Zone 6 Begonias: Exact Planting Dates, 6 Top Varieties, and How to Keep Tubers Over Winter

Zone 6 gives begonias a long enough summer to put on a spectacular show — but winters that routinely hit 0°F mean nothing stays in the ground without a plan. Most begonia guides stop at “plant after last frost,” which leaves zone 6 gardeners with three unanswered questions: which varieties actually perform here, which specific dates apply to your zone, and what exactly do you do in October?

This guide answers all three. It opens with a decision framework that most guides skip entirely: zone 6 offers three distinct begonia approaches depending on how much winter work you want to do. Knowing your strategy unlocks the right variety choice, the right planting dates, and the right overwintering method — so you’re not guessing your way through any of it.

Zone 6 Begonias — Three Strategies

Not all begonias ask the same thing of zone 6 gardeners. Before selecting a variety, choose your approach — it shapes every other decision.

Strategy 1 — Annual treatment. Wax (fibrous) begonias and cane types like Dragon Wing® are grown as annuals in zone 6: planted in late May, enjoyed through frost, then composted. No storage required, no spring restart, no basement space needed. This is the lowest-effort path and works well for mass borders, container color, and gardeners who prefer to rotate plants each year. [1]

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Strategy 2 — Tuber storage. Tuberous begonias (Begonia × tuberhybrida) produce large, showstopping double flowers but are hardy only in zones 9–11. In zone 6, you dig the tubers before the first hard frost, store them at 40–50°F over winter, and replant in spring. The same tubers can produce for a decade or more — an investment that pays back every year you commit to the storage protocol. [2]

Strategy 3 — True zone 6 perennial. Hardy begonia (Begonia grandis) is the only species reliably perennial in zones 6 through 9, tolerating temperatures down to 23°F with a protective mulch layer. [3] Plant it once, mulch it in fall, and it returns each spring without any digging.

6 Zone 6 Begonia Varieties Worth Planting

Variety selection in zone 6 means matching the plant’s biology to your chosen overwintering plan. Each variety below is paired with the strategy it suits best.

The Nonstop® series from Benary deserves a specific note: these tuberous hybrids produce near-continuous 4-inch double blooms from late May through October in zone 6, but only if tubers are started indoors in early March. An April start delays blooms until August — a costly shortcut in a zone 6 season that runs roughly 180 days from last frost to first frost.

For first-time zone 6 begonia growers, wax begonias like BIG® Series are the safest entry point. They tolerate more direct sun than tuberous types, require no storage work, and bloom reliably from May to frost. For a full breakdown of begonia types including Rex, cane, and rhizomatous varieties, our complete growing guide covers each group in detail.

Zone 6 Begonia Planting Calendar

Zone 6a (average last frost around April 15) and zone 6b (average last frost around March 30) follow slightly different schedules. [5] Use this calendar as your planning anchor.

Why does the 50°F night temperature rule matter? Below 50°F, begonias can’t efficiently maintain the metabolic processes that protect cell membrane integrity — chilling injury to cell walls produces the blackened, water-soaked tissue that appears after an unexpected cold snap. The threshold isn’t arbitrary; it reflects where cellular function begins to break down in these tropical-origin plants. [2]

Soil temperature carries equal weight. Transplanting into soil below 60°F slows root establishment and increases vulnerability to soil-borne pathogens that thrive in cold, wet conditions. [1] If your zone 6 May feels cold, a soil thermometer is worth the small investment — surface conditions don’t always reflect what’s happening at the 4-inch depth where begonia roots will be working.

Hardening off over 7 to 10 days is essential for tuberous types started indoors. Start with 2 to 3 hours of outdoor shade exposure, increase gradually over the following days, and protect from wind until the final permanent placement. Skipping this step causes leaves to bleach, curl, and drop — a setback that costs 2 to 3 weeks of recovery time. Like spring bulbs, the indoor start timeline is what separates a June display from a July display in zone 6.

Light, Soil, Water, and Fertilizer

Light. Target morning sun (2–4 hours) with afternoon shade. In zone 6, afternoon sun in July and August regularly exceeds 85°F — above this threshold, tuberous begonias close their stomata to limit water loss, which simultaneously shuts down photosynthesis and stalls flower production. The practical rule: plant where the sun disappears by noon. Wax begonias tolerate more direct sun than tuberous types; darker-leaved varieties handle more light than green-leaved ones.

Soil. Target pH 5.5 to 6.5 with organically rich, well-drained soil. [1] In zone 6 clay soils — common across Pennsylvania, Ohio, and Missouri — work 2 to 3 inches of compost into the top 10 to 12 inches before planting. Begonias’ fine root systems are particularly sensitive to waterlogging: oxygen deprivation at the root zone triggers crown rot within 24 to 48 hours of standing water, producing collapse symptoms that look like wilting but won’t respond to more watering.

Water. Water at the base, not overhead. Wet foliage in shaded conditions invites powdery mildew and botrytis grey mould — both fungal diseases that spread rapidly in zone 6’s humid summers. If you’re seeing leaf spots, distorted growth, or stem collapse, our begonia problems guide covers identification and treatment for the most common issues. Keep soil consistently moist but not soggy; in containers, allow the top inch to dry before the next watering cycle.

