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Why flowering seasons matter

Bees and flowers have to be in the same place at the same time. That synchrony is being pulled apart by warming, and for specialist bees with narrow windows it is a serious problem.

PollinationReviewed 2026-10-31

The synchrony problem

A specialist bee that emerges when its plant is flowering has a life. One that emerges two weeks early finds nothing. This coupling — phenological synchrony — has been maintained for millions of years because both organisms respond to broadly similar cues, principally temperature and daylength.

Warming is decoupling them, because plants and insects weight those cues differently. Where a plant responds more strongly to temperature and a bee more strongly to daylength, or vice versa, a warm spring moves one and not the other.

Who is at risk

Vulnerability to phenological mismatch
GroupRiskWhy
Generalist bees with long seasonsLowSomething else will be flowering
Honey beesLowPerennial colony, broad diet, stores as a buffer
BumblebeesModerateLong season but queens depend on a narrow early window
Oligolectic solitary beesHighOne plant genus and a flight period of a few weeks
Montane and Arctic speciesHighCompressed seasons and nowhere further to move

The specialists are the concern. Melitta tricincta provisions its cells with red bartsia pollen and nothing else. Chelostoma campanularum uses campanula pollen alone. Andrena florea uses white bryony. For these bees a two-week shift is not an inconvenience; it is the difference between reproducing and not.

The gap problem, which is separate

Distinct from mismatch is simple discontinuity. A landscape can have abundant forage in May and August and nothing in between, and a colony that runs out in June does not benefit from what arrives in July.

This is what oilseed rape landscapes do. A vast flow in April and May followed by nothing produces colonies that build enormously and then starve, and it is why beekeepers in arable regions feed in June. The same applies to almond orchards in California, which support two million colonies for three weeks a year and almost nothing afterwards.

Flowering is not a flow, and a flow is not a harvest

Three periods get called 'the season' and they are not the same. Flowering is when the flowers are open. A nectar flow is when they yield enough nectar for bees to store a surplus, which is usually shorter and can fail altogether in a cold or dry spell. The harvest is when the beekeeper takes the honey off, which comes after the flow, once the honey is ripe. Honeydew is a fourth period, and follows the sap-feeding insects on the trees rather than any flowering.

JanFebMarAprMayJunJulAugSepOctNovDecFloweringFlowers open: weeks to monthsFNectar flowEnough nectar for a surplusNHarvestHoney taken off, once ripeHHoneydew flowSet by insects, not flowersDFFloweringNNectar flowDHoneydew flowHHarvestMonths as the source states themMonths derived from season words
Flowering, nectar flow, harvest and honeydew flow drawn as four separate periods, in an illustrative northern-hemisphere year rather than any real place. A plant flowers for longer than it yields: the nectar flow (N) sits inside the flowering period (F), and can fail altogether in a dry or cold spell. The harvest (H) follows the flow, because honey is taken off when it is ripe — the Provence specification says the beekeeper takes off the supers at the end of each flow. A honeydew flow (D) is not tied to any flowering: it follows the sap-feeding insects on the trees. Measured flowering periods for one tree species ran from 14 to 27 days in Hungarian stands across two years. Sources: Cahier des charges — indication géographique protégée « Miel de Provence »; Soil temperature and weather factors as key drivers of flowering phenology and nectar production in black locust; HoneyHQ editorial synthesis. Drawing: HoneyHQ (HEKNO Ltd), original.

The periods also belong to places. The same tree flowers weeks apart at different altitudes and latitudes, and a month means the opposite season either side of the equator. So HoneyHQ records a sourced period only for the place its source describes, keeps the source's own words beside the months, and says when the months were derived from words like 'spring'. The table below is everything held so far; the honey atlas draws it as a calendar.

