Hello, Thank you so much for reaching out! Also, thank you for your patience in my response! 

Double Freeze Events

We are receiving a lot of reports this spring and summer of branch dieback, leaf distortion, leaf and needle scorch on older leaves, and slow leaf emergence.  The damage is likely due to the combination of the sudden temperature plunge last October (where the temps went from daytime '40s and '50s to single digits within a day or two), and the freeze over the Easter weekend April 10-13. In October, plants hadn’t yet hardened off before winter, resulting in the scorch/burn symptoms, which were brought out with the April freeze event. In April, the tender young deciduous tree leaves that had emerged sufficiently were frozen, resulting in small, sometimes black, and distorted leaves.   Leaf buds that had not emerged yet were either delayed or were killed by the freeze.

Healthy trees have enough energy reserves to produce a second flush of leaves, although it may be thinner than the first.  Any needles or buds that were killed will not recover, but new growth will emerge and fill in the gaps over time.  Any buds or branch tips that were killed will not recover, but new growth will emerge and fill in the gaps over time.

To manage:

1. Management strategies at this point include appropriate watering, which means watering the root zone to a depth of 12-18 inches every couple of weeks when there hasn't been rain or snow. Hold off on fertilizing until the tree is fully leafed out again.
2. Check the new buds on conifers, which may not have been damaged: healthy ones will be plump and green if scratched, dead ones will be dry and brittle.  
3. Wait and watch for continued leaf & needle emergence over the next year; prune out dead branches after new growth has emerged. Over the next few seasons, tree growth will fill in any gaps left by pruning.
4. To help protect trees against future sudden temperature drops in fall, and over the winter, hand water monthly when there has not been precipitation and temps are above 40F. In anticipation of a temperature drop, a good soaking to get moisture down 12+ inches will help the tree protect itself. Add 3-4 inches of mulch (pine needles or shredded bark, keeping mulch 2-4 inches away from the trunk) under the tree out to the drip line to moderate moisture and temperature changes around the roots.

References:

• Spring Frosts and Snows https://planttalk.colostate.edu/topics/miscellaneous/2013-spring-frosts-snows/
• Will my Woody Plants Recover From Freeze Damage: https://extension.psu.edu/will-my-woody-plants-recover-from-freeze-damage
• CO State Forest Service  https://csfs.colostate.edu/2020/04/26/ponderosa-pines-spruce-may-exhibit-winter-burn-damage/
• Winter Browning of Evergreens  https://planttalk.colostate.edu/topics/weeds-cultural-problems/2114-winter-browning-evergreens/
• Environmental Disorders of Woody Plants (see drought and frost injury) https://extension.colostate.edu/docs/pubs/garden/02932.pdf
• Fall and Winter Watering https://extension.colostate.edu/docs/pubs/garden/07211.pdf
• For Freeze event history, see
• October 2019 http://coagmet.colostate.edu/cgi-bin/stationsum_results.pl?year=2019&month=10&station=jfn01&cgdd_start_month=03&cgdd_start_day=01&cgdd_end_month=09&cgdd_end_day=31&cgdd_upper=86&cgdd_lower=50.
• April 2020 http://coagmet.colostate.edu/cgi-bin/stationsum_results.pl?year=2020&month=04&station=jfn01&cgdd_start_month=03&cgdd_start_day=01&cgdd_end_month=09&cgdd_end_day=31&cgdd_upper=86&cgdd_lower=50