The Best Way To Grow Dahlias In Containers (& Common Mistakes To Avoid)

If you want to grow vibrant, colorful dahlias but you don't have the space for a garden or if you have a garden and want a touch of color inside your home, you can always plant your dahlias in containers. Dahlias have long blooming season and do well outdoors in USDA zones 7 through 10. To ensure that they thrive in a pot, you'll need to choose the right sized container, allow them plenty of sun, and ensure they have the right nutrients. Similar to the crucial mistakes when planting dahlias in your garden, you'll need to avoid the mistakes of under or overwatering and not supporting larger varieties with stakes.

Dahlias have robust tuberous roots, so you need a deep and wide container, at least 12 to 16 inches wide and 12 to 18 inches deep, to accommodate their expansion over time. Containers that are too small restrict root growth, negatively impacting the plant's health and overall flower production. Even with extra care, root-bound dahlias in small pots will grow slower, and their leaves will look wilted. 

Clean the container really well to prevent contamination, and plant the dahlias in a well-draining potting mix. You don't want to plant the bud too deep or too shallow into the soil. The sweet spot is 2 inches, so it will have enough space to push out its roots. In the soil, make sure that the eye of the tuber is facing up. For proper nutrient supply, apply a fertilizer that is high in potassium and phosphorus and low in nitrogen 30 days after planting.

When picking the best place to plant dahlias in containers, you have endless choices. They do well on well-lit patios and balconies or sunny corners inside the house, as long as the growing tuber has at least six to eight hours of direct sunlight daily. You can even move your plant from one spot to another to maximize sunlight access. 

You must also regularly monitor the soil moisture levels to ensure the growing bud doesn't dry up or rot away. Overwatering causes root rot and, eventually, death of the plant, while underwatering causes dry and yellowing leaves. You likely need to water your dahlias every day, but if you're unsure, dip your finger into the soil up the first knuckle to check for dryness. If you feel moisture, hold off on grabbing your watering can. 

If you plant a variety of dahlia that will grow to be more than 3 feet and have big blooms, it will need support. Dahlia stems, while hardy, are also hollow and brittle. The weight pushed on them by the big blooms will cause them to snap. Bamboo stakes provide the extra support needed for the stems to hold their blooms up, and if you are in a pinch, you can always use tomato cages. Staking also allows for air circulation in and around the plant. Good air circulation prevents fungal diseases caused by dampness. With the right dahlia growing techniques, you will get beautiful blooms all season round.