Zone 7 Begonias: Plant After May 15, Pick Wax or Tuberous, and They’ll Bloom All Summer
Zone 7 gardeners: plant after May 15, choose wax for easy color or tuberous for blooms — and discover the one begonia that comes back every year.
Zone 7 spans a wide arc of the country — coastal Virginia, central Tennessee, Arkansas, northern New Mexico — and what every garden in that range shares is a last frost that clears by mid-April and a first frost that returns around mid-October. That’s a solid six months of growing season, long enough for begonias to put on a real show. The question isn’t whether you can grow them; it’s knowing which type to choose, when to plant, and how to handle the heat spike that arrives in July.
Refer to our complete begonias growing guide for a full overview of all begonia groups. This article focuses specifically on zone 7 — the timing, the varieties that perform, and one begonia most gardeners overlook: the only type that comes back as a perennial in your zone.
Know Your Zone 7 Frost Window
Zone 7 splits into two sub-zones that shift your planting schedule by about 10 days. In zone 7a (parts of Virginia, Tennessee, Arkansas, and New Mexico), the average last frost falls around April 5. In zone 7b (coastal Virginia, the Carolinas piedmont, central Arkansas), last frost averages April 15. First fall frost in both sub-zones typically arrives in mid-October, giving you roughly six months of growing season.
The critical threshold for begonias isn’t the frost date itself — it’s nighttime temperatures consistently above 50°F. Below that point, begonias can’t efficiently run the enzymatic processes that drive root development; plants stall, sit vulnerable to soil fungi, and often suffer more from a cold, wet spring than from a brief frost. For zone 7, that means outdoor transplanting is safest from mid-May onward, roughly two to four weeks after your last frost date.
The second zone 7 challenge is summer heat. July and August routinely bring daytime temperatures above 90°F across much of zone 7. Tuberous begonias — the most spectacular type — will drop buds when daytime temperatures consistently exceed 85–90°F. Siting and shade management matter as much as frost timing in this zone.
Three Begonias Worth Growing in Zone 7
Most gardeners plant one begonia type and stick with it. In zone 7, that’s worth reconsidering: each of the three main types fills a different garden niche, and choosing the right one for your site and time commitment makes the difference between thriving plants and a frustrating season.
Wax Begonias (Begonia × semperflorens) — The Easiest Choice
Wax begonias are the most forgiving option for zone 7. They tolerate heat, handle moderate drought once established, and bloom continuously from transplant until the first frost — no deadheading required. Buy them as transplants in mid-May and plug them directly into beds or containers. No indoor starting needed.
The key zone 7 distinction is leaf color. Bronze-leaf varieties — the ‘Cocktail’ series, ‘Harmony Scarlet’, ‘Senator Rose’ — tolerate more direct sun and handle zone 7’s summer heat better than green-leaf types. Green-leaf wax begonias appreciate at least afternoon shade when temperatures exceed 85°F; bronze-leaf varieties can manage a sunnier position but still benefit from afternoon protection during July and August heat waves.
Tuberous Begonias (Begonia × tuberhybrida) — The Most Spectacular
Tuberous begonias produce 3–4 inch flowers in every color from white to deep red to picotee, blooming from early summer through the first fall frost. They require more effort than wax types: start tubers indoors in late January, provide partial to dappled shade outdoors, and lift them before October frost. The tubers can be stored and replanted — the same tuber often performs for five or more years, growing larger and producing more blooms each season.
The zone 7 constraint to plan around is heat sensitivity. When daytime temperatures consistently exceed 85–90°F, tuberous begonias stop setting buds and may drop existing blooms. Site them where they receive morning sun and afternoon shade, or move containers to an east-facing wall in July. The Nonstop® series (8–12 inches, available in multiple colors) ranks among the most reliable performers for zone 7’s variable summer conditions.
Hardy Begonia (Begonia grandis) — Zone 7’s True Perennial
Most zone 7 gardeners don’t know this species exists. Begonia grandis is the only begonia hardy to USDA zones 6–7, meaning it can survive in the ground through a zone 7 winter. It blooms July through October with pale pink or white pendant flower clusters, reaching 18 inches to 3 feet tall, and spreads naturally via tiny bulbils that form in the leaf axils and fall to the ground each autumn.
The Missouri Botanical Garden notes that Begonia grandis is the only winter-hardy begonia for the St. Louis area — and recommends heavy winter mulch, because the plant “may not be reliably winter hardy in zones 6 and 7.” A 3–4 inch layer of shredded hardwood mulch applied after the first frost is the difference between a perennial colony and a dead crown. It’s also notoriously slow to emerge in spring — new growth typically doesn’t appear until late May or early June in zone 7, so don’t assume the planting has failed.
