Saturday, 13 December 2014

Ivy: strictly for hederophiles

We take Ivy for granted. I don't need to point out that it is extremely common and it regularly gets an honourable mention on my blogs.

So is there anything more to be said?

Ivy is a member of the Araliaceae, a moderately large family of trees, shrubs and herbaceous plants, together with a number of lianas - those rope-like climbers so often featured in films about rain forests. Altogether the family contains about 254 species. I say about, because the situation is confused and modern techniques of DNA analysis seem certain to lead to a number of changes. Examples of the family are found in all the continents - obviously excluding Antarctica.

Ivy, Hedera helix, is found right across the British Isles and the European mainland, avoiding only high mountains and waterlogged or very acid soils. It takes on many forms in some parts of its range and it is this variability which prompted me to write this blog.

Ivy. Typical leaves on a non-flowering shoot.
Daventry. 13 December, 2014

The typical leaf-shape of ivy is very familiar to us all, being palmate with 3 to 5 lobes. The veins are pale and stand out distinctly against the dark green of the rest of the leaf. When these branches come into contact with a suitable surface they will produce roots allowing them to cling to walls, tree trunks and so on. However, these branches never produce flowers.

Ivy. Smooth, cordate leaves on a flowering
branch. Daventry. 13 December, 2014

The leaves on flowering branches are smooth and more or less ovate with a pointed tip although, as in the example shown, they can be cordate, i.e. heart-shaped. These flowering branches do not produce roots.

Contrary to popular belief ivy is not a parasite; it is a nuisance but will not harm a strong-growing tree. Nor will it harm a wall if it is structurally sound.

Hedera helix in the form dubbed 'Clotted Cream'
Daventry, Northants. 13 December, 2014

Some curious variations are to be found.  This form with crinkle-edged leaves was sprawling over the wall of a car park in Daventry. It appears to be Hedera helix 'Clotted Cream'.

Ivy on the church wall at Norton, Northants.
13 December, 2014

But even the common ivy can take one some attractive forms. Claret-hued leaves like those of this specimen on the churchyard wall at Norton are are very frequently encountered. The wine coloured variation is due (and I am taking an educated guess here) to the presence of a chemical, one of the anthocyanins, which imparts hardiness to plants in exposed places, such as this wall top.

All the illustrations so far are examples of common ivy.

"Hedera canariensis" probably just a large-leaved
form (keys shown for scale) of  the common ivy.
Daventry 13 December, 2014
The Canary Ivy, Hedera canariensis, is also very widely grown. It really does hail from the Canary Islands - islands named after dogs (canis) incidentally, not birds -  and is usually grown in the variegated form shown, again from a car park in Daventry. Recent research suggests that is merely a rather large-leaved form of the common ivy and does not merit specific status.
Ivy, bearing flower buds. Daventry.  13 December, 2014

I have, on several occasions, mentioned the fact that common ivy has a very long - September to December - period of flowering, with the fruits ripening early in the new year and providing very welcome fare to many birds. Even so I was astonished to find this ivy specimen with its flowers still in bud! 

Again it was in the same Daventry car park, surely now a mecca for hederophiles. (Incidentally I made that word up only to then Google it and find it really exists - "an ivy-lover". How odd.)

Do I grow any ivies? Not on your Nelly! They're fine confined to pots but when Chris and I lived in Byfield we waged a never-ending war with it, as did neighbours who were similarly overwhelmed with the stuff.

I'll leave the final words to John Clare:

                       Save grey-veined Ivy's common pride
                       Round old trees by the Common side,
                       The hedgers toil oft scare the doves that browse
                       The chocolate berries on the Ivy boughs.

                                         Clare's Shepherd's Calendar, 1827

No comments:

Post a Comment