Salt injury to ornamental shrubs and ground covers

Material Information

Salt injury to ornamental shrubs and ground covers
Series Title:
Home and garden bulletin ;
Francois, L. E
Place of Publication:
Washington, D.C
U.S. Dept. of Agriculture, Science and Education Administration
Publication Date:
Physical Description:
10 p. : col. ill. ; 24 cm.


Subjects / Keywords:
Ground cover plants -- United States ( lcsh )
Plants -- Effect of salt on ( lcsh )
Plants, Ornamental -- United States ( lcsh )
federal government publication ( marcgt )
non-fiction ( marcgt )


General Note:
Cover title.
General Note:
"Issued July 1980"--p. 2.
General Note:
Supersedes Reducing salt injury to ornamental shrubs in the west, Home and garden bulletin no. 95, issued May 1964.
Statement of Responsibility:
Leland E. Francois.

Record Information

Source Institution:
University of Florida
Rights Management:
This item is a work of the U.S. federal government and not subject to copyright pursuant to 17 U.S.C. §105.
Resource Identifier:
025913658 ( ALEPH )
AFX5483 ( NOTIS )
06683737 ( OCLC )


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Full Text
I. 77.'.3(

Salt Injury
to Ornamental Shrubs
and Ground Covers



3 How soils become saline
4 How salinity affects plants
6 Confirming salt injury
6 Plant selection is important
8 Reducing soil salinity
10 Important points to remember

Department publications contain public information. They are
not copyrighted and can be reproduced in whole or in part with
or without credit.

This bulletin supersedes Home and Garden Bulletin No. 95,
Reducing Salt Injury to Ornamental Shrubs in the West, May

Issued July 1980

For sale l), the Superintendent of Documents. U.S. Government Printing Office
Washington. D.C. 20402

Salt Injury

to Ornamental Shrubs

and Ground Covers

Leland E. Francois, SEA research agronomist1

If the ornamental shrubs around
your home exhibit leaf burn or fail to
grow normally despite an adequate
fertilizer and irrigation program, the
trouble may be due to salinity.
Salts of various kinds are found in
more soils and many are essential
to plant growth. However, some
soils contain an overabundance of
salts, which at high concentrations
can damage plants. Salts containing
sodium or chloride are particularly
injurious to ornamental shrubs.

How Soils Become

Salts are usually carried to the
soil in water. Water from rivers and
wells always contains some dissolved
salts. When water containing salts
is used for irrigating plants, the
water is taken up by the plants or
evaporates from the soil surface,
but most of the salt is left in the

1U.S. Salinity Laboratory, Riverside,
CA 92502

soil. Consequently, repeated light
watering without drainage can result
in considerable salt accumulation in
the soil around the roots. The saltier
the water, the faster salts accumu-
late in the soil.
Potted ornamentals may also be
afflicted by salt accumulation. If
only enough water is added to
replace that lost by plant use or
evaporation from the potting soil,
injurious concentrations of salt will
eventually occur.
Fertilizer, applied in amounts
greater than necessary to meet the
plant needs, can be as harmful as
sodium or chloride in the soil. Ade-
quate fertilization is necessary for
healthy shrub growth, but too much
causes more harm than good.
A high water table can also con-
tribute to excess salt in the root
zone. Evaporation of water from the
soil causes ground water to move
upward toward the surface, carrying
salts into the upper soil level.
In most of the United States, rain-
fall normally flushes excess salt out
of the root zone. In areas where the
rainfall is less than 20 inches, as in
many areas of the Western United
States, the excess salt is likely to
accumulate in damaging amounts
unless preventive measures are

How Salinity
Affects Plants

Salinity generally causes stunting
of plants. All plant parts-leaves,
stems, roots, and fruits-are smaller
than normal. The higher the salinity,
the more the plant is stunted.
Sodium and chloride, the two ele-
ments most common in saline soils,
may cause specific injury to certain
plants. The accumulation of these
elements in many ornamentals may
cause leaf burn, premature leaf
drop, or stem dieback. Salt-sensitive
plants may be killed. The color illus-
trations show symptoms typical of
sodium and chloride injury.
Salinity can injure ornamentals in-
directly. The weaker shrubs may be
less able to resist frost injury,
disease, or insect infestation.
Salt injury is generally more
severe during periods of hot, dry
weather. High temperatures intensify
leaf-burn injury caused by sodium or
chloride. Salt also is likely to ac-
cumulate in the soil at an increased
rate during hot weather. Water loss
from the soil-through plant use
and evaporation-is greatest then,
and ordinary watering may not be
heavy enough to leach salts from
the root zone.
Sprinkling with saline water dur-
ing the day time when evaporation
is high may be potentially more in-
jurious to ornamentals than surface
irrigation. Leaves wetted by the
sprinkling water absorb salts directly
through their surface and injury may
exceed that expected from soil
Frequent, light sprinklings with
saline irrigation water should be
avoided to prevent any buildup of
salt on the leaf surface. When foli-
age is sprayed, sufficient water
should be used to wash excess
salts from the leaves.

Other sources of salt spray
encountered in some areas include
salt drift from ocean surf and
deicing salts splattered on plants
along streets by automobiles.

Oriental arborvitae

Chinese holly

Leaf injury typical of sodium and
chloride accumulation.

Chinese hibiscus Rose


Pineapple guava

Confirming Salt Injury

If you suspect salt has injured
your shrubs, it is well to confirm the
cause of damage before beginning
to correct it. Leaf burn and stunting
are likely symptoms of a salinity
problem but they may also be
caused by drought.
To determine whether the damage
is caused by salinity, you may want
to have your soil and irrigation water
tested. Leaf samples may also need
to be tested at times to confirm a
salinity problem. Your county agri-
cultural agent or State Agricultural
Experiment Station can tell you
where to have these tests done.
Be sure that the soil sample taken
is representative of the soil mass in
which the roots are growing.

