The genus Hebe is closely allied with that of Veronica that gives us many popular annuals and perennials that are grown for their attractive and brightly coloured flowers. The seed is usually small and easily germinated in these domesticated varieties. The usual method of propagation is by cutting.
There are approxiametly 100 species in the genus Hebe, with about 80 of them being endemic to New Zealand. Species are widely spread throughout New Zealand, occupying widely different ecological niches. As well as being our largest genus of plants they are a major element in many ornamental native plant gardens due to their hardiness, ease of propogation by seed or cutting, plus the superior colours of their flowers. Many have a restricted distribution in the wild, which could in part be due to the synchronicity and timing of many environmental events that influence flowering, seed dispersal and germination.
The fruit of Hebe is a partially flattened or compressed dry capsule containing between 4 and 42 seeds per capsule, depending upon the species concerned and the size of the seed. A large healthy plant may produce thousands of seeds per plant.
Many species are easy to grow from seed, particularly species with broad distributions or those that inhabit the milder climates. The seed production potential is high in most species and in favourable seasons large quantities of good seed are set. The short time from seed maturity to dispersal by the wind can cause difficulties in gathering seed. However observation over time of the flowers usually leads to plenty of viable seed. When conditions are optimum, germination in most species is even and rapid, sometimes completed in a week or so.
In the paper: Seeds, Seed ripening, germination and viability in some species of Hebe Proceedings of the NZ Ecological society Vol 23 1976; Margaret Simpson tested the germination characteristics of many species. Species that germinate readily at 25C in light include H. amplexicaulis, H. bollonsii, H. cupressoides, H. pinguifolia, H. speciosa, H.stricta, H. diosmofolia, H.elliptica,H. epacridea, H. hulkeana, H. parviflora, H.silicifolia, H.strictissima, H.traversii,H. epacridea, Parahebe decora, P. lyalli.
Most mountain species required either colder temperatures or cold pretreatment for optimum germination. Those species which show a preference for lower temperatures include H. buchanani, H. raoulli, h. lavaudinia and H. recurva. Species that respond to stratification include H. coarctaca, H. ciliolata, and H. paucirimosa.
Some species retained viabilty of seeds for up to 22 months with good germination; H.ellitica, H. salicifola, H. stricta.
Variation in amount of germination at various times of the year; H. amplexicaulis, H. bollonsii, H. pimelioides, H. lavaudinia, H. traversii, H. parviflora.
A gradual decline of germination with senescence of seed. H. diosmofolia, H.epacridea,
H.hulkeana, H. topiaria.