Plums: Calendar of Operations
for Home Gardeners
Pamela M. Geisel is UC Cooperative Extension Farm Advisor in Environmental Horticulture for
Fresno County; Carolyn L. Unruh is UCCE staff writer for Fresno County; and Paul Vossen is
UCCE Farm Advisor in Fruits, Vegetables, and Marketing for Sonoma and Marin Counties.
University of California
Agriculture and Natural Resources
Publication 7262
Plum and prune trees can grow in almost all climate
zones of California. There are European plums,
Japanese varieties, prunes, and cherry-plum or apricot-
plum interspecific hybrids. Many varieties require a
compatible pollenizer to ensure a good fruit set. Be sure
to determine this before you plant, since the pollenizer
variety will need to grow in close proximity or be graft-
ed into a branch of the tree you select. Most plums tend
to overbear, so you have to thin the fruit at the appro-
priate time in the growing season to produce quality
fruit and minimize limb breakage.
Winter Dormant Season
If San Jose scale, mites, or aphids have been
problems in previous growing seasons, spray the
tree with dormant oil late in the dormant season,
just prior to bud break. Oil sprays applied late in
the dormant season are least likely to cause shoot
injury. Be sure to provide thorough coverage of
the tree, including the trunk.
On mature trees, prune out any dead, diseased,
or broken branches. Thin branches out (usually
20 percent of last years growth) to allow good
light penetration into the tree. The purpose of
thinning cuts is to reduce crop load and increase
light penetration. Do not make heading cuts that
shorten the tips of the shoots.
Spring Bloom Season
Begin to fertilize large, mature trees when they
start to push foliage out in the spring. Use a high-
nitrogen fertilizer such as ammonium sulfate at 3
to 4 pounds per tree per year. Use lower rates for
very vigorous trees. Divide the total amount of
fertilizer into two portions to be applied in
spring and fall (April and early August).
Thin the fruit to about 4 to 6 inches apart when
they are 1/2 to 3/4 inch in diameter. If you want
to produce larger mature fruit, leave even fewer
immature fruit on the tree.
Plum aphids often cause curling of the young
leaves in spring, but you only need to control
them when 50 percent of the leaves are curled
and live aphids are present. Insecticides general-
ly are not required during the growing season. If
aphid populations become intolerable, however,
control them with insecticidal soap, summer
weight oil, or malathion.
To prevent sunburn injury and to reduce borer
infestations in very hot regions, paint the trunks
and lower branches of young trees with a 1:1
mixture of white interior latex paint and water.
Apply the paint mixture from 2 inches below the
soil line to 2 feet above. This generally is not a
problem if trees receive adequate irrigation dur-
ing the growing season.
Summer Growing Season
If you use drip irrigation, apply just the amount
of water needed to replace what is used by the
tree and lost from the soil through evaporation. If
you use sprinkler or flood irrigation, water about
every two to three weeks and provide enough
water to wet the soil to a depth of 18 to 24 inches.
Water requirements will vary depending on
environmental conditions and your soil type.
Fertilize young or newly planted fruit trees
monthly to encourage good strong growth. Use a
total of a 1/2 to 1 pound of ammonium sulfate
per tree during the growing season, dividing it
into three equal applications.
In late June or early July, remove the strong, vig-
orous shoots from the interior portion of the
canopy to improve light penetration and air cir-
culation in the trees interior.
Harvest the fruit when it is firm ripe. Fruit of
early varieties may need to be harvested over a
period of weeks, while that of later varieties can
usually be harvested all at once. Store the har-
vested fruit under refrigeration to maintain opti-
mum quality. Plums may also be sun-dried,
canned, or frozen for longer storage.
Autumn
Fertilize and irrigate trees just after harvest.
Apply 1 to 2 pounds of urea, 3 to 5 pounds
of ammonium sulfate, or 20 to 40 pounds of
manure per mature tree. Water well after
fertilizer application.
