Home Gardening Advice from the Help Desk of the
UC Master Gardener Program of Contra Costa County

Client's Request (from previous phone conversation):  I've just moved into my new house. There's a small “fruit tree orchard” in the back garden. I'm not acquainted with growing fruit trees, but my neighbor tells me that the previous owner pruned them this time of year. Can you give me some advice on what and where to prune the trees.

MGCC Help Desk Response:  Thank you for contacting the UC Master Gardener Program's Help Desk. 

In our earlier phone conversation this morning, I neglected to ask you about all the fruit trees you have to prune. I may have also led you astray suggesting that most fruit trees can be pruned this time of the year. Apricots cannot be pruned in winter, especially with frequent rains. They just won't tolerate the moisture of the season.

You may be interested in a free Master Gardener library talk about growing apples and pears on Feb. 28 at the Lafayette Library from 6-8 pm.  I am sure pruning will come up during that talk. To RSVP or to ask about upcoming talks contact higginssierra@gmail.com.

Since you are beginning on your newly acquired "home orchard" and you have several different types of fruit trees, below are a number of links from UC that you might consult for both general and specific information on tree pruning.

General and Specific Information for the Home Orchard, including pest control and pruning, please see: http://homeorchard.ucanr.edu/. This one reference will probably cover most of your concerns.

Figs:  hhttp://ipm.ucanr.edu/PMG/GARDEN/FRUIT/ENVIRON/figpruning.html

Cherries:  http://ipm.ucanr.edu/PMG/GARDEN/FRUIT/CULTURAL/cherpruning.html

Citrus:  http://ipm.ucanr.edu/PMG/GARDEN/FRUIT/CULTURAL/citruspruning.html

Tree Pruning:  http://ipm.ucanr.edu/PMG/GARDEN/PLANTS/CULTURAL/pruningtrees.html

Vine (e.g. grape) Pruning:  http://ipm.ucanr.edu/PMG/GARDEN/FRUIT/ENVIRON/trainprune.html

Good luck on your home orchard.

Thank you for contacting us. Let us know if we can be of further service.  

Help Desk of the UC Master Gardener Program of Contra Costa County

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Note: The  UC Master Gardeners Program of Contra Costa's Help Desk is available year-round to answer your gardening questions.  Except for a few holidays, we're open every week, Monday through Thursday for walk-ins from 9:00 am to Noon at 75 Santa Barbara Road, 2d Floor, Pleasant Hill, CA  94523. We can also be reached via telephone:  (925) 646-6586, email: ccmg@ucanr.edu, or on the web at http://ccmg.ucanr.edu/Ask_Us/ MGCC Blogs can be found at http://ccmg.ucanr.edu/HortCoCo/ You can also subscribe to the Blog  (http://ucanr.edu/blogs/CCMGBlog/). 

Client's Question: I apparently missed a recent program at MGCC's Our Garden on “Summer Fruit Tree Pruning”. Summer fruit tree pruning is a new concept to me. Can you please provide me with more information?

Help Desk Response:  Thank you for contacting the UC Master Gardener Program Help Desk with your question about summer fruit tree pruning. Sorry, you missed the Our Garden program on this subject. I hear it was excellent.

Post-harvest summer fruit tree pruning can have a beneficial effect on fruit trees that tend to grow too vigorously (e.g. apricots, cherries, plums). It also has the "benefit" of reducing the overall growth rate, if that's a concern. Summer pruning can also promote more blossoms the following spring.

In July and August, you can prune out excessively vigorous shoots that shade lower fruiting branches. Use thinning cuts (removing a branch entirely) rather than heading a branch (by cutting off a portion of it) so that you don't stimulate even more growth. You can also train young branches by bending and staking them to grow in the desired direction.

Cherries and Apricots are also typically pruned during the summer before the rain starts (hopefully)--rather than winter--to avoid a branch dieback disease called Eutypa, which can infect wounds made during wet weather.