For shaded beds under mature trees, Begonia grandis earns its place: plant it once, mulch it each November, and it gradually naturalizes into a colony that peaks every August — just when summer annuals start looking tired.
| Type | Zone 7 Status | Bloom Period | Best Light | Effort Level | Best Use |
|---|---|---|---|---|---|
| Wax begonia | Annual | May–frost | Morning sun; afternoon shade | Low | Beds, edging, containers |
| Tuberous begonia | Annual (tubers reusable) | June–frost | Partial to dappled shade | Moderate | Show containers, patio pots |
| Hardy begonia (grandis) | Perennial with mulch | July–October | Partial to deep shade | Low once established | Shade beds, woodland gardens |
Zone 7 Planting Calendar
Start times for indoor-grown begonias are calculated backward from mid-May, the safe outdoor window for both zone 7 sub-zones. Zone 7a gardeners with a sheltered, warm microclimate may push outdoor transplanting two weeks earlier — but wait until nights are reliably above 50°F before risking it.
| Timing | Action | Notes |
|---|---|---|
| Late January | Start tuberous tubers indoors | Hollow side up, barely covered with compost; 65–70°F; 8–12 weeks before mid-May transplant date |
| February | Start wax begonias from seed under grow lights | 12 weeks before mid-May; press seeds onto damp seed-starting mix — do not cover, they need light to germinate |
| March | Sow Begonia grandis seed indoors if starting from seed | Must be sown after the spring equinox — long-day conditions trigger stem growth; earlier sowing causes seedlings to form dormant tubers instead of growing |
| Mid-April to May 14 | Harden off indoor starts | 7–10 days: start with 2–3 hours in sheltered shade, increase daily exposure |
| After May 15 | Transplant all types outdoors | Nights consistently above 50°F; soil temperature at 60°F minimum |
| June–July | Peak care: base watering, monitor shade, watch for pests | Move tuberous containers to east-facing locations when daytime temps exceed 90°F |
| August | Begonia grandis at peak; reduce fertilizing for tuberous | Hardy begonia blooms through October; letting tuberous slow prepares tubers for storage |
| October | Lift tuberous tubers; apply mulch to grandis beds | Zone 7b average first frost: October 15 — lift tuberous within a few days of first frost |
| November–January | Store tuberous tubers at 40–50°F | In vermiculite, dry peat, or wood shavings — never plastic bags, which trap moisture and cause soft rot |
Soil, Light, and Handling Zone 7 Heat
All three begonia types share one soil requirement: good drainage. Pythium root rot — triggered by waterlogged conditions — is the most common begonia killer during zone 7’s humid summer periods. Amend clay-heavy beds with compost before planting; target a slightly acidic pH of 5.5–6.5. A 2–3 inch layer of organic mulch (shredded hardwood or bark chips) around plant bases keeps the root zone cooler during July and August and significantly reduces irrigation frequency.
Light requirements vary by type. Tuberous begonias need partial to dappled shade throughout the day — even a few hours of direct afternoon sun in July causes bud drop. Wax begonias with bronze foliage can handle a sunnier position but still appreciate afternoon shade above 85°F. Begonia grandis prefers partial to deep shade and spreads most readily under deciduous trees where summer canopy filters light.
When temperatures exceed 90°F, avoid fertilizing and pruning any begonia. Stressed plants can’t efficiently repair tissue, and a nitrogen surge during a heat wave pushes weak foliar growth at the expense of roots. Wait for a cooler morning — below 80°F — before cutting or feeding.
Watering and Feeding
Clemson’s Home & Garden Information Center classifies begonias as not heavy feeders — a point worth emphasizing, since many gardening sources recommend weekly liquid fertilizing. In practice, work a balanced slow-release fertilizer into the planting hole at the start of the season. Container-grown tuberous begonias benefit from a monthly liquid feed during peak bloom; garden-bed wax begonias and Begonia grandis rarely need supplemental feeding beyond the initial amendment.
Water at the base of the plant rather than overhead. Drip irrigation or a soaker hose is ideal; evening overhead watering creates the leaf moisture that botrytis blight needs to spread. Wax begonias in garden beds: water when the top inch of soil is dry. Tuberous begonias: keep consistently moist but never waterlogged. Small containers (4–6 inch pots) may need daily watering when daytime temperatures are 75–90°F.
Overwintering: Three Different Plans
Wax begonias: Treat as annuals or take stem cuttings in September. A 4-inch cutting set in water, rooted, then potted up will overwinter on a bright windowsill and can be planted out again after May 15. See our begonia propagation guide for cutting-by-cutting instructions.
