The Great Dahlia Debate: Clumps vs. Single Tubers

If you are a member of the Facebook group Dahlia Growers, you may already have seen this fascinating conversation, sparked by a member asking how people felt about buying and growing tuber clumps, versus individually-separated tubers..

This was not a Q & A for beginners. It was a peer-to-peer exchange among active growers about how they handle dahlia tubers: whether to keep and plant whole clumps, or divide them into singles; how and where to store them; and what trade-offs they see in performance, disease, and convenience.

Most contributors were home gardeners or semi-serious hobbyists in the U S and Canada. A handful of voices joined in from the U K, Belgium, Australia, and a few other countries. The mix of climates—from Alaska to Florida, from the Pacific Northwest to interior Canada—shaped many of the opinions.

Only about a dozen people asked basic questions such as “Do I really need to dig them up?” or “What’s the plastic-wrap method?” The great majority were sharing their own practices and results. That made it a rich snapshot of the grower community: hundreds of observations, experiences, and sometimes contradictory conclusions.

A striking divide runs between countries and between types of growers.

In much of Europe, including the U K, it is still common to plant and re-plant whole clumps. Retail packages often contain several viable tubers, and many gardeners don’t divide them unless the clump has grown too large or they want to share pieces with a friend.

In the United States the default commercial practice is to sell single tubers. Sellers say this lets them stretch limited stock of popular varieties, ship more easily, and keep prices in line with customer expectations. For anyone selling, it also brings in more revenue per original plant. Several U S participants openly acknowledged that this custom is driven more by economics and logistics than by plant performance.

Hobby gardeners—especially those with room for storage bins or with mild winters—often prefer clumps. They dry out less, tend to sprout faster and more vigorously in spring, and give a bushier start. Show growers and cut-flower producers lean the other way, favoring singles or cuttings for their uniform, stake-friendly plants and predictable bloom timing.

Some European voices noted the price difference: what a U S gardener might pay for a single tuber would often buy a full clump in their market. That contrast underlined how traditions and market expectations influence what growers consider “normal.”

The way growers handle tubers often reflects storage options and climate as much as gardening philosophy.

In mild-winter zones such as the U S Pacific Northwest or parts of the U K, many gardeners leave clumps in the ground under mulch. Others dig them and store them whole in bins, crates, or even pots.

In cold regions—the U S upper Midwest, Canada, interior New England, Alaska—storage space and long winters push people toward dividing. A whole clump takes up far more room and may dry out or rot if kept under the wrong conditions.

Common storage approaches included:

• Cool rooms or basements: around 40–50 °F (4–10 °C) with moderate humidity; clumps often kept “dirt-on.”
  
  

• Bins or boxes with loose medium: peat, vermiculite, sawdust, or pine shavings; used for both clumps and singles.
  
  

• Plastic-wrap method: for well-dried singles, often in wine coolers at about 45 °F; saves space but prone to rot if wrapped damp or to shriveling if the air is too dry.
  
  

• Pots or grow bags: some people overwinter the plant in its pot, especially where storage or soil conditions are difficult.
  
  

Growers agreed that getting the temperature and humidity right matters more than the choice of medium.

Many gardeners reported that clumps wake up earlier and produce a fuller, bushier plant in the first weeks of growth. Multiple viable eyes push several stems at once, often leading to an earlier and heavier flush of blooms.

Singles can catch up as the season progresses, especially if started indoors or pinched to encourage branching. For some growers the difference between clumps and singles disappears by mid-summer. Others feel clumps simply outperform singles year after year in their climate.

Very old, undivided clumps sometimes decline. A few contributors said that dividing them every two or three years seemed to restore vigor and bloom size.

Growers who favor singles often cite more uniform stems for cutting, easier staking, and simpler spacing in production beds.

Several experienced voices, including one who grows many seedlings, warned that clumps can sometimes hide signs of crown or leafy gall, while singles make it easier to inspect the crown and discard suspect material. Imported, mass-market tubers were often mentioned as higher-risk and, in some cases, treated as annuals.

Show growers and some cut-flower producers favor rooted cuttings for their predictable single stems and bloom timing. A few contributors mentioned pot-tuber production as a bridge between cutting culture and clump re-planting.

A number of growers store or even overwinter dahlias in pots, sometimes “sinking” the pots into garden beds. Opinions differ on whether clumps or singles do better in containers, but many say success has more to do with pot size and moisture management than with the choice of clump or single.

A few broad patterns emerge:

• Climate and storage conditions often dictate practice more than philosophy.
  
  

• Growers focused on cut flowers or propagation favor singles and cuttings.
  
  

• Hobby growers with space and mild winters often keep clumps.
  
  

• There is no single “right” way; both approaches can succeed when matched to local conditions.
  
  

• The economics of the U S tuber market—higher prices per tuber and an emphasis on shipping singles—helps explain why Americans are more inclined to divide.
  
  

What made this discussion engaging was the variety of lived experience. People weren’t simply trading instructions; they were explaining why they chose their method and what trade-offs they accept—whether that’s maximizing stock, saving storage space, keeping things simple, or aiming for early and abundant blooms.

Taken as a whole, the thread highlights that dahlia growing is as much about adapting to local constraints and personal goals as it is about following a single recipe. It also shows how market habits and traditions can steer horticultural practice in ways that aren’t strictly biological.

For anyone who enjoys growing dahlias, the conversation offers both practical insights and a glimpse into the culture of the grower community.