Hill Gardens of Maine - Dahlia Care & Culture

Click on "Teddy" for Fred's Amazing Journey Back In Time

Answers to your gardening questions

Article Archives

Complimentary Copy of "Keys to the Garden Gate"

Five-part article series on flower-drying starts here

Eight-part article series on vegetable gardening starts here

Asian Lily Beetles

A new scourge in New England ornamental and veggie gardens.

Japanese Beetles

They can be controlled...but not the way you think.

An effective Deer Fence!

Only three feet tall...and no deer has ever jumped over it!

Those Wonderful Dahlias
by Fred Davis, MG, Hill Gardens of Maine (To view other articles, click Archives)

Welcome through Fred's Garden Gate! Few gardeners, from no matter what climate zone, are able to resist the allure of Dahlias. My first experience with this incredible garden delight came in 1951 but they had been a staple in many gardens long before that. Then, as now, the rage were those with gigantic 8" to 10" double blossoms in absolutely startling colors. Then, unlike now, tubers in a wide range of heights, sizes and colors could be found for something in the range of a dollar...many were much less expensive. Nowadays, true aficionados are willing to pay big money for choice new cultivars, sometimes valued (actually over-valued) into the hundreds of dollars. Not to despair, however; many very nice varieties at more realistic prices ($1.99 to $3.99) are readily available in garden centers and those ever-present box-stores with 20-acre parking lots. Keep your eyes open because they should be showing up on store shelves during early spring.

Dahlias are planted outdoors in day-long sunshine, after danger of frost has past in the Spring. Since varieties range widely in height and expansion potential, choose your planting site carefully. Very short varieties - those commonly found in 6-packs at about the same time as pansy, snapdragons and petunias in the Spring - provide a colorful and interesting border or pathway-edger and require very little care beyond removing spent flowers. Intermediate heights, like the shorty types, also require less maintenance and, if given an early pinch (when just a few inches tall - well before flower buds form), will thicken into delightfully colorful 12" to 18" mounds). Really tall types - normally those with the largest and showiest blossoms - should be placed well back from the garden's edge and, as you might already have guessed, will need to be staked and frequently tied.

Strive for deep, exceptionally rich soil into which a little extra, fine, gritty sand has been added. Adjust soil pH to about 6.5 to 7.0 (slightly-acid to neutral). Maintain constant moisture but don't make their environment a soggy-bog. Almost any high-phosphorus fertilizer (10-20-20 or organic equivalent has worked well for us) can be used twice during the season: once thoroughly incorporated into the soil at planting time; again about mid-Summer. I prefer not to use proprietary liquid formulas because most of them include far too much nitrogen for my taste. Nitrogen, recall, stimulates foliage growth; what we're after with dahlias is flowers...lots of them. That's what phosphorus does best!

One of the tricks expert dahlia growers use to encourage huge flowers with long, straight stems, is to "dis-bud", (remove all lateral buds) allowing only the tallest, strongest, largest central bud to remain. Show competition is vigorous and enthusiastic. If you ever have an opportunity to visit flower displays and judging at county fairs, look for dahlias...they're hard to miss and truly spectacular!

Fall and Winter Care

Dahlias arise from fairly large, thickened roots called "tubers" which cannot survive a frozen New England winter in the ground. Actually, since the really important parts are below ground, a couple of early, nippy frosts shouldn't cause any damage to submerged tubers. Before the ground begins to freeze, however, they must be lifted and properly stored until they can be replanted the following season.

Before the onset of serious, sustained Fall frost, begin watching the plants for signs of tiring – they'll look for all the world like they wish the growing season would end! Leaves will droop and appear ragged, perhaps turning a little yellowish. Flowers will become "daisy-eyed" and the production of new flower buds will be slowed dramatically . Make sure you've correctly labeled every plant for color and height. If you don't, it's a sure bet you won't be able to remember by spring, when all you have in your hand is a cluster of tubers. The best type of labels are the ones with little copper wires for tying them on.

On average, here in the Northeast, early- to mid-October is about right for harvesting dahlia tubers. With a sharp pair of snips, cut the stems just above soil level...at a node. A node is like a joint where the plant stem is solid, not hollow as it is on either side of the joint. If you cut in the hollow part, rain or dew will collect there and you may end up with a serious case of rot.

If it doesn't look like rain for a few days, leave the now-trimmed-back tubers in the ground for about a week to allow next-year's buds to form. Watch the forecast, however, and if rain's a-comin', dig them out fast.

We use a spading fork to loosen the soil all the way around the clump...about 8- or 10-inches out. Then gently lift and remove almost all of the soil. If your soil is healthy (rich and loose), it should just fall away. Poorer soil, like that found in too many of today's' gardens, will need to be carefully pried loose. Washing the tubers is not recommended because a light coating of soil will prevent dehydration, and wetting with water will lengthen the drying time.

Now spread the tubers out on the porch or garage floor where rain or frost won't be a problem, and allow them to air-dry for a couple of days. Once air-dried, place tubers, stems up and exposed, in boxes of dry peatmoss, perlite or sand, in a cool (40º to 45º F.), dry place where they'll not be exposed to wide fluctuations of temperature or humidity. Check them once a month or so, looking for soft spots or unpleasant odors. Remember: one bad apple spoils the barrel...so remove any sign of rot quickly. It's possible to remove any soft, rotten spots with a sharp, clean knife - normally causing no harm to the tuber. Dust knife-cuts with a commercial fungicide or sulfur to prevent further rot.

In the spring, after all danger of frost has passed, bring them out, give them one last look-see for rot, divide, if necessary, and re-plant into freshly-rebuilt soil.

Given a little care, you should have no trouble at all getting dahlia tubers through winter storage. And don't forget: they multiply handsomely...so there's plenty to share with a friend.

Our Local Weather

Find your State and County Cooperative Extension Office

Which Maine Hardiness Zone Do I Live In? (.pdf)