Visit to the Tropical Ravine, Botanic Gardens, Belfast

On Friday 14 October 2022 Matthew Reeve and I were lucky enough to be escorted

round the Tropical Ravine in Belfast Botanic Garden, located between the Ulster Museum and Queen’s University, by Chloe Rice of Belfast City Council, and Adrienne Armstrong, the gardener in the Tropical Ravine. Chloe had previously participated in a

BPS Zoom Autumn Meeting on Victorian Ferneries back in November 2021. Her interest is particularly horticultural history and architecture.

She told us that the Tropical Ravine was created as a brick building over a sloping site by Charles McKimm between 1887 and 1889. The Tropical Ravine was largely filled with temperate plants and viewed from a high-level walkway (Figure 1). Lighting was by candles and mirrors and there was a waterfall that was manually operated. The design was largely for entertainment rather than education.

In 1900 the Tropical Ravine building was extended to include a hotter, drier area for tropical plants such as cycads and palms. In 1902 a heated pond was added to accommodate a giant Amazonian waterlily, and culture of that continues to this day with new selected seed from Longwood Gardens in Pennsylvania being set every year (Victoria ‘Longwood Hybrid’, V. amazonica × cruziana, Figure 2). The Tropical Ravine fell into a state of poor repair in the 1960s and 70s and had a new glass roof fitted in 1980. Thirty years later it was decided to return the design to the original Victorian specification and a new accessible walkway was created, a new roof fitted, and everything brought up to modern health and safety standards for public visiting.

Matthew, who had visited before this recent 2013–2018 rebuild, had fond memories of the profusion of plants growing in the walls and pathway, now cleared for wheelchair access. However, the improvements in the new build were considerable with triple-glazing, a misting system, heating pipes but, oddly, no additional lighting for the winter months. Supplementary lighting to extend the day length during the winter months would certainly be a worthwhile addition to the infrastructure and would allow a broader range of species to be grown.

Adrienne explained that, at the moment, the Tropical Ravine did not hold any National

Collections and the aim of the Tropical Ravine was still one of creating an attractive environment in keeping with the Victorian intention. However, there were learning panels along the walkways and there were to be discussions with the adjacent Ulster Museum about adopting a more academic role.

I had visited the Tropical Ravine twice in 2018 and had been impressed by the profusion of greenery, the tree ferns, and the use of the misting system. Unfortunately, the pandemic had taken its toll and the misting system had become blocked with limescale as they had used mains water for this. Also, in restocking the Tropical Ravine, they had inadvertently introduced cockroaches, as they had no quarantine facilities (Figure 3). These insects had proved to be very damaging to the tree ferns in particular, both eating the new uncurling croziers and burrowing into the stipes of the larger tree ferns. Their Alsophila cunninghamii (syn. Cyathea) was almost certainly killed by these insects. Both Matthew and I were surprised at this, although I have since found a reference to

cockroach damage in David L. Jones, Encyclopaedia of Ferns (1987, p. 106). It may be that the failure of the misting system led to a drier atmosphere at higher levels in the Tropical Ravine that was conducive to the growth of the cockroach population. The Alsophila cunninghamii was the tallest of the tree ferns. In addition, the casings of the hot-water pipes were perfect breeding grounds for the insects. This was an interesting lesson and professional help was being sought to eradicate the problem.

The plants themselves all looked very healthy, with the exception of the damaged tree ferns. Mealybug had been a problem in some of the Cycads but was biologically controlled with a type of ladybird lava. There wasn’t a huge range of ferns but we identified fourteen species and there may well have been more under the exuberant

growth of Tectaria gemmifera (Figure 4). This fern spreads by both spores and by plantlets which form on the rachis and drop off (Figure 5). This was plainly a very successful strategy in the Tropical Ravine as it was by far the most abundant fern in the building. The ferns that we saw are listed at the end of this article.

Adrienne was keen to reintroduce the Killarney Fern, Vandenboschia speciosa, as that had been a feature of the original Victorian Ravine. However, she was struggling to find anywhere dim enough and cool enough for it to flourish, although an old well, recently unearthed, was a promising site (Figure 6). At the moment they have both the gametophyte and the sporophyte living in an old, damp building in the delivery yard which we were taken to see (Figure 7).

The enthusiasm of Adrienne and Chloe was enormous. The restoration of the Tropical Ravine has certainly helped to preserve this Victorian Fernery for many years to come. There are clearly still teething issues whilst the team are getting to grips with the environmental conditions of the refurbished building. It’s essential that resources and funding can be maintained to allow the development and diversification of the fern collection at the Tropical Ravine.

PETER BLAKE

Peter became interested in tropical ferns whilst making regular trips to India in the

1990s and 2000s. He retired from the NHS in 2012 and was able to develop his interest in growing tropical ferns from spores. He now lives in Norwich where he can provide much more space for their culture. He maintains a particular interest in the ferns of South India and Sri Lanka.