Seed Cleaning in South Africa

Carly Cowell in primary dry room

Kirstenbosch

The SANBI partner at Kirstenbosch Botanic Gardens carries out collecting in the Western Cape area of South Africa. The majority of Western Cape species are orthodox and fairly small seeded showing high levels of endemism and species diversity.

When staff from the MSBP visited the Kirstenbosch site to review current facilities, collections were being held in an air conditioned dry room for up to 2 months prior to cleaning. When tested, it was found that the relative humidity of this room was not significantly different from ambient conditions, so seeds were not being kept at a safe moisture status. Seeds were cleaned in two small laboratories, then transferred to a main dry room for 1 month before despatch to the MSBP. It was found that the dehumidifying unit was too small for the amount of material in this room, so the conditions did not meet the 15% relative humidity standard recommended for long term seed storage. It was recommended that an existing cold room could be converted to a dry room, by sealing the floors and walls with plastic based paint and installing a dehumidification system, creating more capacity for drying collections.

SANBI Kirstenbosch

Carly Cowell in seed cleaning lab at SANBI Kirstenbosch

At the time of visiting, primary seed cleaning was being carried out on ambient dried collections, using sieves and hand cleaning, with assistance from students and volunteers. It was decided that Carly Cowell, project officer at SANBI Kirstenbosch, and her staff could achieve full cleaning if additional seed cleaning facilities were provided. This would help to reduce costs of shipping collections from South Africa, and would considerably cut handling time for staff at the MSBP.

A zigzag seed aspirator would be required to remove infected and empty seed from collections. Some unused cabinets in the laboratories could be cheaply converted into dust hoods for seed cleaning. A good quality vacuum cleaner with a suitable filter would be purchased in-country, for cleaning the equipment and laboratories. Staff were advised that fully dried and cleaned seed collections should be sent to the MSBP in sealed foil packets, containing an indicating silica gel sachet. A bag sealer would thus also be needed. A humidity sensor and a data logger would also be provided so that seed and ambient relative humidity and temperature could be monitored. Finally, health and safety issues were discussed, including the segregation of laboratory space from offices where food and drinks may be consumed, and the purchase of lab coats, disposable gloves and dust masks. South Africa is home to some very toxic and irritant seed material, and a high degree of containment of dust is advisable, especially when the material is dry.   

Erich van Wyk in seed storage room

Pretoria

Following the review of facilities at SANBI Kirstenbosch, a similar visit was conducted at SANBI Pretoria. The team at Pretoria spend approximately 40% of their time on seed collecting, 30% on cleaning and 30% on administration. The seed facility is located at the National Herbarium in the botanic gardens. The ambient seed store had an air extraction system, enhanced by a large desk fan under timer control, with collections being held for 3 to 6 months prior to despatch to the MSBP. The room was found to be neither insulated nor sealed, but at the time of assessment, these facilities were suitable for short term storage. However, if ambient humidity were to rise, conditions would rapidly become unsuitable for seed storage. Based on assessment of the dry-room facilities at Pretoria, it was recommended that mature seed material should be transferred to the MSBP as soon as possible after collection.

An open area in the basement was being used for primary seed cleaning, carried out manually using sieves. There is only sufficient space for Erich van Wyk, project officer at SANBI Pretoria, and his two staff to clean seeds in this area. Dust and pest issues are of concern in the laboratory due to lack of containment of dust. As space is at a premium at the National Herbarium, it is unlikely that additional internal space could be re-allocated for seed processing activities.

In view of the available facilities, a wild plant seed bank for South Africa will be established at Kirstenbosch, with the project herbarium material being centralised at Pretoria.