Tuesday, March 5, 2013

Dinner Plate Dahlias

 Spring is right around the corner so that means more gardening and flower posts here on Stepford Sisters!

I love Dahlias, and my favorite are the dinner plate dahlias! Named for their size, the blooms really are as large as dinner plates!

First thing to know is about Dahlias is that they are grown from tubers and not bulbs. A bulb is an underground storage part of the plant. A tuber is formed from an underground stem or root. Tubers have “eyes”, for example a potato is considered a “tuber.”  Bulbs, such as tulips and daffodils, can be planted in the fall when the ground is cold and wet. Dahlias should never go into the ground until the soil has warmed to 60 degrees F. In some regions, that may be as late as May or June. Select tubers from champion plants with large flowers. Tubers can also be purchased bare root in the spring.

Planting Dahlias

Dig a planting hole twice as deep as the length of the dahlia tuber. Optionally you can add a tablespoon of Superphosphate fertilizer or other low nitrogen fertilizers to each planting hole to provide provide extra nutrients necessary to develop root growth. Do Not overfeed your dahlias, doing so will promote lots of foliage, but not a lot of bloom. Fertilizer makes foliage and water makes bloom.  Proper watering and good soil will create the best flowers. If you are planting more than one, plant your tubers 36 inches apart.

Place the tuber in the bottom of the hole and fill in the soil only to the top of the stem. The hole should remain partially filled with just the top of the stem sticking up until you begin to see growth. Do NOT  water at  planting time. Spring time offers enough rain to fulfill the tubers needs until the sprouts appear above the ground. Fill in the hole gradually to cover the new growth as the tuber begins to grow. Covering the stem inch by inch as it grows causes the stem to grow strong so that it will support the flowers.

Begin watering when the plants are actively growing above-ground. Water deeply to encourage strong roots. Water regularly. The soil should never dry out below a depth of 2 inches. Fast draining soil is the key to success with dahlias.

Once your dahlias have begun growing it is a good idea to stake them. Any dahlia plant taller than 2 feet should be staked and tied to keep it from collapsing during inclement weather. To simplify things you can plant your tubers and place the stakes at the same time, but if you put the stakes in after planting your tubers be careful not to damage any roots. Dahlias are surface feeders and their root systems can be easily be damaged. 

Pinching Dahlias
Top or pinch the growing tip of all large flowering (4 inch bloom or larger) dahlias after they have developed three to five sets of leaves. This produces more early flowers and a compact bush. You "top" the plant by snapping off the center of the uppermost growth at about 15" tall, or 3-4 leaf sets. It will produce a fuller plant, not shorter than it is destined to be genetically. Just reach in with thumb and forefinger nails and snap off the center tip between two leaf nodes. This is easiest when the plant is cool and fullest of moisture: evening or early a.m.

Weed and Pest Control

Hand weeding is the only type of weed control you should use. Using herbicides around your dahlias is not advised!

EARWIGS –  You can spray over-the-counter insecticides or insecticidal soap. Granular insecticide sprinkled on the soil will help as well. I have not tried this myself, but have heard you can make traps for earwigs as well. Just put a two inch pot upside down on top of the stake. Inside the pot put a loosely folded napkin. Use the top of the stake to hold the napkin in the pot. Earwigs go into the napkin in the early morning and remain there until dusk. They usually attack plants after the first month when the foliage is getting larger and buds are starting. Put some water and a bit of dish soap into a bucket. Carefully remove pots from stakes and napkins from pots and shake out over the soapy water. Earwigs will drown and you should have earwig free blooms! 

 SLUGS LOVE DAHLIAS !!  Especially as they are emerging from the soil. Use the slug bait of your choice until your dahlias are at least 12″ tall.  After the dahlia has reached full height, no slug bait is necessary.


Dahlias can be susceptible to powdery mildew and other types of fungus. Keeping the leaves dry as possible will help to control fungus. Fungus thrives in wet conditions. At the first sign of any fungus, spraying with any type of fungicide every 7-10 days, until the fungus is under control. Preventative sprays can be used to control fungus from starting also. If you had any problems with fungus on your dahlias last summer, soaking them in a mild bleach solution will kill any overwintering fungus. After cleaning up the tuber clump or dividing your tubers, soak them in a mixture of 1/2 cup household bleach to 1 gallon of water for 15 minutes. After soaking, rinse tubers thoroughly with clean water. Let dry for 3-5 days in an environment that is above freezing, then store for winter.

Dahlias should be dug up for the winter

Digging and dividing will keep your dahlias returning year after year when they are dug and stored properly. Dahlias left in the ground will create a massive tuber clump underground that will send up many weak, unproductive stalks that have small blooms. Eventually, if left undug year after year, they won’t come back at all.  

Be sure to wait for your dahlias to freeze before digging them up. You need to wait at least 1-2 weeks after the first hard freeze before you dig them up. Leave them intact and don’t cut them down. Wait until the foliage has turned black and has completely died back. During this time, the dahlia is ‘ripening’ and preparing itself for winter. Dahlias dug too early will not store over winter. 

After the foliage has died back, then you can cut the stems to a height of 6″-8″. Use a shovel or pitchfork to gently loosen the soil and lift the clump out of the soil. Tap off the soil from the clumps and allow the clumps to dry in an area above freezing for at least 3-5 days. You can divide then or leave in a clump and divide in the spring. Then store for winter.

Winter Storage

Clean the soil off your tubers and allow them to dry for 24 hours. They can be left outside in the sun, but do not allow them to freeze once you have removed them from the soil. 

Remove any skinny hairlike roots and place the tubers into a box or tub with sand, peat moss, or sawdust to keep them from drying out completely. Store in a cool dark place like a garage or basement. You want to shoot for a temperature around 40 to 50 degrees F. Check your tubers monthly to make sure they aren't rotting or shriveling up. If they seem too wet take them out for a day or two to dry out and if they seem too dry add a little water to the mix.


  1. Wow! This post was so helpful! As a first-time dahlia-grower, I had many questions. You not only answered all of them--you answered questions I didn't know enough to have! Thank you!

    1. Thanks! Last year was my first year growing dahlias and so I did a lot of research throughout the summer and compiled it into a post so I wouldn't forget it :)

  2. Hi! Here in California weather won't freeze, but as a first time dahlia grower, if I get a flower anything like the ones shown here, I will just make it gets photographed a put into my albums!


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