Citrus Pruning by Cindy Fake, County Extension (UCCE), California

1. Pruning Mandarins
Cindy Fake
University of California Cooperative Extension,
Placer & Nevada Counties
January 2012

2. Why Prune Mandarins?
• Improve fruit quality & marketable yields by:
– Increasing light in the canopy
– Pruning out non-productive branches (gourmands)
– Reducing risk of soil borne pathogens affecting fruit
• Reduce costs by:
– Facilitating weeding, mowing, & mulching
– Reducing tree height (also injury risk)
• Improve tree health
• Reduce insect and disease problems

3. Essential Pruning Tools
• Secateurs or hand pruners
• Lemon clippers for harvesting
• Loppers for branches >½” diameter
(1.25 cm)
• Pruning saw

4. Pruning Tools for Larger Trees
• Pole pruner/saw
• Orchard ladder
• Chainsaw

5. Pruning Tool Care
• Tools need to be sharp &
clean
• Sterilizing pruners is not
necessary for most bacterial
and fungal diseases
• For vascular diseases and
those which form oozing
cankers, pruning shears can
transmit disease.

6. Sterilizing Pruning Tools
• Sterilization of pruners is important
in orchards with virus diseases or
wet cankers
• Sterilize with bleach
• Heat does not kill viruses

7. When to Prune?
• After freeze risk has
diminished
• Before summer heat
• February/March is optimal
• Pruning too early may stimulate growth flush, late
frost may then damage new growth
• Winter maintenance pruning should only be small
branches <0.5 cm

8. When to Prune…after freeze damage
• After freeze damage, do not
prune until the spring growth
flush shows you where the
damage is
• Pruning too early can cause
more damage
• If the freeze has damaged fruit,
however, remove as much of the
fruit as soon as possible to
prevent further injury

9. When to Prune…mitigate alternate bearing
• Alternate bearing = phenomenon
where a tree carries a very heavy
crop load one year and a very light
crop the next
• Heavy crop depletes tree’s resources
• Produces less new growth, so only
produces small amount of fruit
the next year
• Pruning can mitigate alternate
bearing – about 30% of difference
at best

10. When to Prune…after a light harvest
• Heavy pruning is done after the light
crop year
• Reduces bearing wood and potential
fruit load for the next “heavy” year
• Major branch pruning and canopy
thinning should occur at this time
• Prune heavily after a light year to:
– allow the tree to replenish its reserves
– reduce heavy crop so more moderate
crop in off year

11. How to Prune…
• Carefully!
• Citrus bark is thin and
easily damaged so avoid
nicks
• Make pruning cuts with the
blade toward the tree
• Cut cleanly and avoid
damaging remaining
branch

12. How to Prune…
• Do not cut branches flush
with trunk
• Preserve branch collar =
ridge in bark around base
of branch
• Branch collar contains cells
that make woundwood which
grows over a pruning cut
• Branch collar also makes compounds to
defend tree against decay
• Do not paint or tar wounds

13. How to Prune…
• When cut too closely,
wound includes trunk wood
• Do not leave long stubs –+/-
1 cm above branch collar is
sufficient

14. How to Prune…
• Citrus has brittle wood
• Use a three-cut system for
branches larger than 2.5 cm
• Prevents bark tearing or
damage to remaining branch
• 1st cut: 30 cm from branch union
• Cut 1/3 to ½ way through the branch from underneath
(undercut)
• 2nd : A few cm up, cut from above, removing the
branch. Make the final cut just above branch collar

15. How to Prune…
• If previously shaded branches are
exposed to sun, protect them from
sunburn
• Sunburn causes bark cracking and
cankers, which may kill the tree
• Paint exposed branches with
whitewash or 1:1 mixture of
interior latex paint and water

16. What to Prune?
• Best is to prune branches less than
5 cm in diameter
• Why? …because they are mostly
living tissue and can protect
themselves against decay better
than larger branches
• This means pruning regularly, not
leaving it until you need to take
out large branches

17. Types of Pruning: Topping
• Top young trees at planting,
esp. if they are tall and
spindly
• Promotes side shoots which
develop into a lower, fuller
canopy
• The shorter the tree, the
easier and more cost
effective the harvest