Wait for winter dormant pruning to remove other crowded or unwanted branches. I have attached a link to a great MGCC article about fruit tree pruning which includes more links to calendars of fruit tree maintenance throughout the year: http://ccmg.ucanr.edu/files/77175.pdf.

Good luck with your summer pruning. Please do not hesitate to contact us again with your questions.

Help Desk of the Master Gardener Program of Contra Costa County (JLW)

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Note: The  UC Master Gardeners Program of Contra Costa's Help Desk is available year-round to answer your gardening questions.  Except for a few holidays, we're open every week, Monday through Thursday for walk-ins from 9:00 am to Noon at 75 Santa Barbara Road, 2d Floor, Pleasant Hill, CA  94523. We can also be reached via telephone:  (925) 646-6586, email: ccmg@ucanr.edu, or on the web at http://ccmg.ucanr.edu/Ask_Us/ MGCC Blogs can be found at http://ccmg.ucanr.edu/HortCoCo/ You can also subscribe to the Blog  (http://ucanr.edu/blogs/CCMGBlog/). 

Help and Advice from the Master Gardeners of Contra Costa's Help Desk

Client's Request:  I am considering ordering on-line or buying locally some bare root fruit trees to plant this winter. In determining the appropriate variety, I'm reading that the number of “chill hours” is an important criteria in the selection. What are chill hours and where can I find the chill hours for my garden?

MGCC's Help Desk Advice:  Chill hours are the cumulative number of hours of temperatures lower than 45^OF that are required by deciduous fruit and nut trees for fruit production. The hours are tracked during the traditional dormant season, measured from November 1 to February 28/29.

Available Data: The University of California (UC) provides cumulative chill hours, current year and historical, for more than 100 locations throughout the state. The data is collected from UC's CIMIS (California Irrigation Management Information System) weather stations. There are now 4 Cimis weather station located in Contra Costa County – Brentwood, Concord, Moraga, and the relatively recent installation in El Cerrito. The former Oakland Hills CIMIS site and the current Pleasanton CIMIS site, both in Alameda County, are also provided below for possible interpolation.

Average and the range of chill hours for the last 14 years from the CIMIS active sites in Contra Costa County are below. You can obtain the original data yourself at the UC website: http://fruitsandnuts.ucdavis.edu/Weather_Services/chilling_accumulation_models/Chill_Calculators/?type=research.

Contra Costa County Current CIMIS Weather Stations	Average of and Range of Seasonal Chill Hours November 1–February 28/29, 2001-2015 .. see notes below
Brentwood (#47)	818 (234 to 1066)
Concord (#170)	930 (679 to 1152
El Cerrito (#213)	191 (132 to 250
Moraga (#178)	1030 (891 to 1226)
Oakland Foothills (Alameda County)	560 (560)
Pleasanton (#191) (Alameda County)	881 (656 to 1217)

Notes: 
Brentwood: only 12 of 14 years reporting;
Concord: 14 of 14 years reporting
El Cerrito: only 2 of 14 years available (only several years in operation)
Moraga: 13 of 14 years reporting
…Alameda County CIMIS for use as possible interpolation…
Oakland Hills: ~10 years data from previous report; data now not readily available
Pleasanton: 11 of 14 years reporting;

Note: if you are really interested in the weather and climate data closer to you than the current 4 Contra Costa CIMIS stations, there are many other sources of data available on the web (http://bit.ly/1PyM1N3). However, much of the data aren't of the length of time of CIMIS and CIMIS has already done the tedious hour-by-hour calculations, but I'm sure there is/are somebody out there with enough computer skills to do it… and maybe they could share their expertise.

