Tuberous Begonia Planting Guide

Tuberous begonias are the can-can girls of the large and varied begonia clan; showing up with layers of crenulated ruffles, vibrant colors and robust flouncy performances for months. Theses showy summer flowers are glorious and if you haven’t grown them, here’s your chance to correct that.

That said, not all tuberous begonias are equal. The ones here are the result of over 100 years of careful breeding. These are Amerihybrids and we’ll throw down against any other varieties. Nonstops, individual named varieties and others – we’ve tried them all and stand by the Amerihybrids. Bigger flowers, stronger plants, richer color choices, much longer blooming periods – the Amerihybrids have it. And as with most other bulbs, size matters; ours are big tubers because those produce larger plants, to have you smiling ear to ear.

Choosing a Growing Site

Begonias prefer bright shade. They’ll do well in sites with a few hours of morning sun but will burn in scorching afternoon sun. Hanging baskets on porch edges and pots on shady patios are ideal. The hotter the region, the less direct sun your begonias will do well to receive.

Soil Prep

Begonias are usually planted in containers, allowing you to choose your soil rather than amend an existing planting area. Choose a commercial planting mix. Consider adding slow release fertilizer pellets.

When to Plant

To get a jump on the season, start your bulbs indoors. Begonia bulbs need warmth to encourage sprouting and room temperature are usually sufficient. Cool temperatures delay initial bulb activity; starting in 70 to 80 degrees in ideal. Bulbs can take 2-5 weeks to sprout.

Plant outdoors when frost danger has past and nighttime lows are at least in the 60s. Begonias are tender; avoid freezes.

Spring purchased begonia bulbs need to be planted in the spring. They cannot be held, without planting, for a future season.

How to Plant Begonia Bulbs

Examine the bulb and find the side with the slight indentation. This is where the new growth will sprout. Place the concave side facing upwards. Tuck the bulb in and cover with ½” of soil. Roots will develop from the bottom, sides and even the top of the bulb. Water sparingly until top growth develops; you're just trying to nudge the bulb out of dormancy. Too much water can encourage bulb rot.

During the Growing Season

Begonias prefer soil that’s slightly moist but not wet. Consistent wetness can results in rot. For nutrients, water with half strength liquid fertilizer monthly if slow release fertilizer was not added to the soil at planting time. Feel free to pick flowers. Float a giant bloom in a low bowl for a simple, but stunning, centerpiece.

Saving Tubers at Season’s End

Begonia tuber can be lifted, overwintered indoors and saved for next year. As the season winds down and your begonias prepare for dormancy their leaves will yellow and flower production will cease. This usually occurs between October and December depending on your climate. When you see this, stop watering.

For begonias that are in pots, feel free to leave them in place. Tip the pot on its side and overwinter in a cool (not freezing) dark place, like a garage where temperatures remain in the 40s and 50s.

If you are lifting your bulbs for indoor storage, wash off soil and allow to completely air dry. Given them a week for moisture to evaporate. Then store dry bulbs in single layers place in shallow boxes filled with dry peat. Good holding temperatures are 40-50 degrees.

Insider Tips

  1. Begonia stems are less fibrous than those of many plants. When treated roughly, begonia stems may snap rather than bend. For best results, place your begonias where they are protected from winds.
  2. Begonia blooms orient outwards from between leaf tips. If you are transplanting tubers, point the leaves away from pot center so the flowers will face outward.
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Success Snapshot

Light: Half day shade or dappled shade

Soil: Fertile and well drained

Depth: Cover bulbs with 1/2" soil

Water: Moist, but not wet, soil

Uses: Beds, borders, hanging baskets & windowboxes

Tips: Start indoors for longest season of bloom

GUIDE: Tuberous Begonia Planting Guide

They Start Out Looking Like This:

How Many Bulbs per Pot?

Note: this info is for extra large (2-2.5") Amerihybrid begonia bulbs and the bigger plants these produce.

Rose Form, Ruffled and Picotee Begonias

Pot size – 8" Tuber - 1
Pot size – 10" Tuber - 1
Pot size – 12" Tubers - 2
Pot size – 14" Tubers - 2

Scented Begonias

Pot size – 6" Tuber - 1
Pot size – 8-10" Tuber - 3

Hanging Basket Begonias

Pot size – 8" Tuber - 2
Pot size – 10" Tuber - 2
Pot size – 12" Tubers - 3
Pot size – 14" Tubers - 3
Pot Size - 16" Tubers - 5
Pot Size - 18"
Tubers - 6