At this point in their growing cycle, the dahlias are sprouting rapidly, so they’ll recover quickly. You can continue to remove new growth throughout the growing season to encourage even more flower production. New growth is easy to remove with just your forefinger and thumb, although you can use a sharp tool if you prefer.
Since dahlias have tough, stringy stems, it’s easiest to remove the flowers with sharp scissors, pruning shears, or a knife. Cut back the flower stem to where it meets a main stem.
While removing dead heads will encourage new buds to begin blooming, removing the buds will delay flower development.
Make sure to discard the diseased leaves, buds, and stems, such as by throwing them away or burning them.
This fungus favors cool, wet conditions. If you live in a climate where this weather is common, you may need to spray the plant with a fungicide, such as iprodione, mancozeb, or fenhexamid, which you should be able to find at a garden supply store.
If your soil is infested with root knot nematodes, you will need to treat it with a nematicide before you can grow healthy plants.
If burning isn’t allowed in your area, discard these plants in the landfill. You will also need to destroy the entire dahlia plant if you see mosaic mottling on the leaves, which is usually due to a virus spread by aphids.
Instead, try to water close to the base of the plant, so the water will go directly to the roots.
If you don’t want to store the bulbs over the winter, just buy new bulbs in the spring. In the U. S. , dahlias can be left in the ground starting at Zone 8 and warmer.
Gently shake the soil off the roots. If there are any rotten bulbs on the root clump, cut them away with a sharp knife.
The bulbs should be completely dry before you store them, otherwise they could rot.
The container should be loosely covered with a breathable material like burlap.
Once spring arrives, separate the bulbs from the main clump and plant them again.
