CITRUS LEAF MINER DAMAGE

During the winter of 2014, which was extremely dry and cold, I lost my sweet little young Meyer lemon. I was flummoxed as to the reason. Yes, I had listened to the frost predictions and conscientiously covered the tree during the nights the low temperatures were predicted. Yes, I had augmented this arrangement with outdoor-certified extension cords and flood lights to create heat.

When the sun came up in the morning, I removed the coverings and turned off the lights to allow the tree and the soil beneath it to absorb as much daylight and ambient daytime heat as they could. What had I done wrong?

My poor tree was so stressed from lack of water that it didn't stand a chance. I had stopped irrigating in November and never gave it a second thought. But think back to that winter. We had very light precipitation and frequent frosts. Being a baby, the tree had no reserves.Faced with the lack of water and the cold, it could not cope.

I have since decided that the tree's location was not the optimum choice. Napa Valley is blessed with a mediterranean climate, characterized by mild, wet winters; mostly prevailing westerly winds; and warm, dry summers. Coupled with the many micro-climates in our gardens, this weather allows us some options for placing citrus trees.

Microclimates are the distinctive climates zones within your garden. At the end of a hot day, walk around your garden after the sun has gone down. I did this recently when I took the dog out late at night. As I walked by the west-facing side of our stucco house at midnight, the day's heat was still radiating off of it. Any frost-sensitive citrus tree would love living there. So choose a west- or south-facing location, preferably against a wall or fence that will capture and return the daytime heat.

Frost protection is a major issue with citrus. Stay informed about the weather and be prepared. Keep tender plants hydrated, and keep the area beneath your citrus trees' canopies free of mulch or any cover. This will allow the soil to absorb heat during the day, and after the sun goes down, the rising heat will warm the trees.

Cover your citrus when frost threatens to protect delicate foliage. The entire neighborhood gets to see my taste in linens because I use old sheets, but a cloth tarp works, too. Plastic isn't recommended as it does not breathe. Try to keep the cover off of the foliage by draping it over some kind of structure. If the cover touches foliage, those leaves may freeze. Uncover when the sun comes up.

Christmas tree lights (the old-fashioned type, not LED) can add a few degrees of protection. Drape them around the trunk and branches, or place a large spotlight on the ground under the cover. Use only outdoor-rated lighting and cords.

Citrus have shallow roots that are easily damaged, so plant them where the soil does not get disturbed. Monitor soil moisture even in winter. Don't allow container-grown trees to dry out completely.

Consider growing citrus in containers to have more location options. You can put wheels on the pot and position the tree in your best location to take advantage of microclimates. Container-grown citrus needs to be transplanted every three to four years and monitored closely for nutrient deficiencies.

Choose the citrus varieties best suited to your area. Check for pests frequently. Feed regularly to keep the foliage green and the fruit coming, especially with young trees.

Fifteen years ago, the citrus leaf miner turned up in California citrus. Recently,citrus greening disease has become a huge concern for California growers. Be aware of these pests and diseases and be proactive in caring for your trees. For more information, consult the University of California Agriculture and Natural Resources web page (www.ucanr.edu), using the key phrase “citrus.”  

Workshop: U. C. Master Gardeners of Napa County will host a workshop on citrus on Saturday, October 24, from 9:30 a.m. to 11:30 a.m., at the University of California Cooperative Extension Office (address below). This workshop will focus exclusively on caring for citrus, large and small. Potting and repotting container citrus, pruning, watering and fertilizing, frost protection and recovery from frost damage are part of the program. The workshop will also cover using the University of California IPM website to identify and understand citrus diseases and pests. Online registration (credit card only); Mail-in registration (cash or check only).

