Dahlias bulbs have a root system of smaller tubers growing underground. The tubers deliver nutrients to the dahlia plants above ground. The blooms make excellent cut flowers. If you are in Zone 8 or higher, dahlias can be left in the garden all year round. You can treat them as perennials. For colder climates, however, the roots should be dug up every fall, stored indoors in the winter, and replanted the following spring.
Propagating Dahlia Bulbs
You can propagate dahlia bulbs three ways:
First, prepare a hole in a different location for the offspring plant. It needs to grow on its own. Then cut off with a sharp knife the root connecting the offspring to its parent plant. Place the offspring in the prepared hole. To prevent the tubers from becoming too dense, cut off the other tubers that grow on the parent’s side. This practice will help keep the dahlia plants healthier.
By Leaf Cutting
The dahlias are ready for leaf cutting when the meristems (growing tissues forming the tips of growth shoots) are noticeable. Use a sharp knife to remove the stem near the base of the leaf. Cut across several of the larger veins on the leaf’s underside. Do not slice all the way through the leaf. Brushing some rooting hormone on the severed veins will help the forming of new roots.
This propagation method is best done during the first week of March. Fill the rows of your tray with mix specifically for starting seeds. Sow the dahlia seeds allowing an inch in between rows. Cover with approximately one-quarter inch of soil. You can transplant the young dahlias as soon as you have two or more sets of true leaves.
Planting Dahlia Bulbs
For dahlia bulbs in containers, plan on hybrids that can be “forced” for indoor blooming in the winter. For ground planting, the best time is between the months of May and June. Place them in the ground with the eyes facing upward. Whether ground or container planting, good soil drainage is important. Also, wait until the dahlia plants are several feet tall before removing the lower leaves. That will help with air circulation. Be regular with removing weeds, and take out all broken and damaged foliage.
Location and Soil
In the fall, choose a sunny location that receives at least half a day of sun, sheltered from direct wind, and distant from trees. Work some organic matter like peat moss, humus, or well-rotten manure into the soil. If you prefer to use commercial fertilizer, look for one that has low nitrogen content. For dahlia bulbs, 5-10-10, 10-20-20, or 0-20-20 are good ratios.