For More Information
Cousult these UC IPM Pest Notes online at
http://www.ipm.ucdavis.edu:
Aphids
Bordeaux Mixture
Leaf Curl
Scales
Spider Mites
Thrips
Youll also find detailed information on many aspects of
fruit and nut tree care in these titles and in other publi-
cations, slides sets, and videos from UC ANR:
California Master Gardener Handbook, publication 3382
Drip Irrigation in the Home Landscape, publication 21579
Pests of the Garden and Small Farm, publication 3332
Pruning Fruit and Nut Trees, publication 21171
Sweet Cherries for the Home Grounds, publication 2951
The UC Guide to Solving Garden and Landscape Prob-
lems, CD-ROM 3400
ORDERING
To order these products, visit our online catalog at
http://anrcatalog.ucdavis.edu. You can also place
orders by mail, phone, or fax, or request a printed cata-
log of publications, slide sets, and videos from
University of California
Agriculture and Natural Resources
Communication Services
6701 San Pablo Avenue, 2nd Floor
Oakland, California 94608-1239
Telephone: (800) 994-8849 or (510) 642-2431
FAX: (510) 643-5470
E-mail inquiries: danrcs@ucdavis.edu
For a free catalog of other publications, telephone
(800) 994-8849.
Visit the ANR Communication Services website at
http://anrcatalog.ucdavis.edu.
Publication 7262
© 2002 by the Regents of the University of California,
Division of Agriculture and Natural Resources.
All rights reserved.
2 Plums: Calendar of Operations for Home Gardeners
The University of California prohibits discrimination against or harassment of any person employed by or seeking employment
with the University on the basis of race, color, national origin, religion, sex, physical or mental disability, medical condition (can-
cer-related or genetic characteristics), ancestry, marital status, age, sexual orientation, citizenship, or status as a covered veteran
(special disabled veteran, Vietnam-era veteran or any other veteran who served on active duty during a war or in a campaign or
expedition for which a campaign badge has been authorized).
University Policy is intended to be consistent with the provisions of applicable State and Federal laws. Inquiries regarding the
Universitys nondiscrimination policies may be directed to the Affirmative Action/Staff Personnel Services Director, University of
California, Agriculture and Natural Resources, 300 Lakeside Drive, 6thFloor, Oakland, CA 94612-3550; 510-987-0096. For informa-
tion on how to obtain this publication and other ANR CS products, call 800-994-8849.
pr-1/02-JWC/CY
This publication has been anonymously peer reviewed for technical accuracy by University of
California scientists and other qualified professionals. This review process was managed by the
ANR Associate Editor for Pomology, Viticulture, and Subtropical Horticulture.
http://www.ipm.ucdavis.edu
mailto:danrcs@ucdavis.edu
http://anrcatalog.ucdavis.edu/
http://anrcatalog.ucdavis.edu/
WARNING ON THE USE OF CHEMICALS
Pesticides are poisonous. Always read and carefully follow all precautions and safety recommendations given on
the container label. Store all chemicals in their original labeled containers in a locked cabinet or shed, away from
foods or feeds, and out of the reach of children, unauthorized persons, pets, and livestock.
Confine pesticides to the property being treated. Avoid drift onto neighboring properties or gardens containing
fruits and/or vegetables ready to be picked.
Dispose of empty containers carefully. Follow label instructions for disposal. Never reuse the containers. Make
sure empty containers are not accessible to children or animals. Never dispose of containers where they may conta-
minate water supplies or natural waterways. Do not pour down sink or toilet. Consult your county agricultural
commissioner for correct ways of disposing of excess pesticides. Never burn pesticide containers.
PHYTOTOXICITY: Certain chemicals may cause plant injury if used at the wrong stage of plant development or
when temperatures are too high. Injury may also result from excessive amounts or the wrong formulation or from
mixing incompatible materials. Inert ingredients, such as wetters, spreaders, emulsifiers, diluents, and solvents,
can cause plant injury. Since formulations are often changed by manufacturers, it is possible that plant injury may
occur, even though no injury was noted in previous seasons.
Funding for this publication was made possible through a grant from the Elvenia J. Slosson Fund.
Plums: Calendar of Operations for Home Gardeners 3
Introduction
Winter Dormant Season
Spring Bloom Season
Summer Growing Season
Autumn
For More Information
WARNING ON THE USE OF CHEMICALS
Text1: ISBN 978-1-60107-053-1