1. By Annette Truong Love Apple Farms
Citrus Trees
By Annette Truong
Love Apple Farms

2. Agenda 9-10 Lecture 10-10:30 Planting outside 10:30-11 Tasting
Budding

3. 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

4. For Northern California
Citrus Basics
For Northern California

5. 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

6. 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.

7. Thorns! Citrus trees are thorny!
Australian citrus have smaller leaves and more bristly thorns

8. 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

9. 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)

10. 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

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

12. Nutrition Foliar as well as ground feeding Monthly feeding
Acid-loving fertilizer:
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

13. Micronutrients Probably in your soil
Potassium deficiency results in smaller fruit
There are a myriad of reasons why citrus leaves yellow!

14. 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)

15. 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

16. No Salt!
Citrus will NOT tolerate Boron or salty soil.

17. Temperature effects

18. 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

19. 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).

20. 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

21. Sugar Level Sugar level Acid & Sugar in balance == high flavor
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

22. …and there’s also bitterness
Grapefuits & pummelos will also not get very sweet in our area
takes months to sweeten up
Bitterness vs. sourness: Not the same thing
bitter & sour == cold climates
California grapefruit
bitter & sweeter == hot climates
Florida grapefruit

23. 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

24. 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

25. Problems

26. 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

27. Macronutrient deficiencies
Low Nitrogen = yellow leaves, pale & smooth fruit peel
Low Phosphorus = hollow core, thicker rind
Low Potassium = smaller fruit

28. Micronutrient deficiencies http://www. crec. ifas. ufl

29. 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

30. 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

31. 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

33. Irrigation Drip irrigation makes watering easy Mulching
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

34. End