Workshop: U. C. Master Gardeners of Napa County will host a workshop on El Niño on Saturday, October 31, from 9:30 a.m. to 11:30 a.m., at the University of California Cooperative Extension Office (address below). An El Niño winter is on the horizon, no doubt about it. Napa County could well see heavier than average rainfall. This workshop will focus on measures to take now to prepare your home and garden for heavy rain. You will also learn steps to take during and after a flood.Online registration (credit card only)Mail-in registration (cash or check only).

Master Gardeners are volunteers who help the University of California reach the gardening public with home gardening information. U. C. Master Gardeners of Napa County ( http://ucanr.org/ucmgnapa/) are available to answer gardening questions in person or by phone, Monday, Wednesday and Friday, 9 a.m. to Noon, at the U. C. Cooperative Extension office, 1710 Soscol Avenue, Suite 4, Napa, 707-253-4143, or from outside City of Napa toll-free at 877-279-3065. Or e-mail your garden questions by following the guidelines on our web site. Click on Napa, then on Have Garden Questions? Find us on Facebook under UC Master Gardeners of Napa County.

As you clean up your garden and remove summer annuals, take care to banish weeds and their seedpods, too. Pick up a truckload of well-aged compost, or schedule a delivery, from one of Napa County's two excellent compost companies. Nourish tired garden soil with fertilizers that replace potassium and phosphorous. After you fertilize and amend soil, water well to disperse the nutrients. If your fertilizer comes in a bag, box or bottle, carefully follow abel directions.

Be merciless in removing weed seedpods. However, if you grew calendulas, violas, forget-me-nots or zinnias, shaking their seed heads as you weed will reward you with color spots the following spring. Even some edible crops like lettuce, onions and parsley will often reseed if you encourage them.

In fact, some annuals are such vigorous self-sowers thatWeeds of California and Other Western States,a University of California publication, considers them weeds. Violets, forget-me-nots and many others are in this group. Luckily for me, they are some of my favorite flowers. Denim-blue or yellow violas, sweet-scented purple violets (Viola odorata) and bold-faced pansies ranging from deep blue to pink can all be planted now. Plant violas in garden beds and put more in pots to bring some cheer to the coming winter days.

Tuck calendulas, also called pot marigolds, in any bare spot in the garden, and they will reward you with bright gold flowers throughout the winter. They will fade in summer's heat, but then a shake of their tough little seed heads will sow the next season's color. In the kitchen, calendula petals can brighten salads and are sometimes used as a “poor man's saffron.”The golden petals can tint rice dishes and other recipes needing a dash of color.

Plant perennials and California natives now so they can benefit from still-warm soil and grow strong before winter comes. If you plant foxglove seedlings from six-packs now, they will be six feet tall and have towering blossoms by next year. Small snapdragon plants, which children will enjoy, will be covered with little snappers by summer and provide bright flowers through the winter months, too.

Even decorative vegetables can perk up a walkway or bed. Pink and lime-green cabbages and vivid purple and red kales can provide color all winter long.

Sow seed now for the golden California poppies and red poppies that grace many an Impressionist canvas. It's a good time to sow other wildflowers, too, before the rains come. Look for seed packets of your favorites, or pick up one of the many wildflower blends formulated for shady or sunny spots.

Bulbs, corms and tubers are on nursery shelves now. Plant daffodils, sparaxis and freesia in garden beds or pots to brighten decks and indoor rooms. Some bulbs do benefit from pre-chilling, so read directions that come with the bulbs. Make sure beds and pots have good drainage.  

Although many people are removing lawns, October is a good month to plant new lawn or renovate an older one. Over-seed now to correct bare or stressed spots.  

Napa County Cooperative Extension recommends a premium blend of grass formulated for California's cooler growing areas. If you are curious about which turf grass is best, you can get reports from Cooperative Extension on how the different grasses and blends perform. Lawns and turf are often criticized as being wasteful of water, but they do provide some fire protection around a home.

Sweet peas can be planted now. Dig beds deeply and amend with aged compost.Tall varieties can be grown along fences or trellises and short varieties in beds or containers. Heirlooms with rich fragrances are my favorites, but last year I planted a dwarf sky-blue variety that bloomed tirelessly in a half barrel on the deck until the first summer heat finished them.

