Dahlias light up the summer and fall garden with big, showy blooms that can be as big as softball until the first hard frost withers the plant into a crumpled, mushy mess.
Yet, the underground tubers that will become next year’s dahlias live on in the soil.
And that’s the dilemma dahlia lovers face every fall: to dig, wash, separate and store the tubers in a dim, cool, humid spot or just leave them in the ground?
This issue – to dig or not to dig – is much more than a debate between energy or laziness. Western Washington farmers that grow dahlia tubers for gardeners all over the planet find merit in both methods.
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“The easiest thing to do for more people is leave them in the ground,” said Kerry Connell, one of the owners of the Tacoma-based Connell’s Dahlias.
Tubers left in the ground often start growing earlier than tubers planted in late April or early May. That means the big, gaudy show of blooms arrives earlier as well.
But there’s a catch to Connell’s advice.
Dahlias tubers will die and rot if the soil is too wet or if they freeze.
SOIL IS KEY
Now is the time to check the soil, and, if it is mostly wet, sticky clay, you probably should dig the tubers out this fall, Connell said.
But if your garden has fluffy, loamy soil – that delightful mixture of sand, dirt and compost – it likely will drain away excess water this winter and preserve your dahlia to sprout and bloom for years.
About 5 inches of mulch on top of the soil will help insulate the dahlia tubers from winter frosts, Connell said.
Dahlias are originally from Mexico and Guatemala, so a frozen tuber is a dead, mushy tuber.
THE COLD-SNAP FACTOR
Another grower, Andy Hunter of Shelton-based Lynch Creek Dahlias, agrees that loamy soil with a topping of mulch will preserve dahlias to sprout and bloom another summer, but he worries about a hard cold snap, one that freezes the ground from 4 to 6 inches deep.
“If the frost line reaches the tubers, they will turn to mush and rot,” Hunter said.
A hard frost that comes with a lot of snow – such as the winter storms South Sound enjoyed last year – is not as bad as a dry freeze, Hunter said.
The snow actually insulated the ground from the arctic cold, Hunter said. Hunter said dahlia growers on the east side of the Cascades – where the winters are much colder than on Puget Sound – should always pull their dahlia tubers out of the ground each fall.
WHAT TO DO
If the soil looks good, dump on the mulch and hope for a mild winter.
If the soil is wet and sticky, it might be best to yank those tubers out of the ground.
Here’s Hunter’s advice on that chore:
Wait about a week after a good frost, which gives the tubers a chance to go into dormancy.
Dig up the tubers. Look for the “eye” that means it will sprout a new plant next year.
“The eyes are easier to see right after you take them out of the ground,” Hunter said.
Use a hose sprayer to watch the dirt off the cluster of tubers and let them dry for a couple of days.
Gardeners can divide the tubers in the fall or spring. Remember that each tuber must have an eye to sprout a new plant.
Place the tubers in damp sawdust, cedar shavings, peat moss or vermiculite. Cardboard boxes, paper bags or wood boxes work well for storage. Plastic bags keep tubers too damp. They will die and rot.
An insulated, unheated garage is perfect for storage, as the tubers should be kept at about 40 degrees.
It’s a good idea to check the tubers throughout the winter. If the tubers start to get wrinkly, dampen the sawdust, peat moss or other storage medium.
FINDING NEW DAHLIAS
The serious dahlia addict spends this time of year picking out new varieties to try next year.
Most dahlia growers have Web sites with photos of the blooming plants – and start taking tuber orders now for delivery in the spring.
Local dahlia growers such as Lynch Creek and Connell’s are good places to visit now, as you can see the flowers in person.
“Dahlias begin to sell out in January,” Hunter said. “You can pick your variety now and have it shipped to you just in time for spring planting.
Connell said it always is fun to try new dahlias. There are thousands of colors and varieties to choose from.
And then comes the next dilemma.
Of course, that dilemma is when to plant new tubers and the ones you carefully saved this fall.
Connell said the best time to plant tubers is when the soil warms – from late April through early May.
“If you plant them too early, the soil will be too cold, and they won’t do anything,” Connell said. “And they might just rot if it rains a lot.”
Learn about dahlia history, types and care on Page C3. Dahlia history, types and care
The Spanish conquerors of Mexico and Guatemala took dahlias back to Spain – with the notion of using the tubers for food.
That idea didn’t pan out, but European gardeners were soon charmed with the beauty of dahlias – and how easy it is to create wild new hybrids. There are now more than 50,000 varieties in just about every color imaginable. Dahlia plants can be short or tall, and the flowers can range in shape, size and form. Dahlia blooms range from 2 inches to 10 inches across.
There are solid-colored dahlias. Variegated dahlias come with two or more colors.
Bicolor dahlias have two colors on each petal.
Flame dahlias are mixtures of yellow, orange and red.
Dahlias left in the ground all year long should be divided every four years. You might find yourself with a lot of extra-eyed tubers.
“Give them to the neighbors,” Andy Hunter said.
It’s OK to leave tulip and daffodil bulbs in the ground all winter long, although daffodils should be dug up and divided every five years or so.
Now is the time to pick out new tulip and daffodil bulbs and get them into the ground sometime during the fall. Remember to plant the bulbs with the pointy side pointing up, and between 5 and 8 inches deep.
Large calla lilies don’t need to come out of the ground in the fall, but it probably is a good idea to divide them.
Chester Allen, The Olympian