Why Are Chill Hours Important? During the fall season, shortening day length and cooler temperatures stimulate a tree to produce growth inhibitor hormones that stop it from growing. It is these hormones that keep a tree in dormancy during the winter months. Dormancy is broken when sufficient cold temperatures break down the growth inhibitors within the tree. The simplest model uses a specific number of cumulative hours of chill (temperatures lower than 45^oF) required to break dormancy. Once the appropriate number of chill hours has been achieved, and only after trees are exposed to longer daylight hours and warm enough temperatures for natural growth processes to begin, will active growth resume in the spring. There are also more sophisticated chill hour models that attempt to take into account warm spells during the winter, but for purposes of home garden fruit trees the model described should be adequate.

Effects of Insufficient Chill:  With insufficient chill, trees will leaf out late in the season, blossoming can be prolonged, buds may deteriorate and/or drop, and few if any flowers are produced. Without flowers, there is no fruit. Both the absolute number and the distribution of chill hours have an impact. Periods of a few days to a week or more of mild weather may offset or reduce the effectiveness of accompanying periods of good chilling weather. Greater seasonal totals are usually necessary when there is prolonged interruption of cool weather.

Chill Hour Requirements: The number of chill hours required varies by the type and variety of fruit or nut. In order to assure the tree you plant is appropriate for your area's environmental conditions, you should know at least the average chill hours in your area as well as the chill hours required for the specific fruit or nut tree you wish to plant. For general information on the chilling requirement for various fruit and nut trees you can go to the UC website: http://homeorchard.ucdavis.edu/The_Big_Picture/Tree_Selection/#chill.

Fruit Tree Selection:  For information on fruit tree varieties for the home garden, including low chill varieties (varieties requiring less than 300 hours of temperatures lower than 45^OF to break dormancy), go to the University of California free publication “Growing Temperate Tree Fruit and Nut Crops in the Home Garden” at http://homeorchard.ucdavis.edu/varieties.pdf. You may also find more information on fruit tree varieties and required chill hours of interest on the web sites of commercial wholesale and mail-order web nurseries.

Editor's Note: This response is an updated and edited version of a MGCC article by Emma Connery that was originally published in the January 11, 2015, Contra Costa Times. Any errors are the responsibility of the HOrT COCO editor. 

Help Desk of the UC Master Gardeners of Contra Costa County

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Note: The  UC Master Gardeners of Contra Costa's Help Desk is available year-round to answer your gardening questions.  Except for a few holidays, we're open every week, Monday through Thursday for walk-ins from 9:00 am to Noon at 75 Santa Barbara Road, 2d Floor, Pleasant Hill, CA  94523. We can also be reached via telephone:  (925) 646-6586, email: ccmg@ucanr.edu, or on the web at http://ccmg.ucanr.edu/Ask_Us/ MGCC Blogs can be found at http://ccmg.ucanr.edu/HortCoCo/ You can also subscribe to the Blog. 



 

Advice for the Home Gardener from the Contra Costa Master Gardener Help Desk

Client's Questions and Requests
Client called and discussed about his need for more information about pruning his numerous backyard fruit trees. He lives in central county. CCMG Help Desk followed up with an email on advice about pruning his fruit trees.

CCMG Help Desk Response and Advice:
Thank you for calling the Master Gardener help desk this morning. It was nice to speak with you. It was also great to get a new recipe for cooking fava beans!

You have a wide variety of wonderful fruit trees in your yard, many of them not commonly planted in this area. You asked about pruning them. Basically, the idea behind pruning is to control size for easier care in maintaining and picking fruit (taller trees do not bear more fruit!); increase strength – develop strong limb structure; distribute sunlight evenly throughout tree; regulate fruit bearing – removes excess fruitwood; renew fruitwood – to continue strong buds and flowers; and to remove undesirable wood- dead, broken, and crossing branches. 

University of California and its Cooperative Extension provides a wealth of information, most of it free through their catalog (http://ucanr.edu/Publications_524/)which you can order from (see also link on CCMG home page (http://ccmg.ucanr.edu/), column left). You can also find extensive UCCE information published on the web. Here is a link to a great publication that describes fruit tree pruning and includes diagrams to help you figure out how to prune your own trees: http://homeorchard.ucdavis.edu/8057.pdf.