Tuberous begonias: Start the process 8 weeks before your expected first frost by halving watering and stopping fertilizer. After the first frost blackens the foliage, dig the tubers, shake off loose soil, and cure them in a cool dry shed for 2 weeks. Remove the dry stem stubs (they’ll pull away cleanly when ready) and store tubers in vermiculite or dry peat at 40–50°F through winter. Well-stored tubers grow larger each season, often producing more and bigger blooms after year two.
Begonia grandis: After frost kills the foliage, cut it back to the ground and apply 3–4 inches of shredded hardwood mulch over the planting area. The tubers overwinter in the ground. Expect no visible growth until late May or early June — Begonia grandis is reliably slow to emerge and will reward patience. To expand your planting, collect the small round bulbils from the leaf axils in early fall before they drop and press them onto moist seed-starting mix; they sprout readily the following spring.
Troubleshooting Common Zone 7 Problems
The issues below are most common in zone 7 conditions. For a wider diagnostic, see our guide to begonia problems and solutions.
| Symptom | Most Likely Cause | Fix |
|---|---|---|
| Yellow leaves, mushy stems at soil line | Pythium root rot from waterlogged soil | Improve drainage; reduce watering; remove affected plants before the rot spreads |
| Gray fuzzy mold on leaves and stems | Botrytis blight (high humidity, poor air circulation) | Remove infected tissue; improve plant spacing; switch entirely to base watering |
| Tuberous begonias dropping buds or refusing to bloom | Heat stress (daytime temps above 85–90°F) | Move containers to an east-facing location; add afternoon shade; do not fertilize during heat waves |
| White powdery coating on leaf surfaces | Powdery mildew (common in fall temperature fluctuations) | Improve air circulation; avoid overhead watering; apply neem oil or a sulfur-based fungicide |
| Leggy stems, pale green leaves, few flowers | Insufficient light | Move to a brighter spot — wax begonias in deep shade produce foliage at the expense of flowers |
| Ragged holes in leaves, mostly overnight | Slugs or snails (thrive in zone 7’s humid summers) | Apply iron phosphate slug bait around plant bases; water in the morning so leaves dry by evening |
Frequently Asked Questions
Are begonias perennials in zone 7?
One type is: Begonia grandis (hardy begonia) survives zone 7 winters in the ground under 3–4 inches of mulch. Wax and tuberous begonias are annuals in zone 7, though tuberous tubers can be dug, stored, and replanted each spring for five or more years.
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→ View My Garden CalendarCan I plant begonias before May 15 in zone 7?
Zone 7a gardeners with a warm, sheltered microclimate may transplant in late April if nighttime temperatures are consistently above 50°F. A premature transplant into cold soil sits vulnerable to Pythium and fungal crown rot for weeks before establishing — the risk rarely pays off.
Do begonias need full shade in zone 7?
Not necessarily. Bronze-leaf wax begonias can handle a half-day of sun. The reliable zone 7 rule: morning sun with afternoon shade works for most types. Full afternoon sun in July and August is too much for any begonia.
How long do tuberous begonias bloom in zone 7?
From outdoor transplant (mid-May) to the first fall frost (around October 15 in zone 7b) — roughly 5 months, with a potential slowdown during peak heat in July and August. The bloom pause during a heat wave typically lasts 3–4 weeks before plants resume flowering as temperatures ease in September.
Key Takeaways
- Zone 7 last frost: April 5 (7a) to April 15 (7b) — safe outdoor planting is mid-May when nights hold above 50°F.
- Three types for zone 7: wax (easy, heat-tolerant annual), tuberous (spectacular, shade-needing, reusable tubers), and Begonia grandis (the only zone 7 perennial begonia, blooms August–October).
- Start tuberous tubers indoors in late January — 8–12 weeks before the May transplant date.
- Bronze-leaf wax varieties handle zone 7 summer heat better than green-leaf types.
- Mulch all begonias in summer to cool roots; mulch Begonia grandis beds in late fall to protect overwintering tubers.
- Save tuberous tubers each fall — well-stored tubers grow larger each year and produce more blooms.
Sources
- Begonia — Clemson Home & Garden Information Center
- Begonia grandis (Hardy Begonia) — NC State Extension Gardener Plant Toolbox
- Begonia – Wax Types — NC State Extension Gardener Plant Toolbox
- Begonia – Tuberous Types — NC State Extension Gardener Plant Toolbox
- Begonia — University of Arkansas Cooperative Extension Service
- Begonia grandis — Missouri Botanical Garden Plant Finder
- When to Plant Begonias in Zone 7b — FrostDate.com
- When Can You Plant Begonias? — Longfield Gardens
