This is the post-harvest time for Oregon Christmas tree producers and the best time for both soil sampling and petiole testing.
The ideal timing for petiole sampling Christmas trees in Oregon is right around the corner during the third week of February. This sampling time was recently established through research work conducted by a host of researchers at Oregon State University including John Hart, Chal Landgren, Rick Fletcher, Mike Bondi, Brad Withrow, and Gary Chastagner of WSU. Their publication, Christmas Tree Nutrient Management Guide (EM8856), was finalized and published in September of 2009 so this is very new information hot off the presses. EM8856 is a complete guide to nutrient level targets in the soil and how to interpret tissue nutrient levels as well as summarizing much of the research conducted in Christmas trees over the years.
Christmas tree ground often has a great deal of variability. From steep, rocky terrain, to rolling hills, to flat and sometimes wet, Christmas trees are grown everywhere in this state. With this lack of uniformity, Christmas tree ground is a prime candidate for grid sampling. We can adjust the grid size for smaller blocks so that we capture all the diversity of the landscape in a nice georeferenced and color coded map for each nutrient in the soil sample. You really can't change the physical variation in your field, but using this technology you can address the nutritional variation.
Here are a few more resource articles for your information:
Growing Christmas Trees in the PNW, 2003, OSU, UoID, WSU
Christmas Tree Producer Resources, OSU College of Forestry
Christmas Trees, OSU, Washington County Extension Service
Take some time to talk with your CPS fieldman about Christmas tree nutrient management now.