Advice for the Home Gardener from the Help Desk of the
UC Master Gardener Program of Contra Costa County
MGCC's Help Desk Response: Thank you for contacting the UC Master Gardener Program Help Desk with your questions about grape culture.
Based upon the information you have provided, here are several reasons your grapevines may not flower and produce grapes:
- Grapevines need full sun to activate the flower blossoms. Without sufficient sunlight, the flower buds won't develop properly.
- Pruning the vines incorrectly may affect the blossoms. Most wine grapes are pruned severely in the winter, leaving only short spurs on the woody trunk and main branches. However, some grape varieties, such as "Concord," "Crimson Seedless" and "Thompson Seedless" are cane pruned. These varieties require longer branches, or canes, because the lowest buds may not produce fruitful vines. The non-productive vines should be trimmed back in spring and early summer to prevent them from shading the developing flower buds and blocking the sunlight, thus reducing the number of flowers produced that season.
- Grapevines thrive in well-drained, rich soil. However, if the soil contains too much nitrogen, or if you've over-fertilized, the grapevine may put all of its energy into foliage instead of flowers and fruit.
- Grapevines harbor a variety of pests that can affect the development of flowers and fruit.
- Grape blossoms are mostly wind pollinated, however, varieties that require both a male and female plant require cross pollination to produce fruit. This may be accomplished by wind or insects
Following are several links from UC leading to further useful information about grape culture and pests. These links also cover and expand on the reasons for lack of flowering and production listed above:
Hope that information helps. Please do not hesitate to contact the Help Desk again if you have further questions.
Help Desk of the UC Master Gardener Program of Contra Costa County (SLH)
Note: The UC Master Gardeners Program of Contra Costa's Help Desk is available year-round to answer our 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, although we will be moving this spring. We will notify you if/when that occurs. We can also be reached via telephone: (925)646-6586, email: firstname.lastname@example.org, 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/)/table>
Garden Advice from the Help Desk of the
UC Master Gardener Program of Contra Costa County
Client's Request: I have several citrus trees. I would like advice on why my citrus aren't producing. What's wrong? What can I do?
One possible cause of the non-fruiting could be the age of the tree. Many varieties of citrus do not produce fruit until their third year. I have a satsuma mandarin tree growing in a large container that took four years after planting to start producing. Some other citrus varieties (including, for example, Meyer lemons) may start producing at a younger age, but the fruit that is produced in the early years is often smaller than the tree will produce as it matures, and in the early years the fruit can also appear very rough and misshapen.
Another possible cause of non-fruiting could be a lack of sun or inadequate irrigation. Citrus performs best when it receives the sun for most of the day. Proper irrigation is also important. An under-watered citrus tree will produce few if any fruits. But it is also important not to overwater citrus which can also cause problems. This link from the UC Master Gardener Program of Orange County has some very good guidance on how to water citrus: http://mgorange.ucanr.edu/Edible_Plants/?uid=58&ds=530
Lack of soil fertility could also cause problems. Citrus does need to be fertilized. The Orange County MG site referenced above also has good information on how and when to fertilize citrus with guidance on how much fertilizer to use (which depends on the age and size of the trees).
Another possible cause for nonproducing citrus trees is a lack of pollination. While many citrus varieties are capable of producing fruit without bees or other pollinizers visiting the flowers, a few varieties do require cross-pollination. For example, some clementines and mandarin hybrids require cross pollination by another tree to produce fruit. (Other mandarin varieties can produce without pollinizers and commercial growers sometimes try to keep pollinizers away from the trees so that the fruit will not contain seeds.)
Finally, some citrus trees will produce well only every other year, producing a good number of fruits one year and only a few fruits (or none at all) the next year. So, if you've observed the trees for less than two full years, you may have seen them in their non-productive year.
Hopefully, with this information you can determine and correct the cause of the problem. If not, here's the type of information we would need to help focus on your particular trees.
- In what City or part of the County are the trees located?
- What varieties do you have?
- When were the trees planted? What was the size of the tree when initially planted? What is the current size?
- How many hours of sun per day do the trees receive in spring and summer months?
- How are the trees irrigated? How much water is provided and how often do you irrigate?
- Are the trees planted in the ground or in containers?
- If the trees are in the ground, what type of soil do you have (for example, is it heavy clay or are you one of the lucky souls who have more loamy soil? If the trees are in containers, what type of soil mixture was used to fill the container?
- Is the area under the canopy of the trees mulched (which helps the soil retain moisture)?
- How have you been fertilizing the trees? (frequency, amount and type of fertilizer used)
- Does the foliage on the tree look healthy? Are the leaves green or are they yellowing? If the tree does not look healthy or you have yellowing leaves, it would help to have some photos of the trees. Take some close-up shots of the leaves but also, send us some photos taken further from the trees so that we can get a better sense of the environment and the overall look of the trees. In fact, even if the trees look healthy to you, it would be helpful for us to have photos.
- Any signs of insect damage? (for example, holes in the leaves, curled leaves, sticky substances on the leaves which could be honeydew from insects, ants crawling in the tree)
- Do the trees have flowers in the spring time? (A few varieties of citrus are just starting to show signs that blossoms will appear soon; other varieties won't bloom for a few more weeks. Some varieties may bloom at other seasonal times…. Editor's note: This response was originally written in late February)
- If the trees have bloomed in past years, have you observed any bees or other pollinizers visiting the blossoms? Are there many bees or just a few?
In addition to answering these questions, feel free to add any additional observations about the tree that you think could be relevant.
We hope that this information is helpful in getting your trees in shape to produce. If not, we encourage you to provide the additional information described above so that we can focus more precisely on your particular problems.
Help Desk of the UC Master Gardener Program of Contra Costa County (tkl)
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: email@example.com, 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/)./span>/span>