18. Types of Pruning: Shaping young trees
• Prune downward growing
shoots to allow upward
growing buds to become
dominant
• Cutting the shoot just above
an axillary bud pointing
upward will redirect growth
upward
• Helps shape the tree for
optimal future production

19. Maintenance Pruning
• Remove discolored, damaged,
or dead wood from trees as
necessary through the year
• Remove crossing branches or
branches that shade out
lower branches
• Remove branches infected with
citrus blast (Pseudomonas
syringae) when weather warms in
the spring

20. Suckering
• Remove shoots below the bud
union as soon as they appear
• They are growing from the
rootstock and will not be
productive
• For Trifoliate rootstocks,
(Poncirus trifoliata) the rootstock
thorns can be a hazard to workers
and may damage fruit

21. Removing Gourmands
• Long, thick, very vigorous
branches = water sprouts or
gourmands
• Grow very rapidly, using large
amounts of nutrients and water
• Typically remain vegetative for
multiple years
• Produce poor quality, large, rough
fruit, with dry segments
• Do not contribute to production, so
should be removed at the base.

22. Reducing Tree Height
• Without regular pruning, fruit
production is on top of the tree
• Increases harvest time and costs
• Cutting major branches back to the
base is too hard on tree
• Only ¼ to 1/3 of tree height should
be reduced at a time
• Leave a few branches with good
foliage to photosynthesize and draw
water through the plant

23. Canopy thinning
• Sunlight develops flavors and sugars
in the fruit
• A dense canopy prevents
sunlight from reaching fruit
• Thin canopy every 2-3 years
• Should see dappled sunlight beneath
tree at midday
• Thin out center branches
before they get large => increase
fruiting wood in the center

24. Canopy thinning
• To facilitate thinning,
divide trees into
quadrants based on
scaffold or primary
branches
• Assess what is best in
each quadrant
• Prune one section at a
time

25. Canopy rejuvenation
• This tree has too much trunk
and a very thin canopy, which
means yields are low
• Canopy needs to be brought
down so fruit is accessible
• Large branches with few
leaves and low bearing
potential need to be removed
to stimulate new growth in
center

26. Skirt Pruning
• Branches that hang to the ground
• “Skirts” impede weeding, and fertilizer or
compost application
• Allow ants to access trees
• With heavy fruit loads, branches bend and
fruit touches the ground
• Fruit may be contaminated by soil
borne pathogens
• May cause plant disease, e.g. Brown rot
• Also potential food safety risk
• Skirt trees 50-75 cm above ground

27. Pruning for Pest Management
• Soft-bodied, sucking insect pests
such as scale and mealy bugs thrive
in dense canopies
• They like high humidity and little
air movement
• The canopy protects pests from
predators and parasitoids
• Thinning the canopy often reduces
pest populations to the point that
insecticide sprays are unnecessary.

28. Pruning for Pest Management: Citrus Blast
• Pseudomonas syringae bacteria
cause disease
• Common where Satsumas grow
• Usually starts at the base of the
petiole on small shoot
• Can move into larger branches
• Can cause cankers which kill limbs
• Prune out damage each spring to
remove as much of the infection as
possible
• Cut 15 cm below visible infection

29. What to do with Prunings?
• Significant amount of green
material
• Could be returned to soil to the
benefit of trees
• Difficult to leave prunings lie in
orchard…hazard
• Burning loses all good benefits
• If prunings are not from diseased trees,
– Compost with cow or other manures
– Use compost as mulch along tree rows, under trees

30. Benefits of Pruning
• Improve quality through better flavor and color
• Increase yields
• Increase percentage of larger fruit
• As pesticides are restricted, need cultural practices to
manage pests
• Cut costs by reducing labor for harvesting, weeding,
and pesticide application

31. Benefits of Pruning
• Good Agricultural Practices
(GAPs) may open more markets
• BUT, each grower must weigh the
cost of pruning against the
increased revenue from higher
quality or higher yields
• Pruning must provide an
increased return to compensate
for the increased cost of
production

32. Questions?
Thank you!