Flowering, flows and harvests, as a source gives them for one place
WherePhaseWhatWhenHow the source puts itPrecisionEvidence
Australia — TasmaniaFloweringLeatherwoodNovember–FebruaryFlowering months: November, December, January, February. Confined to high-rainfall rainforest of the west, centre and south with low fire frequency.Months as statedOfficial institution
France — Corsica (the PDO area)Nectar flowSweet chestnutJune–AugustAmong the island's seasonal nectar staples, "chestnut at the start of summer" (HoneyHQ's translation from the French of the Corsica specification). The specification says the start of summer; the whole season is drawn, because it does not say which month it means. The quantity varies with the year's weather.Season words; months derivedProtected-name specification
France — Corsica (the PDO area)Nectar flowStrawberry treeSeptember–FebruaryAmong the island's seasonal nectar staples, "strawberry tree in autumn–winter" (HoneyHQ's translation from the French of the Corsica specification). The source of the bitter autumn-maquis honey. The quantity varies with the year's weather.Season words; months derivedProtected-name specification
France — Corsica (the PDO area)Nectar flowSweet chestnutJuneSome of the colonies made early in the season "can go into production on the chestnut flow (mid-June)" (HoneyHQ's translation from the French of the beekeeping institute's case study). The study places the flow in mid-June and gives no end month, so only June is drawn. Since the chestnut gall wasp arrived in 2010 the chestnut flow has become less reliable, the study notes.Months as statedBeekeeping authority
France — Corsica (the PDO area)Nectar flowStrawberry treeOctober–November"At the end of the season (October or November), beekeepers can take their hives to strawberry tree"; the season "can run until November or even December with the autumn maquis flow (mainly strawberry tree)" (HoneyHQ's translation from the French of the beekeeping institute's case study). Drawn October to November; "or even December" is an extension the study does not make regular, so it is kept in the words and not drawn. The flow may yield honey for sale or only the colonies' winter stores.Months as statedBeekeeping authority
France — Corsica (the PDO area)HarvestCorsican maquis honeyJanuary–December"Harvest periods take place throughout the year", from capped combs and at good ripeness (HoneyHQ's translation from the French of the Corsica specification). The six named types follow the island's flowering sequence through the year, from spring to the autumn maquis; the specification gives no month for each type.All year, as statedProtected-name specification
France — Corsica (the PDO area)HarvestCorsican maquis honeyApril–November"The harvests are spread through the whole year, from April to October–November or even February" (HoneyHQ's translation from the French of the Corsica specification). Drawn April to November; the specification's "or even February" is a late extension it does not make regular, so it is kept in the words and not drawn.Months as statedProtected-name specification
France — Corsica (the PDO area)HarvestCorsican maquis honeyMarch–MayThe spring honey (clementine, asphodel) is "harvested from March to May" (HoneyHQ's translation from the French of the regional tourism agency's page). The PDO's "Printemps" type.Months as statedBeekeeping authority
France — Corsica (the PDO area)HarvestCorsican maquis honeyMay–SeptemberThe maquis honeydews (rockrose, oaks, mastic tree) are "harvested from May to September" on the coast and the wooded land around the maquis (HoneyHQ's translation from the French of the regional tourism agency's page). The PDO's "Miellats du maquis" type. A harvest of honeydew honey: it says when the honey comes off, not when the insects are active.Months as statedBeekeeping authority
France — Corsica (the PDO area)HarvestCorsican maquis honeyAugustThe summer maquis honey is "harvested from August" (HoneyHQ's translation from the French of the regional tourism agency's page). The PDO's "Maquis d'été" type. The page gives when the harvest begins, not when it ends.Onset as statedBeekeeping authority
France — Corsica (the PDO area)HarvestCorsican maquis honeyOctober–FebruaryThe autumn maquis honey, mainly strawberry tree, is "harvested from October to February" (HoneyHQ's translation from the French of the regional tourism agency's page). The PDO's "Maquis d'automne" type; it crosses the new year.Months as statedBeekeeping authority
