Digging, dividing and storing dahlia tubers is a huge part of life on the farm. We spend far more time doing these jobs than actually picking the flowers. It certainly requires some practice so read on for our tips!
We have found that the most efficient way of lifting clumps is with a garden fork. For small clumps, we lift them with one fork and the larger clumps we lift with two forks - one on each side. This limits damage to the tubers - especially at the fragile 'necks' of the tubers
Many people wash their clumps before storing, however, we don't. It is too time and resource consuming to make it viable on our scale. Washing can make it easier to see the eyes when you are learning to divide so could be an option for you.
We simply scrape as much soil off each clump as we can in the paddock and store about 8-10 clumps per plastic crate.
You can store clumps whole for many months. We recommend storing them upside down so that the stalk can drain of water. This reduces the chance of rot. You will need to cover the clumps with potting mix when they are dry (regardless of if you've washed them or not). Make sure not to cover them if they are still damp as this could lead to rot.
When to divide
If you are new to growing dahlias we would recommend waiting until spring to divide. In spring when the dahlias start to wake up again ready for planting, the eyes will start to sprout and it is much easier to divide.
At Florelie we start to divide our clumps after we finish lifting them from the ground. We usually start in early June and continue dividing until the end of August. We put all the tubers that have eyes at the time of dividing in a labelled crate and set aside any that don't appear to have eyes to check again in spring - I'm still surprised at how many start to shoot once the weather warms!
What does a tuber need to be viable? It needs to have a body, an intact neck and an eye.
So let's look at the anatomy of a dahlia tuber and clump. When you dig up a clump you will notice that the individual tubers are all connected to each other through a central point that grew into the stalk. Sometimes a clump will have more than one stalk. The eyes grow at the crown of the clump - the part where the old stalk attaches to each tuber. They will never grow anywhere else.
The neck is usually thinner than the body and nearer to the central stalk, the tuber then widens into the body. At the end of the body you can often find the root or 'tail'. You don't need the tail for the plant to grow so we cut these off for ease of storage, shipping and planting. Cutting off the tail also allows you to check for any hidden rot that may be in the tuber but not at first apparent.
Here on our farm we do not sell mother tubers and usually do not replant the mother tubers ourselves.
So what is a mother tuber and why don't we plant mother tubers?
The mother tuber is the original tuber that you planted at the beginning of the season. This tuber will have grown over the course of the season and you will have dug up a clump of tubers at the end of the season. Being the first tuber you planted it will be the oldest tuber in the clump. You can usually identify it as the oldest - it's also often the biggest, hairiest, sometimes even the wrinkliest tuber!
Mother tubers are prone to rotting even if it looks ok on the outside. When we first started growing dahlias we didn't realise that there was any difference between dahlia tubers within a clump and after dividing each year just planted them all. We were disappointed to find that they often rotted or didn't produce any tubers the next year.
Personally we haven't noticed an obvious difference with the productivity of plants as far as flowering so for varieties that we don't have a lot of tubers of and want more flowers, we will on the rare occasion, plant a mother tuber.
Just a note that sometimes there is more than one mother tuber! This is dependent upon how many tubers you plant the first year, so if you plant 2 tubers connected together then you can expect to have 2 mother tubers when you dig up that clump. If you plant a small chunk (which is absolutely ok if you aren't confident in dividing smaller!) then you will have many mother tubers.
We recommend planting single tubers only each season so that you only get 1 mother tuber each year.
There are some examples of mother tubers below. You can see that they all have a number of roots forming on the 'tail' end and some of them have vestigial tubers on them too - more on those below.
So what is a vestigial tuber and why don't you want to keep them?
Vestigial tubers are the tubers which grow off the sides of other tubers. They do not have eyes and will never grow eyes, so they are not viable if you plant them by themselves. We cut these off the good tubers we are storing because they will often break and because we prefer a smaller, neater tuber for packaging and for planting.
When you are dividing, you'll end up with a huge range of different sized tubers from one clump. We aim for AAA battery sized or larger - if you see smaller tubers than this with eyes, leave them in a chunk of two or three. Remember, even tiny tubers will grow into full sized plants.
For our tips on storage and more detailed information on tubers, read this blog post.
The photo above shows some of the waste tubers we feed to the sheep after dividing. It's a messy job and many tubers don't survive. We get anywhere from 2 to 15 viable tubers off a clump.
If you've found this information helpful then please share this so that others can learn from it too. If you have a question that we didn't answer please send us an email at email@example.com and let us know, chances are there are others who are wondering the exact same thing and we can include it in the FAQ section below for future readers.
Frequently asked questions:
- Can I store my dahlia clumps whole?
Yes. I would recommend dividing at some point before replanting though.
- I'm a home gardener. Can I plant my mother tubers?
Yes. Absolutely. Be prepared that some may rot and if they don't they may not produce a large clump but the flowers will still be good!
- Do I need to dig my dahlias up every year?
No. In Australia you can leave them in the ground provided it is well draining soil and not at risk of freezing. I'd recommend that you dig and divide every second year if possible though.
If you're in a wet climate with high rainfall and soil is not well draining then digging is recommended as they may rot.