Dahlias are one of the most popular flowers of the year, beloved for their wide variety of interesting colors and shapes and their ability to last in a vase. But, if you don’t want to waste their fleeting beauty as a cut flower, you can always plant the tubers in containers to enjoy their flowers for months on end.
As these flowers are on the larger side, many don’t consider container growing. It can be tricky, but with a few tips, you can keep your container dahlias flowering year after year.
There are several dahlia species and hundreds of hybrids to choose from. But, not all are suitable for container growing. Some are small and compact, while others have flowers larger than the size of your palm, aptly named dinnerplate dahlias.
Large dahlias can reach well over one meter tall. With the right support, you can grow these in containers, but they can be tricky to care for. Instead, choose small to medium varieties about half a meter tall and under. This will ensure the height of the plant does not overwhelm the size of the pot, giving you a balanced and pleasing container feature.
With your dahlia variety chosen, you’ll need to pick the right container. Dahlias are grown from tubers that can differ in size depending on the plant. Find a pot wide enough to comfortably accommodate the size of the tuber and deep enough to balance the expected height of the plant.
Terra cotta pots are always a great option for both design and plant health. Terra cotta draws moisture away from the soil, stopping the tuber from rotting. Fabric pots or recycled containers are also popular choices and can compliment your chosen variety in color and texture.
No matter which type of container you choose, it should have enough drainage holes. If your pot does not drain well, the tuber will quickly rot, ruining your flower display.
If you’re growing a taller variety that requires staking, make sure you install the stake right after placing the tuber. This will stop you from disturbing the plant during growth later on.
When growing dahlias in containers, it can be difficult to get watering right – especially for those new to dahlia care. While they are known to prefer moist soil, they cannot be watered too often soon after planting as this will rot the tuber.
Once planted in light and well-draining soil, leave the soil to dry out before watering again soon after planting. When the plants are established in the containers, you can up the watering schedule to keep the soil moist as the roots will be ready to absorb the excess moisture.
In the early stages of growth, dahlias get all the nutrients they need from the tuber. This is designed to store nutrients required for root, stem and leaf growth, keeping the plant happy for several weeks without any feeding. It’s important to choose a healthy, plump tuber, as this will give your dahlias the best start in these early stages.
When the leaves begin to emerge, start fertilizing around once per month with a fertilizer high in phosphorus and potassium to promote flowering and strong growth.
Dress Them Up
Your dahlias will die back when the flowering season is over. But, this doesn’t mean your container has to remain bland for the rest of the year. While the tuber stores nutrients over the dormant period in preparation for reflowering, you can fill the top layer of the pot with cute short-lived annuals to provide a pop of color in the empty space. The dahlia stems will emerge around the plants the following season.
By Madison Moulton
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