Transcript the Powerpoint.

Citrus Trees
By Annette Truong
Love Apple Farms
Agenda
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9-10
10-10:30
10:30-11
11-12
Lecture
Planting outside
Tasting
Budding
Background
• Volunteering at Gene
Lester’s citrus
orchard for 1.5
years.
• Gene grows over
200 varieties of
citrus and provides
his citrus to Manresa
restaurant
Citrus Basics
For Northern California
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
Characteristics
• Citrus trees are
evergreen. The
leaves look like
those of deciduous
trees but they
don’t fall off in the
same way and the
tree doesn’t go
dormant.
Thorns!
• Citrus trees are
thorny!
• Australian citrus
have smaller
leaves and more
bristly thorns
Fruiting times
• They bear fruit all
year long, favoring
late winter
• I don’t really
understand charts
like this: most
orange trees will
have some ripe fruit
present all year long
Climate
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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)
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
Basic conditions
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In general, citrus are heat-loving
Southern exposure, full sun
Well drained (sandy) soil
Soil pH: low (high acid) 6 or lower
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
Micronutrients
Probably in your soil
Potassium deficiency
results in smaller fruit
There are a myriad of
reasons why citrus
leaves yellow!
Fertilizing (con’t)
• 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)
Soil pH & nutrition uptake
• Lowering the pH of your soil will
help your tree’s 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
No Salt!
Citrus will NOT tolerate Boron or salty soil.
Temperature effects
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
Cold Hardiness
(most hardy)
Kumquat
Satsuma
Sweet Orange
Navel Orange
Mandarin
Grapefruit
Tangerine
Tangelo
Lemon
Lime
(least hardy)
Sustained <28 degrees will
cause damage, any lower could
kill the plant. Frost protection for
may be needed (mulch & wrap).
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
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
…and there’s 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
Color of blood oranges
• Blood oranges don’t “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
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
Problems
Most CommonProblems
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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
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http://www.ipm.ucdavis.edu/PMG/C107/m107bpleaftwigdis.html
Macronutrient deficiencies
• Low Nitrogen =
yellow leaves, pale
& smooth fruit peel
• Low Phosphorus =
hollow core,
thicker rind
• Low Potassium =
smaller fruit
Micronutrient deficiencies
http://www.crec.ifas.ufl.edu/extension/greening/ndccg.shtml
Pollination
• For fruit set, pollination is required (bees or by
hand)
• Self-pollination (same-variety) results in fewer
seeds
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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
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
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
doesn’t run out after the
cone solidifies
Staking is not required
Irrigation
• Drip irrigation makes watering easy
– 2-3 hours on mature trees, when the
trees seem water stressed. Don’t 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
End