Posts Tagged: Dahlia
Dahlias--Pretty Garden Additions!
Dahlias! In my opinion, there is no more striking addition to a garden than dahlias. With their...
All About Dahlias, Part 2
The hour of the Dahlia August and September are when dahlia plants are at peak performance. It is...
How to Plant and Care for the Dahlia imperialis or “Tree Dahlia”
How to Plant and Care for the Dahlia imperialis or “Tree Dahlia”
To all the lovely people,
I had never seen or heard of a “Tree Dahlia”until I enrolled in the Master Gardener class in 2004. I was familiar with the Dahlia tuber and grew many large and beautiful tuberous Dahlia’s over the years but this plant was new to me. Like many or even most of the Tree Dahlia’s grown by Master Gardener’s in this area the original canes most likely came from the garden of Al Derrick, a truly superior Master Gardener who has taught many of our propagation classes over the years.
A little information about the plant. Originating in Central America, the plant comes from the family: Asteraceae; Genus: Dahlia; species: imperialis. Flower size is somewhere in the 4” to 6” range and colors vary from Pink to White, Lavender, and Purple. The most common color seems to be the Purple or Lavender (at least around the central coast area). The Purple or Lavender flowers are singles and the White flowers are complex. The plants grow tall – reaching 10’-20’ in height. The canes have the appearance of Bamboo and are hollow with interior dividers every 6” to 12”. The plants flower in late September – December and attract Bumblebees and Butterflies. It is quite a site to see a couple of dozen Bumblebees flying from flower to flower in November!
Soil with a pH of 6.1 to 6.5 (mildly acidic) is preferred by the plant. They can be grown from seed by allowing the flowers to mature and dry out and then breaking them apart and collecting the seed that are similar in appearance to Zinnia seed but smaller. The usual method of propagation is by cutting the canes into pieces that include at least one dividing wall. Please see the photos for a detailed explanation.
Since the canes grow so tall they can be pruned back in mid-summer to encourage side branches if desired. They also should be protected from strong winds to avoid damage to the canes. They do well against a house or fence and like full sun and rich ground. Three of four inches of good compost added after the canes are pruned back and that will be all the plant needs until mid to late summer – then add a couple of inches of compost and you will see the results in November. If you are planting several pieces of cane at a time then the spacing should be about 3 to 4 feet because each year the plants will add more canes and increase in diameter. If a length of cane is left to lay on the ground then roots and new shoots will emerge from each section so be careful unless you want growth every 6” to 12” apart. Plants can be started in pots or directly in the garden bed. The sections root quickly and growth is fast during the season. If you don’t have a Tree Dahlia in your garden and would like to include it in your landscape ask someone who grows them for a section or two and follow the pictorial instructions below and you will have flowers next fall. Simple and easy to grow.
See the attached PDF for pictures and step by step instructions.
http://cesantacruz.ucanr.edu/files/163686.pdf
Dazzling Dahlias
Dahlias just amaze me with the dazzling colors and masses of flowers they produce. My first dahlia was a gift from a school colleague, who shared her tuberous roots with me. Year after year it pops up in late May and grows and grows until it starts flowering in late summer. Then the show is on from summer through fall.
This summer, I attended the San Francisco Dahlia Society show in Golden Gate Park and found a whole new world of flowers. The blooms can range from under 2 inches (mignon) to over 10 inches (giant). The American Dahlia Society classifies the plants by flower form such as ray florets. One of the many forms I learned about was the Laciniated Single. Each ray of this bloom curls and splits at the tip giving a fringed appearance. Another unusual form was the Incurved Cactus that rolls downward with pointed tips.
The San Francisco Dahlia Society’s web site, http://www.sfdahlia.org , has five simple steps in growing dahlias in the Bay Area. I will certainly start with their first step by attending their annual sale next year, held the first Saturday in April at the Hall of Flowers in Golden Gate Park. If a friend shares their dahlias, step 2 is planting, done from April to June. Check the website for soil tips, staking, thinning, and pests.
When you pick your flowers do it early in the morning or in the evening. Immediately place cut stems in 2-3 inches of hot water letting them stand in the gradually cooling water for several hours or overnight. The cut flowers will last for several days. You will be very satisfied with the results of these tuberous roots.
Waterlily form. (photos by Karen Norton)
Single form.
Pompon form.
Lacinated form.
Cactus form.
More Than A "Tall Novelty"-The Tree Dahlia
Sometimes a garden is something more than the carefully plotted plants for the outdoor space, the cohesive plan, the coordinated palate. Sometimes, it’s the whimsical that makes the garden. For me, it’s the tree dahlia (Dahlia imperialis) that amuses me in the late fall and early winter months. I planted it in the wrong place entirely, but can’t bear to move or replace it.
The tree dahlia is native to Central America, but it seems to survive, and even thrive, in our mild-winter region. The tree dahlia is a multi-stemmed plant, growing to 10-20 feet tall (actually, I’ve never seen one as “short” as only 10-feet tall) on bamboo-like, hollow, stems that are about 3-4 inches thick. It has daisy-like 4-6-inch wide lavender flowers with yellow-orange centers blooming at the end of the branches in late fall. I count on it blooming sometime between Thanksgiving and Christmas. Although it is frost sensitive, in my experience, it is the early winter windstorms that take the real toll on the plant. If we get a Thanksgiving windstorm, I’m likely to lose my tree dahlia before getting to see it bloom. It’s such a shame seeing the stems reach their 20-foot height and getting knocked down before they bloom!
After blooming, the tree dahlia dies back in mid-spring (around March). The Sunset Western Garden Book says that this annual dieback “relegates [the tree dahlia] to tall novelty class” instead of a “valued landscape plant.” The stems can be cut back and the plant will sprout again to put on its show in the late fall. Sections of stem with 2-3 nodes can be used to start new plants. While most gardeners will tell you to plant the sections in sand or soil to start the cuttings, I’ve left them piled up in a sideyard and they will begin to sprout without any care. The fast-growing new plants should be placed in full or partial sun, in a wind-protected area.
Years ago, I planted my tree dahlia in a shady, windy, narrow sideyard, naively thinking that the plant would get no bigger than one of those 4-inch stems. Today, it has several multi-stemmed trunks of at least 12-inch in diameter. It sprouts a fringe of sideyard-blocking leaves seemingly daily in the summer, making me feel like an intrepid explorer as I hack my way through. And then, if I forget to look up—20 feet up!—in late fall, I may miss the lavender bursts of flowers completely. It is in the wrong place entirely. But each year, at some point, I happen to look up high, catching a glimpse of this “tall novelty” in full bloom, and I can’t help but to be amused knowing that Thanksgiving is near and that spring has arrived near the roof of my house.
Flower from tree dahlia. (photos by Erin Mahaney)
Tree dahlia.