CO-Horts Blog

Monday, March 29, 2021

Weather can be our Friend or Foe.


Color to come, hopefully.
Last October, Colorado saw some crazy weather with cold weather come in after really warm weather.  Several days in early October were in the 80’s.  First there was a big wind event.  Then temperatures hitting below normal around Oct 13th, hitting just above freezing, followed by temperatures as cold as 11 degrees F and ended toward the end of the month with a big snow storm.  Of course the moisture was needed and appreciated, but rain would have been better.  Yearly average temperatures in mid to late October in the Grand Junction area are 67 / 41 Degrees F.

Plum Tree, pre-pruning, L. Masters
Plants, like people, do not like quick change.  Many perennial plants like trees had not had the chance to appropriately harden off, or acclimate, so they were ready for winter.  There are still trees that still have their leaves and not the normal ones like Oak trees.  This is because the trees did not have time to form the hormone that creates the abscission layer, causing leaves to drop in fall.  I predict we will see samples of tree damage from the cold for months to come.

Our fruit tree growers and the CSU Western CO Research Center in Orchard Mesa was tracking how the fruit trees were acclimating, or in this cause the lack of acclimating.  Here is what David Sterle reported in early December from the Western CO Research Center: “We are seeing between 10 and 40% dead (peach) buds after the freeze depending on variety. The bigger worry is probably the shoot tissue, and an important thing about the shoots is that from the middle of the shoot to the base there is a lot less damage. The damage in the tip 1/3 of the shoot is about 3 times as common as on the base. So from that point on I will only be looking at buds from the basal half of the shoot, where there are more live buds. We are recommending spraying Captan / Topsin / lime sulfur if possible to prevent cytospora from getting into the damage shoot tissue.  The good news is this varied by location and peach variety and some trees did go on to acclimate as winter went on.  And of course last year we saw a late frost that impacted the number of peaches that were available.  So I predict peaches will be at a premium again this year.

Checking for life, WCRC

Many of the growers have seen twig death.  No studies have been done on the combination of the cold combined with the drought, but certainly the drought has not been helpful.  Many of the peach growers worked to prune out the dead.  Typically over 50 % of the tree is pruned to stimulate new growth for next year, so it just took some modifying to do more tip pruning to remove the obvious dead.  Pending not having any damaging spring frosts, we should still have a peach crop.  But the wine growers have not fared as well.  Many wine growers have moved to grafted Vitis vinifera varieties of grapes, native to the Mediterranean area, that are hardy against phylloxera, which is basically a root eating aphid that slowly kills the vines.  However, these grafted grape varieties are not as hard.  It is expected up to 100% of these winery hybrid grapes are gone.  And sweet cherries are a very similar story.  Several of the local sweet cherry growers had just recovered from drought damage on their fruit trees.  Drought stress can affect trees for several years.  Areas in Delta County have irrigation that is very dependent on natural precipitation levels.  Recent drought years they have seen no irrigation in late summer or fall.

drought and insect damage, S. Carter

In doing multiple orchard visits, many of the orchards have decided to wait on pruning the grapes and cherries to see if they sprout.  CSU Research specialist Horst Caspari did a session for grape growers on how to prune and what to look for the cold damage.  Many will be depending on the vines sprouting from the lower portion of the vine, or may be replanting and starting over.  Last summer the grape growers in the area had to deal with possible smoke taint from the local wildfires.  Combine that with a decrease in visits to tasting rooms, and it has been a very bad wine year.

So, appreciate your local fruit and wine producers as it has been a tough year for them beyond what the rest of us have experienced.  Colorado climate can be a challenge to grow plants in, but when we are successful nothing tastes better.

By Susan Carter, Extension Horticulture and Natural Resource Agent, Tri River Area

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