Growing Dahlias
Tips from our farm
WHEN TO PLANT
Dahlias are frost sensitive plants. Plant them out in spring after your last frost date, for me that means planting out the first week of November, or the week before if they don’t have shoots that are yet above the ground.
WHERE TO PLANT
Dahlia tubers like to be positioned where they will get lots of sun during the day with well-drained soil. You may need to prepare your soil by adding lime to adjust the pH and organic matter or fertilizer. We add lime and blood and bone to the soil about a month prior to planting.
SPACING
Here on our farm, we plant dahlias 40cm apart. Our drip tape has holes every 20cm so whilst I originally intended to plant 45cm apart it makes much more sense to plant them at every second drip space. I wouldn’t recommend planting them any closer than this as tubers can get tangled which makes digging them up more of a challenge.
Dahlia tubers should be planted on their sides, with the eye facing up about 10cm deep. We plant the ‘tail’ end slightly lower than the ‘eye’ end.
You don’t need to water dahlia tubers until there is growth visible above the ground, it has enough energy stored in the tuber for initial stages of growth. Watering too early can contribute to rot.
ONGOING CARE
Dahlias are thirsty plants and heavy feeders. We water deeply roughly twice a week, more often in hot weather and sometimes multiple times a day for short periods on VERY hot days. Dahlias are heavy feeders and we use 4 different custom fertiliser mixes here. We alternate 2 vegetative fertilisers weekly until flowering is getting closer & then we alternate another 2 flowering/fruiting fertilisers. These are custom made fertilisers with trace elements my husband Ethan mixes up, however using a general purpose fertiliser at home would work just fine. You just don’t want too high a nitrogen content during flowering as it encourages more leafy growth. Too much nitrogen can also mean that tubers are more prone to rotting over winter when you store them.
We don’t stake or support our dahlias in any way on our farm, however it is commonly recommended to either stake each individual plant or if you grow a lot of plants to put stakes around the edge of the garden bed and corral them in with twine. If you are doing this I’d recommend putting the stakes in before or at planting so that you don’t accidentally damage your plants by driving a stake through a tuber.
So you want more flowers? Of course! Here are some things I do to help…
PINCHING
In order to get more flowers it is recommended that you ‘pinch’ or ‘stop’ dahlias, this means cutting out the central growing tip of the plant so that the plant is forced to put growth into lateral development, resulting in longer stems and more flowers. Win win in my opinion! I usually pinch my plants back (either with my fingers, or a pair of snips) when they are about 20-30cm high back to 4 sets of leaves. If you forget and notice your plant has set a bud and is about to flower don’t worry, just make sure you cut a nice long stem on that first flower to encourage more lateral (sideways) growth.
DEADHEADING
Removing old or damaged flowers before the plant has a chance to start developing seed is another way to prolong flowering. Here on our farm we go through the patch every couple of days with a bucket and pick off all the old or damaged flowers from the plants and feed them to our sheep. They love them! The plant’s goal is to reproduce – one way it does this is by making seed. By removing the flowers before it has a chance to do this it sends a message to the plant to keep making more flowers.
If you’ve found this helpful then please share this so that others can learn from it too. If you have a question that I didn’t answer please send me an email at hello@florelie.com.au and let me know, chances are there are others who are wondering the exact same thing and I can include it in the FAQ section below for future readers.
Happy growing!
Lorelie
I live in Port Campbell and this is my first time planting dahlias I had no idea I should wait to plant them and planted them about a month ago :/ should I pull them out and wait till November or just let them grow.
Hi Milly,
The main reason to hold off is that planting too early while it is still cold and wet can result in tubers rotting because they are not actively growing yet. It’s getting pretty close to planting now so as long as the soil is well drained they should be fine. If you have a frost risk I’d recommend covering them though as that can damage the plants.
Lorelie
Awesome blog post Lorelie! Thanks for the tips. We actually planted ours every second dripper yesterday ( Robs suggestion ) so I will have to let him know he good good! haha x
That sounds great Katie. Can’t wait to see them in bloom. 🙂 Lorelie
Thank you for this very helpful info. It’s my first year at growing dahlias so your experiences are much appreciated. I noticed you don’t apply any mulch to your plants. Here in Toowoomba, we are still experiencing below average rainfall so organic mulch in the garden is a must for moisture retention. Do you not need to use mulch in your growing climate?
Hi Rose, Thanks for letting me know you’ve found the blog helpful. No we don’t mulch out plants. Mulching can help with moisture conservation but also encourages pests such as slugs, snails and earwigs. We are in a cooler part of Vic so prefer not to have the pests and don’t have as much need for mulch as those growing in warmer climates. We do mulch other crops but have decided it works better for us not to mulch with our dahlias because of the pest pressure. 🙂
Lorelie
Hi Lorelie,
Are you open to the public to visit and buy tubers? I live in Portland
Thanks Ros
Hi Ros. No the farm is not open to the public. Tubers can be ordered through the website for farm pick up though and we do occasionally run on-farm workshops. Lorelie
Is August too early to plant tubers in Parramatta NSW, we do not get frost here
Hi Brian,
If you don’t get frost and the weather is starting to warm up then you may be ok. The risk of planting earlier is that tubers may rot if they are cold and wet. I’d see what others in your area who are experienced with dahlias in your climate are doing.
Lorelie
Very helpful and useful information Lorelie, especially tip pruning to encourage more flowers.
Thanks Wendy! Glad you found it helpful.
Lorelie
Great information very helpful and explained clearly. I’m looking forward to planting my first 2 tubers after next week and giving them a crack for blooms in my home.
Do dahlias grow in Brisbane QLD climates??
Thanks Rozzy, yes many QLD gardeners grow dahlias. Dahlias can often be planted earlier where it is warm because there is no frost. The QLD dahlia society has some great information so look them up for more local advice. 🙂 Lorelie