All plants grown at Auckland Botanic Gardens are assessed to determine their performance in Auckland conditions. Plants must earn their place and prove their merit. Those we determine to be outstanding are promoted as Star Performers, and those that are very close to this are regarded as Recommended Plants. Most trials are undertaken at the designated trial grounds at the Gardens, however by their nature trials are ongoing and plants throughout the Gardens are still considered under trial.
The aim of ongoing plant evaluation is to:
- Ascertain the best plants for growing in Auckland conditions to feature in our main displays (poor performers are culled unless special considerations require them to be retained)
- Ascertain the value of certain plants in ecological and environmental applications
- Influence the range of plants grown by private gardeners, landscapers and in public places
- Identify plants that may be used in breeding programmes
Plants are selected for trials based on trends in the gardening world, new plants to the market, gaps in a garden (e.g. a colour palette or seasonal feature) or function (e.g. annual bedding or a device such as a rain garden). Known experts and publications are used when researching the content of proposed trials. Only plants which are available in the trade, or likely will be, are trialled.
Plants are assessed through a combination of data collection and evaluation.
A trial plan is drafted for every trial to guide data collection and frequency resulting in a field data collection template specific to each trial. Common data collected includes flowering period and quantity, foliage, form, health (without pesticides), suitability for purpose, and overall appearance (e.g. flowering time, maintenance requirements), weed potential and growing times (e.g. from seed to flower, and to a maximum size). Characteristics specific to each crop will also be considered such as self-grooming, colour fade and attractiveness to pollinators.
Formal evaluations are scheduled periodically during each trial to coincide with peak flowering and at other strategically timed dates. While evaluations are based primarily on performance data, there is an element of subjectivity by an evaluation panel when reaching final determinations. It is also important to recognise that taste varies widely, and a plant that is unappealing to some will be admired by others. This subjectivity will mainly apply when rating aesthetic qualities of a particular trial subject, and it will also apply when taste-testing edibles or assessing perfume.
A points-based rating system is used to provide a final score for each trial crop. Set thresholds determine whether a plant becomes a star performer or a recommended plant.
A Star Performer is a plant of proven excellence in suitable conditions in Auckland. Star performers are plants with a 9 or 10 rating from trials/evaluations and receive a sticker on the plant label or branding on collateral (e.g. brochures).
Recommended plants have consistently performed to high standards in suitable conditions in Auckland. Recommended plants are those that have scored an 8 or higher in trials/evaluations. They are included in garden displays but are not identified on in-garden plant labels.
Findings of plant trials are prepared at the conclusion of each trial or garden evaluation. Trial reports are made available to various publications including the Friends of Auckland Botanic Garden Newsletter, and papers may be published in scientific and garden journals. Plant recommendation collateral (Plants for Auckland Database and brochures) is based on trial results.