When Do Begonias Start to Grow? Timing, Types & Planting Calendar

Begonias begin active growth when soil temperatures consistently sit between 18–24°C (65–75°F) and nights stay reliably above 10°C (50°F). In practice, that means most gardeners can expect seeds to sprout within 7–21 days of surface-sowing indoors, tubers to push visible shoots within 2–6 weeks of pre-sprouting, and stem cuttings to anchor with roots within 2–4 weeks under gentle bottom heat. Outdoors, that growth window typically opens after your last frost date, once nighttime temperatures have stabilized above 50°F for at least a week or two.

How begonia type changes your timing

Begonias are not one plant. The group includes six commonly grown types, and their growth habits are genuinely different enough that the timing advice for one type can actively mislead you on another. I learned this the hard way when I started tuberous begonias on the same schedule as my wax begonias and wondered why they were so far behind. Here is how variety shapes your planting calendar.

Wax begonias are the fastest from seed and the most forgiving. Tuberous types, including the popular Nonstop series, are slower and need a longer indoor head start. Rex and rhizomatous begonias are almost exclusively grown as houseplants through vegetative propagation, so their timing is less about frost dates and more about ambient temperature and humidity in your home or greenhouse.

When to start each type: seeds, tubers, rhizomes, and cuttings

Seeds

Wax begonia seeds should be started 14–16 weeks before your anticipated last frost date. That sounds like a long lead time, but these seeds are tiny (they look like dust) and the seedlings grow slowly at first. Tuberous begonias grown from seed, including Nonstop varieties, need an even longer head start: 16–18 weeks before last frost. The extra time accounts for their slower germination (15–20 days compared to 10–14 days for wax types) and the additional weeks needed to build a strong enough root system to survive transplanting.

Tubers and rhizomes

Tuberous begonias started from dry tubers are best pre-sprouted in damp vermiculite or peat about 10–12 weeks before your last frost date. At room temperature (around 20–22°C), you will see buds pushing through within 2–4 weeks. Once sprouts reach about 1 cm (roughly half an inch), move them into pots with proper potting mix. Rhizomatous begonias and rex begonias can be divided or propagated at almost any time of year if you are growing them as houseplants, but late winter to early spring is a natural choice if you want new growth to coincide with the longer light days ahead.

Cuttings

Stem cuttings from fibrous and cane begonias root most reliably when taken in early spring or late summer. Spring cuttings benefit from increasing day length and rising temperatures. Late summer cuttings can be rooted and overwintered indoors. Rex and rhizomatous types are best propagated from leaf or leaf-wedge cuttings, which produce rooted plantlets from the wounded veins within 4–8 weeks.

Planting calendar by method and climate

The single most useful thing I can tell you is to anchor your entire begonia schedule to your last spring frost date and the point when nighttime temperatures stop dipping below 10°C (50°F). Use whichever comes later as your outdoor planting date, then count backward to set your indoor start dates. The table below translates that into concrete calendar windows for the three main USDA climate bands. See our detailed guide 'Begonias: How to Grow' for complete, step-by-step instructions on timing, sowing, and care begonias how to grow.

If you are in Zone 6 with a last frost around mid-April, your seed-sowing window for wax begonias opens in late December or very early January. That feels early, but those plants need the full 7–9 weeks to develop into transplant-ready plugs, plus the hardening-off period before they go outside.

Indoor sowing versus outdoor planting: temperature rules and dates

Begonia seeds require a substrate (not air) temperature of 21–24°C (70–75°F) to germinate well. That is warmer than most homes in January, which is why a heat mat is one of the most useful tools you can buy for starting these plants. Air temperature is less critical at this stage than the warmth at root level. Once seedlings have their first true leaves and you are approaching transplant, you can drop temperatures slightly (to around 18–21°C) to promote sturdy, compact growth.

For outdoor planting, the hard rule is this: do not put begonias outside until nights are consistently above 10°C (50°F). A single cold night at 7°C will not kill them, but repeated chilly nights will stall growth, cause leaf yellowing, and leave plants vulnerable to fungal problems. In cool climates, that often means waiting until June even though the last frost passed in May. The extra patience is worth it: plants put out after this threshold almost always catch up to and outgrow plants set out too early and then damaged by cold.

Germination and sprout timing in days and weeks

One of the most common beginner frustrations is staring at a tray of nothing and wondering whether anything is happening. Here are the realistic windows to set your expectations.

