Sudden drops from seasonably unusually warm weather is usually the biggest culprit in killing stem tissue, though severe low temperature freezes that affect stem and root survival is also a concern, but will simply just be “what we get”. Mulching can provide some moderation.
1) Tim Malinich poetically notes, there will be a “Loss of bloom for precocious bloomers”. For the sparsely flowering forsythia and the spotty blooms on rhododendron this will probably not even be noticeable in the spring. For the flowering cherry Dan noted, ornamental effect may indeed be a low show for spring.
2) For woody plants, the first test of the winter season will be how rapidly temperatures drop. Freezing of water into ice crystals for intercellular water even of dormant plants in unusually warm winter weather is always a concern. Concern may be multiplied this year due to the missing autumn, but the closer to normal 30s-40s in the day and 20s at night that during New Year’s week succeeded the 50s-60s of Christmas week was probably useful, providing more normal fall-ish weather. This issue will possibly repeat, and all depends on the January-March weather to come.
3) Tim Malinich also brings up an interesting dilemma with regard to weed control. He notes: “Winter annuals are loving this, lots of new germination and growth. Should be a bumper crop waiting for the landscapers in April. If it doesn’t slow down a bit they may be in seed before the crews can get them out next year meaning extra weed problems for the next couple seasons; plan on proper identification and precise timing of pre-emergent applications next spring AND fall. This goes for containers in production as well. Make sure beds are clean prior to mulching.”
4) Bee gardeners should note the words of Barb Bloetscher, from ODA, who notes that: “The honey bees have been active through fall and Nov-Dec. reports of them bringing in pollen during the first 2 weeks of December. With honey bees still active and very little nectar/ pollen available, they are eating stored pollen and honey which could deplete the amount of food necessary to survive winter and early spring. Researchers are seeing and predicting losses throughout the northeastern and northern U.S. “
5) On the turfgrass side, Joe Rimelspach (OSU-Plant Pathology) notes a similar concern with sudden temperature drops: “On the lawn side of the landscape, at this point we should not see any serious problems. One exception would be newly seeded lawns with juvenile seedling. These could be injured if there is a severe and sudden drop in temperatures or if covered in ice (standing water that freezes). Turf type Tall Fescues are usually the most vulnerable.” Hopefully, we shall enter more traditional winter weather with a continued moderation of the transition that occurred in late December.