When you receive a tuber the first thing you should decide is when to plant. Everyone knows their area best but a good rule of thumb is to plant about the same time you would a tomato plant. Don’t know when that is? You are looking to avoid a frost after you see any growth. Some plants bloom early within 75 days, the average is 90 days and others are considered to be late bloomers at about 120 days.
Here are the important things to do before planting:
Plant in areas that are mostly sunny or in full sun. The only time that would vary is in hotter areas such as some southern states.
Work up your soil with some sort of mechanical tiller preferably. Soils vary from clay to very loamy but the one truth about them all is that you should add organic matter. If you have a compost pile, that would be a great additive. The things I would avoid would be commercial fertilizers that are too high in nitrogen. Also, avoid anything that would result in the soil having a high acidic level such as oak leaves or pine needles.
The planting depth is an area that varies. I have found that what works best for me is usually based on the tuber itself. I choose to plant the tuber at a depth of about four times the thickest part of the Dahlia. Keep in mind this is a general rule of thumb. The one area that may vary is if you have a tuber that is three inches thick … don’t plant it a foot deep. The Dahlia would most likely grow but it would take a little longer and be more difficult to dig up the next winter. Average planting depth is 6 to 8 inches.
Dig a hole about three inches deeper than you are planting and add a handful of bone meal in the hole. As with most tubers, bulbs, and a lot of veggies, this is a must. Fill the hole back in to proper planting depth. Bone meal stimulates root growth and will produce a healthier plant. Plant your tuber in a horizontal position with the eye facing up. Cover the tuber and wait.
This is important: DO NOT WATER! You will rot the tubers. The only time this would change is if you were planting late and it was much hotter weather or if you live in a drier southern state. Even then, let them settle in their new beds for a couple days before watering. Note that if you start your tubers in pots, you may need to add a ‘little’ water due to the fact that smaller contained areas may try out quicker, especially in hotter regions.