Exploring Pigeon Valley: Isoglossa woodii

This is the 34th in an ongoing series that highlights the riches of Pigeon Valley, the urban nature reserve in the heart of Glenwood. The focus of this article will be on Isoglossa woodii (Buckweed).

I have had visitors look around the thick undergrowth of Pigeon Valley and say, gloomily, ‘Well, are these invasive alien plants?’ The answer is no. Buckweed, the plant that sprawls under the forest canopy across much of the reserve, is exactly what was here for many thousands of years, no doubt. Its leaves do indeed form part of the diet for the Duikers and it hosts butterflies and the occasional nest, like that of the Cape Batis, so it provides many useful services to wildlife.

In midsummer this plant, that seems to lean on the ground, can reach over 3m in height, with a mass of green leaves. In a dry spell its leaves will start to shrivel, but it responds swiftly to rain, the leaves turning lush and green as if it had always been like this.

ALSO READ: Exploring Pigeon Valley: The ways species interact

However, its life cycle is distinctly strange. After about eight to ten years of growth, during which it never flowers, almost all the plants in the area burst into flower, providing bees with a rich source of nectar. Then they set seed that is dispersed as the capsules burst open, and the whole plant dies. The success of this strategy is evident in the profusion of seedlings that cover the forest floor within a few weeks. Somehow a patch of plants here and there is on a different cycle; in the photo one can make out a single plant that still has flowers on it, while the dead material around is what is left of the previous generation. Carpeting the ground are the upcoming seedlings.

While Buckweed dominates the lower section in the forest, its dominance is never complete. There are always a few other species that grow there, and the great die-off is the occasion for some seedlings to make a sprint towards growth as they can get sufficient sun. The seed of a forest giant may occasionally germinate here and grow at minuscule pace, waiting for the ten years to be up. It may have perhaps 18 months before the Buckweed overtakes it again.

Crispin Hemson chairs the Friends of Pigeon Valley, a group that undertakes clearing of alien plants, keeps records of bird and mammal sightings and alerts management to any problems.

The Friends have a monthly walk at 7.30am on the second Saturday of each month. Email: friendsofpigeonvalley1@gmail.com.

Do you want to receive news alerts via Telegram? Send us a message (not an sms) with your name and surname to 060 532 5535.

You can also join the conversation on Facebook, Twitter and Instagram.

PLEASE NOTE: If you have signed up for our news alerts you need to save the Berea Mail Telegram number as a contact to your phone, otherwise you will not receive our alerts

Here’s where you can download Telegram on Android or Apple.

To receive our free newsletter click here.