AMES, Iowa — Tuberous begonias are available in upright and trailing types, single and double flowers and a wide variety of vibrant colors and flower forms and are a gardener’s favorite for easily brightening a shady corner of the garden. Unfortunately, they will not survive harsh winter weather outdoors and must be dug in the fall and stored indoors through the winter months.
Now is the time to begin thinking about getting them out of storage and ready for spring planting. Here are some tips from Iowa State University Extension and Outreach horticulturists on dates and procedures for starting tuberous begonias.
Tuberous begonias are beloved for their showy, vibrantly colored blooms and ability to thrive in shady areas. By starting begonia tubers early indoors you can enjoy larger fuller plants and earlier flowers once moved outside. This complete guide will teach you the proper techniques for starting tuberous begonias indoors.
Why Start Begonia Tubers Indoors?
Getting a head start on begonia growth indoors offers several key advantages:
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Earlier blooms – Begonias started indoors bloom weeks sooner than planting the tubers directly outdoors Enjoy color faster!
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Bigger plants – With more time to develop roots and foliage indoor-started begonias are often larger and fuller.
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No frost risk – Begonias are very frost sensitive. Starting tubers inside eliminates any chance of cold damage.
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More variety – A wider selection of begonia varieties is typically available as tubers versus young plants at garden centers.
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Cost savings – Purchasing tubers is usually more affordable than buying pre-grown begonia plants.
For impatient gardeners in short-summer climates, there are lots of compelling reasons to get a jump on begonias indoors!
When to Start Begonia Tubers Indoors
Most gardeners start begonia tubers 6-8 weeks before the estimated last spring frost date for their area. This provides adequate time for roots and leaves to develop before moving the started plants outside.
Use this general timeline as a guide:
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Begin starting tubers in January/February for zone 7 and warmer.
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Start tubers in February/March for zones 5-6.
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March/April starts work for cooler zones 3-4.
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Aim for begonias to have 3-5 leaves by the time they are transplanted outdoors.
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Monitor your area’s long-range weather forecasts to pinpoint the optimal starting window.
Selecting High Quality Begonia Tubers
When purchasing begonia tubers for starting indoors, look for:
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Firm, not shriveled – Avoid tubers with mushy spots or excessive wrinkling.
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Unbroken skin – Damage or cuts provide entry points for rot.
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Visible buds/eyes – Look for a distinct depression with small buds protruding from the hollow side.
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Medium size – Bulbs 2-3 inches across have good nutrient reserves to fuel growth.
High quality, healthy tubers will have the best chance of vigorous sprouting when started indoors.
How to Plant and Grow Begonia Tubers Indoors
Follow these steps for success with starting begonias inside:
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Use Small Pots – Plant one tuber per 4-5 inch pot so roots have room to expand. Terra cotta pots allow excess moisture to evaporate.
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Provide Drainage – Add pebbles in the bottom of pots to promote drainage. Tubers rot if soil stays too wet.
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Use Loose Potting Mix – A light, fluffy starting mix gives tuber roots the aeration they need. Blends with peat/coir work well.
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Plant Tubers Correctly – Lay bulbs horizontally with the indented hollow side up, 2 inches deep. Gently cover with soil.
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Water Sparingly At First – Until sprouts appear, water just enough to keep soil barely moist. Too much moisture causes rot.
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Increase Water As Growth Starts – Once shoots emerge, begin watering more frequently to encourage growth. Fertilize lightly.
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Give Warmth and Light – Ideal soil temperature is 70°F. Provide bright indirect light or use grow lights to spur development.
With proper planting and care, most begonia tubers will sprout in 4-6 weeks when started indoors.
Hardening Off Begonia Seedlings
Begonias started indoors must transition slowly to outdoor conditions to avoid damage:
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Set plants outdoors in filtered shade for a few hours at first.
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Gradually increase outdoor time over 7-10 days.
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Monitor weather forecasts and avoid cold nights or frost.
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Allow plants to return indoors at night until fully acclimated.
Hardening off toughens plants by slowly adapting them to sun, wind, and outdoor temperatures. Take it slow for best results.
When and How to Transplant Started Begonias Outdoors
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Move begonias outside only after danger of frost has passed.
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Plant in morning or evening to avoid midday heat stress.
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Water transplants well and provide shade for 1-2 days.
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Pinch off any weak, damaged leaves and stems.
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Use rich organic potting mix with excellent drainage.
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Give plenty of space between plants for good air circulation.
With proper hardening off and attention to weather conditions, transplanted begonias will transition smoothly and continue thriving.
Ongoing Care of Started Begonias
Once your begonias are settled into the garden, keep them looking their best:
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Water thoroughly when the top inch of soil dries out. Avoid soggy soil.
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Fertilize every 2-3 weeks with a balanced diluted liquid feed.
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Pinch off spent blooms to encourage more flowering.
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Monitor for pests and treat any found immediately.
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Prune back leggy growth to keep plants full and compact.
With the right care after transplanting, your begonias started indoors will reward you with vivid, plentiful blooms all season long!
