At our May General Meeting, we were given a presentation on planting dahlias by John Kooiman and Larry Bagge who shared their methods and expertise. Here are some notes and takeaways from the presentation.
Many growers start their tubers indoors before planting them in the ground. This allows you to know what you have growing before dropping your tubers in the ground. Tubers can be placed in pots or trays with potting soil with the eye(s) pointed up. Water your tubers when sprouts are above the soil and don’t allow the soil to become saturated which will cause tubers to rot.
Do not plant your tubers until ground temps have reached 60 degrees. In general, it is safe to plant your dahlias when you plant your vegetable garden. Cool weather and rain will cause tubers to rot in the ground.
When planning the layout of your dahlia garden, keep in mind each plant will need a minimum distance of 2 feet of space between each plant. This allows for air circulation, ease of access to work on the plant, and prevent the plants from fighting for growing space.
Both John and Larry use no-till or low till methods on their established gardens. Tilling can cause compaction of the soil by destroying the soil structure and disrupting the natural microbial ecosystem of the soil. However, both of them make sure to add lots of organic matter to their garden beds by top-dressing or by light/shallow cultivation of the soil.
Be sure to water your plants before planting them out in the garden. Dig a hole about 6 inches deep and large enough to fit the root system. At this time you should add a slow release (granular) fertilizer/amendment to the planting hole. Some growers use bone meal, earthworm castings, or a bulb and bloom fertilizer. Mix the fertilizer lightly with some of the soil and place your tuber in the hole.
Some growers will plant their tubers horizontally in the ground and some will angle the tuber in the hole with the root system resting at a lower point than the shoot.
Plant your tuber so that the sprouts are oriented South and the tuber and root system are oriented North.
There are many different ways growers support their dahlias. However, be sure to always place your support system at the time of planting to prevent accidentally piercing the tuber or its root system. The method you choose to use all depends on the number of plants you have, the time you want to spend on your plants, and what works for your budget. John discussed his method of staking his plants in conjunction with a heavy duty tomato cage. This method reduces the amount of tying needed for his numerous plants. The stake allows him to tie up his plants when they reach above the tomato cage.
When choosing your materials for supporting your plants, be sure to use sturdy materials. Rebar is a top choice for staking dahlia growers. Rebar is cost-effective, sturdy, and lasts for several decades (unless you live by an ocean).
Protect your young sprouts from rabbits and squirrels. These garden pests love the tender young shoots. Many growers buy rolls of chicken wire and create “cages” or cloches until plants are more mature.