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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 year’s 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 tree’s 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


You’ll 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

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University Policy is intended to be consistent with the provisions of applicable State and Federal laws. Inquiries regarding the

University’s 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

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