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Pretty poppies and their two species.

Byline: By Graham Porter

It's time for our monthly garden science lesson. And today I continue with the Ss.

Let's start with Sessile. Its literal meaning is "without a pedicle or petiole".

This can be seen when plants do not have a leaf stalk or a flower stalk. It may not seem to be of any particular relevance to practical gardening but, if you are struggling to identify a particular plant, it is one of the factors to look out for.

Oaks are prime examples of plants that demonstrate this feature. Quercus petraea is known as the Sessile oak because its fruits do not have a pedicle. However, Batram's oak, Quercus x heterophylla has leaves with no stalk.

Short-day. All plants respond to the seasons in one way or another because of daylength, temperature and rainfall.

Short-day plants flower when the days are short.

A good example is the chrysanthemum. It produces vegetative growth early in the season, as the days are getting longer and then initiates flower bud production as the days get shorter and there's more than 14 hours of total darkness.

Because this is understood in very fine detail by the commercial growers, they can control the length of daylight and darkness and so provide us with chrysanthemum flowers all year round.

Plants have special cells, usually on the underside of the leaf, through which they can take carbon dioxide gas in and exhale oxygen and water vapour. The stoma is an oval hole protected by two guard cells. If the plant gets short of water, it will close the stomata and so prevent too much water loss. To keep a plant growing well, having the ability to exchange the gases it needs, the stomata must be open as much as possible - this means ensuring the plant has enough water when it needs it.

Soil. The Huddersfield area has a complex geological history and this has produced a lot of different soils. If you live in Lepton you are likely to have a clay soil. Whereas, if like me, you live in Netherton, you will have a very sandy soil. These two extremes need to be understood by gardeners. Clay soils are very rich but difficult to cultivate and sandy soil are very poor but easy to cultivate. We also have variations in acidity and alkalinity in the area. High above Holmfirth the soils are very acid and support a limited range of plants. The Huddersfield area tends to be neutral to alkaline and can grow a wider range of plants. The most important thing about our soil is that we look after it for future generations, remember that it contains billions of living organisms that keep the soil alive, and that it takes many thousands of years to form.

Species. If, in your garden, you have two different types of poppy, you are likely to have two different species. Papaver somniferum is the large pink or mauve poppy that has just finished flowering. Papaver nudicaule is the lovely apricot poppy that is still flowering now. These two different species have the same flower characteristics but different habits of growth, flower colour and times of flowering. In the animal world, you might see this as two different cats - a lion and a tiger. Two species have the ability to interbreed and so you might experiment with two different poppies but don't try exchanging pollen from a tomato to a poppy.

Sport. The horticultural meaning of this word is perhaps a little more complex than the other meanings. We should think of this as a plant mutation that causes growth habit change, flower colour change and foliage colour change. Some plants such as chrysanthemums are particularly prone to it and, when it occurs, growers can take advantage of the change to create a new plant. Most of the variegated shrubs that we have available to us have occurred as sports, often in domestic gardens. As it thought to be caused by faulty genes, it is possible for the change to reverse itself - this is why you often see green shoots in amongst variegated foliage.

Next month I will look at plants beginning with T.
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Title Annotation:Features
Publication:Huddersfield Daily Examiner (Huddersfield, England)
Date:Jul 13, 2004
Words:696
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