Hebe – “young maturity” or “bloom of youth” (Greek); honoring the Greek goddess of youth and cup-bearer to the gods, serving them nectar and ambrosia

• she was the youngest of the Olympian gods and believed to have the power to restore youth

Native range: New Zealand, SE Australia, Chile, and Rapa (French Polynesia)

Leaves:

• strongly opposite, decussate (pairs of leaves are perpendicular to the pair above and below)
• ~entire
• sometimes scale-like
• conspicuous scars once leaves fall

Flowers:

• inflorescence – upright dense spike-like heads in leaf axils, may be greatly reduced
• 4-lobed (~3-5 parted)
• 2 stamens, exserted
• 1 style
• white, purple
• herkogamy (spatial separation of pollen and stigmas within flower)

Fruit:

• capsules (non-fleshy)
• 2 cells
• many small seeds

Other notes:

• evergreen
• vary in life-form from large leafy shrubs to matted plants with whipcord-like branches, on which the leaves are almost reduced to scales
• branches w/ conspicuous leaf scars
• Hebe cultivars are used in gardens in California and along the coast of WA and OR
  • smaller leaved cultivars are hardier
  • others are sensitive to cold, best in sun and protected conditions
  • cultivar near Graham Visitors Center (WA Park Arboretum) appears to be - or resembles - Hebe pinguifolia ‘Pagei’
• classification is unresolved
  • genus moved to Veronica (hence common name shrubby Veronica) and back to Hebe
  • family was formerly Scrophulariaceae, which some sources still use
• largest genus of New Zealand shrubs, with 80+ species
  • New Zealand is where the most adaptive radiation (evolution of species) of this genus has occurred due to its isolation, heterogenous landscape, and latitudinal range
  • population of original species were fragmented by changing sea levels, mountain-building, volcanism, and glaciation
  • then the combined influences of inbreeding, genetic drift, and strong selection acted upon small populations
  • distributions of species are generally limited in area

Ecology & Adaptations:

• Native to New Zealand, SE Australia, Chile and sites in the South Pacific
• found in a variety of habitats but are most common in alpine shrubland, grassland, and fellfield (treeless, rock-strewn areas)
• several occur in coastal, lowland, and montane shrubland
• the following adaptations are representative of various species within the genus:
  • sexual reproduction & pollinators:
    • some spp. have long flowering period (Nov–Mar) because flowers are produced sequentially in pairs at the growing end of branches
    • characterized by herkogamy (spatial separation of pollen and stigmas within a flower) to minimize self- pollination
    • some groups display gender dimorphism, which is positively correlated with altitude: pollinator fauna also changes with altitude, going from mainly solitary bees at lower altitudes to dipteran flies and beetles at higher altitudes (>1,000 m)
    • separate sexes (flower dimorphism) may have been selected to enforce outcrossing in higher altitudes where pollinators are less efficient at cross-pollination/ selected as a consequence of high rates of selfing at higher altitudes.
    • Short-tongued bees move quickly, fly between plants frequently, and prefer to visit flowers with pollen that is used to feed young
    • in contrast, beetles rarely move between plants and tachinid flies visit flowers in all stages in their search for nectar
    • therefore likely that bees outcross flowers to a greater extent than other pollinators
    • High-altitude species adapted by separating the sexes to enforce outcrossing
  • seed dispersal – dried capsules dehisce seeds
  • seed germination:
    • requires light
    • seed is small and readily buried, but remains viable for at least a year, so can form a persistent soil seed bank
    • most mountain species require colder temperatures as low as 6oC to germinate while seed of species from lowland and lower mountain habitats germinate at higher temperatures of 20-25°C
  • herbivore defense:
    • phenolic glycosides interfere with digestion in herbivores
    • divaricate (branching) growth form may be an adaptation to deter browsing by extinct avian herbivores (moa, flightless bird that went extinct ~600 yrs ago when humans arrived on the NZ islands)
    • wide angle branching makes plants difficult for birds to swallow
  • drought tolerance:
    • lowered water potential in tissues (via concentration of compounds) prevents water loss
    • dense mats of fibrous roots efficiently absorb available water
  • wind tolerance – in exposed areas, stems are prostrate (low- growing, with branches lying on ground and only new growth growing erect)
  • frost tolerance – wide-angle branching of divaricate plants may provide a ‘frost-screen,’ protecting interior leaves from frost damage
  • tolerates low-nutrient conditions:
    • evergreen leaves prolong value of investment in photosynthesizing structures
    • mycorrhizae aid nutrient uptake