Anatomy of a foxglove

August 29th 2018

As a birder, and as probably happens with any primary natural history subject, you are very likely to find yourself, despite yourself, developing an interest in other related subjects.

In my case, for example, sea-watching for birds led to seeing cetaceans in the water which led to training as a Shorewatcher for Whale and Dolphin Conservation. Another route in was when carrying out butterfly transects, in a previous life, at Loch Leven NNR I started to be more aware of the plants visited by the butterflies. Then, during my many years of visiting and now living in Assynt, I inevitably came across Ian Evans. Resistance was futile, you simply developed an interest in plants way beyond what you ever thought possible!

I can now recognise/identify more and more plants thanks to the grounding drip fed to me by Ian. Hence the reason for this article – a method to help me, and hopefully others at my level, understand a bit more about the workings of plants. See there I go again, not happy simply to know what they are I now want a basic appreciation of why they are; another school day!

Why choose FoxgloveDigitalis purpurea, for this exercise? Simply because it has big individual flowers which made it a bit easier to work out the ‘bits’.

So, a typical text book might describe Foxglove a bit like this; “A tall biennial that can reach 1.5m in height. The leaves can be 30cm long and are wrinkled, oval in shape and they form a rosette in the first year from which the flowering spike appears in the second. Flowers are 4-5cm long and are found in tall terminal spikes with the corolla being pinkish-purple (occasionally white flowers are seen); there are a few long hairs inside the corolla tube, two long and two short stamens and a slender style. It can be found in woodland, moors, sea cliffs but most numerous in recently disturbed ground.”

Great description, if you know what it all means! If you would like to gain a bit more of an understanding please keep reading.

Firstly, Foxglove is a ‘biennial’ – that’s a flowering plant that takes two years to complete its life cycle. First year it grows roots and leaves from the seed of a plant which may have flowered that year/the previous year/many years ago. After forming the rosette, the plant stays dormant over the colder months. Then, in year two, it rapidly increases the length of its stem, produces flowers, and, if successfully pollinated, produces fruits and seeds before it dies.

The leaves form a ‘rosette’ – fairly self-descriptive, but why produce this rosette of leaves? Lots of rosette forming plants are biennials since they spend their first year absorbing nutrients and storing energy. They therefore don’t want long stems with leaves as that is just a waste of energy. Then, come their second year they are ready to quickly produce the long flowering stem.

‘Flowering spike’ – simply this plant produces a long stem at the end of which a spike of flowers is produced as opposed to, for example, the Common Poppy. The poppy produces single slender stalks which carry only a single flower.

The ‘corolla’ – this is the collective name for the petals. In the case of our Foxglove there are five fused petals. Not mentioned in the description above are the sepals but these can be seen in the accompanying photographs. These are an important part of most plants as they protect the flower while it’s still a bud and then they help support the petals when in bloom.

‘Long hairs’ inside the corolla tube – I can’t find a definitive answer as to why they are there. My own thoughts are that given where the stamens and style are located, i.e. high up in the corolla, then the hairs force visiting bees upwards as they enter the corolla pushing their bodies against the stamens, etc.

Two long and two short ‘stamens’ – these are the male parts of the flower. They are made up of long stalks, called filaments and at the end of these are the anthers. The anthers produce pollen which is the male sex cell. The pollen is slightly sticky so that it will adhere to the body of visiting insects and hopefully be transferred to another flower.

Slender ‘style’ – the style forms part of the carpel, the female reproductive system of the flower. The carpel comprises the ovary, style and stigma. The ovary produces eggs; the style is involved in transferring the pollen to the ovary and, at the end of the style is the stigma. The stigma is sticky and it ‘collects’ pollen from the bodies of visiting insects.

We’re not quite finished yet though. The majority of flowering plants rely on insects for pollination. However, different plants have adopted different strategies to attract their ‘chosen’ insect.  With Foxglove, it’s typically bees that do the work. If a bee successfully transfers pollen from one Foxglove flower to one on a different Foxglove plant then, later in the season, that flower will produce a fruit which can contain thousands of tiny seeds.

A few of those seeds may go on to produce a Foxglove plant and so the whole process will be repeated.

The Foxglove distribution map in the Flora of Assynt (Evans, Evans and Rothero, 2002) shows that this plant is widespread and common in Assynt, having been recorded in 128 tetrads. In some years it can flower in profusion, particularly in recently disturbed ground.

Hope that made some sense, my accompanying photos might help a bit.

 

David Haines

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