France — Provence (the PGI area)FloweringRosemaryFebruary–March"Early flowerings — from February–March for rosemary" (HoneyHQ's translation from the French of the specification). The specification gives when rosemary begins, as an example of Provence's long season; it does not say when it ends.Onset as statedProtected-name specification
France — Provence (the PGI area)FloweringHeatherSeptember–October"Late flowerings — September–October for heather, for example" (HoneyHQ's translation from the French of the specification). The specification names tree heath, ling and bell heather among Provence's heathers. Heather honeys are harvested in the Maures, the Estérel and the Var coast.Months as statedProtected-name specification
France — Provence (the PGI area)Nectar flowRosemaryMarch–May"This flow takes place in spring, or very rarely in autumn" (HoneyHQ's translation from the French of the specification). An autumn flow is possible but rare, and is not drawn.Season words; months derivedProtected-name specification
France — Provence (the PGI area)Nectar flowLavenderJune–AugustHives move to the mountains "until the end of spring", then "to the lavender honey production areas, before returning to the more southerly wintering areas in autumn" (HoneyHQ's translation from the French of the specification). The lavender flow falls between, in summer. A violent mistral can 'dry' the lavender nectar, the specification notes; yields vary widely from year to year.Season words; months derivedProtected-name specification
France — Provence (the PGI area)HarvestThyme honeyMarch–May"This harvest takes place in spring, after the rosemary flow" (HoneyHQ's translation from the French of the specification). Later in spring than rosemary; the specification does not narrow it further, so the whole season is drawn.Season words; months derivedProtected-name specification
Germany — Baden-Württemberg (sampled stands)Honeydew flowLarge silver fir aphid on silver firMay–JulyMay to July in the sampled years. Honeydew follows the insects' populations, which rise and crash from year to year; a forest can yield nothing in a poor year.Months as statedPeer-reviewed study
Germany — Baden-Württemberg (sampled stands)Honeydew flowBlack spruce aphid on Norway spruceMay–JulyMay to July in the sampled years. Honeydew follows the insects' populations, which rise and crash from year to year; a forest can yield nothing in a poor year.Months as statedPeer-reviewed study
Germany — Baden-Württemberg (sampled stands)Honeydew flowSpruce bud scale on Norway spruceMay–JulyMay to July in the sampled years. Honeydew follows the insects' populations, which rise and crash from year to year; a forest can yield nothing in a poor year.Months as statedPeer-reviewed study
Germany — The Lüneburg HeathHarvestHeather honeyAugust–SeptemberHeather honey is only harvested at the end of the season, in August and September. Only when the weather is right and the heather flowers are well developed; the page gives no flowering months, so none is drawn.Months as statedOfficial institution
GreeceHoneydew flowGiant pine scale on Calabrian and Aleppo pinesMarch–AprilThe insect's heaviest honeydew production is in March and April. The heaviest production, not the only one: beekeepers work pine forests at other times of year too.Months as statedPeer-reviewed study
Hungary — Isaszeg, Debrecen and Kecskemét standsFloweringBlack locustApril–MayAverage flowering periods of 14 to 27 days. At Isaszeg in 2024, flowering began on 14–20 April and, in one stand, ran in two phases to 18–20 May. Lower rainfall and lower soil temperature delayed the onset; the number of chill and heat days also moved it.Measured in named years (2023, 2024)Peer-reviewed study
ItalyHoneydew flowCitrus flatid planthopper on a very wide range of trees, shrubs and cropsJune–AugustSummer. An introduced planthopper on a very wide range of trees, shrubs and crops.Season words; months derivedPeer-reviewed study
United States — Highlands County, FloridaFloweringSweet orangeFebruaryMid to late February in Highlands County is the beginning of the orange blossom bloom. The extension agent gives when the bloom begins, not when it ends or when the honey is taken off.Onset as statedUniversity extension
United States — North CarolinaNectar flowSourwoodJune–AugustFlower bloom time: summer. A nectar plant in early summer and mid-summer; bees produce a rich and popular honey from the nectar. The extension service gives early and mid-summer, not months; the whole summer is drawn.Season words; months derivedUniversity extension