Key Tips for Starting Begonia Tubers Indoors
Follow these top guidelines for success with begonias:
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Select plump, blemish-free tubers – discard any that are shriveled or damaged.
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Use containers with drainage holes and a lightweight starting mix.
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Plant tubers horizontally with indented hollow side up, just below soil surface.
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Provide bottom heat of 70°F and 14+ hours of light per day.
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Once sprouted, give more light/water but avoid overwatering.
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Harden off before transplanting outdoors to prevent shock and leaf scorch.
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Move started plants outside only after risk of frost has passed.
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Pinch off weak growth and deadhead spent blooms to encourage more flowering.
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Fertilize regularly and monitor for pests.
With the proper techniques, growing begonias from tubers started indoors is extremely rewarding. The extra time and care you invest will pay off abundantly once those vivid, bold blooms start brightening up your garden!
When should I plant tuberous begonia tubers indoors?
Plant tuberous begonia tubers indoors eight to 10 weeks before the average last spring frost in your area. (Flowering typically begins 12 to 14 weeks after planting.) Start tuberous begonias in pots or other suitable containers. All containers should have drainage holes in the bottom. Use a well-drained potting mix. When planting the tubers, place the concave or indented side upward. The rounded side is the bottom. Cover the tubers with one-half to 1 inch of potting soil. Water well. Then place the containers in a warm, 70 degree Fahrenheit location. Since the tubers are susceptible to rotting, keep the potting soil moist, but not wet. Once the tubers sprout, move the plants to a sunny window or place under fluorescent lights. Fertilize plants with a dilute fertilizer solution every two to four weeks.
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AMES, Iowa — Tuberous begonias are available in upright and trailing types, single and double flowers and a wide variety of vibrant colors and flower forms and are a gardener’s favorite for easily brightening a shady corner of the garden. Unfortunately, they will not survive harsh winter weather outdoors and must be dug in the fall and stored indoors through the winter months.
Now is the time to begin thinking about getting them out of storage and ready for spring planting. Here are some tips from Iowa State University Extension and Outreach horticulturists on dates and procedures for starting tuberous begonias.
How to Start Tuberous Begonias Indoors
FAQ
Can tuberous begonias be grown indoors?
Yes, tuberous begonias can be grown indoors, especially as temporary flowering plants. While they’re often grown outdoors as annuals, they can be brought inside during colder months or even kept as houseplants if given the right conditions.
Should you soak begonia tubers before planting?
If roots grow against the edge of the pot, you may want to repot your plants to enable more growth. Watering correctly is very important to good results. The American Begonia Society says that some growers soak their tubers in water or a sterilizing solution before potting them, which helps initiate growth.
How do you start tuberous begonias from cuttings?
Tuberous begonias can be propagated from stem or leaf cuttings. For stem cuttings, take a 4-6 inch cutting just below a node, remove lower leaves, dip in rooting hormone, and place in a warm, humid environment. For leaf cuttings, use a healthy leaf and its petiole, or slice the leaf into wedges, ensuring each piece includes a vein. Place cuttings in moist soil, cover for humidity, and maintain warmth.
How long does it take for begonia tubers to sprout indoors?
Expect to see growth in 3-6 weeks’ time, depending upon your overall growing conditions. (Note: In zones 2-8, if you do not start Begonia tubers ahead of time indoors, you may only see minimal blooms late in the season.) The photo shows a sprouted begonia tuber.
When should I start my Begonia tubers?
Pre-start your begonia tubers inside, 8 weeks before the last frost. As previously mentioned, begonia tubers won’t survive in cold weather so you will want to start them indoors. Follow these easy steps to give your begonia tubers the best start in life: You can buy your tubers in garden centres between January and April.
How do you grow tuberous begonias?
If you are growing tuberous begonias in the ground, allow these plants to grow as long as possible up to the first frost. At this point, dig up the tubers with a small amount of soil around them and allow to dry in a sheltered location like a garage or shed.
How do you acclimate begonias to outdoor conditions?
Gradually acclimate tubers to outdoor conditions after frost. To grow tuberous begonias from tubers, start them indoors 8 to 10 weeks before the final frost. This gives them a headstart on development for earlier blooming. If planted later outdoors in northern climates, blooms won’t begin until late summer.
How do I start begonias indoors?
Starting begonias indoors requires a few supplies and a little extra work, but the rewards are worth it months later. The first step to planning for starting begonia tubers is to buy begonia tubers. When shopping online for begonia tubers at Holland Bulb Farms a wide selection of begonias are available.
Can tuberous begonias grow indoors?
To ensure that your tuberous begonias grow successfully indoors, there are several factors to consider: Light: Tuberous begonias require bright, indirect light to grow well. Be sure to place them near a window that receives plenty of sunlight, but avoid direct sun exposure, which can scorch their leaves.
How long does it take to grow a tuberous begonia?
Dormant or store-bought tuberous begonias can be started indoors in late winter or early spring (about 8 weeks before the last frost) by placing them in a warm area with indirect light to reacclimate and sprout. This should take a few weeks.