Articles

Growing Dahlias in Containers 

Our first thought of growing dahlias in a container is only to use the small bedding-type dahlias, but believe it or not, raising four-foot dahlia plants is just as easy. Tall dahlias could also give you needed privacy from neighbours and lessen street noise if planted on a patio or balcony. There are Lazy Susan type bases on the market now that can be placed under your heavy pots that allow you to easily move them around your patio for privacy.

To begin, you will need a large heavy pot that is deep enough to place a stake in to support your dahlia plant, say 14 to 16 inches wide and as deep as you can find. Make sure to drill several holes in the bottom of the pot for drainage. Place moistened potting mix in the container and, at this time, it is beneficial to add a couple of spoonfuls of slow-release fertilizer to feed the plant in the early stages of grow.

It’s now time to plant. Insert your stake first and then plant the dahlia tuber horizontally two to three inches deep, ensuring the shoot or eye is facing upwards, about an inch or so away from the stake, and then cover with the potting mix. Water slightly as you just want to keep the soil moist and not wet until the dahlia shoot breaks the surface and starts to grow green leaves. At this time, you can place a tomato cage over your sprouted dahlia plant and attach it to your stake for extra support. As the plant grows it will use up the slow-release fertilizer and so you will have to start applying a fertilizer like 20-20-20 once or twice a week as your plant grows. When your dahlias start to bloom, they require even more water and fertilizer to produce a nice display. Happy growing.

History of Our Tuber Sale

When the Dahlia Society started, we hadn’t really thought of having a sale of our excess tubers to raise funds for the club. We seem to function quite well on collected dues and the sale of blooms from our dahlia displays.

In 1987, we held a small dahlia tuber sale in the Bayer’s Road Shopping Center and raised $187.00. The next year, we moved to the Micmac Mall [in Dartmouth] and continued to have larger tuber sales every year up until 2017, when renovations to the mall caused us to lose the site. We then moved to Bedford Place Mall. Our four sales tables were set around a free standing 4x4 foot black display with colourful posters of dahlias.

In 1992, we decided bid on hosting the American Dahlia Society National Show in Halifax for the year 1997. This spurred members to bring in many more tubers for the sale then normal, because we would need a substantial nest egg to carry off such an event. For the next five years the society banked $2,000 to $3,000 at each sale. We were in good shape to host a wonderful dahlia show at the Sheraton Hotel and Casino on the waterfront. Things went so well that we decided to repeat the event and host again in 2006 at the Weston Hotel. We still had a reasonable amount in our bank account after both of these shows so it was decided that in the future, there would be an even split of the profits between the grower and the society. Now, the money generated from the tuber sale covers all of the societies cost throughout the year.

We are grateful to all the growers who take the time and effort to bring their tubers to the sale every year: the Society thanks you. Many buyers usually don’t have the chance to show their appreciation to you for the opportunity to purchase top quality dahlia tuber at reasonable prices, but returning customers year after year speaks volumes. The popularity of the dahlia has been growing in recent years and the past two years has shown an almost fever pitch demand for tubers with many dahlia suppliers putting their lists online earlier than ever and then selling out in record time. Our sale in a new location was no different as there was very little left after the dust settled. It was our best sale ever.

Dahlia Tuber Loaf Recipe 

2 eggs

1 cup sugar

1 ½ tsp. vanilla

½ cup oil

Mix well and add the following.

1 ½ cup flour

½ tsp baking powder

½ tsp salt

½ tsp soda

1 ½ tsp cinnamon

Mix and then add the remaining ingredients.

1 cup peeled and grated dahlia tuber (pour off excess liquid)

½ cup chopped nuts

½ cup chocolate chips

Pour into a greased loaf pan and bake at 350 for 1 hour. 