Flowering, a nectar flow and a harvest are different periods and are listed separately: a plant can flower without yielding, and honey comes off after the flow. Where a source gives only season words, the months are the meteorological season for that hemisphere and the precision column says so. These are the places HoneyHQ has a source for, not a calendar for the world; the typical windows on honey and plant pages are HoneyHQ synthesis.

Checked 2026-10-31 against: Leatherwood (Eucryphia lucida) — tree species profile (Private Forests Tasmania (Tasmanian Government), 2026); Cahier des charges de l’appellation d’origine « Miel de Corse – Mele di Corsica » (Ministère de l’agriculture (Bulletin officiel n°48-2013); INAO (EU register, eAmbrosia PDO-FR-0066), 2013); Cas-type apiculture — Corse : miel en AOP et vente en demi-gros (ITSAP – Institut de l'abeille, with the Syndicat AOP Miel de Corse – Mele di Corsica (Réseau d'exploitations de référence), 2020); Le miel corse (Agence du Tourisme de la Corse (Collectivité de Corse), visit-corsica.com, 2026); Cahier des charges — indication géographique protégée « Miel de Provence » (Syndicat des apiculteurs de Provence (EU register, eAmbrosia), 2005); Sugar, amino acid and inorganic ion profiling of the honeydew from different hemipteran species feeding on Abies alba and Picea abies (PLOS ONE, 2020); Heather honey — sweet heather on bread (Naturpark Lüneburger Heide (c/o Landkreis Harburg), 2026); The effect of cold periods on the biological cycle of Marchalina hellenica (Insects, 2022); Soil temperature and weather factors as key drivers of flowering phenology and nectar production in black locust (Journal of Forest Science 72(4): 202–211, 2026); Main European unifloral honeys: descriptive sheets (Apidologie, 2004); The bees are coming (UF/IFAS Extension, Highlands County (University of Florida), 2022); Oxydendrum arboreum (sourwood) — NC State Extension Gardener Plant Toolbox (North Carolina State University Extension, 2026).

What is actually being observed

  • Spring flowering in Britain has advanced measurably over recent decades, with the effect strongest in early-flowering species.
  • Several bumblebee species have shifted uphill and northward at the trailing edge of their ranges.
  • The bilberry bumblebee's retreat to higher ground in Britain is one of the more clearly documented examples.
  • Some Arctic and montane bumblebees have no available uphill range remaining.

What helps

Continuity is the practical answer at every scale. A garden that flowers from February to November buffers against shifts in any one species' timing. A farm with hedgerows, margins and a mix of crops does the same. A landscape with only one flowering event, however enormous, does not.

The claims on this page

Every substantive claim is placed on a tier, and the top two tiers must also state what they are not claiming.

Established evidence

Supported by systematic reviews, meta-analyses or clinical/regulatory guidance. The claim would survive a careful reader checking it.

Established evidence

Spring flowering and insect emergence have both advanced with warming, and not always at the same rate.

Long-term phenological records show advancing spring flowering dates across many plant species and advancing emergence in many insects. The rates of advance differ between taxa because plants and insects weight temperature and daylength cues differently, which creates the potential for mismatch between specialist bees and their host plants.

What this does not claim: This does not claim mismatch has been demonstrated as the cause of decline in any particular bee species. Habitat loss remains the larger documented pressure, and attributing specific declines to phenological mismatch is considerably harder than documenting the shifts themselves.

  • Assessment Report on Pollinators, Pollination and Food Production — Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services (IPBES) (2016) · Systematic review Link

Sources

  • Assessment Report on Pollinators, Pollination and Food Production — Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services (IPBES) (2016) · Systematic review Link
  • Bumblebees: Behaviour, Ecology, and Conservation — Oxford University Press (2010) · Monograph
  • Field Guide to the Bees of Great Britain and Ireland — Bloomsbury (2015) · Field guide
  • Cahier des charges — indication géographique protégée « Miel de Provence » — Syndicat des apiculteurs de Provence (EU register, eAmbrosia) (2005) · Standards document Link
  • Soil temperature and weather factors as key drivers of flowering phenology and nectar production in black locust — Journal of Forest Science 72(4): 202–211 (2026) · Peer-reviewed article Link

How sources are selected and weighted is set out in the sources and evidence policy.

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