Between now and early June is the best time to plant your dahlia tubers – as long as the risk of frost has gone.
With some dahlia varieties like Café au Lait being so popular and selling out fast, it pays to get the planting right so you can enjoy your blooms to the max.
Lucie Bradley, gardening and greenhouse expert at Easy Garden Irrigation, agrees, ‘It is vitally important that when you are planting dahlias that you plant them to the correct depth otherwise you risk the chance of things going wrong later on.’
What you’ll need
Border D-shaped fork, 185mm
This fork is perfect for turning soil and breaking up clumps. The D-shaped handle is comfortable and this fork will be reliable for many years.
RocketGro Farmyard Manure, 40L
Once planted, give your dahlia tubers some goodness with this well rotted microbe-rich manure from RocketGro’s Somerset farm.
6 Pack Plant Support Stakes 25 x 44cm
Keep your dahlias supported with these metal rings that you stake into the ground. They have a powder coated finish and are weather resistent.
The correct depth
Like any bulbs and tubers, it’s important to plant them correctly, especially when you’ve invested in them and want good results.
‘We recommend planting dahlia tubers 4-6 inches deep, so roughly about the length of your hand,’ advises Julian Palphramand, head of plants at British Garden Centre.
You do need to prep the ground first, says Lucie, ‘Use a fork to break up and loosen the soil to a depth of sound 25 to 30cm, removing any weeds, stones or debris so the tubers can grow without any obstructions. Then add in a generous layer of leaf mould, garden compost or well-rotted manure (we like RocketGro’s manure, £9.99 from Crocus), mixing it into the soil so it prepares the ground for these heavy feeders to start growing.’
Julian adds, ‘Water sparingly until shoots emerge, stake early for wind support, and pinch out the first buds at 20-30cm for bushier plants with more flowers.’
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Why is the depth important?
‘Planting them correctly avoids thick, fleshy tubers rotting, delayed blooming when planted too deep or if not deep enough, then when in bloom, they may not be anchored in the ground securely enough, and the top-heavy stems will fall over,’ explains Lucie.
It also protects them according to Julian, ‘The depth shelters the tuber from frost and from drying out without delaying shoots. Plant them horizontally with eyes (growth points) facing up in fertile, well-drained soil, spaced 45-60cm apart.’
But what about different soil types? ‘You can tweak the depth you plant your dahlia tubers if you have either sandy or clay soil in your garden,’ advises Lucie. ‘Whilst the perfect soil for dahlias to thrive in would be loam soil, a balanced mix of sand, silt and clay so that it retains moisture without becoming waterlogged, holds nutrients and has good aeration for strong root growth, in reality we are usually faced with soil which is not perfect.’
If you’re not sure of your soil type, have a look at the UK Soil Observatory website, input your location, and it will give you that information.
Where to buy dahlias
There are some great dahlias tuber deals around currently:
Planting dahlias in containers
‘Dahlia tubers are usually available from February, which is too early to plant them directly outside, so I pot mine up first and pop them in the greenhouse, polytunnel or coldframe,’ says Nick Hamilton, owner of Barnsdale Gardens. ‘They are potted at the same depth they should be planted if putting them directly in the ground, so that the tubers are just covered.’
Lucie likes to use the ‘hilling’ method when she plants her dahlia tubers in pots. It involves covering the tuber with 3 to 5cm of soil and once shoots start to emerge above the surface of the soil, you would add more compost to cover the shoots, progressing in this fashion until the pot is full.’
Follow our guide to perfect planting depth for your dahlia tubers and in a few months, you’ll have wonderful displays of colour from this fabulous variety in your containers and borders.
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