*Note: Do not use varieties that have a pungent odor

Taking Dahlia Cuttings 

 Step 1: Sometime in late January or early February pull tubers out of storage and pot up either in trays or in 4-inch pots with moistened Pro Mix BX™. Put potted tubers under 16-hour florescent lights with bottom heat. Don’t overwater at this stage as it could rot the tuber.

Step 2: When shoots have developed two or three sets of leaves and are about three inches tall, it is time to take your first cutting. Using a one-sided industrial razor blade or a sharp hobby knife that has been sterilized (either with a 1% bleach solution or other means) slice off the dahlia shoot about 1/16 inch or the thickness of a dime from the crown of the tuber. Careful! No new shoots will develop if you slice off the base of the shoot where it connects to the tuber crown. Remove bottom leaves and place in water. Don’t forget to make a label for the variety from which you are taking the cutting.

Step 3: Dip the cut end into a #1 powder or liquid rooting hormone prior to placing in a 4-inch pot filled with moistened Pro Mix BX™. Insert the cutting in a half-inch deep hole made with a dibble or pencil and press soil firmly around the stem to remove air pockets. Place over bottom heat and under 16-hour florescent lighting until rooted. To help increase humidity around the plant, place the 4-inch pot with cutting into a plastic bag. Do not seal the bag but tie a loose knot in the top. You still want air movement within the bag. Another way to increase humidity is to put a plastic dome over the cuttings.

Starting Dahlias Inside 

In years past, I have been pushing the limits on how early I can get dahlia blooms. One way to accomplish this is to start your dahlia tubers inside and transplant an established plant. However, there are several challenges to overcome. I generally will remove my dahlia tubers from the cold room at the beginning of February and allow them to warm up for a week. I plant the tubers in a 4-inch pot using moistened Pro Mix BX™ and give them a light watering. I usually water from the bottom so that the Pro Mix BX™ is evenly moist.

You do not want to overwater at this stage as you can rot the tuber fairly quickly. Once tubers are planted, you place the pot under a florescent light, making sure that the light is 4 to 6 inches above the pot. If the light is too far from the pot your plants will become leggy and fall over or break at the base. I also cover the light rack with plastic to keep the heat in and sometimes I will provide bottom heat to help it along. It is important to provide the tuber with warm moist conditions to allow for the eye to sprout and form roots. Once there is an established plant I will water when the plants dry out. Plants are then hardened off for a week before they are planted out. Once planted the plants are watered in they are protected with a row cover for about a week. It is important not to let dahlia plants to become root bound as dahlias do not like to be transplanted. By doing this method I generally get dahlia blooms about 1 to 2 weeks earlier in the season.

Micro Mini Dahlias 

The most amazing thing about growing dahlias is the diversity of flower forms, color and flower size. In

recent years we have seen an eruption in different dahlia flower forms, and each one began with just one

unique cultivar that catches the eye of exhibitors and other breeders. Before long there are several similar

cultivars and the American Dahlia Society starts looking at starting a new classification for these new

types. 

A group of cultivars that have been flying below the radar in most parts of the dahlia world are the Micro

Mini Dahlias. These little gems less than two inches across have had to compete with the larger similar

forms in open competition at most shows, and despite that, a number of them win against this competition.

I think it is time to level the playing field and give these cultivars their own classification in our shows.

Right at the present time there are only about ten cultivars that should be considered Micro Mini Dahlias

but I’m sure if we include classes for them at shows our great originators will step up and produce many

more. At the present time a number of the California societies have classes for these dahlias and they are

popular with their exhibitors.

Next year’s ADS National Show in Chicago will feature a special class for these dahlias and I hope that this

national coverage will spur on more societies to include them in their shows. The next question that

needs to be addressed is where to get stock of the Micro Mini Dahlias. The primary supplier of a number

of these cultivars is Corralitos Dahlias who sells U2 Ania (novelty), U2 Drew (col), U2 Fire (col), Cher Ami

(col), they also sell the Munchkin Series - Henry, Alfonso,Granville, Elizabeth, Elise, Conner and Kaili all

of which are peony types, all produce blooms less then 2 inches across.

