Growing begonia from seed

Begonias come in distinctive types, semperflorens and tuberous being most commonly used in the garden. There are many hybrids and cultivars - more than 1,900 hybrids and many more cultivars. They are tender perennials grown as annuals in the UK when grown outside, requiring frost protection. Some are evergreen. Many are used as houseplants.

Semperflorens or waxy begonias. These Begonias are fibrous rooted and are often used as annual bedding plants. Examples are our Heaven series and Summer Rainbow

Tuberous begonias. These are more tricky to grow from seed. They can be single or double flowered, often grown in pots or hanging baskets which then makes them easier to protect by bringing them inside in the winter.

Sowing Semperflorens begonias 

Semperflorens begonias such as JustSeed ‘Heaven’ range, Mr Fothergill’s 'Summer Rainbow' or Franchi 'Semperflorens Mix', are the easier ones to grow from seed.

Start in January or February as begonias are initially slow growing

In a seed tray put moist but not waterlogged compost. Level the compost lightly to remove ridges and hollows.

Sprinkle the fine seed sparingly or place pelleted seed on the surface of the compost. Begonia seeds are best not covered with compost as they need light to germinate. If you have growing lights then set them for a 12-14 hour day as once germinated this will provide the light levels to help them grow and get established.

Begonias need a consistent temperature of 22-24oC including overnight and will take approximately 14-21 days to germinate. Ideally this should be with a heated propagator but a consistently warm and light environment is worth a try but germination will be less.

To keep them from drying out, cover with a propagator lid, cling film or glass sheet.

Once the seeds have germinated allow them to establish but then remove the cover to avoid fungal issues causing wilt.

Pot on when they have 2-3 true leaves into plugs or a seed tray. They will be very delicate to transplant. Cover the young seedlings with a propagator lid for a few days while they re-establish.

When watering both seeds and seedlings, soak from the bottom of the seed tray so as not to dislodge the very tiny seedlings.

Once established then the seedlings can be grown on in a slightly cooler but not cold environment. As they are frost tender acclimatise the begonias to outdoor temperatures  in May ready for planting out after the danger of frost has passed in your area.

Sowing Tuberous Begonias

Tuberous begonias are more tricky than semperflorens varieties. Examples of tuberous begonias are Kings ‘Chanson’ mix, Unwins and JustSeed ‘Illumination’  and JustSeed ‘NonStop’ varieties

The instructions for sowing seed are similar to semperflorens varieties but tuberous begonias are more picky. They need a longer growing season than semperflorens varieties so start in December or January if possible. Consistent temperatures of 22-24oC including overnight and 12-14 hours of (day)light, is a must to prevent them creating tubers before flowering in the first year. They can also take longer to germinate than anticipated - up to 60 days.