When we first started flower farming we thought winter would be a quiet time on the farm. Boy were we wrong!
Winter brings different tasks to the farm and is still quite busy although in a different way to when we are harvesting. We hope you find some of the tips we share helpful as your garden heads into winter.
In Ballarat, near where the farm is located, we have very distinct seasons. Late autumn is signaled by cold mornings and nights which cause the dahlias to go to seed more rapidly. These conditions cause flower quality to deteriorate quickly. Ideally we get a frost to send plants into dormancy in late April. If we get a hard frost the plants quickly turn black and we are able to start lifting them a week or two after frost.
Without a frost, we need to encourage dormancy, as the flowers are no longer harvestable.
To do this, we cut the plants back in thirds. First, we remove one third of the plant, wait one week and remove the next third, then wait another week before lifting the clumps. Cutting back the plants in stages encourages the plant to store energy in the tubers and prepare for dormancy.
In some parts of Australia it is not always necessary to dig up your dahlias. The main reason growers lift dahlias over winter is because of the increased risk of rot. When plants are no longer actively growing they go dormant. Tubers sitting dormant in cold, wet, ground have an increased chance of rot.
The farm is in a higher rainfall area with clay soils, consequently, we must lift our dahlias to avoid rot. For people in areas with lower rainfall and more sandy soils, dahlias can be left in the ground over winter.
We have two people go down a side of the row (each with a garden fork) lifting the clump together. We find this the most efficient and results in the least damage to clumps. We clean the loose dirt off and cut the stem back to the level of the tubers with loppers. If lifting clumps by yourself work slowly at the clump from a range of angles to minimise damage to the necks of the tubers.
After lifting the clumps of tubers, some farmers wash the soil off each clump. Despite clean tubers making dividing easier for beginners, we find that our tuber clumps store better with the soil as a protective layer. This helps to regulate the moisture of the clumps and it is more time and resource efficient than washing thousands of clumps. We simply scrape as much soil off the clumps as possible before putting them in crates. We find we can fit between 8 and 15 clumps in the crates we use.
NOTE: If you care about keeping varieties separate make sure you label them as you go as once they are lifted clumps look very similar and are impossible to tell apart. We use flagging tape to label the crates with the variety name.
Think of your dahlias like potatoes. Store them somewhere dark and cool but not at risk of freezing. We store undivided tuber clumps in crates with plenty of holes for ventilation. Preferably store clumps upside down so the hollow stems can drain if needed. This reduces the risk of rot. As we divide the clumps, we transfer the individual tubers into crates with either potting mix or sawdust.
If you're interested in more detailed information about growing and storing dahlias come to a winter workshop on the farm. There'll be hands on experience dividing dahlia clumps and plenty of opportunity to ask questions. It's a great time chatting with other dahlia enthusiasts as well. We would love to see you at a workshop!