How to Grow Dahlias

Famous for their exotic shape and vivid colour, dahlias are highly sought-after flower plants among the gardening community. As perennial flowers, they can bring colour and vibrance to your garden year after year, offering a lasting supply of stunning cut flowers to display around the home. 

Introduce a new kind of luxurious vividity to your sunny borders and find out how to grow dahlias from tubers and seeds with Johnsons’ guide. As a heritage brand with over 200 years of experience, we are known for our high-quality dahlias, so you can rely on us to provide the best advice for enjoying mesmerising blooms in your garden. We’ll be answering questions like ‘when to plant out dahlias’ and ‘how to take dahlia cuttings.’ Keep reading for our expert advice below.

Ground Preparation

In order to get the best results from your dahlia plants, you should take the time to prepare the ground to best suit your plant’s needs. Dahlias thrive in warm, sunny spots under shelter. They prefer free-draining, moist soil with feed and fertiliser dug in.

Sowing

If you’re more familiar with growing dahlias from tubers, you may be wondering how to sow dahlias. We recommend sowing your dahlia seeds indoors in trays and containers between February and April. Space your seeds around 2.5cm apart and 0.5cm deep in your compost. 

As mentioned earlier, dahlias thrive in the sunlight, so be sure to keep your containers in a warm location in view of the sun. When your seedlings grow large enough to handle, it may be time to transplant them into larger indoor pots to ensure they have plenty of room for further growth. 

When to plant out dahlias

Before you consider planting them outside, your dahlias will need hardening off. You can do this by gradually leaving your pots outside for increasing amounts of time over around ten days in May or June.

Planting

If you’re wondering how to grow dahlias from tubers, this section of our guide is sure to help. 

Dahlias are tender and don’t fare well in the frost, which is why we recommend planting your bulbs indoors during the springtime. Planting your dahlia tubers inside earlier in the season allows your dahlias to bloom far sooner, meaning you can enjoy their captivating colours for longer. 

Mix a healthy supply of peat-free compost into your pots and allow your bulbs to grow on a windowsill in view of the sun. Just as we advised with dahlia seeds, take the time to harden off your plants, and by the end of May, they should be ready to be transplanted to their final position in your garden.

Plant Care

The upkeep of the health and well-being of your dahlias is integral to maintaining the beauty, shape, and colour of their blooms. So, take the time to give your flowers the care they deserve to enjoy beautiful displays throughout the season.

Pinching out

When your plants have developed three true pairs of leaves, pinch out the growing tips to encourage lots of bushy growth and prevent plants from becoming leggy and unproductive. Pinching will also help your plants develop more side shoots, which in turn will lead to more flowers.

Feeding

Not only do dahlias like plenty of water, they also enjoy plenty of food. Once planted out in the early stages, use a feed rich in nitrogen to help develop plenty of leafy growth. Do this once a week until the middle of June. After this time, switch to a high potassium-based fertiliser, such as tomato feed, and continue feeding weekly until around the end of September.

Stalking

Depending on their height, your plants might need staking to provide extra support. A bamboo cane against the plant or a tepee of twigs should do the job well enough.

Deadheading

Deadhead regularly to keep the flowers coming – this is the most important thing you can do to ensure you have flowers through to the first frosts. Also, cut plenty of blooms to enjoy inside – the more you pick, the more flowers you’ll have!

Overwintering

As dahlias are not frost-hardy, it’s usually best to lift and store tubers over winter. Once the first frost has blackened the foliage, lift each tuber with a fork and brush the soil away from the roots. Cut back the stems and place them upside down, allowing moisture to drain away freely and naturally. Once dry, wrap them in a newspaper or pack them in dry sand or compost and place them somewhere dry and frost-free.

In warmer parts of the country or areas that are particularly sheltered with well-draining soil, it may be possible to leave tubers in the ground. A good layer of mulch, well-rotted manure, straw, or garden compost will help to protect tubers from light frosts.

Cutting

Why not take the opportunity to bring a natural element into your interior decor when you take cuttings of your stunning dahlia blooms? Introducing the outdoors to the indoors is a perfect way to liven up your home and implant vivid bursts of colour into your inside spaces. It’s one of our favourite parts of growing dahlias in our cut flower gardens. 

We recommend taking a sharp pair of secateurs and cutting your chosen dahlia stems at a node. Remove the leaves that would sit below the water level and arrange your bouquet in a way that best matches your vision.

Shop Dahlias at Johnsons

Hopefully, we’ve given you a better idea of how to grow dahlias from tubers and seeds. The next step is to shop our range and grow your very own captivating display of dahlia plants. Get ready to beautify your indoor and outdoor spaces today and integrate these must-have flowers into your breathtaking arrangements. 

Why not take a look at our garden essentials to help you out along the way and explore the many possibilities for your garden with Johnsons.