If you are past 21 days and still seeing nothing from seeds, the most common culprits are substrate temperature that is too cool (check the surface of the tray, not your room thermostat), seeds that got buried under medium instead of staying on the surface, or medium that dried out even briefly during the critical first week. Begonia seeds are photoblastic, meaning they need light to germinate, so covering them even lightly can block the signal they need to break dormancy.

Step-by-step checklists for each starting method

Starting from seed

1. Fill a seed tray with fine, sterile peat/perlite or peat/vermiculite mix and moisten thoroughly before sowing.
2. Scatter seeds on the surface without covering them. Press very lightly to ensure contact with the medium.
3. Place a humidity dome over the tray and set it on a heat mat calibrated to 21–24°C (70–75°F) substrate temperature.
4. Position the tray under grow lights (14–16 hours of light per day) as soon as seeds are sown. Light is required for germination.
5. Check moisture daily. Mist the surface if it begins to lighten in color. Never let it dry out completely.
6. Expect cotyledons in 10–21 days depending on type. Remove the dome once most seedlings are up.
7. At first true leaves (1–3 weeks after germination), thin or prick out into individual cells.
8. Grow on at 18–21°C under bright light until the plug holds together and 2–3 sets of true leaves are present before transplanting.

Starting tubers

1. About 10–12 weeks before your outdoor planting date, place dry tubers hollow-side up in a shallow tray of barely damp vermiculite or peat.
2. Keep the tray in a warm spot at 20–22°C. Do not bury tubers or overwater at this stage.
3. Check weekly for bud development. Expect visible buds or shoots within 2–4 weeks.
4. Once shoots reach approximately 1 cm (0.5 in), pot up individually into well-draining potting mix with the tuber just below the surface.
5. Water modestly at first and increase as shoots develop. Place in bright, indirect light.
6. Grow on until plants are sturdy and nighttime temperatures outside are reliably above 10°C before considering outdoor placement.

Starting cuttings (stem and leaf)

1. Take a 7–10 cm (3–4 in) stem cutting just below a node, or cut a healthy leaf with an inch of petiole for rex/rhizomatous types.
2. Allow the cut end to callus for 30–60 minutes before inserting into rooting medium.
3. Optionally dip the basal cut end in IBA rooting hormone (150–500 ppm for stem cuttings) to speed rooting.
4. Insert cuttings into pre-moistened perlite, vermiculite, or a 50/50 perlite/peat mix.
5. Cover with a humidity dome or clear plastic bag and place on a heat mat at 21–25°C substrate temperature.
6. Check for rooting by gently tugging at 2-week intervals. Resistance means roots have formed.
7. Once roots are established (typically 2–4 weeks for stems, 4–8 weeks for leaf cuttings), pot up into standard begonia mix and grow on in bright indirect light.

Temperature, light, soil, and water: the four levers that start growth

Temperature is the main switch. Below 10°C, begonias stall or die. Between 10–18°C, they grow slowly and reluctantly. The sweet spot for active, healthy growth is 18–24°C (65–75°F), and that is the range you want to maintain from germination through the seedling stage. For practical care steps and troubleshooting on how to help begonias grow, see our detailed care guide. Tuberous begonias are comfortable at the cooler end of that range (around 18°C for plugs), while wax and Nonstop types prefer the warmer end (21–24°C).

Light matters almost as much as temperature, especially for seeds. As noted above, begonia seeds will not germinate without light because they are photoblastic. Once seedlings emerge, they need bright, consistent light for at least 14–16 hours per day under artificial conditions, or a south or east-facing window supplemented with grow lights during the short days of winter. Stretchy, pale seedlings are a sign of insufficient light, not insufficient warmth.

Soil should be fine-textured, well-draining, and sterilized for seed starting. A peat/perlite or peat/vermiculite mix at roughly 50/50 works well. Once seedlings are potted on, a quality peat-based potting mix with added perlite (about 20–25% by volume) keeps the medium from compacting and reduces rot risk. Begonias are extremely susceptible to stem rot if media stays waterlogged.

Watering during germination should keep the medium consistently moist but not saturated. After germination, allow the top 1–2 cm of medium to approach dryness before watering again. Bottom watering (placing trays in water and allowing the mix to absorb moisture from below) works particularly well for begonia seedlings because it keeps the soil surface drier, reducing the risk of damping-off fungus.

