UC Master Gardeners of Napa County answer garden questions at our Help Desk on Mondays, Wednesdays, and Fridays from 9:00 a.m. - 12 noon. Free advice is given for growing conditions in Napa County and there are three ways to contact us:

Drop-in: UC Cooperative Extension-Napa County, 1710 Soscol Avenue, Ste 4

By phone:
707-253-4143
877-279-3065 (toll free for American Canyon/Up valley residents)

Complete the diagnosis form or e-mail mastergardeners@countyofnapa.org 

The Help Desk fields a range of questions. Thanks to UC Master Gardener Monica Finigan for writing about the following recent inquiries to the Help Desk.
Strange-looking Strawberries: Client called about the strange-looking strawberries growing on his strawberry plant. The strawberries looked “hairy.” They had small leaves sprouting around the seeds on the fruit. The strawberry plants had been growing in a wine barrel for eight years. This strange appearance is called a “phylloid.”  Although there are several possible causes, the recommendation was to destroy the plants and plant new strawberries in new soil and in a different location. Strawberries are subject to several soil borne diseases and should be replaced every three years (or sooner if needed) and planted in a new location.

Meyer Lemon: Client called to ask why her Meyer lemon had not borne fruit. Her tree is four feet tall. She did not know the age as she “inherited” the tree from someone. She also indicated that it did not look good when she received it, so she pruned it during the summer. There are many possible reasons for its failure to bear. She may have pruned off the buds or the tree might not have had buds due to insufficient watering, lack of nutrients, not enough exposure to sunlight, or because it is a young tree. Citrus bear little or no fruit during their first three-to-four years.

Yellow leaves on Meyer Lemon: Client called regarding yellow leaves on a Meyer Lemon tree. Patterns of yellowing on the leaves can be an indication of a nutrient deficiency. The most common nutrient deficiency in lemons is a lack of nitrogen. The most important time to apply fertilizer is late winter or early spring, but application can also be divided into three times during the year for lemons. Fertilizer needs to be scattered over the entire root area of the tree, which extends one to two feet beyond the drip line. Consult the application directions on the fertilizer package.

Mysterious Orange Growth in Mulch: Client called to ask about a bright orange “something” in his mulch. Should he be worried about it? He was told that it was probably a fungus or slime mold. Most fungi are decomposers, and he should not be concerned, but he should make sure that a child or pet doesn’t eat it. He later called back to say he had looked more closely and the orange growth appeared to be a cluster of small mushrooms.

Flies in Walnut Husks: Client reported that there was an infestation of flies in the walnut husks of his tree, and the husks were stained black. Walnut husk flies primarily damage the husks and the walnut shell. Generally, the flies do not damage the nutmeats. The damaged husks can be placed in a damp burlap bag for a few days before attempting to remove the hull. Infested husks should be disposed of in a tightly sealed bag. Good sanitation can help reduce the number of husk flies overwintering nearby. Remove and dispose of damaged nuts as soon as possible. Spread a tarp under the tree from July through August to prevent the maggots from entering the soil to pupate. For severe infestations, spinosad can be sprayed on a 7-to-14 day interval beginning in July until within one month of harvest.  Adding a bait to the spray would eliminate the need to cover the entire tree since the flies would be attracted to the bait and would eat the spray. The home gardener might want to consider using molasses as the bait (4-to-6 tablespoons per gallon of water) and always follow label instructions.

Olive Fruit Fly: Client requested information on preventing a re-infestation of olive fruit fly on her trees. Her neighbor leaves the olives on his tree every year. She also wanted to know how to dispose of the infected fruit. Management of this problem will be a challenge with an uncooperative neighbor. Infected fruit can either be disposed of at the landfill or buried in the ground, at least four inches below the surface. In the following year, a combination of bait traps to reduce the population and application of barrier film sprays on the trees should be considered. The barrier film should be applied as the flies begin to attack the fruit in late summer. See Pest Note 74112 for more information.

