Darling Dahlias
This was a tough growing season for many perennials. With the driving, extensive rains in the early spring followed by near drought conditions in the summer, fungal diseases flourished and plants suffered. However, one plant that seemed impervious to the onslaught of negative weather conditions was the dahlias. They continued to thrive and put forth stunning blooms.
Dahlias are native to the mountainous regions of Mexico and Guatemala. In fact, the dahlia is the national flower of Mexico and was first cultivated by the Aztecs. When the Spanish conquistadors arrived, they brought botanists who transported plants back to Spain. Originally the tubers were thought to be a food source similar to potatoes, but when that was unsuccessful, hybridization efforts continued to develop the blooms. Over time the plants and tubers from the Royal Botanical Gardens in Madrid spread over Western Europe and eventually back to the Americas. Today there are multiple organizations across the world devoted to developing and displaying these stunning beauties.
In 1971, a dahlia trial garden was established as a collaborative effort between the University of Minnesota Arboretum and the Minnesota Dahlia Society. One of eight official trial gardens in the United States, it is located along Three Mile Drive at the Arboretum in Chaska, Minnesota. Each year the Dahlia Society and arboretum staff plant new selections, identified only by a number, which are evaluated for growth, habit, disease, flower quality and other characteristics. Flowers must receive a composite score of 85 before being released to the public. Visitors are welcome to this site and dahlia aficionados will find the display astounding.
If this tickles your fancy and you want to dabble in dahlias, plant the tubers in full sun after all danger of frost has passed. Each section must have at least one eye, the point of new growth. Begin by preparing the top 12 inches of soil, digging deep and wide, and amending with compost. Plant far enough apart that there is adequate air circulation and space to work. Place the tubers 4-6 inches deep with the eyes facing upward.
Dahlias also do well planted in a pot. Choose a 12-14 inch pot that is at least 12 inches deep with good drainage. Plan on staking these exceptionally tall plants.
When the plant is about a foot tall and has several branches, pinch the top shoot to encourage branching and get a stockier plant. To get one large bloom, remove side buds when they are pea-sized.
Summer care is minimal, but be certain that the plants get adequate water. They are fast growers and as such will require moist, but not saturated soil. Monthly, low nitrogen (5-10-10) fertilizer is advantageous, but not absolutely necessary.
Dahlias are not winter hardy and the tubers must be dug, cutting back the foliage to a 3-4 inch stem. Allow the tops to die back after frost, but dig before a hard freeze. Tubers can be divided in the fall, but waiting until the spring will prevent spoilage while in storage. The tubers bruise easily, so handle with care. Gently remove the soil, and dry them thoroughly before storing, Place the tubers in a wood, cardboard, or plastic container and cover with vermiculite, sawdust, or peat moss. Store at 32-50 degrees for best results. Check them periodically during the winter and remove any that show signs of rot.
For a riot of color in your landscape, dive into dahlias in 2025.
Carol Shirk
Certified Master Gardener