Signs of early growth and when to pot on or plant out

For seeds, the sequence goes: cotyledons emerge, then the first true leaves appear 1–3 weeks later. True leaves on begonias look distinctly different from the tiny rounded cotyledons: they have the characteristic asymmetrical, lobed shape you recognize from mature plants. The seedling is ready to prick out or move to an individual cell when it has at least one set of true leaves and the root system holds the tiny plug together without crumbling.

For tubers, the transplant cue is a shoot of around 1 cm with at least one visible node. For cuttings, gently tug the cutting after two weeks and every few days after that: resistance indicates rooting. Visible roots emerging from drainage holes or the sides of a clear cup are a more obvious signal.

For outdoor planting, wait until your plugs or potted transplants have 3–4 sets of leaves and have been hardened off over 7–10 days. Hardening off means gradually introducing plants to outdoor conditions: start with a couple of hours of morning shade, then increase exposure over the week to include some direct sun and outdoor temperatures. Plants that skip this step get leaf scorch and set back noticeably.

From start to first flowers: realistic timelines

Setting clear expectations here saves a lot of anxiety. Begonias are not fast bloomers from seed, and the tuberous types especially require patience.

• Wax begonias from seed: 7–9 weeks to a transplantable plug, then 6–10 weeks after transplant to first flowers. Total from sowing: approximately 13–19 weeks.
• Tuberous begonias from dry tuber: 2–4 weeks to bud break, then pot up and grow for another 8–12 weeks to first flowers. Total: approximately 12–15 weeks.
• Tuberous begonias from seed (including Nonstop types): 14–21 days to germination, 16–18 weeks to a flowering-size plant. Total: up to 20 weeks or more.
• Cane begonias from stem cutting: 2–4 weeks to rooted cutting, then 6–12 weeks to first flowers depending on variety and light levels.
• Rex and rhizomatous begonias: grown primarily for foliage; leaf cuttings take 4–8 weeks to produce rooted plantlets, and mature leaf display follows over several more weeks.

Variety recommendations from beginner to experienced grower

If you are new to begonias, start with wax/fibrous types. If you're wondering are begonias easy to grow, wax and fibrous types are among the simplest for beginners. They germinate reliably, tolerate minor neglect, handle both sun and shade reasonably well, and flower prolifically right through summer. The Ambassador and Cocktail series are widely available and forgiving. For anyone keen on trying Nonstop begonias (a tuberous hybrid bred for continuous flowering and compact habit), they reward the longer sowing schedule with spectacular blooms, but expect a steeper learning curve around watering and overwintering. Experienced growers who enjoy a challenge often gravitate toward rex and cane types for their foliage drama or tuberous heirlooms for their large, rose-like flowers.

Keeping them blooming: deadheading, feeding, and pinching

Wax begonias are largely self-cleaning, meaning spent flowers drop on their own, but removing faded blooms by hand when you see them speeds up the next flush and keeps plants tidy. Tuberous begonias benefit more noticeably from deadheading: the large male flowers fade before the smaller female side-flowers, and removing them promptly keeps the plant's energy directed at new growth.

Feeding should begin once plants are established and actively growing (about 2–3 weeks after transplanting outdoors or into final pots). Use a balanced, water-soluble fertilizer (roughly 10-10-10 or similar) every two weeks during the growing season. As flowering peaks, you can shift to a slightly higher potassium formula to support continued bloom. Avoid overfeeding with nitrogen, which pushes leafy growth at the expense of flowers.

Pinching, which means removing the growing tip of young plants, encourages branching and a denser, more floriferous plant. Do this once when seedlings have 3–4 sets of true leaves and you want a bushier habit. Nonstop and wax begonias do not always need pinching because they naturally branch, but cane and fibrous types grown for a specific shape benefit noticeably from one or two early pinches.

Propagation timing and practical how-to cues

The best time to take stem cuttings from fibrous and cane begonias is early spring (when new growth is soft and active) or late summer (August through early September) before temperatures drop. Spring cuttings take root under improving light and warmth; late summer cuttings can be overwintered indoors as established plants ready to bloom again the following year. Stem cuttings should be 7–10 cm long, cut just below a node, and the lower leaves removed before inserting into your rooting medium. For quicker, more reliable rooting, propagation manuals commonly recommend basal quick‑dips or continual sprays of IBA in the ~150–500 ppm range for herbaceous/soft cuttings, with foliar/spray methods using lower concentrations around 50–250 ppm (Hortus, Plant Propagation from Cuttings (rooting‑hormone concentration guidelines)) blank" rel="noopener noreferrer">Hortus — Plant Propagation from Cuttings (rooting‑hormone concentration guidelines).

