How To Train Young Walnut Trees

Training young walnut trees occurs in the first 1 to 6 years in the life of an orchard. Traditionally it has been done using a modified central leader with a minimum pruning style; the basics are similar for standard spaced or hedgerow orchards. We believed for decades that if lateral bearing walnuts were not pruned, their growth would stall out from early cropping. Research conducted since 2004 investigating pruning versus non-pruning on young walnut tree growth and productivity however, has challenged that paradigm.

Results from trials on Howard and Chandler have shown that young walnuts do not need to be pruned in order to keep them growing or to produce adequate yields. In general, unpruned trees have produced higher early yields and equivalent yields in year 5 and beyond compared to minimally pruned trees.

With more knowledge comes more complexity. Growers now need to decide when trees are a year old (first dormant pruning), whether to stick with the modified central leader and train using minimum pruning or to not prune, which saves on labor and brush disposal. Growers interested in trying the unpruned method may want to start small and compare their results to the minimal pruning method to make sure it fits their management system.

If you start with minimum pruning, we recommend that you continue with the same method until the trees are mature. Changing midstream from pruning to no pruning may lead to limb breakage, especially if trees were heavily pruned, and this leads to lower early yields and is not recommended.

An unpruned tree on left (note short shoot growth on primary branches) and a minimum pruned tree on right (note secondary scaffold extension growth  from heading cuts) at the end of the third growing season.  (Photo Credit: Bruce Lampinen)
An unpruned tree on left (note short shoot growth on primary branches) and a minimum pruned tree on right (note secondary scaffold extension growth from heading cuts) at the end of the third growing season.
(Photo Credit: Bruce Lampinen)

Below are the main steps comparing training walnuts for years 1 to 3 using the modified central leader with the minimum pruning method to the unpruned training method. The assumption is you are using a standard-spaced orchard and differences for hedgerow systems are noted. Always remove suckers from the rootstock.

Modified Central Leader With Minimum Pruning Method
Pruning 1-year-old walnut trees:
• The shoot (leader) selected to be the trunk should have reached a height of at least 7 to 8 feet. Ten feet or more of growth is better (7 to 8 feet is sufficient for hedgerow orchards).
• Heading the leader at 8 feet will give more area for the scaffolds. The leader should not be headed any less than 6½ feet since the first primary scaffold should be at least 5½ to 6 feet above the ground so as not to interfere with equipment operation (for orchards, hedgerow head at 6 feet, and the first primary should be about 4 feet above ground). Make the heading cut into mature round wood.
• Any lateral shoots on the leader should be removed. One or two nonvigorous shoots arising below the leader can be stubbed to two to three buds to provide shade on the southwest side and aid caliper growth. They will be removed in the next dormant season.
• Primary buds above 5 feet from the ground that are necked should be rubbed off to the side so as not to damage the secondary bud. If left, necked buds form weak limb attachments that are subject to breakage. The secondary bud which is forced to grow will form a wide angle and develop a strong crotch.
• If the shoot selected to be the trunk has not reached sufficient height, cut it 3 to 6 buds above the point of origin and remove competing shoots. A stronger shoot can then be trained as the trunk over the summer.

Pruning 2-year-old standard-spaced walnut trees:
• The goal is to select four to six primary scaffolds arising from the trunk in years two and three. Select the central leader which is typically the topmost branch.
• As with the 1-year-old trees, the height of first primary scaffold should be 5.5 to 6 feet above ground.
• Select other primary scaffolds to form a spiral pattern around the trunk. Space them at least 8 inches apart. Primary scaffolds should never originate directly opposite each other to prevent the leader from getting ‘choked out’.
• Selected scaffolds should be angled about 45 degrees from the vertical. Limbs with narrower angles or bark inclusions are usually poorly attached and cannot support heavy crops. Branches with wider angles of attachment may fail to grow vigorously.
• For most lateral-bearing varieties, head all primary scaffolds to ¼ to ⅓ of current growth, depending on vigor and variety. Tulare are very vigorous and need only tipping or no heading of the scaffolds. The leader should be left the longest.
• Remove forked branches on chosen scaffolds to a single branch. Leave remaining unselected branches and small caliper wood unheaded to create early fruiting wood.

