Threatened Plants Programmes: Zimbabwe
Lobelia and Scadoxus

The Zimbabwe Threatened Plants Programme (TPP) chose Lobelia stricklandiae and Scadoxus pole-evansii as its flagship species.

Lobelia stricklandiae
Lobelia stricklandiae is a large, robust perennial with a giant rosette growth form. The leaf rosettes may be up to 1m in diameter. Individual aerial stems do not branch (unless the apex is damaged). They grow 2–3 m high in vegetative form before producing a very tall (up to 3 m) inflorescence that consists of one main axis with 15–25 lateral branches.

It forms a narrowly pyramidal panicle with scattered ascending branches. The 10–30 flowers on each branch are clustered at the tips, but only a few flowers on each branch will be open on any given day as flowering proceeds.

After flowering and fruiting, each aerial stem dies back to the base of the plant, which develops the perenniating ‘crown’ just below the soil surface. Each aerial stem may require up to 2–3 years to reach reproductive size, but the growth rate in the field is unknown. The plant Lobelia stricklandiae (like other Lobelias) has a milky sap.

We chose this plant because is one of many plants that are threatened by the conversion of land use to Eucalyptus and Pine plantations. We observed that this herbaceous plant could become a horticultural specimen in gardens, because of its outstanding vegetative form. It flowers after a long wait, but when it does its light purple flowers are a pleasing sight.

Scadoxus pole-evansii
The second plant that we chose for the TTP was Scadoxus pole-evansii, an endemic species of the Eastern Highlands of Zimbabwe. In the same manner as its relative, Scadoxus multiflorus, this plant is sought after for horticultural exploitation. It is a bulbous plant that appears during the rainy season and soon produces beautiful crimson flowers (between October and December).

All the staff of the National Herbarium and Botanic Garden contributed in one way or another to the TTP. The following staff members carried out the research work: Soul Shava (Curator of the Botanic Garden), Anthony Mapaura (Red Data List National Co-ordinator), and Andrew Mangwarara (TTP Manager).

Implementation
With funds from SABONET, the TTP was implemented with Soul Shava, Anthony Mapaura, and Andrew Mangwarara embarking on a field trip to the Eastern Highlands of Zimbabwe from 21 – 26 October 2002. The aim of the trip was to assess the distribution and quality of the habitat of the aforementioned species and to collect material for use in the Programme.

Of the various sites visited during the field trip, the first was Penhalonga, where the first specimen of Lobelia stricklandiae was observed. The area has been converted to forest land dominated by Eucalyptus and Pine plantations. Although we carried out an extensive search, we found no Lobelias at Penhalonga.

On the next day, we hiked to the Mtarazi falls, which are a known Scadoxus pole-evansii site. However, despite a whole day’s walking, climbing and crawling, we did not manage to find Scadoxus.

Next we tried other sites known for Scadoxus pole-evansii, including Nyamhingura River in the Tanganda Tea Estate, the Mtarazi falls, and Pungwe Gorge. After almost losing the way, we returned without having spotted any plants.

On the last day, we visited the Chimanimani sites of Lobelia stricklandiae and we were amazed to find two significant sites in the area. The first site had about 50 Lobelia plants. The second site resembled a sown field with its more than one thousand plants, including juveniles in an open patch 10 km wide and 1 km long within the forest.

We collected our starting material for the TTP, including seedlings and seed. We made our selection randomly from the populations in an effort to represent the genetic diversity of the population.

Back at the garden, a site was chosen that would serve as the ex situ conservation site. The collected plants were planted on site and we began our effort to propagate the seed of Lobelia stricklandiae, which later proved an immense task.

Before the commencement of the TTP, Andrew had an opportunity to attend an internship at Lowveld National Botanical Garden, in Nelspruit, South Africa from 28 July to 3 August 2002 as manager of the Programme. There Johan Hurter introduced the concepts of in situ and ex situ conservation. During the internship, the focus was mainly on Zimbabwean cycads, but the same principles can be used for other threatened plants.

We learnt why it was important to establish an off-site preservation site, namely:

Progress and experiences
The road we have travelled from the time when we commenced the Programme to where we are now has been uphill. When we started, we had to devise a method to propagate the seed of Lobelia. The seed is very small, less than a millimetre in diameter, and when planting such small seed it is easy to make mistakes.

In the first trial, we used Kalahari sand and planted the seeds in 12 cm diameter clay pots. The seeds were placed on the soil surface and were not covered. The clay pots were placed in water-filled trays that were kept moist while the seeds germinated and the seedlings grew until they were big enough to be transplanted.

Before germination, the clay pots were covered with glass to create a humid microclimate and to prevent water from splashing away the seed. We had a 100 percent success rate with germination.

However, the plants from the first trial did not grow well and eventually died. We attributed this to the lack of nutrients in the Kalahari sand. We had assumed that we were going to transplant the plants early enough, but we learnt that they were too small to transplant and the growth was too slow.

Instead, we decided to use sterilised well-rooted compost with a 1 cm thick layer of Kalahari sand on top, on which we spread the seed. The Lobelia plants rewarded us and we managed to transplant them into individual plant sleeves. We managed to grow 26 plants from this first successful trial.

Of these, we planted 11 plants on the chosen site in the garden and kept 10 in the nursery. We planted out five plants on the periphery of a lake within the garden. These plants did not do well, and died because of excess moisture. The rest of the plants are growing well.

After the lessons learnt, we have managed to raise 110 plants from seed. All these plants were propagated from seed collected in Chimanimani. We have also managed to germinate Lobelia seedlings, which are still being nursed in the nursery.

The road ahead
The future of the Zimbabwe TPP is bright. We have been very successful, because we managed to learn from our mistakes and salvage the situation by raising plants from seed. The TTP has allowed us to gain experience in propagating this rare and threatened plant.

In the near future, we hope to raise enough plants to be able to introduce this important plant into the nursery trade. Our hope is that we can disseminate this plant to such an extent that there will always be Lobelia stricklandiae growing somewhere in the country.

We intend to train local nurseries to propagate this plant. As a start, we will be supplying them with seedlings, but we hope that they will also be able to collect seed and propagate it from their collections.

Without the TTP we intend to select possible sites for re-introduction of Lobelia stricklandiae and undertake this project until we see that the plant is well established in these sites.

Since we failed to collect bulbs of Scadoxus pole-evansii we intend to go on a follow-up trip to search for this horticultural gem.

—Andrew T. Mangwarara

SABONET News 9.1: 52