Dahlias are easy to grow. Follow these quick tips to growing perfect dahlias and enjoy dahlias blooming in the flower garden and as cut flowers, too.
Dahlias (Dahlia pinnata) are gorgeous additions to the summer flower garden and every flower garden design should include at least one or two varieties of dahlia, if not more. This continuation of Growing Dahlias includes more tips and pointers on how to grow dahlias successfully. Also see Directions on How to Dig and Store Dahlia Tubers for Winter Storage.
For richness, many gardeners amend the soil each spring at planting time. This can mean adding good quality compost or well rotted manure along with any needed amendments such as lime, as indicated by soil tests. (The preferred soil pH for dahlias is about 6.5, just to the acid side of neutral.) Loosen the soil and work in the amendments to about ten inches deep.
Since dahlias are heavy feeders, most gardeners fertilize them. A general recommendation would be to use a low nitrogen granular or slow release fertilizer with an analysis of 5-10-10 or similar proportions at planting time, followed by monthly feedings through mid August.
Taller plants need to be tied or staked. It is better to insert the stake at planting time to avoid risk of damaging the tuber. Label your plants with the variety name if you know it, or by a description. This is useful when it is time to replant next year.
When cutting dahlias, work in the morning while it is still cool and take a container of water to the garden with you. Immediately put the cut end under water for best long term freshness. For the best display, cut only flowers that are fully open.
Some gardeners believe the cut dahlia flowers last better if the cut ends are dipped into very hot (not boiling) water; others simply plunge them into cool water. You could experiment and see what works best for you. I have never figured out how to get that hot water out to the garden! (Maybe a camping stove?)
The cut flowers will keep better if you remove the foliage that is under water and also use a commercial floral preservative in the water. As with any cut flower, keeping them at a cool room temperature and out of direct sun and out of drafts will also help them to last longer.
Dahlias are winter hardy to about USDA zone 8. In colder areas, dahlia tubers are customarily dug (lifted) in the fall once frost has killed back the foliage. (Directions on How to Dig and Store Dahlia Tubers for Winter Storage.) This allows you to keep favorites from one year to the next and increase your plantings or share with friends. Or, you can purchase new ones each spring. It's up to you!
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copyright 2006 Barbara Martin