Two others that I know of are Cobequid Celestial Star (O) and Suitzus Julie (WL). All of the above could be

considered Border Dahlias being short enough for the front of the dahlia bed or grown in containers on a

patio or deck. This could be a nice way to still involve society members who have downsized to an apartment

or condo but still want to take part in the dahlia show using blooms from their container gardens. 

Dahlias are one of the most dynamic and rewarding flowers that any gardener can discover, so let’s keep

the momentum going and bring even more gardeners into the dahlia world through the exposure to these

little beauties.  The dahlias below are Suitzus Julie (L) and Cobequid Celestial Star (R)

No End in Sight 

When I first started to grow dahlias, close to forty years ago, the selection of different dahlia flower types was quite basic: formal and informal decorative, semi-cactus, cactus, ball, mini ball, pompon and a few collarettes. Then along came a lady named Evie Gullikson from the United States northwest who, through her own initiative, triggered a revolution in the dahlia world. Up until that time the above flower types were the only forms recognized by the American Dahlia Society. Most of the growers and exhibiters wanted to keep it that way and treated any new and different flower form as just a trash dahlia to be composted rather than displayed on the show bench. Eve Gullickson persisted and slowly but surely we began to see new and interesting flower forms, totally different from the established types. The waterlily form was considered a very poor decorative for years and not worth keeping. It was finally recognized by the ADS and the floodgates opened, with breeders introducing new and exciting waterlily cultivars which otherwise would have been discarded.

Evie gathered an army of excited dahlia breeders behind her who began to introduce many more unique and different flower types; soon many more began to be recognized by the ADS. Evie stood along in the early days, as she battled the old boys club of dahlia exhibitors, finally convincing the ADS to recognize some of these unique and interesting flower forms especially the open centred types. Evie passed away a number of years back, but her influence is still being felt today through breeders who are pushing the envelope even further than she could have imagined in developing new forms of dahlias.

Dahlias have become one of the most popular garden and wedding flowers, and the efforts of people like Evie Gullikson have contributed greatly to this success. We now have about twenty different dahlia flower types recognized by the ADS, with the orchette being a flower with the petaloid characteristics of the collarette and the involute form of an orchid being the latest. There seems to be no end in sight when it comes to developing new and exciting dahlia flower forms which should continue to interest current dahlia growers as well as entice new gardeners to try these wonderful flowers called dahlias. The flower below is an Orchette Red and White dahlia.

What's in a Bag of Fertilizer 

For example a bag of fertilizer labeled 6-12-12 contains 6% nitrogen, 12% phosphorus and 12% potassium the rest is just filler like sand.

• N Nitrogen needed for leaves and stems

• P Phosphorus needed for flowers and roots

• K Potassium needed for roots

Nitrogen is used up quickly by the plants but Phosphorus and Potassium are used up at a much slower rate. This could lead to excessive amounts of P and K in your soil.

Getting a soil test done is a good idea. Fertilizers are expensive and if you can add less, you will save more money then you paid for the soil test.

A soil test will also give you the pH level of your soil: this is very important as that will determine how much fertilizer will be made available to the plant.

Sources of Fertilizer

• Nitrogen - Urea 34-0-0

• Manures - Chicken very high, Cow and Horse much less. Be sure to compost all fresh manures before using as they will burn your plants.

• Phosphorus - Superphosphate 0-64-0

• Bone Meal

• Potassium - Muriate of Potash 0-0-60

• Manures, Compost, and Seaweed

Research Project 

My sessional lecture position at Dalhousie University Faculty of Agriculture has given me an opportunity to supervise third- and fourth-year plant-science degree students in their project course. This course consists of conducting a research project on a plant crop throughout the summer. Last year, [2014] two students completed projects involving dahlias. The results were very interesting and one student is currently working on a paper to be published in the Canadian Journal of Plant Science.

