Yucca is familiar as a house plant, with stout woody stems and a rounded top of spiky leaves. As a house plant, it often grows too tall and, on some occasions, these plants are planted out in the garden as a way of getting rid of them.

Even though this species is not supposed to be hardy enough to survive outdoors at all, it has in many places for years, until it was finally caught out by the very severe frosts of the exceptionally cold winters in recent years.

Despite having survived outside in gardens, this is only a curiosity and this species, Yucca elephantipes, is not for outdoors. It does not flower indoors, or outside, as it does in Mediterranean countries, with tall spikes of white flowers on plants that can be four metres tall or more.

Hardly grown in gardens until a couple of decades ago, outdoor species of yucca have become an important plant in modern gardens. Although this trend took a severe knock due to frost losses, its value as a structural plant is still widely recognised.

The big rosette of sword-like, spiky leaves offers great contrast with the general run of rounded shrubs, differing dramatically in leaf shape and texture. It makes a great contrast with flat areas of paving or plain blank walls. It looks really well with stone or concrete in any form, especially with large rock-work or gravel. It is naturally a native of dry landscape, desert and arid parts of Mexico and the southern United States.

Some species of yucca, just as the house plant type, have woody stems and grow tall, such as Yucca recurvifolia and Yucca gloriosa, both of which can reach about two metres and are hardy, tolerating normal winters easily. Others have no, or a very short, stem, making a large rosette, which sprouts smaller side rosettes that later develop. Such species include Yucca filamentosa and Yucca flaccida. Both of these species have curling threads at the edges of the leaves and are capable of flowering in gardens, although they may take a number of years to reach flowering size. When they do, they normally flower every year, or at least some of the bigger rosettes flower. In a really good, sunny, warm summer, most of the rosettes on a plant flower.

Quite a sight in flower, yucca makes one of the biggest of garden flowers, towering upwards often to over two metres. The flower spike is a solid structure, many branched, carrying hundreds of bell-shaped flowers. These hang down mostly and the stems are crowded with flowers. The flowers are mostly carried in late summer and into autumn – Yucca gloriosa, the Spanish dagger, being later than others.

The flowers of Yucca whipplei are arguably the most beautiful, with very delicate white flowers on light branches at right-angles to the bolt-upright stem. They can be creamy or slightly purple-flushed too and are fragrant. The only problem with this species is that it takes a few years to reach flowering size, five or more, and then it only flowers once, expending all of its energy in a massive display and then withering away.

Try any of the kinds mentioned in full sunshine and fertile soil with excellent drainage, even a bit gravelly or sandy, which helps against frost. Be careful, as some kinds have a sharp tip at the end of the leaves. The variegated kinds are not as attractive, nor do they flower as well, as the green forms. Watch for snails, which hide amid the leaves, feeding on leaves and often on the sides of the flower stems, which can cause distortion and spoil the effect.

Measure of a summer

While all plants respond to good or poor weather, there are a few that clearly indicate a good summer. One of these is the hardy hibiscus, originally from Syria and the adjoining region. If there is a good summer, it manages to begin to flower in August. In a poor summer, it might not start until September.

In a really bad summer, the bush might not open a single flower successfully. In good years, it can open flowers by the dozens.

This year, it was in flower by mid-August, with plenty of buds to open in the coming weeks. But the question is: will the weather allow the plant to do so?

If the weather is cold, it will simply call a halt, its leaves soon turning yellow, and the wasted buds dropping off.

Fruit, veg and herbs

Remove old crops. Over-mature cabbage, cauliflower and other vegetables pull out easily when the soil is soft. Take the opportunity to clear out weeds. Later, the soil will grow colder and wetter and these removal jobs will be more difficult. Lift potatoes before the small, underground slugs become active.

Flowers

Hanging baskets could be kept going a little longer with some liquid feeding. Soil conditions are ideal for sowing hardy annual flower seeds. Buy and plant spring bulbs as soon as possible. There is some heat in the soil and adequate moisture to encourage rooting immediately, and a full choice of varieties.

Lawns

There has been good growth of grass. Keep on mowing as necessary – there is a second peak of grass growth at this time of year in most years and it is invaluable for thickening up the grass sward before winter. Apply autumn lawn fertilizer or a low N, high K product to strengthen grass before winter.

Trees, shrubs and roses

Conditions have been excellent for the growth of trees and shrubs during most of the summer – a mixture of sunshine and heavy showers. Roses have responded with a lot of secondary growth that is flowering now. But many plants suffered badly with blackspot disease due to the dampness.

Greenhouse and house plants

The greenhouse tomatoes are coming on strongly but generally, growth is winding down. Be careful not to over-water from now on. Water should be given only on the basis of need and soil and compost should be just moist, not wet. Ventilate on dry, breezy days to air the greenhouse.