CO-Horts Blog

Thursday, April 7, 2016

Spring has arrived to some parts of Colorado

Spring is upon us in the Grand Valley.  The apricots have been blooming for several weeks, peaches are just starting.  On the ornamental front, ornamental plums, pears and magnolias are in full bloom.  I have been fielding some calls about the fruit crop this year.  I don’t have a direct line to Mother Nature so we will need to wait and see what she has in store over the next month.  Typically our last “average” last frost around here is Mother’s Day in early May.  Last year however, we had a heavy frost two weeks after that average date.  Luckily, most crops were just thinned by the frost with a few exceptions in Delta County were we had a loss in apple crop in 2015.  So all we can do is keep our fingers crossed that Mother Nature won’t bring a killing frost. 

So what temperature produces a killing frost, well temperatures of 32 degrees F bring very little damage.  It is when we hit temperatures of 28 degrees that we see about 10% loss depending on the bloom and fruit development.  Temperatures down around 21 degrees bring closer to 90% loss.  The nights to be aware when this is there is the biggest chance of freeze is when it is clear and still.  When there is a chance of freeze, the fruit growers stay up all night and use big fans to pull warmer air down to the trees.   This can increase the temperature around the trees by several degrees.   For the homeowner that just has one to several trees, if the trees are not too big, throw a blanket on them overnight.  Don’t use plastic or something that warms up too fast as you can burn overheat the trees.  Another method some growers use is to use propane heaters in the orchard or they will run the sprinklers allowing water to freeze on the trees 
which forms a layer of insulating ice.  I would still recommend the blanket method to homeowners.

Other questions I have had recently is it too late to spray dormant oil on my fruit trees.  And the answer is yes here in the warm valley where buds have expanded or bloom has started.  For areas in Colorado that are still cooler and there is no bud expansion, go ahead and get the application of dormant oil on the trees.  It is a great way to get rid of overwintering eggs and insects on the trees.

Weeds are also rearing their ugly, or not so ugly heads.  Here is a blue mustard which is an annual mustard.  Mustards always have 4 pedals in a x shape.  Pull these before they go to seed.  For weed id and their specific controls, pull the entire plant and take it to your local Extension office or email them some good pictures.
Now is a great time to seed or plant those cold loving crops if you haven’t already done so. Things like lettuce, spinach, argula, cabbage, broccoli don’t mind the cold and will actually prefer to grow before it gets too hot.  For more questions on what to plant when, call your local Extension office and ask for a Master Gardener or an Agent.

 Hopefully Mother Nature will cooperate this year and bring us a fruitful 2016.  
Posted by Susan Carter, CSU Ext Tri River Area April 7, 2016

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