In most of North America, this is the planting month. Mother’s Day is a common benchmark, but my friends in the Adirondacks probably should hold off until the end of the month.
Here in Northern Virginia, my tubers are eyeing up and many have foliage. At the National Capital Dahlia Society (NCDS) meeting this week, there were rooted tubers 8 inches tall - ready to be topped. The major caution is the need to “harden off” the plants if you have started them inside. This means to close the pores on the leaves so outside weather conditions, heat and breeze, do not dry them out. View this video for some comments on hardening off plants.
One year we had a very late cold snap that froze some of the plants from tubers. Within two weeks new shoots appeared. If you are planting cuttings, you need to be more cautious. For seedlings and cuttings I will wait until the first week in June.
Time-release fertilizer should be spread at least two weeks before planting and scratched into the surface. There is general agreement that dahlias are surface feeders. Still, many internet sites recommend putting something in the planting hole below the tuber. If you choose to do this, be sure to create a buffer between the fertilizer and the tuber. Here's some info on planting in pots with fertilizer in the bottom of the planting hole.
Make a map or diagram of your dahlia plantings when you plant. Tags put out with the tubers occasionally disappear.
We generally direct this newsletter to the casual grower. As we approach 4,000 free subscribers, we agreed it would be informative to include links to the practices of the serious exhibitor. Look for this in future newsletters.
One last thought: dahlias grow like tomatoes.
Have a great gardening season,
Harry Rissetto
