Digging into the Dahlia Numbers, Again
I know you guys are here on the blog to see dope pictures of spreadsheets and dirty dahlia dividing, so I thought, well, gotta give the people what they want!
How do you keep track of your dahlia tubers at dividing time? Do you log how many tubers each clump produces, or do you not care that much?
Back in 2020, I shared the numbers from our dahlia dig and divide, including staff time spent dividing and a brief cost-benefit analysis. This year, I don’t have staff time written down, but I thought I’d share the way we keep track of our tubers and clumps while dividing, and also give an analysis of best and worst tuber producers.
The perks of getting COVID and having to divide tubers in quarantine. This is my cutie, Frankie (aka Francesca, Frank & Beans, or MuShu Pork).
I use a simple paper sheet to track what variety of dahlia we are dividing, how many clumps we have, and when we’ve finished dividing, we count the number of tubers we cut before we pack them away. After we’ve used a sheet, I take it home to the computer or my phone and enter it into a Google spreadsheet. I use the spreadsheet to tell me about the tuber production capacity of each variety, and to help me know how many tubers I have to sell after reserving for my own stock. I can also estimate my potential income from tubers.
The sheet we use to keep track of clumps & tubers. You can click it to download the PDF.
The sheet in action. Using pencil helps keep things neat and the lines won’t bleed.
Quick Takeaway Numbers
Wyn’s NEW Pastel ⇨ Highest producer at 13.8 tubers/clump
Maarn ⇨ Runner up at 10.9 tubers/clump
Purple Flame ⇨ Lowest producer at 2.29 tubers/clump
Myrthe ⇨ Runner up at 2.93 tubers/clump
6.37 ⇨ Average tubers per clump across all varieties
944 ⇨ Highest stock of one variety, for Blizzard
10,853 ⇨ Total tubers in storage
$43,966 ⇨ Total retail value of tubers, after reserving for field production, using an 80% survival factor, and offering discounts for lots of 5, 10 and 20 tubers.
$52,323 ⇨ Total retail value of tubers, with above adjustments, but selling all tubers individually
Very interesting numbers this year and I certainly wasn’t expecting to see Wyn’s NEW Pastel at the top of the production list. What I did notice this year was that there was somewhat of an inverse relationship between tuber production and flower production. Myrthe, for example, was very floriferous for us, but you can see it was at the bottom of the list. Café Au Lait, too, can sometimes be a great tuber producer, but was also low on the list this year, at somewhere around 3 tubers per clump. I am curious how the plants decide to produce tubers vs. flowers, and if there is some kind of nutritional or weather-related association. My average tuber production this year was lower than it has been in the past, and I think this could be due to the low available nitrogen in our soil.
But how did I get those numbers in the first place? Below, I share some screenshots of my spreadsheet that helps me calculate all these things, and the questions I was trying to answer. Most of it is basic arithmetic, but the spreadsheet does all that repetition for me and then sorts the data so I can compare between varieties and different sales scenarios.
If you’d like to download and use the spreadsheet I created, you can do that below.
Just make a copy and you can play to your heart’s content!
How Many Tubers Can I Sell?
This portion of the spreadsheet is sorted by tuber production, which I got by dividing the number of tubers by the number of clumps for each variety. The “Remaining” column shows how many tubers I can expect to sell. It is based on my “survival rate” of 80%, and on the number of tubers I want to keep for my own production (“Keep” column). You can adjust this rate according to how many tubers usually shrivel or rot in storage in your method. This is a low number for me - I often get 90% survival or more, but I’ve found that with new staff who haven’t spent thousands of hours dividing, tubers may survive, but may not have viable eyes.
How Many Beds Will I Plant Next Season?
This time, the sheet is sorted alphabetically by the variety name, but here I’m interested in the total line at the bottom. I can see I have 41 varieties in total, and that I’m keeping 2677 tubers for myself. This works out to more than 13 beds of dahlias. I plant dahlias in two rows per bed, 1 foot apart, so I can fit 200 tubers in each bed. I can play with my “Keep” numbers for each variety to make this work out to an approximately even number of beds, or to make my dahlia planting plan fit in the space I have available. I can also factor in any tubers I intend to purchase next season (Brown Sugar, I hope I get my hands on you this time!).
How Much Income Can I Expect From Tubers?
Above, you can see the somewhat complicated way I’ve chosen to sell tubers, and how I calculate potential income. Because I sell tubers individually and also in bulk lots of 5, 10, or 20, things get a bit more complex, but I like being able to offer this to folks who want more tubers and don’t want to pay $10 or $20 a pop. So the formula in column P helps me do that, by subtracting the number of tubers by lot size from my total for sale (“Remaining”). Then I can play around with the lot sizes to see what makes sense. You can see that for some varieties, I won’t offer every lot size, or will only offer it as an individual tuber. Obviously, if you’re only selling by individual tubers, you don’t need any of these columns, only the “Remaining” column.
A Quick Note on Storage
This year, we changed up our storage technique a bit, because we are dealing with larger volumes. In the past, I used recycled plastic shopping bags, but we’ve moved up to plastic crate liners, and now we’re storing one variety per crate, for the most part. I covet the micro-perforated plastic bags that my peony roots come in, but I have yet to find a good source for those. So we just open the top of the bag a bit to ensure there is some way for excess moisture to escape the bag. I’m sure there is a more appropriately sized bag, but right now we’re using 20”x 24”x 48” gusseted bags from Uline. These are about 4x as tall as we need, but there ya go.
We store our tubers in a slightly moistened 50/50 mixture of peat moss and wood shavings, which has been the best for us so far. This year, I also experimented with packing in vermiculite, but I don’t know if I’ll scale that up because the volume of material is so large and vermiculite can be expensive comparatively. Peat ain’t cheap either though.
I hope this all helps a bit. Please contact me if I can answer any questions.
Thank you for reading!
How we stored our tubers this year, packed into crates by variety with a 50/50 mix of peat & wood shavings.