This ‘miniature woodland’ is growing well in one of the larger planters and is currently my favourite part of the DINA rooftop garden. It illustrates the idea of multi-layered growing, albeit in a simplified manner. If this was a well-functioning ‘natural’ woodland then three layers might be expected: the tree canopy, the shrub understory and ground flora. In this container there are just two but it is still an effective use of space, with roughly twice as much vegetation per square metre than if it were just trees or just herbaceous perennials. This means more variety, more complexity and more potential incentives for different invertebrates to visit our garden.
The bees cannot get enough of the foxgloves, they are fighting over the flowers. Bumble bees are the main pollinator for this plant simply because they have the right equipment for getting to the nectar: their super-long tongues. Not to be put off, short-tongued bees have found a handy way around this and in the base of one of the trumpets I noticed a tiny hole where a burglar has been in to steal the sweet stuff.
It would ideal to have more planters with this capacity but we are restricted by access to the necessary materials. Although the plants and wooden palettes were free, our main difficulty is getting holding of reasonably priced compost. This planter easily takes 400 litres and soil costs money, so my my ambition to make more of the same size is looking like a bit of a pipe dream.
One way we have tried to get around the problem of growing in pots, which are often only big enough for a single plant, is to group them together. The idea is to create a better refuge for visiting insects and birds, with more links between plants and a greater number of hiding places. It seems to be working – aside from bees, wasps and hoverfiles we have dozens of ladybirds, both larvae and adults, and there are a few different beetle species present. The ‘seeping’ sound from nearby buildings indicates that there are still young birds who have yet to fully fledge; I like to think that the birds are fully exploiting the various food sources available on the roof. However, it is hard to observe their feeding behaviour as our presence makes them understandably cautious.