This year, I have another student working on another project using dahlias. Li Ni, a previous student of mine in both Greenhouse and Floriculture Production, and Landscape Plant Nursery Management is a fourth-year degree student in plant science is very excited to be working with dahlias.

Li is trying an optimum balance between inorganic fertilizers and organic amendments that will optimize both the flowering quality and tuber quality. Her experiment is using the mignon variety "Reddy" in a potted experiment being conducted in the greenhouses of Dalhousie University Faculty of Agriculture. She plans to track the nutrient use within the plant.

The organic amendment is sheep manure, as previous work found that sheep manure had the best influence on tuber production. Li will be using a foliar spray for the inorganic treatments, doing three sprays throughout the year.

I will be giving regular updates on these projects at the meetings. In the October newsletter I will give some preliminary results on both projects. If anyone is interested in any further details of these projects you can email me at rsveitch@eastlink.ca .

Powdery Mildew

In other parts of the world, the dahlia is known as the Queen of Fall and offered only a short - but extraordinary - period of reign. Not so in Western Washington, where its rule is sustained from early summer well into November’s killer frost. [One] consideration is the prevention of fungus or bacterial disease that often develops. 

Usually the first unwelcome guest, powdery mildew appears just when late August brings out the best blooms. Hot days and cooler nights encourage mildew growth on top of foliage. Later it may be joined by another fungus, entyloma, whose circular colonies infest lower leaves in particular. This dahlia smut needs your attention, since its spores winter over in the soil. Removing excess foliage and diseased leaves also opens the plant to better air circulation. 

Dahlia growers also note that botrytis can affect young plants that are over-watered. Fusarium wilt may cause visible damage and partial weakening of foliage, but it also can lead to complete collapse of the dahlia. The bloom of botrytis is easily detected, so that the grower can apply remedies. Fusarium, on the other hand, exhibits different symptoms (such as discoloration, necrotic areas, or stunted growth). Warm temperatures and humidity, over-watering, and poor drainage may lead to wilt spreading.  

The most pernicious fungus, though, came into my garden years ago. One dahlia was infected by sclerotinia, whose mycelium grows rapidly inside the hollow stem of dahlias. As it matures, the fungus causes collapse of a branch here or there, but it eventually will kill the entire plant. Its sclerotia look like black, hard pellets as they develop within the stem. Allowing these to fall to the ground ensures their survival. Like other mushrooms, they develop into fruiting bodies with a wealth of spores. If a dahlia branch exhibits signs of distress, look at the juncture of branch with stem. When you find a brown area there, suspect sclerotinia, remove the branch and investigate further. Since excessive moisture is often the cause of sclerotinia and those other fungi, reducing overhead watering is necessary. And in all those cases, infected foliage should never be composted but consigned to trash. 

New dahlia growers mention the appearance of gall diseases, suspecting that these bacterial diseases may be spread by commercial mass marketing of dahlias with little understanding for plant health. The topic is still under investigation, but let me refer you to my recent article posted on the ADS website under the “Know” tab entitled You’ve Got Some Gall! The valuable research by Oregon State University’s Melody Putnam also can be found online; her articles offer numerous examples and photos of these and provide effective remedies. 

The past four years have taught us all a lesson on transmission of infectious diseases, such as Covid viruses. No longer can we take lightly our parents’ admonishments to wash our hands, cough into elbows, and clean counters and door knobs. In the past I admittedly was rather casual in cleaning or sterilizing dividing tools. After all, several different approaches were proposed, and the formula for bleach/water solutions seemed to be based on personal preference, rather than any empirical evidence. Moreover, using bleach certainly corroded and damaged those tools, so I was hesitant to follow. But as our knowledge of dahlia pathology increases, we need to steer away from home remedies and follow the science. Like others, I now sterilize my pruners and other cutting instruments in Virkon-S, a veterinary disinfectant that also is claimed to be an effective agent against virus contagion.