Q. I just bought a dwarf ‘Algerian’ and dwarf ‘Dancy’ mandarin
orange. The Dancy is doing fine but the Algerian’s leaves are getting brown
spots and falling. Is this a pest or disease? I don’t want it to spread!
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| ‘Algerian’ mandarin (tangerine) with spots on its leaves. One person in Las Vegas growing citrus claims the secret to growing citrus here is soil drainage. |
A. Our humidity is so low that I doubt it’s a disease
problem. The reason for the difference in leaf brown spots could be its landscape location, adequate soil prep at the time of planting, or the genetics of the plant. The spots are most likely cultural,
management; something you have done, or should be doing. Since it happened
after transplanting, I’m guessing it has something to do with how it was
planted, where it was planted or how the tree was irrigated.
Citrus Origin
Both
trees grow in the subtropics to tropics so make sure the tree was planted with
a mixture of compost and soil in a planting hole about three feet wide and
about 12 to 18 inches deep. The additions of organics in the soil should darken
it. Cover this planting with a layer of woodchips to keep the wood chips rotting,
full of organics and moist between irrigations. Make sure it is staked after
planting in case there are strong winds.
Landscape Location
If
planting in full sun on the West or South side of a building and it’s showing
signs of sun or heat stress, consider shading the tree’s canopy for the first
year of growth. Shading doesn’t require shade cloth. It can be done with
anything that provides some late afternoon shade. It is probably a good idea to shade the plants from the afternoon sun the first year.
Cultural
Do not
water trees daily except immediately after planting. Daily irrigations are meant
only to settle the soil around the roots, not to give the tree a daily “sip” of
water. Make sure it’s staked during its first season of growth. During the hot
summer months, water as infrequently as every other day if two days of water is
applied all at once.
With a newly
planted 5-gallon fruit tree, the tree should receive 4 to 6 gallons of water
each time it’s watered. This water should be distributed through three , 2
gallon per hour emitters or four, 1 gallon per hour drip emitters under the
canopy of the tree at about a foot from the trunk. As the tree gets larger over
time, it needs more water applied over a lager area. Plan for it. Add
additional drip emitters (not extra minutes) further from the trunk under the
expanding canopy to give it this extra water. When the tree is fully grown at 20
to 25 feet, it should need about 30 gallons of water at each watering.
Plant
these trees at least three or four feet from hot walls and they should handle the
reflected high temperatures okay if the soil is amended and they are watered before
it gets hot. Fertilize the trees right after harvest with a citrus fertilizer. Prepare the soil with compost and make sure it has good drainage.
Dwarf Types
Dwarf versions are grafted onto different rootstocks than the standard sized trees. This will impart a slightly different flavor to the fruit. The
dwarf version of mandarin orange should get about 12 feet tall and 12 feet wide
if unpruned. ‘Dancy’ mandarin oranges (sometimes called tangerines) are the
most popular mandarin orange fruit in the world (sometimes called “cuties” in
the supermarket). ‘Algerian’ mandarin oranges are noted for their winter cold
hardiness.