The Madman Discovers Dahlias

I don’t know what took us so long to discover Dahlias. It seems they should always have had a place in our garden beds. But we only started growing them a few years ago on a whim. We found a cheap bag of tubers and figured why not? We’ve got the room.

Why not, indeed! The flowers were gorgeous, prolific and, stupid us, we left the tubers in the ground over the winter. They died, but not our interest in the Dahlia.

Central American Flower

Dahlias have been around for a long time. This member of the Asteracea family is native to the mountains of Mexico and Guatemala. Little is known about them before the time of the Aztecs, and even that information is sketchy. But, historians believe the Aztecs used the plant for food and medicine. They even used the long hollow stems of the Tree Dahlia for irrigation.

In 1570, conquering Spanish armies found the impressive Dahlia tree among the plants growing in King Montezuma’s royal gardens. Unfortunately, the detailed drawings of all the plants sent back to Spain were later lost in a fire. The next time Dahlias appeared in horticultural history was 1789. The Director of the Botanical Garden in Mexico City sent Dahlia parts to Antonio Cavarilles, a horticulturalist at Madrid’s Royal Gardens. Cavarilles named the plant after his friend and fellow scientist Andres Dahl. By the 1800s, seeds and plant parts of the original Dahlias were sent all over Europe and the games began.

Blame The Chromosomes

We say the games because Dahlias hybridize very easily. The madman says that’s because Dahlias are Octoploids, meaning they have eight pairs of matching chromosomes as opposed to the two pairs most plants (Diploids) have. The combinations are mind-boggling. So now we have thousands of Dahlias in every size, shape and color. Every color except blue, that is. Unfortunately, Dahlias lack the specific enzyme that creates a blue flower – so mauve and purple are the closest we get with Dahlias.

Since there are over 57,000 named varieties, every gardener should find at least one Dahlia for summer bloom. Lucky for all of us, they are easy to grow. Dahlias are best grown from tubers planted in the spring. My main problem is keeping the madman from putting them in the ground too early. They hate cold soil. So, wait until the soil warms to 60˚ and all danger of frost has passed. The Old Farmer’s Almanac suggests planting the tubers a few days after putting tomatoes into the garden. I have learned that if we plant them in pots in the greenhouse a month early I keep the madman happy and get a start on the season.

Select Good Tubers

Whichever way you wish to do it, start with plump, healthy tubers. A shriveled tuber is dehydrated and may not grow. Misting may help, but we’ve found only about 50% of our rehydrated Dahlias make it.

Although you should plant your Dahlias just below the surface, remember they like loose garden conditions. We dig a 10-12” deep hole just to loosen the soil and add some compost. After planting the tuber, don’t bother with water or fertilizer: the tuber is self-sufficient. But do keep a good eye on them – as soon as you see a sprout, it’s time to begin caring for them. Dahlias are thirsy – keep them watered. A good rule of thumb is to provide 1” of water a week – sound familiar? And, while you’re at it, hit them every three weeks or so with a low-nitrogen fertilizer (5-10-10).

Staking Is Crucial

Dahlias need staking – the sooner you do it, the better. When you find your 5’ tall Dinnerplate lying on its side after a July rainstorm, it’s awful hard to fix it. And we speak from experience. Over the years we have used a variety of staking systems, but the best idea we have seen was at Longwood Gardens last year. There, sturdy grids of twine woven around strong stakes supported beds of Dahlias.

We had planned a similar grid for our beds this summer. But, with the summer being what it was, we didn’t get to it until early July and the Dahlias didn’t wait for us. Armed with twine and stakes, both metal and bamboo, we did manage to weave some support around the unruly plants. Next year, the twine grids are going to be put in place as the Dahlias are planted, the madman promises.

Dig Them Up

As soon as frost kills the plants, we’ll carefully dig up the tubers. In the past, we have stored clumps of Dahlias in shredded newspapers. The key is to keep them from drying out. At this point, commercial growers separate the individual tubers, making sure each one has at least one eye (growth point). Home gardeners can either separate them in the fall or in the spring when the eyes are easier to spot. The madman says, just remember, no eye – no Dahlia.

The hardest part of growing Dahlias is deciding which variety to grow. The madman has always associated the Dahlia with the well-known Dinnerplate. You’ve all seen the picture of a little kid standing next to the flower as big as her head. Kids and animals sell, you know. Dahlias are classified by color, form and size.

Complicated Classification

That’s about as deep as we want to get into this topic. Here’s a link to the National Dahlia Society’s classification page – good luck. Remember, we don’t grow them to sell or to show them. We grow them for ourselves and the visitors to our garden. The madman likes the big showy ones. The bees and other pollinators like the ones with easy-to-find pollen. I like them all.

As we examined the staking system at Longwood Gardens, we discovered the Collarette Dahlias. The flower was much simpler and is actually a cross between a single and a double flower. The madman just had to have some. They were more difficult to find since they are not as common or popular as the big fancy Dahlias. But, well worth the search. Your own selection will depend upon your own personal preference. Some are good for landscaping, some are good for bouquets, and some are good for pollinators. All are beautiful. This is one plant we buy based on the picture in the catalog.

Try Seeds

If you don’t care what color your Dahlias are, try some seeds. If you’ve ever looked at Dahlia seed packets, you’ll notice they are all mixed colors. That’s because Dahlias cross-pollinate easily and you never know where the pollinating bees have been.

If planted by seeds, Dahlias take 120 days to bloom – sounds like the madman’s hot peppers. Most will be single-flowered blooms, and each one should produce a small tuber by season’s end. It is possible but difficult to save these tubers if you really like the bloom.

The King’s Dahlia

Luckily the madman isn’t ready to start planting Dahlia seed. But, he has announced he would like to grow the Dahlia imperialis, otherwise known as the Tree Dahlia, next year. This is the closest he can get to the plant in King Montezuma’s Garden that wowed Spanish explorers. He says he wants to honor the Aztecs, but something tells me that he wants to grow it for the stem. I shudder to think what he plans to do with it.

Looks like we’ll have fun this winter looking for new Dahlia varieties in our seed catalogs while drinking hot cocoa. But now it’s time for some lemonade.