Nature on our doorsteps: Holly and Ivy are not just for Christmas-time

Rosaleen Dwyer is the County Heritage Officer at South Dublin County Council – every week she gives us an insight into nature on our doorsteps and the beautiful biodiversity of its plants and wildlife.

The evergreen plants Holly and Ivy have a strong association with Christmas.

In that season of the year, we see them mostly as decoration in our houses or on Christmas cards.

Throughout the rest of the year, however, both plants are important in the life cycle of many different insects, birds, and spiders. One such special relationship occurs with the lovely Holly Blue butterfly.

In April and May, the Holly Blue is noticeable as it flitters along hedgerows and in gardens and parks. While the upper wings of the male and female are a very light shade of blue, the females have darker tips to their front wings.

Underneath, both are a silvery white colour with scattered black dots.

Adult Holly Blues sip nectar from hedgerow flowers, including Blackberry. They will also feed on the sticky honeydew left behind by greenfly and aphids on plants and leaves.

Females lay their eggs in late spring, seeking out the flowers and the developing berries of Holly.”

Underneath their wings, Holly Blues are silvery-white with scattered black dots

The eggs hatch into larvae that look more like slugs than caterpillars, and these begin feeding on the green berries. They can also feed on the soft new leaves of Holly if there are not many berries available. When mature, these larvae pupate, and by late summer they emerge as new adult Holly Blue butterflies.

When these new adults mate, the females lay their eggs for the second generation in that year.

This time, however, eggs are laid not on Holly but on Ivy. Ivy produces its flowers at the end of summer and its berries develop over autumn. This is perfect timing for Holly Blue’s larvae which prefer to eat green developing berries.

The larvae continue to feed on Ivy’s green berries throughout autumn, until colder weather triggers them to hibernate as pupae over the winter.”

In the following spring, the new adult Holly Blue butterflies emerge, and the pattern of switching between Holly and Ivy begins all over again.