Fertilizer. Feed every two weeks with a balanced liquid fertilizer through July. In late August, stop fertilizing tuberous begonias entirely. [2] This timing matters more than it might seem: withholding nutrients signals the plant to begin shifting stored carbohydrates back into the tuber — a process that produces a denser, firmer tuber with better storage potential and stronger regrowth in spring than one that’s been pushed with fertilizer right up to frost.

Overwintering Tuberous Begonias in Zone 6

The goal is to hold tubers at 40 to 50°F through winter — cold enough for deep dormancy, warm enough to prevent freeze damage. Most overwintering failures in zone 6 happen at the cold end: an unheated garage that drops to 25°F will destroy tubers just as effectively as leaving them in the ground. [2]

Step 1 — Stop feeding and slow watering. In late August, cut fertilizer entirely and begin reducing watering frequency. This triggers the natural senescence cycle and concentrates energy back toward the tuber.

Step 2 — Dig before hard frost. Once foliage yellows naturally — typically September in zone 6 — or if frost threatens, cut stems back to 3 to 4 inches and carefully lift tubers with a fork. Work wide of the plant: bruised or nicked tissue is the primary entry point for rot fungi during storage. [4]

Step 3 — Cure at room temperature. Lay tubers stem-side up in a single layer on newspaper or a wire rack at room temperature (65–70°F) for two to three weeks. The remaining stem tissue dries and detaches cleanly during this stage — do not rush this step by applying heat.

Step 4 — Pack and store. After curing, twist off dry stem remnants and brush away loose soil. Nestle tubers individually in dry peat moss, vermiculite, or sawdust inside a perforated paper bag or open wooden crate. Store at 40–50°F in a dark, dry location — a basement corner, root cellar, or interior closet works well. [2][4] Check monthly and remove any tuber showing soft spots before rot spreads to its neighbors.

Step 5 — Restart in spring. Around early March for zone 6a, set tubers concave-side up on barely damp potting mix in a warm, bright location indoors. Roots and shoots appear within two to three weeks. Once shoots reach 1 to 2 inches, pot into full growing mix and continue indoors until late May outdoor planting. [2][4]

Hardy Begonias — Zone 6’s True Perennial Option

Begonia grandis is the low-maintenance answer for zone 6 shade gardeners. Hardy to 23°F and perennial in zones 6a through 9b, it needs only a 3 to 4-inch mulch layer over the root zone after the first frost — no digging, no storage, no spring restart. [3] In zone 6a, the colder half, that mulch layer is non-negotiable: without insulation, the shallow rhizomes freeze solid.

Expect the plant to emerge slowly in late spring — growth rarely appears before June, which surprises gardeners used to spring bulbs. From July to October, it produces pendant clusters of 1-inch pink flowers on 18- to 36-inch branching stems, making it one of the longest-blooming shade perennials available in zone 6.

The self-propagation mechanism is worth understanding: as days shorten in September, B. grandis forms pea-sized bulbils in the axils where leaves meet stems. These drop to the soil naturally, overwinter in the leaf litter, and sprout as new plants the following spring. [3] Within two to three seasons, a single plant will colonize a shaded bed without any intervention. If you want to manage the spread, collect bulbils in September before they fall. ‘Wildwood Premier’ adds red-tinged foliage alongside the pink flowers for a stronger ornamental statement in woodland settings; ‘Alba’ carries the same zone 6 hardiness with white flowers.

Frequently Asked Questions

Can begonias survive winter in zone 6?

Wax and tuberous begonias are not winter-hardy in zone 6. Treat wax types as annuals and dig tuberous tubers in October before hard frost. Begonia grandis (hardy begonia) is the exception: it survives zone 6 winters as a true perennial with a 3 to 4-inch mulch layer and returns each spring.

When should I start begonia tubers indoors for zone 6?

Start tuberous begonia tubers indoors in early March for zone 6a, or late February for zone 6b. A February or early-March start produces blooms by late June or early July. An April start delays blooms until August — a significant loss in a zone 6 growing season of roughly 180 days. [2]

What’s the difference between zone 6a and 6b for begonias?

Zone 6a averages a last frost around April 15; zone 6b around March 30. Zone 6b gardeners can start tubers two weeks earlier and move plants outside roughly two weeks sooner, gaining additional bloom time at both ends of the season. [5]

How do I keep begonia tubers over winter?

After a 2 to 3-week curing period at room temperature, store tubers individually in dry peat moss or vermiculite inside a perforated bag at 40–50°F in a dark, dry location. Check monthly for soft spots and remove any affected tubers immediately to stop rot from spreading. [2][4]

Sources

1. University of Minnesota Extension — Begonia
2. University of Minnesota Extension — Tuberous Begonias
3. NC State Extension — Begonia grandis (Hardy Begonia)
4. Oregon State University Extension — Save and Enjoy Tuberous Begonias Year After Year
5. FrostDate.com — Zone 6a Begonias Planting Dates