Growing Crocus: Client wanted to know if crocus bulbs need to be pre-chilled before planting and whether crocus bloomed for only one day. Bulbs do not need to be pre-chilled in the SF Bay area. Crocuses bloom for an extended period of time, not just for one day. They do well in this area, since crocuses originated in the Mediterranean area.

As gardeners we often love to push the envelope for our planting zones or desire a plant that may not be well suited to our climate. Some of the popular subtropical plants we love to grow that are marginal in our climate include citrus, avocados and Bougainvilleas. In Napa County, depending on your gardens microclimate, you may be able to grow many plants native to subtropical climates. But these plants need frost protection when temperatures dip into the 30 - 20 degree F range. Some of these plants will tolerate and recover from short exposure to mild frost with only minor frost damage but prolonged frost for several hours or days in a row may kill some plants. Below are some tips for frost protection and for management after frost damage has occurred. 

HEALTHY GARDEN TIPS
Web site: http://cenapa.ucdavis.edu
Telephone: 707-253-4221
University of California Cooperative Extension – Napa County

Freeze Protection Simplified
By Dean Donaldson, Farm Advisor Emeritus

1. Make sure your plants are well watered before frost occurs. Well hydrated plants will tolerate colder tempertures and the wet soil will hold some heat. 

2. Throw a blanket or sheet, etc. over the plant. Remove when sunny. Recover each night.
‘Engineer’ types can build a cage (OK, but not necessary). Expect burnt leaves and twigs
but plant will be OK. Lightweight fabric or woven cover is superior to plastic. 

3. Citrus – fruits will be damaged. Damaged fruit will dehydrate inside. Within a few days
following a frost, fruit should be picked and squeezed. You can freeze juice for later use.
Do not prune until re-growth is visible next spring. 

4. Supplemental heat from small wattage bulbs can help reduce frost damage. Use 15
watt, 20-25 watt (outdoor-type) bulb to avoid leaf burn from light bulbs. Outdoor
Christmas lights (larger, old-fashioned) work well if +15 watts (smaller, LED Christmas
lights do not release heat). Place bulb in lower tree canopy and keep lit all night until
temperature is above 32° F. Be sure to also use outdoor-type extension cord and fixture. 

5. Do not prune damaged parts until after plants re-grow, usually in April or May.

Frost Protection and best varieties of Citrus to grow in Napa County:

 Varieties of citrus with lower heat requirements do best in Napa County. Although frosts are infrequent in the winters near San Francisco and in the thermal belts of many valleys in this region, low-lying inland areas can have temperatures below freezing. Citrus variety, site selection and winter protection are important factors for success in growing citrus in Napa County.

Cold-hardiness depends on the type of citrus grown. Early ripening varieties in our freeze-prone area can facilitate harvesting before the danger of frost. Citron and lime trees are the most tender types, sweet orange and grapefruit varieties are intermediate; and Satsuma mandarins, Meyer lemons and kumquats are the most cold-hardy.

Among sweet oranges Robertson Navel, Skaggs Bonanza, and Washington Navel can be harvested as early as December in Napa County.

Valencia oranges ripen later, but some newer varieties are sold as "improved" Valencias, which ripen earlier, set fruit inside the canopy (more protected), and boast bigger fruit. Three sold under separate names are Delta, Midknight, and Rhode Red.

If blood oranges suit your fancy, Moro is the only choice for color and flavor recommended for Napa County.

Early ripening Clementine Mandarins have excellent flavor. There are many selections, but those that require a pollinizer for good production have seedy fruit. Dancy and Kinnow mandarins, Orlando tangelo, and Valencia orange are commonly used as pollinizers. If you have room for only one tree, choose a variety that does not require a pollinizer. Clementine has produced many hybrids, such as Page, Fairchild, Ambersweet, Lee, Nova, and Robinson. Satsuma Mandarins are the most cold-hardy citrus and the earliest bearer. They can be grown in areas normally too cold for citrus. Ripening occurs before dangerous frost occur, and the foliage survives temperatures to about 22F degrees. Dobashi Beni, Okitsu Wase and Owari  are selections that thrive in cooler regions.

