Ivy’s been part of our Christmas decorations for centuries. It’s one of my favourites but because it wilts so quickly in a warm house, we’ll wait till tomorrow to bring lots in to wrap round some pillars. That will make it stay fresh right through our midwinter celebrations till after Ne’erday.

But we’re not alone in valuing ivy, Hedera helix. Long-established ivies offer endless nooks and crannies where birds can shelter and bees and little flies will home in on the pollen and nectar and then there are berries for birds.

Yes, I see some of you scratching your heads, wondering what I’m on about when I mention pollen and nectar, never mind berries at this time of year. Ivy flowers from August to October in England and late autumn in the most sheltered parts of this country. Two hundred metres up in the Borders, this is the first time I’ve seen ivy flower prolifically and this must apply to lots of my fellow Scots. One of the few benefits of warmer winters, perhaps.

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The appearance of the ivy bee, Colletes hederae may be another benefit linked to warmer weather. First identified in mainland Europe in 1993, it made it across the channel to Dorset in 2001, then spread gradually northwards to the rest of England and Wales.

By September 2021, ivy bees had crossed the Border and were seen near Dunbar in September 2021 and close to Thorntonloch, also East Lothian, last September. So they seem to like nesting in the dry, sandy soil we often find along the coast and in the ground where ivy thrives.

Ivy bees are part of a genus known as plasterer bees as they “plaster” the walls of their burrow. They do this by making a secretion from their Dufour gland near the sting and then use their mandibles as trowels. This gives the grubs a dry, cosy wee nest.

But when the poor female emerges from her burrow, she attracts every nearby male with single-minded intent. So it would certainly liven up your walk if you chanced upon a heaving mound of fiercely squabbling males.

In much the same way, my lunch in the garden is often enlivened by the sight of a gang of drakes driving some poor, but presumably not unwilling duck into the ground.

Back to the more strictly botanical side of ivy and its growth habits. In the Botany in Scotland blog, Chris Jeffree featured ivy in 2021. The plant has extensive leaf coverage so in hot weather would need to transpire large quantities of moisture while photosynthesising.

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Because ivy usually grows in fairly dry ground, the roots might not be able to pump up enough moisture to all the foliage.

So the plant temporarily shuts down the stomata, thereby protecting itself against embolism in the xylem tubes. As a consequence, photosynthesis temporarily stops and the plant doesn’t manufacture as many sugars as it needs.

Jeffree wonders if one reason that ivy is an evergreen is that during the cooler, wetter winter months, the dry soil provides as much moisture as the plant needs for photosynthesis, thereby compensating for any leaner times during the spring and summer.

The Herald:

Plant of the week

Holly JC van Tol is the only variety of holly that reliably produces berries since it is self-fertile. Other hollies are either male or female and the names offer no clues: ‘Queens’ can be male and ‘Golden King’ is female so has berries. Hardy and evergreen hollies are great garden plants and have many uses other than Christmas decoration. They can be clipped into balls or more elaborate topiary shapes, they make a dense and secure hedge and a single holly will provide a striking focal point.