Citrus Pruning: How? (Fake, 2012)

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Citrus Pruning: How and What? by Cindy Fake, County Extension (UCCE), California

Text of Citrus Pruning: How? (Fake, 2012)

  • 1. Pruning Citrus How and What Cindy Fake University of California Cooperative Extension, Placer & Nevada Counties January 2012

2. 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 2 3. 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 3 4. How to Prune When cut too closely, wound includes trunk wood Do not leave long stubs +/- 1 cm above branch collar is sufficient 4 5. 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 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 5 6. 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 6 7. 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 7 8. 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 8 9. 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 9 10. 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 10 11. 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 11 12. Removing Watershoots 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. 12 13. 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 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 13 14. 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 14 15. 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 15 16. 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 16 17. 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 17 18. 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. 18 19. 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 19 20. 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 orchardhazard 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 20 21. How and what? Thank you! Cindy Fake University of California Cooperative Extension, Placer & Nevada Counties January 2012 21