Rhizome division for rex and rhizomatous types is best done in early spring. Use a clean, sharp knife to cut the rhizome into sections with at least one healthy growth node each. Dust cut surfaces with powdered cinnamon or sulfur to reduce rot risk, then press sections onto (not into) barely moist medium and wait for shoot development.

For tuberous begonias, tuber division is an option when tubers have become large and multi-crowned. In late winter or early spring before pre-sprouting, cut the tuber into sections ensuring each piece has at least one bud or growing eye. Again, dust cut surfaces to discourage rot, allow them to dry for a day, then pre-sprout in moist vermiculite as you would a whole tuber.

Overwintering: when and how by type

Tuberous begonias must be lifted and stored before the first frost. In most climates, that means watching the forecast from September onward. When foliage starts to yellow and die back naturally (or when frost is a week away), cut stems down to about 5 cm, dig the tubers, brush off excess soil, and let them cure in a dry, airy spot for 1–2 weeks. Then store in barely damp peat or vermiculite in a cool (7–13°C), dark, frost-free location through winter. Check monthly for shriveling or rot.

Wax begonias are treated as annuals in most climates and composted at season's end, though you can take cuttings in late summer and overwinter rooted plants indoors. Nonstop begonias can be overwintered the same way as other tuberous types.

Cane, rex, and rhizomatous begonias are frost-tender houseplants and need no dormancy treatment: simply bring them indoors before temperatures drop below 10°C and reduce watering through the lower-light winter months. They will slow down but should not be allowed to dry out completely.

Troubleshooting the most common problems

Poor or no germination

The most likely cause is seeds that were buried or covered, even lightly. Begonia seeds need light to germinate. Second-most common is substrate temperature below 21°C. Check with a soil thermometer, not a room thermometer. Old seed (begonia seed viability drops significantly after 1–2 years) is also a real factor. If you are past 21 days with no signs of life, the seed batch is probably the issue.

Slow sprouting from tubers

Older or dried-out tubers that were stored poorly may take longer to break dormancy. Soaking dry tubers in tepid water for a few hours before pre-sprouting can help rehydrate them and trigger faster bud break. If a tuber shows no signs of life after 4–5 weeks, press gently on it: if it feels hollow or very soft, it has likely rotted internally and will not recover.

Stem rot and damping off

This is the number-one killer of young begonia seedlings and freshly potted cuttings. It is caused by overwatering combined with poor airflow. Improve drainage, water from the bottom rather than overhead, and increase airflow around seedlings by lifting dome vents or removing the dome for short periods each day once germination is complete. Sterilized growing medium is non-negotiable for seeds and cuttings.

Pests to watch for

Begonias in humid indoor conditions attract fungus gnats (larvae damage roots), mealybugs (especially in rex and cane types), and occasionally spider mites when conditions are warm and dry. Fungus gnats are best controlled by allowing the medium surface to dry between waterings and using yellow sticky traps. Mealybugs respond to repeated dabbing with a cotton swab dipped in rubbing alcohol or neem oil spray. Spider mites are discouraged by maintaining humidity and washing foliage regularly.

Nutrient issues

Yellowing lower leaves on established begonias often signal nitrogen deficiency, especially in containers where nutrients leach with repeated watering. Resume a regular feeding schedule. Conversely, pale, stretched growth with few flowers typically indicates excess nitrogen and insufficient light, not a nutrient deficiency. Brown leaf edges in low-humidity environments are usually a moisture stress or salt buildup issue, not a disease.

Seasonal action plan: from first sow to reliable bloom

Use this stage-based checklist alongside your local frost calendar. Adjust each stage's timing backward from your outdoor planting date using the guidelines covered earlier.

Begonias reward the gardener who plans ahead more than almost any other summer flower. The initial investment in getting timing right: counting back from frost dates, starting seeds early enough, pre-sprouting tubers at the correct temperature, is what separates reliable, floriferous plants from the sparse, struggling ones. Once you have done it once and seen those Nonstop begonias blooming all summer long or watched your wax begonias fill a border from June to frost, the planning becomes second nature.