Archive for the ‘Tubers’ Category

Master Your Dahlias

Monday, March 15th, 2010

With such a wide variety of dahlias and incredible displays of blossoms it’s no wonder we love them. From all the colors of the rainbow and every combination in-between, anybody can find a dahlia that suits them.

Mastering your dahlias requires only your time, and a working knowledge of proper maintenance practice. Guiding you through the steps is my goal! Making them happen should be yours.

Congratulations! You have inherited a prized tuber (root) from a friend or purchased one from the store. A “Tuber” is a type of root similar and resembling a potato. Energy is stored in a tuberous root to help the plant survive its dormant period. Including favorites like dahlias and daylilies tubers are the source of many beautiful plants.


First I like to inspect my new tuber for rot and for eyes. Just because a tuber may not be really firm doesn’t mean it’s rotten. I only throw away a tuber that has wet spots and is mushy making it pretty clear it will not likely produce. Usually rot is caused by freezing or improper storage; we’ll cover both topics later. Given the tuber has passed the rot check I then look for eyes (buds).  These generally appear near where the tuber was separated from its cluster. Although we would prefer to only plant tubers with eyes apparent, I still plant those without just in case, but not as the centerpiece. Sometimes I don’t clearly see the eyes but they come up to see the sunshine never the less.

Best time to plant

The best time to begin planting is April-May although I have planted left over tubers as late as the 2nd week of June and they did fine. Better to plant in faith than to just throw them away because you missed the optimal planting time. It’s important to note this season is for western Washington and western Oregon, where threat of deep frost has past. In cooler or warmer climates your season will vary according to the last deep frost.

Where to plant

Plant dahlias where they’ll receive a reasonable amount of sun during the day. Planting a dahlia in shady area would not be recommended. The lack of direct sun will inhibit growth and encourage mildew; there are also fewer blooms.

Keep in mind the area should be well draining, as a wet area will just rot your tubers and all may be lost.  Wherever I plant a dahlia, adding some compost, manure, or peat moss or other organic material always seems to help. We planted in both clay and sandy type soils without success until we began adding organic materials to help loosen the soil and provide nutrients. In the clay type soil, the ground would pack down after the spring rains or with our watering. We found the tubers had a higher tendency to rot in the clay soil.

The sandy type soil also seemed to pack down and water would run off the top or drain right through depending on how compact it was. This would cause the tubers to dry rot or shrink to where they were not very productive.

Condition the soil

Dahlia farmers often recommend a soil loosened with organic material and containing a soil pH of about 6.5-7.5 a little on the acidic side is good. Unless you’re into testing the soil pH, experimenting is fine. Old-timer dahlia enthusiasts have recommended to me over the years mixing 1 part manure or compost and 1 part peat moss with the soil from the hole to be planted. Some have suggested also adding bone meal which you can find at your local garden store. You can add more or less compost, manure, peat moss, etc if you like. Soon you’ll discover what works best for your patch of planet Earth.


You have found a sunny well draining location and are ready to put your tuberous friend to work. Simply dig a hole that’s roughly 10”x 6” or 12”x 8” depending on the size of your tuber. Work your organic material into the mix and leave an inch or two in the bottom of the hole. Your tuber prefers no deeper than about 6” and no shallower than about 4”. Place your tuber into the hole with the eyes near the center of the hole leaving a little space between the other end and the side of the hole. Don’t cover the hole until you have placed the support stake. Once the stake is in place cover the tuber with your soil mixture so that it’s flush or even just slightly raised from the ground around the hole.

Support Stake

There’s a variety to choose from, steel post, wood, and bamboo.

When picking the right stakes, everybody has his or her own opinion. While steel lasts many years, wood and bamboo can be cut below the top of your dahlia as it reaches maturity. Whatever you choose, it should have enough strength to support the weight of the blossoms.  I like to see a wood or bamboo stake ¾”-1” in diameter. Place the support stake near the center of the hole pounding it down about 1’ and leaving enough above the surface 2’-4’ to support the stalk. You will use twine, gardening tape, or even twisty ties when the time comes for tying the stalk to the stake. Always be sure not make the tie tight against the stalk, this will choke your dahlia stalk of nutrients and can make a weak breaking area. Stake in place cover the tuber, do not water.

Prepare for invaders

With your future flower bouquet in the ground, add measures to protect it from pests. Slugs and snails have been waiting to attack the fresh new shoots working their way to the surface. Place your method of bait before it’s too late. My grandmother didn’t like regular slug bait. She would use a short plastic dish filled with beer placing it about 6” from the stake. She managed to drown a few pests and it worked for her, some beers better than others — who would have guessed! As for me I use Dead line in a bottle and simply squirt a line about 6”-8” from the stalk in a circle around the stalk. You can’t find it in the beer section of your grocery store, but you should be able locate some at a garden center.