Common name

Samples from ridges or surface soil
where salts tend to accumulate may
not give a true representation of the
root area.

Plant Selection Is

Proper shrub selection can mean
the difference between success and
failure in landscaping when irri-
gating with saline water. The more
saline the irrigation water is, the
fewer the number of plants available
for selection. The following table
presents the salt tolerance of 41
shrubs, trees, and ground covers
tested at the U.S. Salinity Labora-
tory, Riverside, Calif.

Botanical name

High Tolerance
(Soil salinity no higher than 10 dS/m)

Croceum Iceplant
Purple Iceplant
Rosea Iceplant
VJhite Iceplant

Hymenocyclus croceus
Lampranthus products
Drosanihemum hispidum
Delosperma alba
Leucophyllum frutescens

Brush cherry Syzygium paniculatum
Bougain ,illea Bougainvillea spectabilis
i'aial plum Carissa grandiflora

Good Tolerance
(Soil salinity no higher than 8 dS/m)

Aleppo pine
European fan palm
Spindle tree
Blue dracaena
Weepring bottlebrush

Pmnus halepensis
Chamaerops humilis
Rosmarinus lockwoodii
Euonymus iaponica
Cordyline indivisa
Nerium oleander
Callistemon viminalis

Botanical name

Moderate Tolerance
(Soil salinity no higher than 5 to 6 dS/m)
Spreading juniper Juniperus chinensis
Pyracantha Pyracantha fortuneana
Thorny Elaeagnus Elaeagnus pungens
Oriental arborvitae Platycladus orientalis
Indian hawthorn Raphiolepis indica
Japanese black pine Pinus thunbergiana
Dodonaea Dodonaea viscosa
Xylosma Xylosma congestum
Japanese boxwood Buxus microphylla
Yellow sage Lantana camera
Glossy privet Ligustrum lucidum

Poor Tolerance
(Soil salinity no higher than 3 to 4 dS/m)

Compact strawberry tree
Chinese hibiscus
Heavenly bamboo
Japanese pittosporum
Algerian ivy

Arbutus unedo
Viburnum tinus
Hibiscus rosa-sinensis
Nandina domestic
Pittosporum tobira
Hedera canariensis

Very Poor Tolerance
(Soil salinity no higher than 2 dS/m)

Southern yew
Glossy abelia
Chinese holly
Pineapple guava
Oregon grape
Star jasmine
Pyrenees cotoneaster

Podocarpus macrophyllus
Abelia grandiflora
Photinia fraseri
Ilex cornuta
Feijoa sellowiana
Mahonia aquifolium
Trachelospermum jasminoides
Cotoneaster congestus

Common name

If the soil salinity exceeds the
limits given in the table, injury such'
as severe leaf drop, leaf burn, and/or
stunting will usually occur. Shrub
size makes little difference in ward-
ing off the injury.
Frost, heat, smog, and drought
tolerances should also be con-
sidered in selecting shrubs suitable
for your area. All of these environ-
mental factors can weaken the plant
and thus make it less able to with-
stand the detrimental effects of

Reducing Soil

To reduce soil salinity to a level
that your shrubs can tolerate, irri-
gate heavily. This will leach the ac-
cumulated salt down into the soil
below the root zone.
How heavily you irrigate will de-
pend upon how saline the soil is and
the depth of soil to be leached. If
you excavate a shallow basin
around the plant, and water the
plant within that basin, then you will
be able to judge the depth of the
water entering the root zone. In
general, for each foot of soil to be
6 inches of irrigation water will
leach out about one-half of the
12 inches of irrigation water will
leach out about four-fifths of
the salt.
24 inches of irrigation water will
leach out about nine-tenths of
the salt.

Remember though that the salinity
of the water in the soil can never be
less than the salinity of the irriga-
tion water.
After the soil salinity has been
reduced to a tolerable level for your
shrubs, continue to apply extra
water periodically when irrigating to
prevent a new buildup of salt. The
saltier the irrigation water and the
more salt sensitive the shrubs, the
greater is the amount of water
needed for irrigation. The following
table is a guide to the depth of
water required for maintaining a
safe level of soil salinity when 3
inches of water are lost by evapora-
tion and plant use. During hot sum-
mer months, this loss of water could
be expected every 10-12 days.
Care must be taken if heavy irriga-
tions are required, because too
much water can be as harmful to
the plant as the soil salinity. This is
particularly a problem with poorly
drained soils.
Poor drainage may sometimes be
caused by excess sodium which can
be removed by adding gypsum to
the soil. The soil-test report should
tell you if the soil contains too
much sodium and should give direc-
tions for correcting the problem.
If drainage is poor and excess
sodium is not the cause, installation
of drain tile may be necessary to
remove the salt-laden water from
beneath the root zone.


When growing Aleppo pine, soil
salinity should not exceed 8.0 dS/m,
according to the plant selection
table. The irrigation guide shows
that when irrigating with 1.0 dS/m
water, a total of 3.4 inches of water
must be applied to keep soil salinity

from exceeding 8.0 dS/m. If drip ir-
rigation is used, the same total
amount of water should be applied
over the 10- to 12-day period as
would be applied with a single flood
or sprinkler irrigation.

Important Points to Remember

* Confirm that the damage is from salinity and not from some other

* Select the right shrubs for your conditions.

* Leach with enough water periodically to prevent salt accumula-

* Plants can withstand salinity better when healthy-so fertilize
adequately and control insect pests.


3 1262 08850 4062


AGR 101

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