Growing Dahlias

It's a waterlily -- It's a cactus -- It's an orchid -- It's a peony. They're all dahlias. The most versatile of garden flowers, dahlias are available in dozens of shapes and in sizes ranging from petite mignons and poms little more than an inch across to giant decoratives over a foot in diameter. They come in a dazzling array of colors - reds, pinks, yellows, oranges, lavenders -- that complement just about any garden setting.

Unlike the varieties that grandma used to grow, today's dahlias boast much more refined growth habits, with stronger stems and more proportionately sized folliage to better withstand rain and wind. Although dahlias are native to the highland areas of Mexico and Central America, they are particularly fond of our cool-summer Northwest Coast climate in Washington State, and it's easy for anyone to grow them to perfection with very little care.

As members of the Puget Sound Dahlia Association, the largest local group of dahlia growers and admirers in the United States, we'd be delilghted to share with you our knowledge and enthusiasm for these glorious flowers.

Planning The Garden

  • Location:

    The ideal location for dahlias is one in full sun; however the plants will tolerate some shade.

  • Drainage:

    The soil must be well-drained; a neutral soil is preferable to a highly acid one; avoid planting close to shrubs or trees.

  • Height & Spacing:

    Dahlia plants vary in height from one foot to seven feet. Check each variety for its height, and plant where suitable -- the taller ones to the rear of the garden, the dwarf bedders as border decorations. Space your dahlias according to bloom size -- the larger blooming ones should be planted two to three feet from other plants, while the smaller blooming varieties can be planted one to two feet apart.

  • Soil Preparation:

    Most dahlias thrive in well-prepared, well-drained soil A basic soil conditioner that will improve any garden is an application of moist peat moss and manure. Sand can be added if soil is heavy. Thoroughly turn the soil before planting.

  • Fertilizers:

    About two weeks before planting, broadcast 5-10-10 over the soil and spade it in. In mid-July, a light top-dressing of steamed bone meal and muriate of potash will enhance the color of the blooms and help promote tuber growth. If not available, 5-10-10 can be used, but avoid using nitrogen fertilizers (for lawns) or you'll have more leaves than blooms. If cutworms are a problem, add "Soildusto" to the fertilizers.

  • Planting Your Dahlias

    Planting Procedure

    1. The time to plant in the Pacific Northwest area is after the last frost, between April 15 and June 1.
    2. Check your soil for proper moisture; it is better to plant when the soil is slightly moist.
    3. Place stakes where the tubers are to be planted.
    4. Remove about five inches of soil; place the tuber flat with the eye upward, near the stake. Cover the tuber with soil; it should be about five inches below the ground. The tubers should be planted shallower in heavy soil.
    5. Place slug bait around the garden as soon as possible.

    Summer Care


    Water every two weeks -- more frequently during very hot weather, and when buds begin to form. A thorough, deep watering is better than frequent light waterings.


    To have a compact, bushy plant with more flowers, pinch out the center growing point when the plant is about one foot high (see illustratrion).


    For better quality blooms with strong stems, pinch off the side buds at the end of each growing branch (see illustration).


    In the past years, we would recommend establishing a spraying program every few weeks. With the concern of impacts to our environment, many growers are either using organic approaches or "live with the bugs". We recommend that whatever you do, be kind to the environment. Many bugs are really friends of the dahlia helping us control those that are not.


    Since dahlias have many surface roots, only light cultivation is recommended. After July, cultivate no deeper than two inches, and not closer than one and a half feet from the main trunk

    Cutting The Flowers

    Cut early in the morning or late at night. To properly condition the blooms, place them in water away from a draft for eight to twelve hours. Display your flowers in a cool part of your home. By misting regularly and changing the water every other day, your blooms will last several days.

    Digging And Storing

    Around November 1, dahlias are cut down and roots are lifted carefully with a spade by digging around the entire plant about one foot from the stalk. Use care to prevent "broken necks". Stalks are trimmed at root level, roots are wasshed, and soaked in fungicide (Captan recommended). Roots should be labeled and then divided or stored as a clump (see illustration).

    The roots will keep best if the storage area is cool but always above freezing. Most growers store roots in a medium such as slighhtly damp vermiculite in order to prevent shriveling. Line a box with plastic and put in alternate layers of vermiculite and dahlia roots. Be certain to check the dahlia roots ever six weeks.

    Dahlia roots left in the ground will survive cold winter days if kept from freezing. This is usually accomplished by heaping straw or mulch over the roots. Good drainage is essential for roots to be kept successfully in this manner.

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