October weather can be varied, so be vigilant a little longer.  Pay attention to weather forecasts and protect your new seed sprouts and tender seedlings from any final scorching days. Windy days zap moisture from air and soil, so make sure young plants are weathering those conditions, too.

Workshop: U. C. Master Gardeners of Napa County will host a workshop on “Citrus” on Saturday, October 24, from 9:30 a.m. to 11:30 a.m., at the University of California Cooperative Extension Office, 1710 Soscol Avenue, Napa. This workshop will focus exclusively on caring for citrus, large and small. Potting and repotting container citrus, pruning, watering and fertilizing, frost protection and recovery from frost damage are part of the program. The workshop will also cover using the University of California IPM website to identify and understand citrus disease and pests.Online registration (credit card only); Mail-in registration (cash or check only).

Master Gardeners are volunteers who help the University of California reach the gardening public with home gardening information. U. C. Master Gardeners of Napa County ( http://ucanr.org/ucmgnapa/) are available to answer gardening questions in person or by phone, Monday, Wednesday and Friday, 9 a.m. to Noon, at the U. C. Cooperative Extension office, 1710 Soscol Avenue, Suite 4, Napa, 707-253-4143, or from outside City of Napa toll-free at 877-279-3065. Or e-mail your garden questions by following the guidelines on our web site. Click on Napa, then on Have Garden Questions? Find us on Facebook under UC Master Gardeners of Napa County.

Oak trees typically grow in woodlands, in conditions ranging from shallow soils with little moisture to the deep, fertile soils of the alluvial valley floors. These trees are as diverse in appearance as the conditions they grow in, ranging from 15 to150 feet tall. They differ in shape, color, leaf texture and type of acorns, and whether they are deciduous, evergreen to semi-evergreen.

If you are preparing to plant an oak tree (or an acorn), you need to know the soil type, sun exposure and available water at the potential planting site. The valley oak (Quercuslobata) flourishes in the deep, fertile, well-drained soil typical of floodplains and valley floors. The scrub oak (Q. berberidifolia), black oak (Q. kelloggii) and coast live oak (Q. agrifolia) all thrive in Mediterranean-type climates characterized by mild, wet winters and hot, dry summers. These species want no summer water. If you are looking to plant an oak tree in a dry habitat, on shallow, rocky, infertile soil, your best choices would be blue oak(Q. douglasii), canyon live oak (Q. chrysolepis), Oregon oak (Q. garryana), interior oak (Q. wislizenii), or the humble leather oak (Q. durata).

There are many reasons to keep an existing oak tree.They increase your property value, prevent soil erosion, provide shade and shelter for wildlife and are beautiful to boot.

To keep an oak tree healthy, take care to protect the sensitive root system. Roots can extend beyond the tree's drip line by at least one-third of that distance. Do not dig, grade, trench, compact, asphalt, concrete or pave around your oak tree. These activities may fatally damage the root, trunk or crown.

Changing the grade, trenching, mounding or creating a swale may also lead to changing the natural drainage. If a mature oak gets more water than it is accustomed to, it will decline.

Keep thirsty plants and plantings out of the root zone. Irrigation from agriculture plays a big role in the decline of the valley oak. Choose compatible plants to site under and around your oak.

Many California native plants cohabitate happily with oaks. Here are some great resources for suitable plants:

http://www.napavalleycnps.org/

http://www.californiaoaks.org/ExtAssets/CompatiblePlantsUnder&AroundOaks.pdf

http://www.mostlynatives.com/plant-characteristics/under-oaks

http://www.laspilitas.com/groups/oaks/Planting_under_oak_tree.html

http://ucanr.edu/sites/oak_range/Oak_Articles_On_Line/Oaks_and_Landscaping_urban_forestry_/Plant_List_and_Procedures_for_Landscaping_Under_Native_Oaks_of_the_Central_Valley/

The only fertilizer an established oak needs is its own organic leaf litter for mulch. Keep leaf litter in place, just not up against the trunk. Mulching conserves water, helps moderate ground temperature, improves soil structure and increases organic matter.