You mentioned that some of your trees were getting large-here's a link to an article about pruning overgrown fruit trees: http://homeorchard.ucdavis.edu/8058.pdf. Both of these have enough basic information to cover all your deciduous trees, but for the less-common varieties, I'll give you some hopefully useful hints and tips below, as well as links to more information about each one.

Citrus
Prune citrus in late spring or summer to shape trees, only to remove twiggy growth, dead wood and weak branches, or any crossing, broken or shaded branches from the interior. Wait until May to prune out any frost-damaged wood, as it may revive. Here is a link to Citrus for the Home Garden in Contra Costa County: http://ucanr.edu/blogs/slomggarden/blogfiles/4260.pdf. You'll find lots of information specific to growing citrus here. Here is another link that covers diseases and disorders of citrus fruit: http://www.ipm.ucdavis.edu/PMG/C107/m107bpfruitdis.html. You'll see that brown rot is common in citrus—this causes the soft dark decay that develops in citrus and occurs mostly on the bottom side of fruit and happens mostly to fruit lower on the tree (closer to the soil). The dark spots on your Mandarins is possibly from a bacterial infection.

Quince

Quince
photo: simplyrecipes.com

Trim quince trees annually in late fall or in winter, when the tree is dormant and before the new growth appears. Flowers and fruit form on new growth, so do not prune after growth starts in spring. Remove all branches that grow inward toward the center of the tree and those that grow at an angle significantly more or less than 45 degrees from the supporting branches to keep the interior of the tree open for air circulation and light penetration. Prune out all branches that cross other branches. Prune quince tree branches at the point where they emerge from supporting branches, leaving about one-quarter to one-half inch intact to preserve the growth collar next to the supporting branches. 

Codling moths (common on apples, pears and other fruit) can be a problem for quince. They can be difficult to manage, especially if the population has been allowed to build up over a season or two. It is much easier to keep moth numbers low from the start than to suppress a well-established population. In trees with low levels, codling moth often can be kept to tolerable levels by using a combination of nonchemical management methods; however, it is important to begin implementing these measures early in the season. Sanitation should be the first step in any codling moth control program. Every week or two, beginning about six to eight weeks after bloom, check fruit on trees for signs of damage. Remove and destroy any infested fruit showing the frass-filled holes. It also is important to clean up dropped fruit as soon as possible after they fall, because dropped fruit can have larvae in them. Removing infested fruit from the tree and promptly pick up dropped fruit from the ground is most critical in May and June but should continue throughout the season.

Excellent control can be achieved by enclosing young fruit in bags right on the tree to protect them from the codling moth. This is the only nonchemical control method that is effective enough to be used alone and in higher population situations. However, it is quite time consuming to apply the bags, so this method is most manageable on smaller trees with fewer fruit. You can bag all the fruit on the tree or just as many fruit as you think you will need. Keep in mind that unbagged fruit are likely to serve as a host and increase the pest population, so it would be prudent to employ sanitation to keep the population in check.

Here is a link to information about codling moths from the University of California: http://www.ipm.ucdavis.edu/PMG/PESTNOTES/pn7412.html that goes into detail about controlling these pests.

Pomegranates
photo: mixwellness.com

Pomegranates

Prune in late winter after danger from winter freezes, but before the tree blooms in spring. To keep the interior of the tree open during the growing season, prune in summer as needed. Light annual pruning of established trees encourages fruit production; pomegranates tend not to require heavy pruning if maintained regularly. Remove dead and damaged wood during late winter and remove sprouts and suckers as they appear. Heavy pruning will reduce the crop.

Apricots
photo: freepik.com

Apricot
As I mentioned on the phone, apricots should be pruned during the summer in late August because of a fungus that infects trees during the cool and wet season. Remove shoots from the center of the tree and cut out interfering limbs and dead and diseased wood. Here is a link to information about pruning apricots: 

http://www.ipm.ucdavis.edu/PMG/GARDEN/FRUIT/CULTURAL/apripruning.html.

