Arboretum Guide

A real four-seasons botanical phenology reference — real species, real day length, real thermal-time (GDD) forcing. Data from OnlyCSharp.Data.Catalogs.Biology.Botany.

Site

Single real, pinned site — Boston, Massachusetts, USA (42.36°N), home to a real public-arboretum tradition (the Arnold Arboretum). USDA hardiness zone 7 (Boston's current 2023-map zone; historically 6b). The reference clock is a real Gregorian calendar, not an abstract day counter.

Real day length across the year

Solar declination via the Cooper (1969) approximation δ = 23.44°·sin(360/365·(day+284)); day length from the sunrise-hour-angle formula hours = (2/15)·acos(−tan(lat)·tan(δ)). This is what drives real photoperiod-triggered bud break and fall senescence below — never a hard-coded date.

How phenology is modeled

Thermal-time (GDD) forcing → bud break

Each deciduous species accumulates growing-degree-days (GDD) — max(0, dailyTemp − base) — above a habit-appropriate base temperature (5°C for woody trees/shrubs/vines, the classic forcing-unit base behind spring-index models; 0°C for herbaceous wildflowers). This is the growing-degree-day concept applied to budburst forcing the way Cannell & Smith (1983, J. Applied Ecology 20:951-963) modeled it for conifers. Bud-break threshold scales with a species' real hardinessZoneMin: hardier species (lower USDA zone number) need less forcing to break dormancy than tender ones — the counter-gradient pattern documented across tree provenances by Vitasse et al. (2009, Agric. Forest Meteorol. 149:735-744).

Photoperiod-triggered senescence

Fall senescence is not a calendar trigger. Once past midsummer, each day checks whether the real day length has dropped below the species' own critical photoperiod — or the first hard frost has hit, whichever comes first — the real dual photoperiod+temperature control on autumn senescence modeled by Delpierre et al. (2009, Agric. Forest Meteorol. 149:938-948).

Hardiness-zone stress

If a site's USDA zone is colder than a species' real minimum hardiness zone, its bud-break threshold rises (delayed spring) and it carries winter-dieback risk — e.g. a tropical palm like the Coconut palm (hardinessZoneMin 10) is severely stressed at Boston's zone 7.

Catalog stats

Garden trees, shrubs & vines

Perennial woody species from PlantTraitsCatalog — the game-facing horticulture traits table (growth habit, sun/water need, mature height, USDA minimum hardiness zone, days to maturity, edible/perennial flags).

Conifers

ConiferCatalog: family, native origin, maximum height, evergreen flag, typical lifespan. The three deciduous conifers (European larch, Bald cypress, Dawn redwood) go through a full leaf-out/fall-color/dormancy cycle like a broadleaf tree — real botany, not a modeling shortcut.

Wildflowers

WildflowerCatalog: bloom colour, native origin, and blooming season — every real season is represented, so the bed's bloom mix visibly changes across the year.

Vines & climbers

VineCatalog: climbing method, native origin, and whether the vine is woody (a liana).

Roses

RoseCatalog: horticultural class, bloom colour, and fragrance.

Palms

PalmCatalog (family Arecaceae): native origin, maximum height, primary human use, and cold hardiness. The cold-hardy entries (e.g. Windmill palm, Canary Island date palm) are the ones that could survive a temperate arboretum like the Boston site above; the rest are strictly tropical.