Pruning 2-year-old hedgerow walnut trees:
• Select a central leader and two to four side limbs oriented in opposite directions in the tree row.
• Remove branches below three feet that will interfere with shaking and flat limbs that grow out into the middles.
• Depending on variety and vigor, selected framework limbs should be headed or tipped (see above) and cut to an outside bud facing into the tree row. Other branches can be left unheaded to fruit early.

Pruning 3-year-old standard-spaced or hedgerow walnut trees (Photo- right tree):
• Choose the strongest, tallest scaffold for the leader and head ¼ to ⅓ of the current growth. Strong secondary scaffolds in a vertical position can be tipped or left unheaded. Head or tip one strong secondary scaffold on the canopy in each cardinal direction ¼ to ⅓ of the current growth.
• Forked branches can be left but twisted, rubbing or overlapping branches should be removed.

Unpruned Training Method
1-year-old walnut trees:
• The shoot (leader) selected to be the trunk should have reached a height of at least 7 to 8 feet. Ten feet or more of growth is better (7 to 8 feet is sufficient for hedgerow orchards).
• Leave the leader selected as the trunk unheaded.
• Remove lower limbs below 4 to 5 feet (3 to 4 feet for hedgerows).
• Place a long stake extension on existing stakes to support the unpruned leader.

2- and 3-year-old walnut trees:
• No pruning or heading unless lower branches need to be removed for reasons of safety or ease of maintenance and harvest.
• Note that unpruned walnuts tend to put on extension growth in alternate years. Individual shoots follow a pattern of extension growth, followed by side branching occurring on shoot with 5 to 8 inches growth on the end (Photo – left tree), followed by another year of extension growth.
• Unpruned trees tend to grow as a central leader with the primary branches naturally well-spaced along the trunk and at wide angles.