Once shoots emerge from below (usually a few weeks depending on soil temperatures) you can begin watering. Start by just a short sprinkle at first, watering heavier as the stem(s) grow and the weather gets warmer. We don’t want our beloved tuber swimming in mud or drying out. Watering is another experiment and you’ll soon find what your dahlia likes. Deep watering 2-3 times per week is recommended during the growing season, more if there’s very hot temperatures.


When the dahlia discovers the sunshine and starts growing, we need to begin feeding. Fertilize the root area from the stem(s) to about 10”-12” out. You are going to treat your dahlia like a garden tomato. Nobody wants their tomatoes to be all growth and no production. Avoid balanced fertilizers such as 16-16-16 or 18-18-18 these will cause a lot of growth, feeding your dahlia a high nitrogen fertilizer makes a huge plant with little blossoming. Look for fertilizers that have nitrogen at about half of the potassium or phosphorous levels such as a 10-20-20 or 5-10-10. The first number should be nitrogen but always read the label to make sure.


As the shoot(s) rise from the ground make sure to keep the area hand weeded. We are trying to keep your future flower bouquet from being choked out. I say hand weeding because anytime I’ve spayed herbicides near dahlias they were stunted or died. Even though we can see the spray and it appears a safe distance away, there’s a bit that becomes a fine mist and can drift into our precious dahlia. Note: never use Caseron, Excel or any other pre-emergent to control weeds around your dahlia.

Invaders have arrived

Keep an eye out for pests throughout the growing season. You may need to reapply your form of slug and snail control from time to time. Finding a good insect spray early in the season is a good idea. Aphids, mites and other insects can attack with a fury, so having a spray at hand can save valuable time. Some people recommend using dish soap about 1 tsp with 1 qrt of water; you’ll have to see what works for you.


Making your dahlia bushy is an easy one.  Old-timer dahlia enthusiasts and farmers alike recommend pinching.  Simply pinch off the center shoot(s) 1 ½’-2 1/2’ above the ground or above the 3rd-4th leaf set. This helps to stunt the vertical growth of the dahlia and fill in below.

The Flower Shop

Well we’re off and running now, though it sounded like a lot of work it wasn’t that time consuming. Time to pull out your flower cutting tools (scissors or clippers) and reap the rewards.

Keep your dahlia’s flower shop blooming well by regularly thinning out the blossoms. Isn’t this great, a flower that performs better when you take cuttings to enjoy indoors?

I recommend taking cuttings that aren’t fully mature but getting close. Cut blossoms can be prolonged, by taking your cutting early in the day and scalding the cut area with hot water from the sink. This not only sets the blossom but also reduces bacterial growth that shortens cut flowers duration.

Fall has arrived

Fall is upon us, winter is near, dig your dahlias, and toss your fears.

When cold weather sets in you’ll know the right time to dig up the flower shop.

Generally wait until the leaves turn brown and the stalk appears to have died. If you begin to have a hard frost or freezing you should dig the tuber out before it can freeze. I do know several old-timer dahlia lovers who often leave tubers in the ground for 2-3 years before digging and dividing. For myself and some others we prefer to dig tubers every year in case of tuber killing freezes and to discover what lies beneath.

Let’s dig

I like to use a basic shovel digging about a foot from the stalk and all the way around. Then using the shovel to pry up on the dirt I pull out the dirt clod and hello a clump of dahlia tubers.


You planted one tuber and reveled in its glory all summer; now you have more.

Sometimes you’ll get just a few new tubers, sometimes a lot more. Having spent some time caring for your tuber during the summer it has produced buddies to pass along to your friends. First we must care for the clump, take the clump of tubers and wash thoroughly to remove the soil. Take care not to damage the skin by causing scars or scraping off the skin. Let the clump dry for 1-2 days, tubers can be divided from the clump now or you can wait until spring.

To the Garage

With clean, surface dry tubers in hand place them in a box containing slightly moist but not wet sawdust, shredded newspaper, peat moss or similar material.

I recommend using a cardboard box without a lid, boxes that are solid might make the tubers sweat and rot. Whatever you use cover the bottom with 1”-2” placing the tubers on top individually. Then cover the tubers with about 2” and repeat until full if needed. You will need a cool dry place to store them such as a garage, shed, etc. Choose an area that stays well above freezing but doesn’t get to warm or above 50 degrees. The dormant flower shop should be fine for the winter; however an occasional peek would be a good idea. On rare occasions, mice may try to make a meal of your summertime splendor.  You also want to make sure the tubers aren’t to warm or freezing.

That’s it! With some practice, experimenting, and good weather you’ll have a retreat in the form of a tuber turned flower display.

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