Field Notes/Weather

Reference Date

Reference dates recorded are a statewide and varietal-wide average and should be calculated in your area to be more precise. Reference date is considered to be that date when 80 percent of the fruits sliced have hardened pits at the very tip plus 10 days.

Reference Date Sizing Trends

Modesto | KingsburgYuba City | Reference Date Timing

 

Fruit Size Ranges (mm)

Poor

Fair

Good

Excellent

Reference Date 32 or less 33-34 35-37 38 and over
RD & 5 Days 34 or less 35-36 37-39 40 and over

Full Bloom

Full bloom is considered to be that stage of bloom where a few petals have begun to fall. Some years the bloom is sharp and easy to define whereas in borderline chilling years the bloom can be rather straggly.

Effects of Soil Conditions in Frost Protection

Soil conditions make a great deal of difference in frost protection. Heat is absorbed by the soil during the day and released to warm the blossoms at night and early in the morning. Maximum exposure of the soil to sunshine is necessary to provide optimum frost protection.

The following is a table of relative temperature differences as influenced by orchard floor conditions:

image19
  • Bare, firm, moistground……….. warmest
  • Shredded covercrop, moistground…..1/2º F colder
  • Low-growing covercrop……1º-3º F
    colder
  • Dry, firm ground……………….2º F colder
  • Freshly disked, fluffy ground…….2º F
    colder
  • High covercrop……….2º – 4º F colder
  • Where covercrop restricts airdrainage…..6º – 8º F colder

Winter Chilling

To adequately satisfy the chilling requirement for cling peaches (break the dormancy), approximately 800-1,000 total hours under 45ºF are needed. Chilling quality varies. The highest quality chilling for cling peaches would be in December-January temperatures of 28-34ºF at night and a daytime temperature in the 30s-40s. Warm, sunny days in January or December can cancel out the benefits of optimum low temperature chilling. Such years with intermittent warm weather during the chilling period are indicated in the accompanying table.

Year Chilling
Hours
Full
Bloom
Ref.
Date
Full Bloom
to R. D.
2017 874 3-10 5-15 66 days
2016 796 2-27 5-7 70 days
2015 537 3-7 5-8 62 days
2014 957 3-9 5-12 64 days
2013 1,185 3-13 5-14 62 days
2012 1,118 3-8 5-24 77 days
2011 1,239 3-12 5-24 73 days
2010 959 3-9 5-25 77 days
2009 1,212 3-15 5-23 69 days
2008 1,093 3-10 5-22 72 days
2007 1,084 3-9 5-16 68 days
2006 807 3-14 5-27 74 days
2005 988 3-3 5-16 74 days
2004 825 3-9 5-11 63 days
2003 788 3-9 5-23 75 days
2002 801 3-10 5-20 71 days
2001 1,311 3-11 5-18 68 days
2000 769 3-14 5-17 64 days
1999 1,197 3-15 6-1 78 days
1998 1,586 3-14 5-26 73 days
1997 1,309 3-8 5-12 65 days
1996 703* 3-14 5-19 66 days
1995 1,108 2-27** 5-24 86 days
1994 1,050 3-10 5-19 70 days