Last updated 16:06, Wednesday, 01 October 2008

THE nights are quickly cutting in and with a drop in the temperature I have noticed quite a heavy dew in the mornings.

Rudbeckia Goldstrum: Colourful splash among the autumn hues

It’s not surprising, then, for the garden to be changing, particularly when the leaves start to show their wonderful autumn colour.

This is primarily triggered by the increasing length of night and cooler temperatures.

You might recall from your school days that chlorophyll gives leaves their basic green colour, and is necessary for photosynthesis, meaning plants use sunlight to manufacture sugars for their food.

Carotenoids are responsible for the yellow, orange, and brown colours in such things as corn, carrots, and daffodils, and anthocyanins give colour to such things as cranberries, red apples, grapes, blueberries, cherries, strawberries, and plums.

Both chlorophyll and carotenoids are present in leaf cells throughout the growing season and most anthocyanins are produced in the autumn. The carotenoids and anthocyanins then show their colours.

Colour change varies by individual plant species, and the brilliance of leaf colour is related to weather conditions during the time the chlorophyll in the leaves is dwindling – this is why the autumn leaf fall varies from year to year.

Another clear sign of autumn appearing in my garden is through the brilliant display from my Rudbeckia fulgidaw sullivantii ‘Goldsturm’ – commonly known as the golden coneflower. It has large, golden-yellow, daisy-like flowers up to 12cm (5ins) across with cone-shaped, blackish-brown centres from September to October.

This is an award-winning Rudbeckia which looks great planted in bold drifts with other late summer-flowering perennials (Asters) and ornamental grasses. It copes well in sun or partial shade, and it’s ideal for the middle of a border that doesn’t dry out over summer.

There are about 20 species of Rudbeckia, which belong to the same family as asters.

Rudbeckia hirta “Rustic Dwarf” is a well known annual form, which is widely grown and grows about 60cm (24ins). The flowers are a mixture of golden yellow, brownish red, or bronze-orange ray-florets, with some bicolours.

And now for the first ever red Rudbeckia – Cherry Brandy is the result of 15 years‘;’ careful selection at Thompson & Morgan Seeds. It will be available in their 2009 catalogue.