The University of California Division of Agriculture & Natural Resources (ANR) prohibits discrimination or harassment of any person in any of its programs or activities (Complete nondiscrimination policy statement can be found at http://ucanr.org/sites/anrstaff/files/107778.doc ). Inquiries may be directed to Linda Marie Manton, Affirmative Action Contact, University of California, Davis, Agriculture and Natural Resources, One Shields Avenue, Davis, CA 95616, (530) 752-0495.

Peach leaf curl

Did you have peach leaf curl last growing season?  If you had a severe enough problem, now is the time to apply fungicide. Historically, the most commonly used fungicides available to home gardeners have been the fixed copper products. For all copper-containing products, the active ingredient, copper, is listed as “metallic copper equivalent,” or MCE, on the label.

Peach leaf curl is a fungal disease that affects only peach and nectarine trees. Distorted, reddened foliage in the spring is a distinctive symptom. Newly emerging leaves and shoots thicken and pucker and later may die and fall off. A leaf curl infection that continues untreated for several years will contribute to a tree’s decline. To prevent peach leaf curl, treat peach and nectarine trees with a fungicide every year after leaves fall. Treatment in spring after symptoms appear won’t be effective. When planting, consider growing peach varieties resistant to the disease.

Look for symptoms in spring.

• New leaves and shoots redden and pucker. Leaves may yellow or be covered with powdery, gray spores; they also might drop.
• Cool, wet spring weather prolongs disease development.
• A second set of normal leaves will replace fallen leaves, and tree growth will appear normal after weather turns dry and warm (79º to 87ºF), although spores that can infect next year’s growth may remain.
• Symptoms won’t appear later in the season.

Treat trees with a fungicide in late fall.

• Treat just after leaves have fallen, usually late November.
• Although a single treatment is sufficient in most areas, a second application in late winter just before buds swell may be advisable in areas with high rainfall or during very wet winters.
• Don’t apply fungicides during the growing season because they won’t be effective.

Make fungicide applications effective and safe.

• The fungal spores that cause the disease germinate in the spring and spend the winter on twigs and buds. When you spray a fungicide, thoroughly cover all branches and twigs so all spores are killed.
• All peach leaf curl fungicides have environmental and health risks. Wear protective clothing, and follow label directions to stop drift or runoff.
• After many years of use, copper ions from copper-based fungicides can accumulate in soil. This can harm soil microorganisms and, through runoff, aquatic organisms. Take care when using these materials to avoid excessive dripping.

 For complete information on Peach leaf curl go to: http://www.ipm.ucdavis.edu/PMG/PESTNOTES/pn7426.html

This blog will offer information about growing crops, recommend monthly to-do list activities, have a featured plant of the month, and offer some advice about current problems we have received at the UC  Master Gardeners of Napa County help desk. 

About growing those crops... The Field Test committee grows various vegetable and/or fruit crops to learn about their culture and to observe how much success we achieve under Napa County growing conditions.

Grow these crops along with us!

Our fall crop will be French red and French gray shallots. For 2014, radishes will be grown as a spring crop and Asian long beans will be the summer crop. Kale varieties will be grown next fall.

Shallots are available at nurseries and can be planted now to harvest in the spring. Prepare your planting bed with loose soil so the shallots have room to grow. You will need to separate the bulbs into cloves and plant them in rows 10" apart with 6" spacing. The tip of the clove should be even with the top of the soil. Shallots need about 1" of water per week. Mulch lightly as shallots can't push through heavy, compacted material. Shallots are expensive to buy and are easy to grow, making them good use of your plot space.

 Thanks to Sonoma County Master Gardeners for information about shallots.