If you must prune an oak tree, follow the Tree Care Industry Association guidelines, which you can find online. Pruning improperly can lead to wounds that attract insects and promote decay. Poor pruning may also stimulate rapid shoot growth that increases the potential for powdery mildew. It will also compromise the natural beauty of the tree and may make the tree structurally unstable. For the best results, consult a local arborist.

Many organisms have symbiotic relationships with the oak tree. Lichens flourish on oak trees where there is sufficient moisture, taking nothing from the oak. Many creatures find the acorns a carbohydrate-rich and fatty addition to their diet. Acorns are appreciated by deer, squirrels, woodpeckers, livestock and boar. Oak trees also shelter many nesting birds, arboreal salamanders, invertebrates and insects.

The most complicated relationship the oak tree has is with mycorrhizal fungi. These fungi live in and on the roots and extend way beyond the root system. The oak provides carbohydrates (food) for the fungi and brings up deep water that the fungi can't access. In return, the fungi break down minerals and nutrients and make them available to the oak. In addition, they produce chemicals that inhibit bacteria, thus protecting the tree from disease. With some attention, we humans can also be among the organisms that live symbiotically with the oak tree.

Tree Walk: Join the U.C. Master Gardeners of Napa County on Monday, October 5, from 10 a.m. to 11 a.m., for aguided tree walk in Napa's Fuller Park. The walk is free but pre-registration is strongly recommended as space is limited to 20 people. The walk will repeat on Monday, November 2, from 10 a.m. to 11 a.m. Both walks start in Fuller Park at the corner of Oak and Jefferson Streets in Napa.Online registration

Workshop: U. C. Master Gardeners of Napa County will host a workshop on “California Oaks” on Saturday, October 10, from 9:30 a.m. to 11:30 a.m., at the Martha Walker Garden in Skyline Park, 2201 Imola Avenue, Napa. Stroll around Skyline Park and the Martha Walker Garden to view oaks in their native habitat. Discover what grows alongside and underneath oaks. Learn about planting under oak trees in your own garden, how to care for oaks and about Sudden Oak Death and other stresses on oaks. In case of rain, the workshop will move to the University of California Cooperative Extension office,1710Soscol Avenue, Napa.Online registration (credit card only)Mail-in registration (cash or check only)

Master Gardeners are volunteers who help the University of California reach the gardening public with home gardening information. U. C. Master Gardeners of Napa County ( http://ucanr.org/ucmgnapa/) are available to answer gardening questions in person or by phone, Monday, Wednesday and Friday, 9 a.m. to Noon, at the U. C. Cooperative Extension office, 1710 Soscol Avenue, Suite 4, Napa, 707-253-4143, or from outside City of Napa toll-free at 877-279-3065. Or e-mail your garden questions by following the guidelines on our web site. Click on Napa, then on Have Garden Questions? Find us on Facebook under UC Master Gardeners of Napa County.

If you are patient and forgo harvesting tasty green spears the first two years after planting, a properly sited asparagus bed can pay off in bountiful spring harvests of asparagus for the next 12 to 15 years. Some well-tended asparagus beds still produce after 25 years.  

Asparagus is a hardy perennial that adapts to a variety of temperatures. But it is happiest in a climate like ours, where winters are cool and the ground might freeze just an inch or two.

When you are looking around for the best place to plant asparagus, keep a few things in mind. The vegetable wants plenty of sun and good drainage. And because asparagus beds last a long time, put them where they will not be bothered.  