Topics: , ,

Leave a Reply

Nuts Stories
Nuts
July 7, 2017
Lab Opens to Test for Pistachio Problem
AgExperts Inc. is now testing for Rhodococcus bacteria, which has plagued growers for the past few years. Read More
Nuts
July 7, 2017
California Almond Crop Projected to Increase 5%
This year’s California almond crop is forecasted to exceed 2 billion pounds, according to the California Almond Objective Measurement Report Read More
Closeup of a managed bee hive next to a blueberry field
Citrus
June 28, 2017
Felony Charges in Beehive Thefts
The men accused of heading up an operation to steal and re-sell beehives, Pavel Tveretinov and Vitaliy Yeroshenko, 48, have Read More
Citrus
June 21, 2017
Storm Runoff May Recharge Aquifers and Your Crops
A new study hints that tapping into storm water during dry years does more than increase water table levels. Read More
honeybees
Fruits
June 6, 2017
Survey: Bee Loss Drops Last Season
Bee Informed Partnership says preliminary analysis of results show second-lowest loss rate recorded in last seven years. Read More
Nuts
June 3, 2017
Have Flooded Orchards? Keep an Eye out for Damage
While the damage from waterlogging or Phytophthora may not be immediately known, there are some warning signs to be on the lookout for. Read More
Managed bee hive boxes around a blueberry field
Nuts
May 25, 2017
Stolen Hives Recovered in Nearly $1M Heist
Man likely stole hives from across the state of California in the last three years. Read More
Nuts
May 16, 2017
Another Record California Almond Crop Forecast
Bearing acreage officially hits the million mark, though per-acre yields are off from 2016. Read More
Nuts
May 1, 2017
Startup Costs a Challenge to Pecan Growing
University of Georgia Cooperative Extension specialist says as pecan acres begin to increase, growers need to understand the return on investment is longer than other crops. Read More
Nuts
April 27, 2017
Keep an Eye Out for Phytophthora in Your Nut Orchard
After several years of drought conditions, increased water salinity, and a wet winter, your nut orchard may be more susceptible to root rot than you think. Read More
Citrus
April 26, 2017
Perdue Sworn in as Ag Secretary
USDA launches Twitter account to help promote the industry. Read More
GenNext Growers
April 22, 2017
Next Generation of Leaders Gets Yearlong Almond Immersion
Almond Leadership Program enters its ninth year with the 2017 class. Read More
Nuts
April 10, 2017
Study Shows No Harm in Wildflower Plantings Near Almond Orchards
While conventional wisdom may suggest having more than one forage opportunity may detract from bee activity, research shows planting wildflowers boosts bees interest. Read More
Crop Protection
March 31, 2017
New Product Offers 2-in-1 Insect and Disease Control for Specialty Crop Growers
Crossover Pro offers early protection from insects, powdery mildew, rust, and leaf blight. Read More
Nuts
March 30, 2017
Lichens Thrive in Your Orchard During a Wet Year
Above average rainfall has created the perfect environment for growth. Read More
The Latest
Citrus
July 23, 2017
USDA Invests $7.6 Million toward Benefic…
Projects to promote beneficial organisms as part of a pest control strategy. Read More
Fruits
July 14, 2017
Brown Marmorated Stink Bug Predator Egg …
Samuri wasp parasitized egg mass found in Southern New Jersey peach orchard. Read More
Citrus
July 10, 2017
Practical Solutions Are Bringing Precisi…
Growing the budding ag-tech sector to maturity likely will require a deeper meeting of the minds between technologists and agriculturists. Read More
Nuts
July 7, 2017
Lab Opens to Test for Pistachio Problem
AgExperts Inc. is now testing for Rhodococcus bacteria, which has plagued growers for the past few years. Read More
Nuts
July 7, 2017
California Almond Crop Projected to Incr…
This year’s California almond crop is forecasted to exceed 2 billion pounds, according to the California Almond Objective Measurement Report Read More
Citrus
June 28, 2017
Felony Charges in Beehive Thefts
The men accused of heading up an operation to steal and re-sell beehives, Pavel Tveretinov and Vitaliy Yeroshenko, 48, have Read More
Citrus
June 21, 2017
Storm Runoff May Recharge Aquifers and Y…
A new study hints that tapping into storm water during dry years does more than increase water table levels. Read More
Fruits
June 6, 2017
Survey: Bee Loss Drops Last Season
Bee Informed Partnership says preliminary analysis of results show second-lowest loss rate recorded in last seven years. Read More
Nuts
June 3, 2017
Have Flooded Orchards? Keep an Eye out f…
While the damage from waterlogging or Phytophthora may not be immediately known, there are some warning signs to be on the lookout for. Read More
Nuts
May 25, 2017
Stolen Hives Recovered in Nearly $1M Hei…
Man likely stole hives from across the state of California in the last three years. Read More
Nuts
May 16, 2017
Another Record California Almond Crop Fo…
Bearing acreage officially hits the million mark, though per-acre yields are off from 2016. Read More
Nuts
May 1, 2017
Startup Costs a Challenge to Pecan Growi…
University of Georgia Cooperative Extension specialist says as pecan acres begin to increase, growers need to understand the return on investment is longer than other crops. Read More
Nuts
April 27, 2017
Keep an Eye Out for Phytophthora in Your…
After several years of drought conditions, increased water salinity, and a wet winter, your nut orchard may be more susceptible to root rot than you think. Read More
Citrus
April 26, 2017
Perdue Sworn in as Ag Secretary
USDA launches Twitter account to help promote the industry. Read More
GenNext Growers
April 22, 2017
Next Generation of Leaders Gets Yearlong…
Almond Leadership Program enters its ninth year with the 2017 class. Read More
Nuts
April 10, 2017
Study Shows No Harm in Wildflower Planti…
While conventional wisdom may suggest having more than one forage opportunity may detract from bee activity, research shows planting wildflowers boosts bees interest. Read More
Crop Protection
March 31, 2017
New Product Offers 2-in-1 Insect and Dis…
Crossover Pro offers early protection from insects, powdery mildew, rust, and leaf blight. Read More
Nuts
March 30, 2017
Lichens Thrive in Your Orchard During a …
Above average rainfall has created the perfect environment for growth. Read More