access for the egg-laying flies.

Fruit, veg & herbs

Summer pruning of vigorous apple trees could still be carried out to reduce vigour and increase cropping in future years. Tying branches down to the horizontal will also help fruiting. Sow winter lettuce to mature under a cold frame or low tunnel. Remove apples or pears attacked by wasps.

Trees, shrubs & roses

Early flowering shrub roses and ramblers could now be pruned by removing some of the shoots that flowered. Many established trees are showing early autumn colouring, especially maples. This is strange given the plentiful supplies of water, but there has been very good growth.

Flowers

Weed growth has been strong so try to stay ahead of weeding in flower beds and borders. Prevent weeds from going to seed now. It is possible to collect seeds of perennial flowers, if it is desired, to raise some new plants. Take cuttings of tender plants such as geraniums, fuchsias and African daisy.

Lawn

With all the rain and sunshine, most lawns have done quite well. If you have a wildflower lawn, do not use fertilizer, except some phosphorus and potash if the growth is very poor. Prepare for a new lawn or re-seeding a tired lawn by spraying with glyphosate in the coming weeds.

Greenhouse &

house plants

Continue to train and side-shoot tomatoes and cucumbers. Take the tops off tomatoes to boost the green fruit that is already present. Tidy up all kinds of plant debris and be careful not to overwater. Continue watering and feeding greenhouse plants.