Citrus%20Trees

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Citrus Trees

• By Annette Truong
• Love Apple Farms

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Agenda

• 9-10 Lecture
• 10-1030 Planting outside
• 1030-11 Tasting
• 11-12 Budding

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Background

• Volunteering at Gene Lesters citrus orchard for
  1.5 years.
• Gene grows over 200 varieties of citrus and
  provides his citrus to Manresa restaurant

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Citrus Basics

• For Northern California

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Classification (Wikipedia)

• Citrus is a common term and genus (Citrus)
  of flowering plants in the rue family, Rutaceae.
  Citrus is believed to have originated in the part
  of Southeast Asia bordered by Northeastern
  India, Myanmar (Burma) and the Yunnan province
  of China

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Characteristics

• Citrus trees are evergreen. The leaves look like
  those of deciduous trees but they dont fall off
  in the same way and the tree doesnt go dormant.

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Thorns!

• Citrus trees are thorny!
• Australian citrus have smaller leaves and more
  bristly thorns

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Fruiting times

• They bear fruit all year long, favoring late
  winter
• I dont really understand charts like this most
  orange trees will have some ripe fruit present
  all year long

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Climate

• Citrus grow well in subtropical climates
• They can even grow in deserts (Arizona)
• Drought tolerant (similar needs to cactus)
• Somewhat cold tolerant (can withstand some
  freezing)

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Fruit variability by location

• Variability among flavor and other fruit
  characteristics varies widely by climate
• The same tree will produce fruit that tastes
  different if grown in hotter or colder regions.
• San Jose vs Santa Cruz vs San Joaquin valley
  regional differences

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Basic conditions

• In general, citrus are heat-loving
• Southern exposure, full sun
• Well drained (sandy) soil
• Soil pH low (high acid) 6 or lower

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Nutrition

• Monthly feeding
• Acid-loving fertilizer 30-10-10
• Gene recommends Miracid but you can choose
  organic as long as it is high nitrogen
• Foliar as well as ground feeding
• Container-grown need special care with nutrition.
  Nitrogen deficiency is easy to get

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Micronutrients
Probably in your soil Potassium deficiency
results in smaller fruit There are a myriad of
reasons why citrus leaves yellow!
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Fertilizing (cont)

• Container fertilizing
• Much more important than in-ground
• The pot soil leeches out more quickly
• Once per month is ok, just never forget (more
  important)

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Soil pH nutrition uptake

• Lowering the pH of your soil will help your
  trees nutrition uptake
• Acid loving - pH test your soil yourself
• Most soil in this area is neutral.
• Sulfur, peat, iron sulfate will lower pH
• If your pH goes above 7 your tree will yellow and
  look sickly

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No Salt!
Citrus will NOT tolerate Boron or salty soil.
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Temperature effects
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Temperature vs Growth

• Growth happens above 55 degrees
• When the temperature drops below 55 consistently,
  you can stop fertilizing as the tree is not using
  it anyway

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Cold Hardiness

• (most hardy)
• Kumquat
• Satsuma
• Sweet Orange
• Navel Orange
• Mandarin
• Grapefruit
• Tangerine
• Tangelo
• Lemon
• Lime
• (least hardy)

Sustained lt28 degrees will cause damage, any
lower could kill the plant. Frost protection for
may be needed (mulch wrap).
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Acid Level

• Low temperature sour.
• Favors fruit that is attuned to high acid.
• Lemons from Florida will not have the same tangy
  sourness as those from Santa Barbara

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Sugar Level

• Sugar level
• High temperature sweet. Fruit will reach full
  sugar potential
• Grapefruit from Santa Barbara will not be as
  sweet as that grown in Florida

• Acid Sugar in balance high flavor
• High acid / low sugar sour flavor
• High sugar / no acid no flavor

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and theres also bitterness

• Grapefuits pummelos will also not get very
  sweet in our area
• takes 14-16 months to sweeten up
• Bitterness vs. sourness Not the same thing
• bitter sour cold climates
• California grapefruit
• bitter sweeter hot climates
• Florida grapefruit

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Color of blood oranges

• Blood oranges dont color up as well in cooler
  climates
• They color up extremely well at LindCove (UC
  Riverside)
• There is some combination of temperature and
  climate and ripening duration that needs to be
  met for coloration to occur

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Thick Rinds

• Grapefruits and pummelos will develop a thicker
  rind in a cooler climate
• Night time temperatures, plus overall 24 hour
  temperature average
• Also phosphorus deficiency

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Problems
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Most CommonProblems

• Nutrition deficiencies
• Insect damage (mainly snails and aphids)
• Gopher damage (roots)
• Not enough drainage (root rot)
• Fungus, bacteria
• Temperature (too cold or hot)
• Severe drought
• http//www.ipm.ucdavis.edu/PMG/C107/m107bpleaftwig
  dis.html

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Macronutrient deficiencies

• Low Nitrogen yellow leaves, pale smooth fruit
  peel
• Low Phosphorus hollow core, thicker rind
• Low Potassium smaller fruit

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Micronutrient deficiencies http//www.crec.ifas.uf
l.edu/extension/greening/ndccg.shtml
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Pollination

• For fruit set, pollination is required (bees or
  by hand)
• Self-pollination (same-variety) results in fewer
  seeds
• Pollen grain from same plant variety
• This is why orchards plant varieties in blocks
• The middle of the block will be essentially
  seedless
• Trees on the edges may have more seeds due to
  external pollen sources brought in
• Cross-pollination results in more seeds
• Seedless may become seedy
• There is some leeway in the variety itself

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Pruning

• Remove water sprouts
• If shaping remove no more than a third of the
  tree in one year
• Keep the aprons! Citrus will naturally form
  globe-shaped trees with branches to the ground.
  Essential in hot climates
• Can be trained and pruned decoratively

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Planting

• Well-drained (sandy) soil
• Start with some kind of loamy loose soil (top
  soil). Mix in organic matter and sand
• For pots, just use potting soil
• Mound first with sandy soil on top of the
  existing elevation (18 high, 36 diameter), with
  a flat top on the top of the cone with a bit of a
  dish so the water doesnt run out after the cone
  solidifies

Staking is not required
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Irrigation

• Drip irrigation makes watering easy
• 2-3 hours on mature trees, when the trees seem
  water stressed. Dont let them wilt too much.
  Non-water stressed leaves are shiny and flat.
  When they start to get dull and curl a bit, they
  are water stressed.
• In the summer, one deep watering every 3-4 weeks
• New trees every week or 2.
• Mulching
• Use wood chips, a few inches deep
• Shades the roots, helps retain moisture

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End