Dr. Chris Wein and Dr. Lily Calderwood of Cornell University shared tips on dahlia production at the 2017 New York State Cut Flower Growers Conference. They were followed by Tiny Hearts Farm, who shared their best practices. Here are our notes from the presentations.
From Dr. Wein and Dr. Calderwood:
- Dahlias generally like cool temps. They originated in the mountains of Mexico.
- They are hardy enough to over-winter in high tunnels in Ithaca, New York (zone 5)
- If propagating dahlias from cuttings, consider using a rooting medium, like the kind you can purchase from Oasis.
- Dahlias generally take 8 weeks from planting to flowering (2 weeks more if you are pinching them for more stems)
- Dahlias prefer sandy, loamy soil with high potassium and phosphorus and low nitrogen levels.
- You will want to put off mulching around your dahlias (if that is your preferred weed control method) until the stems have emerged from the tuber.
Dahlia pests: (unfortunately I know these too well!)
Potato Leafhopper: Scout for them by tapping dahlia leaves and stems. The tiny bugs will hop away. You may also be able to spot them on the underside of leaves. Potato leaf hoppers travel north with wind and rain storms in the summer time. They are stirred up when hay or weeds are cut on neighboring fields, and then they jump over to your crops. It is important to exclude them early with row cover or monitor plants closely. Leafhoppers cause "hopper burn", a yellowing and curling of the edges of dahlia leaves. You can spray for leaf hoppers (alternate use of Pyganic, Azaguard, and Mpede), but that practice can lead to later-season problems with spider mites.
Tarnished Plant Bug: Lower the risk of Tarnished Plant Bug problems by controlling the land around your crops. Keep weeds mowed and control them around dahlias. Natural insects like the Minute Pirate Bug can help control them. But- Minute Pirate Bugs will also control you! They are unaffected by bug spray and they tiny guys will nibble you, even though they aren't looking for your blood and spread no disease. They are attracted to light colors, rather than dark ones. I saw them often in our around dahlia buds - hopefully warding off the bad bugs. But I felt them, too. Here is an article about them.
Tiny Hearts Farm Dahlia Production Tips:
-Tiny Hearts Farm grows a full acre of dahlias, having upsized their production from an initial 100 to 5,000 dahlia plants last season. Their largest breakthrough seemed to be when they took the advice of neighboring potato farmers and started "treating their dahlias like potatoes."
-They borrowed potato hilling equipment and used it to plant and cover dahlia tubers in narrow, raised beds, just one plant wide. When the plants emerge, they are pinched down to 3 sets of leaves.
-Every 10 days, the dahlias are sprayed with certified organic products Pyganic or Mpede (in rotation) from early June to Mid-August to control pests-- like the potato leaf hoppers that hop right on over from the potato farm.
-Dahlias are harvested when they are 3/4 open into buckets of warm water. They rest the cut dahlias for a couple of hours in the shade before putting them in the cooler.
*Fun fact: Dahlias are edible - both the flowers and tubers. Tiny Hearts Farm says they are kind of like a cross between a jicama and a radish. Their special tip: the cactus-flowering varieties seem to be better for eating.