Cold hardiness

Future

2050

2100

These values are location-based: this location's current hardiness is the baseline, and the 2050 value is a projected future climate for this same location.

Now

Zone 6b

USDA

Published baseline for this location from 1991-2020.

Source: USDA Plant Hardiness Zone Map 2023 (1991-2020 climatology) via ArcGIS FeatureServer

Won't grow here

2050

Zone 7a

Plotwright

Projected zone for this same location in 2050 (2041-2070) using SSP3-7.0 (regional rivalry).

Won't grow here

In plain terms: This location is in Zone 6b today. Its hardiness profile is cold winters, and coldest nights are typically around -3°F. By 2050, the projected hardiness zone is Zone 7a based on SSP3-7.0 (regional rivalry). That is a +0.5-zone shift from Zone 6b to Zone 7a by 2050.

✕

Out of range today and still out of range in 2050.

Heat tolerance

Future

2050

2100

Heat tolerance values are location-based too: heat days today are observed at this site, and the 2050 value projects this same location under a future climate.

Loading AHS heat-zone data for this location...

Where this plant fits

Suitable across 36 ecoregions — 33 climate-resilient through 2070 · 3 newly possible by 2070. Best matches first.

Appalachian mixed mesophytic forests

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Appalachian-Blue Ridge forests

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Arizona Mountains forests

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Atlantic coastal pine barrens

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California coastal sage and chaparral

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Canadian Aspen forests and parklands

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Central Pacific Northwest coastal forests

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Central-Southern Cascades Forests

What it needs

Conditions

Light

Full sun

Water

Moderate water

Spacing

96"

Habit

Dense, rounded small evergreen citrus tree or shrub

Care tips

•

Outside zones 8b-11b, grow it in a large container that summers outdoors and overwinters in a bright, cool, frost-free indoor or greenhouse spot — it is the cold-hardiest citrus relative but still frost-tender.

•

Site outdoor plants in full sun in well-drained soil, sheltered from harsh wind and out of frost pockets.

•

Keep the soil evenly moist but never soggy; consistent moderate water suits it best, and waterlogged roots invite rot.

Lifecycle

Planting

In USDA zones 8b-11b, plant in full sun in fertile, well-drained soil in a spot sheltered from harsh wind and the worst frost pockets. As the cold-hardiest of the citrus relatives it takes brief cold better than most citrus, but it is still frost-tender — in colder climates grow it in a large container that can move indoors or into a greenhouse for winter.

Transplanting

Move container plants up gradually into larger pots, and site outdoor trees carefully at planting, since citrus resents root disturbance once established.

Early growth

Water moderately and consistently while young plants establish, keeping the soil evenly moist but never waterlogged. Feed lightly through the growing season and pinch to build a dense, well-branched rounded crown.

Maturity

A mature plant reaches roughly 8-15 feet tall and 6-10 feet wide as a dense rounded evergreen, flowering in summer and ripening its small whole-eaten fruit from fall into winter. Container specimens stay smaller and are kept in scale by pruning.

Propagation

Kumquats are typically propagated by grafting or budding onto citrus rootstock for hardiness and uniform fruiting; seedlings are slow and may not come true, so buy a grafted plant for dependable results.

Pollination

Self-fertile

Kumquat flowers are perfect and largely self-fertile, so a single plant will set fruit on its own; the fragrant white summer flowers nonetheless draw bees, and insect visitation can improve pollination and fruit set.

Plants don't grow alone

Nectar forage

Bee

European honeybee (Apis mellifera)

The fragrant white citrus flowers are an attractive nectar source for honey bees, though as a non-native ornamental fruit tree it carries no documented North American specialist ties.

Nectar forage

Bee

Common eastern bumblebee (Bombus impatiens)

For people

Edible

The small oval-to-round fruits are eaten whole, skin and all — the sweet, fragrant rind contrasts with the tart inner flesh, and that interplay is the whole point. They are eaten fresh out of hand and are also made into marmalade, candied peel, and preserves.

Climate notes

•

Per established horticulture (GBIF taxonomy + Wikipedia), Fortunella japonica — accepted name Citrus japonica — is a frost-tender but cold-hardy-for-citrus broadleaf evergreen for roughly USDA zones 8b-11b, native to southern China; grown for its edible whole-eaten kumquats and as a container plant.

•

The round kumquat is among the cold-hardiest citrus relatives and tolerates brief cold dips better than most citrus, but it remains frost-tender; hard or prolonged freezes will damage or kill it, which is why it is so often grown in containers or greenhouses where winters are cold.

•

It takes summer heat and sun well, in keeping with its subtropical-to-warm-temperate origins, and wants consistent moderate moisture in well-drained soil — neither drought-stressed nor waterlogged.

•

Like other citrus it can host the usual citrus pests (scale, aphids, mites) and is sensitive to root rot in soggy soil; site it in full sun with good drainage and air movement to keep it healthy.

In the designer

Growth over time

96-180" tall · 72-120" spread

Mature 8-15 ft tree (smaller and kept pruned in containers) carrying a dependable annual crop of whole-eaten kumquats.

Design roles: Edible · Container

Seasonal interest

Spring

Summer

Fall

Winter

Filled = the plant has seasonal interest · ▾ now = your current season

Round kumquat

At a glance

Why it matters

Cold hardiness

Heat tolerance

Where this plant fits

What it needs

Lifecycle

Pollination

Plants don't grow alone

For people

Climate notes

In the designer

Seasonal interest

Sources & citations