Even if home-grown asparagus won't grace your table the first two seasons, the plants provide beauty and interest in your garden. Asparagus makes a beautiful screen with soft, ferny foliage and red berries. But it is tall and can shade other plants, so plan accordingly.

If you prepare your asparagus bed correctly, you will not be digging it again for a long time. Break up the soil 18 to 24 inches deep. Add organic matter to feed the plants and provide good drainage. Aged manure, bone meal, blood meal, wood ashes, compost, worm castings and leaf mold are all good choices.

Dig in these amendments before heading off to the nursery. Asparagus crowns do best when you get them into the ground and watered soon after purchase.

You can start asparagus from seed—more economical than buying crowns—but you will need to wait an additional year before harvest. That's why most gardeners plant one-year-old crowns. At the nursery, choose plump, grayish-brown crowns that look healthy. Remove any rotten or dried roots. Plant crowns 12 inches apart; measure and mark the planting spots before you head to the nursery.

To plant, dig a trench 18 to 24 inches wide and set that amended soil aside. Return 2 to 3 inches of the amended soil to the trench spreading it along the bottom of the bed. Gently spread the roots of each asparagus crown over the mound so the crowns are slightly above the roots. Cover the crowns with 2 to 3 inches of amended soil and firm it well. As the asparagus begins to grow, add more amended soil to the trench to cover the exposed crowns until the trench is filled. Water as needed if nature doesn't.

To maintain your asparagus bed, weed thoroughly in the spring. Pull weeds gently instead of hoeing to avoid damaging the fragile new growth underground.  

Do not harvest the first year after planting. The second year, harvest only lightly. Newly planted asparagus grows long storage roots. These pencil-thin, fleshy roots store the carbohydrate synthesized from sunlight that the ferny foliage captures all summer long. The following spring, this energy pushes up through the earth in exuberant growth. It is an amazing thing to see fresh asparagus spears push toward the light, sometimes growing a foot a day.

When it is time to harvest, snap off 6- to 8-inch spears at or below the soil surface. The plants can get away from me, and I am not averse to using spears that are up to 18 inches tall. But the stalks still have to snap off to make it to my kitchen; if they don't, they aren't fresh. Harvest daily in season and use immediately, or refrigerate in a plastic bag for a few days. Asparagus freezes well and can be steamed, baked, braised, grilled and used in cold and hot soups. Pickled asparagus is wonderful for appetizers or Bloody Marys.

After the harvest, let the ferny foliage grow. Female plants set attractive red berries. When the ferns start to yellow and die, or if there is an early freeze, cut the foliage back to 2-inch stubs.   

Some people have a reaction to eating asparagus; it's harmless but hard to ignore. We will not talk about that, however. You know who you are.

Workshop: The U. C. Master Gardeners of Napa County will host a workshop on “Drought-Tolerant and California Native Plants” on Saturday, October, 3, from 9 a.m. to 11 a.m., at Pope Valley Fire Station, 5880 Pope Valley Road, Pope Valley. Learn about drought-tolerant and native plants and discover the elements that help them thrive in our Mediterranean climate. Learn how to use them in your own garden to replace some of your thirsty ornamentals. You will also learn about irrigation modifications to make your water use more efficient and effective.ONLINE REGISTRATION 
This is a free workshop but pre-registration is requested. A minimum of 10 attendees is required or the workshop will be canceled.

Master Gardeners are volunteers who help the University of California reach the gardening public with home gardening information. U. C. Master Gardeners of Napa County ( http://ucanr.org/ucmgnapa/) are available to answer gardening questions in person or by phone, Monday, Wednesday and Friday, 9 a.m. to Noon, at the U. C. Cooperative Extension office, 1710 Soscol Avenue, Suite 4, Napa, 707-253-4143, or from outside City of Napa toll-free at 877-279-3065. Or e-mail your garden questions by following the guidelines on our web site. Click on Napa, then on Have Garden Questions? Find us on Facebook under UC Master Gardeners of Napa County.