Dahlias are wonderful summer flowers that have graced gardens for centuries. While always spectacular, modern breeding has brought us a wealth of dahlias in all shapes, colors, sizes, and flower types. Here is a quick guide on how to succeed with your dahlias.
Dahlias have large root systems, and the bigger the dahlia plant, the larger the root system. Be sure to follow the spacing instructions that comes with your dahlia, a good rule of thumb is for every foot it gets tall, it will get half that wide. If planting in containers, be sure the container is at least 12 inches deep for dwarf or bedding types, and at least 24 inches deep for larger standards and dinner plate types. Be sure to amend the soil well and pre-moisten the hole you are planting into.
Dahlias require as much sun as possible, but they can overheat. If they are in the full sun, they must be planted a little deeper in the soil. This can be up to 5 inches of soil above the crown. As long as a dahlia receive 2-3 hours of direct sunlight a day it will bloom for you but the more light the plant gets, the more flowers it will reward you with, as long as you can keep it watered well.
Dahlias are pretty thirsty plants while they are growing. They like the soil to be just dry between watering. Large plants can use gallons of water a day so it is best to mulch your plants well after planting to keep them healthy and well-watered with less effort. Water that is chlorinated can easily cause salt burn on the leaves of your dahlia; be sure to use rainwater or to let your tap water sit out at least over night for the chlorine to dissipate.
Dahlias are fast growers so they need a fair amount of feed. Be sure they are planted in soil amended with something containing nitrogen, like compost or composted manure. NPK fertilizer works well too. After planting, fertilize weekly with 10-10-10 or add some balanced slow-release fertilizer around your plant to keep it constantly fed. Amendments like bone meal or eggshells can also be great for helping build strong tubers for next year.
One of the best things about dahlias is that you can keep them year after year. Most places are not warm enough to keep them in the ground but they are pretty easy to dig up and store if you have the space. Wait for the leaves and stems to be killed back by a couple hard frosts and then lift using a shovel or fork. Be careful to dig far enough away from the plant not to damage the tubers. If your dahlia is in a pot, you can just bring the whole pot indoors. The key to proper storage is to ensure that the bulbs are stored dry and in the dark. Next spring you can bring them out and divide them and have even more wonderful blooms to grow or extra plants to share!
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