Figs
Fig trees are productive with or without heavy pruning. It is essential only during the initial years. Since the crop is borne on terminals of previous year's wood, once the tree form is established, avoid heavy winter pruning, which causes loss of the following year's crop. It is better to prune immediately after the main crop is harvested, or with late-ripening cultivars, summer prune half the branches and prune the remainder the following summer. If radical pruning is done, whitewash the entire tree. Here is a link to information from California Rare Fruit Growers (CRFG): http://www.crfg.org/pubs/ff/fig.html.

Mulberry

Mulberry
photo: dreamstime.com

o special pruning techniques are needed after the branches have been trained to a sturdy framework, except to remove dead or overcrowded wood. A mulberry tree can be kept to a tidy form by developing a set of main branches, and then pruning laterals to 6 leaves in July in order to develop spurs near the main branches. It is not advisable to prune the trees heavily since the plant is inclined to bleed at the cuts. Cuts of more than two inches in diameter generally do not heal and should be avoided at all cost. The bleeding will be less severe if the tree is pruned while it is dormant. Here is a link from CRFG: http://www.crfg.org/pubs/ff/mulberry.html.

Jujubes

Jujube dried
photo: inlandempirecsa.com

Unpruned trees produce as well as trees that have been pruned. Extensive winter pruning, however, will keep the plants in better health and produce more easily obtainable fruit. A link from CRFG: http://www.crfg.org/pubs/ff/jujube.html.

Persimmon
lt: fuyul & rt:hachiya
photo: dreamstime.com

Persimmons
Prune persimmon trees to develop a strong framework of main branches while the tree is young. Otherwise the fruit, which is borne at the tips of the branches, may be too heavy and cause breakage. A regular program of removal of some new growth and heading others each year will improve structure and reduce alternate bearing. An open vase system is probably best. Even though the trees grow well on their own, persimmons can be pruned heavily as a hedge, as a screen, or to control size. They even make a nice espalier. Cut young trees back to 1/2 high (or about 3 feet) at the time of planting. Here is information from CRFG: http://www.crfg.org/pubs/ff/persimmon.html and from UC that includes information on pests and diseases of persimmons: http://www.ipm.ucdavis.edu/PMG/GARDEN/PLANTS/persimmon.html.

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Since so many of your trees are not typically grown in our area, one of your best resources is the California Rare Fruit Growers. Their website is http://www.crfg.org/, the local chapter is the Golden Gate chapter (http://www.crfg.org/chapters/golden_gate/index.htm). The Golden Gate Chapter of CRFG conducts meetings throughout the northern San Francisco Bay Area, usually in the odd-numbered months on the second Saturday of the month. Meetings almost always include speakers, tastings, a raffle of unusual plants and the chance to talk to people who live in your area and who share your interests. You would probably find someone who could advise you further on pruning techniques at one of their meetings. In addition, CRFG holds a Scion Exchange in January that you might want to attend. In the past when I've attended, they had classes on pruning of the various fruit trees that you have, let alone the opportunity to get scions that you might want to graft onto your trees (scions are usually free… $5 charge for non-members at the door). Information on the CRFG's Scion Exchange can be found at http://www.crfg.org/chapters/golden_gate/scionex.htm. I have always enjoyed the Exchanges when I attended.

I hope this gives you a start on pruning your backyard orchard. Please let us know if you have more questions.

Contra Costa Master Gardeners Help Desk

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Note: The Contra Costa Master Gardener Help Desk is available year-round to answer your gardening questions.  Except for a few holidays, we're open every week, Monday through Thursday for walk-ins from 9:00 am to Noon at 75 Santa Barbara Road, 2d Floor, Pleasant Hill, CA  94523. We can also be reached via telephone:  (925) 646-6586, email: ccmg@ucanr.edu, or on the web at http://ccmg.ucanr.edu/Ask_Us/