Snoqualmie Valley Master Gardeners Talk Dahlias, Fall Leaves and Plant Sales

NOTE: Interested in being a Master Gardener? Applications are now being accepted for the 2014 Master Gardener training class; deadline is October 18th. Contact Ann Acton at for more information.   **Article by Master Gardeners Barbara Trzebiatowski and Ann Acton**

Addicted to Dahlias

This is one of my favorite times of the year. We are still enjoying the sizzling yellows of summer with the rudbeckia, coreopsis and sunflower blooms while asters, chrysanthemums and coleus are ushering in the fall season with flaming reds, purples and oranges. Dahlias bridge both seasons, blooming from July until the first frost.

For diversity of bloom, dahlias can’t be touched – they can be found in all colors (except maybe true blue); solid, bicolor or multi-dahliacolored, speckled or blended or both. Dahlias also take the prize for height variance – from one-foot dwarfs to eight-foot tall giants – and for form and size. You can find dahlia blooms as cute as a button in tiny inch-size pompons and petite mignons, or go for the wow factor of giant decoratives measuring over a foot in diameter. In between are such types as those resembling orchids, peonies, anemones, water lilies and cactus. Who hasn’t been impressed by a 12-inch dinner-plate dahlia?

As if all that wasn’t enough on the plus side of the balance sheet, dahlias are also relatively easy to grow. The key is proper spring planting and winter storage, along with at least six hours of direct sun. Dahlias can be planted after the last frost in the spring in well-drained neutral soil, about the same time you would plant your vegetable garden. They require a low nitrogen fertilizer such as recommended for vegetables and a support stake is recommended at the time of planting, just in case you need to support a tall grower.

Plant the tuber horizontally with the eye pointing up approximately four inches deep, but do not water until you see the dahlia emerging from the ground.  Slugs love dahlias so bait very early or you may never actually see the dahlia growth emerge, and continue with the slug bait until the plant is about a foot tall.  At this time, for a compact, bushy plant with more flowers, pinch out the center growing point. Cutting the flowers for indoor arrangements throughout the season will promote more blooms.

Dahlias may be left in the ground over winter, however, the tubers are susceptible to rot and freezing. If you do leave the tubers in the ground, after the hard frost or around November, cut the stalks down to below ground level and then cover the area with plastic (to keep the rains out) and layers of mulch (for extra protection). In early spring, just uncover everything and see what sprouts.

To dig and store the tubers each year, cut the stalk down to six inches above ground in November after the foliage has completely died back. Tubers dug up too early will be “green” and will rot in storage.  Start digging one foot away and all around the stalk and then carefully lift the clump out of the soil with a shovel or pitchfork.  Wash the soil off the tuber, cut away any damaged ones and thoroughly dry them three to five days.  You can store the tubers as clumps or divide them into individual tubers; each individual tuber must be attached to a piece of the main stalk where growth “eyes” appear. Store in a cool, but not freezing area in a box or crate with wood shavings, shredded paper to sand.

You can cut your own dahlias Saturday and Sundays 10am-5pm through September at the Dahlia Barn in North Bend, and check out the Puget Sound Dahlia Association website for more dahlia information.

Q & A: Raking Leaves

Q: Every October my To Do list includes raking leaves, and every October I try to find a way to procrastinate until it’s too late. Is it really necessary to rake up all those leaves every year?

A: Every garden question can be answered with “it depends” and this question is no exception. If you have large big leaf maples that dump their leaves on your lawn every year, then yes, you should definitely rake those up. A solid mat of whole leaves will deprive the lawn of sunlight at the very time it’s recovering from summer drought and wear-and-tear. You can, however, run over them with a mulching lawnmower and leave them; the chopped-up leaves will add organic matter, some nutrients and will help suppress weeds in your lawn.

Don’t have a mulching lawnmower? Just push the leaves into your landscape beds and distribute around your shrubs and on top of now-dormant perennials. A layer of leaves will protect roots from freezing temperatures and the soil from erosion caused by heavy rains. The leaves will decompose somewhat over winter, adding organic matter to the soil, which is always a good thing. Better yet, add a couple of inches of compost under the leaves for added nutrition. And while this adds another step to the process, shredding the leaves beforehand hastens their decomposition and has a bit tidier look for winter. Then in early spring, either turn the leaves under or add them for your compost pile, being careful not to damage any new growth from the spring bulbs coming up.

Procrastination Suggestion: Fall Foliage Road Trip and a Plant Sale

The To Do list will still be there next weekend, so why not get out and enjoy some autumn scenery. While fall foliage may not be as abundant and colorful as found on the East Coast – in the Pacific Northwest we’re blessed with more evergreen than deciduous trees – there are several corridors of autumn splendor.

  • Close to home, the Washington Park Arboretum
  • Cascade Loop along SR 2 and SR 20
  • SR 520 to Mt. Baker
  • Columbia River Gorge

If a road trip is not in your future, perhaps some procrastinating can be done at a plant sale. Caution: plant sales may result in additional items added to the To Do list.

  • September 20-21 – Northwest Horticulture Society Plant Sale at North Seattle Community College (near Northgate); Friday, 12PM-6PM and Saturday, 9AM-2PM
  • September 28 – Lee Farmand Nursery Fall Sale, 1720 Redmond Fall City Road SE; Saturday, 9AM-3PM
  • September 28-29 – Chase Garden Fall Plant Sale, 16015 264th Street E., Orting; Saturday-Sunday, 10AM-3PM
  • October 4-5 – Soos Creek Botanical Garden Fall Plant Sale, Auburn; Friday-Saturday, 10AM-4PM
  • October 5 – T & L Nursery, 13245 Woodinville-Redmond Road NE; Saturday, 9AM-2PM


Additional information on dahlias and gardening practices can be found on our website at Bring your gardening questions to the North Bend Library on Saturday, October 5, 11am and also enjoy a talk on getting your garden ready for winter.

[The authors, Barbara Trzebiatowski and Ann Acton, are master gardeners in the WSU Extension Master Gardener Program. Extension programs and employment are available to all without discrimination. Evidence of noncompliance may be reported through your local Extension office.]


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