Please note: Best practise when planting any tubers or cuttings is to quarantine your plants in individual pots for the first three years to ensure they are disease free. I did not do this.
If you are wanting to get the most bang for your buck
The easiest and most cost effective way of having as many plants as possible from a single tuber is to plant your tubers early in a small pot with a mix of potting mix and compost. You can find pots in the pot recycling bin at your local Mitre 10 or Bunnings.
Use a 50/50 blend of potting mix and compost and plant the tubers with the head and crown up and out of the soil. I put these pots on our back deck where they got plenty of sun but there was no risk of frost.
Once the tubers had more than three growing points I would carefully remove a growth point with at least three sets of leave, remove the bottom set of leaves, dip the bottom in rooting hormone and plant the cutting.
Humidity and moisture are essential for ensuring cuttings grow and while I got this right a couple of times, I got this very wrong a few times too. I used a plastic container with a lid and put about 1cm of water with seaweed in the bottom.
You need to put this somewhere warm but not in direct sunlight. I left mine on the outdoor table out of the sun and this was perfect - there was no way I was faffing around with a heat pad and we don't have a hot water cupboard.
Once the cuttings have rooted you can plant these out into your dahlia patch.
Planting directly into the garden
We are in the business of growing grass and practise regenerative agriculture (meaning we move cattle through different paddocks, giving the grass time to grow in behind them) so our soil is especially fertile.
Most people agree that you can start planting from Labour Weekend onwards, but it depends on the climate in your area. Mine didn't go into the ground until Christmas Eve - but I had pre-started my plants in small pots.
If you are planting into your garden you will need to make sure your soil is nice and healthy as well as free draining. You need a spot that's sheltered from the wind that gets a lot of sun - ideally against a fence so you can easily support your plants.
If the soil on your section isn't ideal for plants, you can build up the garden with some top soil, quality compost and apply a general fertiliser in the weeks before you plant. If you can get hold of some sheep poo this is ideal!
When planting tubers into the garden, lie them on their side with the eyes (or growth points) facing up. Don't panic if there are growth points all around the crown - they will find their way to the top.
Plant your tubers about 5cm under the ground and about 50cm apart. If you are going to stake your dahlia plants individually (manageable if you are only planting a few), add your stakes when you plant your tubers.
Most growers suggest to add mulch after you have planted and buried your tubers but I used sheep dags from our woolshed. Sheep dags are wool with bits of sheep poo attached and your local sheep farmer will be happy to give you some I'm sure.
I think this might have been an accidentally genius move because the goodies from the sheep poo leached into the soil as a natural fertiliser and the wool saved the young plants from slugs, snails and earwigs.
Once your dahlia plants start to grow
For best growth, when your dahlia plants have about four sets of leaves and are about 25cm tall, you need to "pinch out" your plants. This is essentially snapping off the top of the plant.
Here is a great video on how to pinch your dahlias (not my video):
You can actually turn the pieces that you pinch into cuttings and grow these if you are still feeling enthusiastic after your previous seedling saving and dahlia cuttings from above.
In the 2023/24 season I used Native Neem Natural Seaweed Tonic as an insect repellent and foliar fertiliser - I would use this earlier in the 2024/25 season as I ended up with a gnarly gnat infestation and then an Army Worm invasion.
Once your plants have leaves it is recommended that you give them a light watering a couple of times a week. Best practise is to use a slow drip system at the base of the plant, but due to afore mentioned low admin model this was not an option for me.
We were lucky to have sporadic rain here in the Waikato through Christmas and into the new year. When a week went by without rain I would give them a sprinkle with the hose late in the evening when there was no chance the sun would damage the leaves of the plants.
I was warned that this would cause an issue with powdery mildew - this is not something I had any issues with during the season but my plants have very good airflow due to the breezy nature of the spot.
Most dahlia pro's recommend you trim the bottom leaves of all of your plants to improve air flow - I had 200 plants and this definitely did not fit into my low admin model.
