When to Plant Blueberries by Zone: Chill Hours and Timing

June 26, 2026

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How Chill Hours Work

Blueberries enter dormancy each fall and need sustained cold to flower and fruit reliably the following season. That cold is measured in chill hours: cumulative hours at or below 45°F between roughly November and February. Each variety has a minimum threshold. Plant a Northern Highbush in Zone 9 and it never accumulates enough cold to break dormancy correctly. Plant a low-chill cultivar in Zone 5 and late frosts kill the early bloom it triggers.

Before selecting a variety, match your zone to the right chill-hour range. The GardeningByZone regional guides map frost windows and seasonal cold accumulation by zone, so you can cross-reference variety thresholds with your actual conditions before committing to a planting.

Zones 3–7 typically accumulate 800–1,200+ chill hours in a normal winter. Zones 8–10 average 150–600 hours depending on elevation and coastal proximity. The variety must fit that band, not just the zone color on a hardiness map.

Blueberry Varieties by Chill-Hour Requirement

The table below maps widely available varieties to their chill-hour thresholds and compatible zones. For pH requirements, spacing, and pruning schedules by zone, see the blueberry plant guide.

Variety Type Chill Hours Best Zones
Patriot Northern Highbush 1,000–1,200 3–6
Northland Half-High 800–1,000 3–6
Polaris Half-High 800–900 3–6
Duke Northern Highbush 800–1,000 4–7
Bluecrop Northern Highbush 800–1,000 4–7
Tifblue Rabbiteye 500–600 6b–9a
Premier Rabbiteye 500–550 6b–8
O’Neal Southern Highbush 300–400 7–9a
Star Southern Highbush 300–350 7b–9a
Emerald Southern Highbush 250–300 7b–9a
Sharpblue Low-Chill 150–200 8b–10
Biloxi Low-Chill 150–200 8b–10

At the low end of the spectrum, varieties rated at 150–200 chill hours were bred for Gulf Coast and South Florida winters, where cold accumulation is minimal and year-to-year variation is high. Live Biloxi Blueberry Bushes (4 Pack) – Southern Highbush Blueberry Live Plants for Planting, Low Chill Requirement, Sweet Fruits. Live Biloxi Blueberry Bushes (4 Pack) – Southern Highbush Blueberry Live Plants for Planting, Low Chill Requirement, Sweet Fruits. — $27.99 is the most widely available cultivar in this range and performs reliably from Zone 8b through Zone 10.

Zone 6b growers fall at the Rabbiteye crossover. Tifblue and Premier reliably accumulate the 500+ hours required in Zone 6b winters and produce heavily in the Southeast’s long warm season, but both need a second compatible Rabbiteye variety within pollination distance.

Planting Windows by Zone

The correct planting season flips at approximately Zone 7. Cold-climate zones plant in spring after the ground thaws and hard-frost risk drops. Warm-climate zones plant in fall so roots establish during the cool season before summer heat arrives.

Zone Season Timing
3 Spring Mid-May through early June
4a–4b Spring Late April through mid-May
5a–5b Spring Mid-April through early May
6a Spring or Fall March–April or October–November
6b Spring or Fall March–April or October–November
7a Fall preferred October–November; or February–March
7b Fall preferred October–November; or February–March
8a Fall October through December
8b Fall October through December
9a–9b Fall through Winter October through January
10a–10b Fall through Winter November through February

Zone 6b timing. Fall planting in October works when winters stay above -5°F before soil freeze. In years with early hard freezes, spring planting in late March carries lower risk. Rabbiteye varieties planted in fall establish quickly in Zone 6b’s mild autumn temperatures.

Zone 7 variety risk. Southern Highbush varieties (O’Neal, Star) break dormancy earlier in spring than Rabbiteye types. In Zone 7a, late frosts can run into March and kill open bloom. Fall planting gives roots several months of establishment before that window. If late frosts are consistent in your microclimate, Rabbiteye is the more reliable choice at Zone 7 even though its chill-hour range overlaps with Southern Highbush territory.

Zone 10 pre-chilling. Zone 10 rarely accumulates enough ambient chill hours for any standard variety in a typical year. Purchase pre-chilled nursery stock, or refrigerate bare-root plants at 34–40°F for 250–300 hours before planting. Without artificial pre-chilling, flowering is erratic and fruit set is unreliable.

Warm-Climate Variety Selection for Zones 8 Through 10

Zone 8a and warmer require varieties rated at 600 chill hours or fewer. The selections below cover the full range from the coolest Zone 8a winters through Zone 10 pre-chilled planting. Plant two varieties with overlapping bloom times; Southern Highbush and low-chill types are partially self-fertile but set significantly more fruit with a cross-pollinator within 6 feet.

150–200 chill hours (Zones 8b–10):

250–400 chill hours (Zones 7b–9a):

500–600 chill hours (Zones 6b–9a):

Soil pH and Planting Depth

Blueberries require soil pH between 4.5 and 5.5. Most native soils read 6.0–7.0, which locks out iron and manganese at the root zone. Test pH 6–12 months before planting and amend with elemental sulfur if the reading exceeds 5.5. Sulfur converts slowly; amendments made the season before planting are far more effective than applications made at planting time.

Plant container-grown stock so the top of the root ball sits level with or slightly above the soil surface. Blueberry roots are shallow and oxygen-dependent. Deep planting reduces drainage and promotes crown rot, particularly in Zones 8–10 where fall and winter rainfall is highest.

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