Don't plant your begonia tubers until you read this – avoid these common mistakes if you want lots of big blooms this summer
They're easy to make but just as easy to fix
Tuberous begonias are one of summer’s great show-offs, delivering months of colour in borders, hanging baskets and containers... yet they’re also surprisingly easy to get wrong. Which is why so many people are googling 'begonia tuber mistakes' right now.
Yes, for many gardeners, these pretty perennials tend to fall firmly into the 'why didn’t this work?' category, with begonia tubers failing to sprout, rotting away, or producing disappointing displays. And it's not just as simple as knowing when to plant begonias, either; part of the issue is that begonias just don’t behave like many other summer bulbs or bedding plants.
They’re particular about warmth, moisture and light, and if those needs aren’t met, they tend to fail quietly rather than struggle on. Even a seemingly small mistake early in the season can mean no flowers at all later on, and the UK’s unpredictable spring weather doesn’t help. So, what is there to be done?
Begonia mistakes to avoid
It’s tempting to get outside and start planting these in your garden borders at the first hint of sunshine, but cold, wet soil can undo even the best intentions. Add in confusion over which way up to plant the tuber (or how much sun begonias really want), and it’s easy to see why problems crop up.
To help gardeners get it right, we asked Morris Hankinson, director of Hopes Grove Nurseries, to share the most common begonia tuber mistakes, as well as how to avoid them.
Morris Hankinson is the founder and managing director of Hopes Grove Nurseries Ltd, the UK’s only specialist grower-retailer of hedging plants. He established the thriving business in 1992, shortly after graduating with a Commercial Horticulture Degree from Writtle College, Essex.
Here's what he had to say...
1. Planting the tuber the wrong way up
'One of the most common begonia tuber mistakes is planting the tuber the wrong way,' says Morris. 'Tuberous begonias have a hollow, concave side at the top and a rounded, convex side at the bottom. The shoots emerge from the top and are planted only lightly covered with soil.'
If you’re unsure which way is up, Morris recommends starting tubers indoors. 'That way, once shoots appear, it’s clear how the tuber should be positioned.'
2. Starting them too early in cold soil
'Tuberous begonias do not like the cold,' Morris explains. 'If planted outside before the soil warms up, they can easily rot and never grow.'
Instead of making this begonia tuber mistake, start yours off indoors before your last frost date and only move them outside once temperatures are consistently mild, both day and night.
3. Overwatering
We've said it before and we'll say it again: too much water is almost always worse than too little.
'Probably the biggest killer of begonia tubers is overwatering,' says Morris. 'Tubers can’t absorb moisture well, so if they’re sitting in wet soil, they’ll very quickly rot away.'
The compost should be lightly moist, not wet. As shoots grow, watering can be increased gradually. Just remember, good drainage is key (which brings us nicely to the fourth point on our list)...
4. Planting in poor soil
Another classic begonia tuber mistake to avoid? 'Tuberous begonias need really good, well-drained soil,' Morris advises. 'Dense clay holds too much moisture and isn’t ideal.'
If your garden soil is heavy, growing begonias in containers or raised beds filled with free-draining compost and plenty of organic matter is a far safer option.
5. Too much direct sun
Sunshine is usually a magic ingredient for flowers, but too much of the stuff isn't great for begonias.
'Despite their tropical look, tuberous begonias actually prefer shade,' says Morris. 'Hot afternoon sun can scorch leaves and fade blooms.'
Plant your begonia tubers in bright, indirect light or dappled shade, then, and take care to find them a sheltered spot, too.
6. Forgetting to feed them
This begonia tuber mistake is also applicable to children and pets: don't forget to feed them!
'Begonias are heavy feeders,' Morris explains. 'Without nutrients, flowering will quickly reduce.'
Feed regularly, then, with a balanced liquid fertiliser during flowering, but avoid high-nitrogen feeds, which encourage leaves at the expense of blooms.
7. Forgetting to lift tubers
Last but not least on our list of begonia tuber mistakes? Forgetting to overwinter them properly.
'Tuberous begonias don’t like cold weather, so they need to be lifted and stored over winter,' says Morris.
After the first frost blackens the foliage, take care to lift the tubers, allow them to dry fully, and store them somewhere cool and dry until spring. It'll be worth the extra effort, we swear!
FAQs
What is the problem with tuberous begonias?
The big problem with tuberous begonias is that they’re often treated like tougher summer bedding plants, when in reality they’re quite particular.
'They dislike cold, wet soil, are prone to rotting if overwatered, and will fail quickly if planted too early outdoors in the UK,' explains Christopher O'Donoghue, director of Gardens Revived. 'They also need excellent drainage and the correct planting orientation or shoots may never break the surface.'
He adds that most failures come down to moisture and temperature rather than the tuber itself, which is why it's so important you research these plants before you begin growing them.
What do overwatered begonias look like?
An overwatered begonia will often look limp and unhappy rather than thirsty, says Christopher O'Donoghue, director of Gardens Revived.
'The leaves may turn yellow or become soft, while stems can get mushy at the base. Sometimes, they might stop growing entirely, especially if the tuber has rotted beneath the soil.'
Unlike drought stress, which plants can often recover from, overwatering causes root and tuber damage that is usually irreversible. That's why it's so important you stick to free-draining compost and very cautious watering.
So, there you have it! Now that you know all of the big begonia tuber mistakes to avoid, you can set to work growing these colourful plants at home. We wish you the very best of luck...
