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 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.
Here on our farm, we plant dahlias at either 37 and 20cm apart. This works for us with the current tractor implements that we use and our irrigation system. Most dahlias sould be planted at around 40cm apart. We plant our Pom Pon cultivars at 20cm spacing, as well as cultivars that we know make grow small plants. The plants we grow from seed are also planted at 20cm spacing for the first two years as we don't require them growing to their full potential.
Dahlia tubers should be planted on their sides, with the eye facing up about 10cm deep.
You don’t need to water or fertilise dahlia tubers until there is growth visible above the ground, there is enough energy stored in the tuber for initial stages of growth. Watering too early can cause your tuber to rot instead of growing in some circumstances.
Dahlias will require adequate water through the growing season - they do not cope well in excessive heat and dry. We water deeply roughly twice a week, more often in hot weather.
It is recommended to fertilser your dahlias throughout the growing season, especially when you are lifting and dividing them each year.
On the farm, we fertilise much more than an home gardener would need to. We alternate 2 vegetative fertilisers weekly until the plant are close to flowering & alternate 2 flowering fertilisers.
The home gardener can simplify things by remembering to fertilizer a couple of times with a higher nitrogen fertiliser before flowering and then switch to a higher phosphorus fertiliser to apply a couple of times through flowering. It is good not to fertilise with too much nitrogen toward the end of the season as this might contribute to tubers not storing as well.
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, make sure to put the stakes in at planting so not to disturb the plants as the are growing.
So you want more flowers? Of course! Here are some things I do to help…
In order to get more flowers it is recommended that you ‘pinch’ dahlias, this means removing the central shoot of the plant so that the plant puts the growth into the side shoots, resulting in longer stems and more flowers. Win win in my opinion! We pinch the central shoot out when they are about 20-30cm high back to 4 sets of leaves by simply snapping the shoot with our fingers. 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.
Removing old or damaged flowers 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.
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