Landbrugsministeriet • Statens Planteavlsforsøg The genus Hebe A botanical report Linda Noack Kristensen Afdeling for Blomsterdyrkning DK-5792 Årslev Tidsskrift for Planteavls Specialserie Beretning nr. S 2034 -1990 Price: 50,00 DKK excl. VAT May be ordered at: Danish Institute of Plant and Soil Science Information Service Skovbrynet 18 DK-2800 Lyngby Danish Research Service for Plant and Soil Science Report no. S 2034 Research Centre for Horticulture Institute o f Glasshouse Crops DK-5792 Årslev The genus Hebe A botanical report Linda Noack Kristensen Hebe hulkeana Contents Page 1. Introduction ......................................................................................................................................... 3 2. Summary ......................................................................................................................................... 4 3. Identification and history of the genus H e b e .................................................................................... 4 3.1. Variation, including worldwide distribution.......................................................................... 5 3.1.1. How many species?...................................................................................................... 5 3.1.2. Worldwide distribution................................................................................................. 6 3.2. Classification and sections, including morphological variation and chromosome num bers......................................................................................................... 7 3.3. Evolution from Gondwanaor long distance dispersal?........................................................ 8 4. Habitat and distribution within the New Zealand Botanical Region............................................. 10 4.1. Habitat, growth form and flow ering......................................................................................... 11 4.1.1. A lpine.............................................................................................................................. 14 4.1.2. Subalpine......................................................................................................................... 16 4.1.3. Forest and low land........................................................................................................ 16 4.2. Distribution in words and m a p s................................................................................................ 18 4.3. New view s..................................................................................................................................... 19 4.3.1. A stable or still developing g en u s.............................................................................. 19 4.3.2. Botanical sections - a slender or firm foundation.................................................... 20 5. Physiology ......................................................................................................................................... 23 5.1. Rates and periodicity of growth, photosynthesis and transpiration ................................... 23 5.2. Cold tolerance.............................................................................................................................. 25 5.3. The unspecialized apical b u d ..................................................................................................... 25 5.4. Intensity and time of flow ering................................................................................................. 28 5.5. D iscussion..................................................................................................................................... 28 6. Breeding systems and hybridization................................................................................................... 28 6.1. Flower structure and fertility...................................................................................................... 28 6.2. Breeding systems.......................................................................................................................... 30 6.3. P ollination..................................................................................................................................... 30 6.4. Seed and fruit structure............................................................................................................... 32 6.5. Hybridization in nature and culture.......................................................................................... 33 6.6. D iscussion..................................................................................................................................... 34 Acknowledgements........................................................................................................................................ 35 References....................................................................................................................................................35 Appendix 1: Habitat and distribution of New Zealand Hebe ta x a ........................................................ I Appendix 2: Climate and geological history of New Zealand.............................................................. XIX Sats: Informationstjenesten 2 Chapter 1. Introduction “Are the alpine and subalpine flora of New Zealand alpine at all, or are the plants just forced into these conditions by competition?” Phil Gamock-Jones 6 June 1989 The New Zealand flora evolved in isolation from other floras from the split up of the Gondwana Supercontinent about 100 million years ago. The flora is rich in endemic plant species, with relatives in both tropical, subtropical and temperate floras. Hebe is an example of a large plant genus widely spread throughout New Zealand, although it is also found in two other countries. In Europe Hebe is widely used as garden plants and pot plants, being exotic and valuable. For more than 15 years, the Danish pot plant growers have produced cultivars of Hebe as flowering pot plants. The interest for these plants is increasing, and with the genetic variation within the genus more species and varieties could be developed for commercial production in future. Linda Noack Kristensen July 1989 3 Chapter 2. Summary Flowering in Hebe occurs all year round in one The genus Hebe (Scrophulariaceae) was first se­ species or another, and intensity of flowering has parated from the genus Veronica in 1926. All taxa, been shown to increase with latitudes. except two, are endemic to New Zealand and outly­ A high degree of gender dimorphism, self-com- ing islands. patibility and self-fertilization is found in Hebe. The The exact number of taxa is not known at present, relationship between these features is discussed. and a major taxonomical revision has recently been Breeding systems in the genus have not been stud­ started by Dr. P. Gamock-Jones, Botany Division, ied. Pollination is carried out by flies, beetles and DSIR, Lincoln, New Zealand. native bees. Both the present and the suggestions for new taxa Hybridization occurs frequently in nature, and are presented in Appendix 1. The suggested new the presence of both monoploids, diploids and tri- taxa are based on interviews with Mr. A.P. Druce, ploids indicates that taxa have developed and adapted Pinehaven, Upper Hutt, New Zealand. to the changeable New Zealand environment. In Evolution of the genus is discussed. The most culture, hybrids are very common. supported theory is that Hebe originated in New Zealand after the split of Gondwana. The two spe­ cies shared with South America and Falkland Is­ Chapter 3. Identification and history lands are suggested to have originated in New of the genus Hebe Zealand and to have become established else where Hebe Comm, ex Juss., 1789, belongs to the tribe as a result of long distance dispersal. Veroniceae of the family Scrophulariaceae (Moore The genus is grouped into ten botanical sections. in Allan, 1961) and all species except two are The major features are the presence of a sinus, the endemic to New Zealand and outlying islands (P. structure of the capsule and the type and position of Gamock-Jones, pers. comm.). inflorescence. Hebe is the largest genus of plants in New Zea­ Within each section, the growth form, habitat land in terms of species number. The plants are and distribution of the taxa vary. Hebe taxa are found evergreen shrubs or small trees with opposite lea­ from alpine to lowland altitudes and in various land ves. They are found from sea-level to the alpine forms. The most common land forms are cliff and altitude, and range in height from a few centimetres rock. The distribution of a taxon is often local in to 7 meters. Leaf size varies widely. The smallest “pockets”. leaved species occur at the higher altitudes. The The reliability of the present sections, and an flowers are 4-5 lobed, small, mostly bom in spikes alternative separation into groups on the basis of or racemes. Flower colours range from white to chromosome numbers are discussed. blue, mauve, purple and red. Very little is known about the physiology of the The history of the genus Hebe formerly started in genus. Growth rate, presence of growth rings and 1926,63 years ago. The name Hebe was suggested persistence of foliage have been studied for two a few years earlier. The important botanical papers subalpine species. are: Hebe tolerates frost to some extent. Much are yet to be studied in terms of lower and upper tempera­