By Tony Nunes, U.C. Master Gardener of Napa County

Knowing basic botany and grapevine structure and selecting a variety and rootstock suited to the location can help vineyard owners succeed. Master Gardeners call it putting the right plant in the right place.

We are fortunate to live in a region with soil types and microclimates that produce world-class wines. Just like commercial vineyard managers, home vineyard owners need to make decisions based on their unique site, goals and conditions and make adjustments driven by Mother Nature throughout each growing season.

It starts with a vineyard management plan for the season. Napa Valley has kicked off the year with rainfall amounts and low temperatures not seen in many years. Determining pruning dates is the first step. In some places, pruning has already started as vineyard managers allocate their resources throughout the valley.

Home vineyard owners may have the flexibility to delay pruning, which in turn delays bud break and minimizes the potential for damage from a late frost. Some people make two passes, first to remove last year's old canes, then to make the final command decision: the pruning of buds created during the 2016 growing season that will produce the crop for this year's harvest.

As our growing season progresses, days get longer, soil temperatures rise and grapevine sap begins to flow. This awakening from winter dormancy is one of many milestones of the growing season.

One element of integrated pest management is a plan for controlling powdery mildew (Uncinula necator) and botrytis (Botrytis cinerea) from bud break to veraison, the color change in grapes that signals the onset of ripening. The spores that cause powdery mildew or botrytis are ubiquitous in Napa Valley vineyards.

Powdery mildew infections from the previous year appear as a blue fungus on individual berries or clusters. Botrytis affects the internal tissues of the berry or the entire cluster. Berries split and fungal spores can grow out of split skins. The spores from infected clusters are distributed easily by wind. Spores can survive the winter on the grapevine bark and cause infections the following year.

Early in the growing season, vine shoots grow rapidly. Like a jack-in-the-box, buds produce shoots and a self-pollinating flower blooms to produce the year's crop. Bloom and fruit set are critical periods driving yield and fruit quality. Temperature swings and rain are not welcome during this time.

Grapevines do not required special fertilizers but should be kept in balance with nutrients available in the soil. Too much nitrogen in the soil can cause vines to produce excess canopy, creating issues with pest management and crop quality.

When applying fertilizer, first ask yourself why. Testing can help you determine what the vine needs. The first test of the growing season, petiole testing, should be performed after fruit set. Petioles connect leaf blades to the vine shoot. Samples of 25 to 50 petioles are selected for each block and tested to determine what nutrients might be deficient or present in excess. Fertilizers are then applied according to the specific needs of that block.

Grape clusters need leaves and sunshine to ripen the crop. Additionally, new buds require sunshine to produce energy for next year's crop. Managing the amount of leaves and their health is referred to as canopy management.

Removing leaves at the base of the canes surrounding grape bunches allows for better sunlight penetration and airflow. To guide decisions about leaf removal, growers observe weather conditions and how the vineyards are oriented to the sun. Leaf removal on the west side facing the afternoon sun is limited during July and August to minimize sunburn and bunch rot. Home grape growers may also need to observe their microclimates or placement of buildings when determining how to manage the canopy.

Irrigation decisions also affect canopy health. Vineyard managers monitor soil moisture levels and visual clues from leaf blades and tendrils during the early season's rapid shoot growth, flowering and fruit set. When irrigation is needed, it is best to irrigate deeply according to the site's soil-moisture holding capacity.

Roots don't grow in dry soil. The goal is to encourage roots to grow as deeply as possible given the site's soil conditions, with just enough water stress to produce high-quality fruit.

Home vineyard owners are generally optimists or at least try to be. Each year, they look forward to a successful harvest, drawing on the knowledge gained from previous growing seasons.

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.edu/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.

Pat Hitchcock, U.C. Master Gardener of Napa County

Weeds aren't the only troublesome invaders in many Napa Valley gardens. Several other plants, not usually thought of as weeds, can be equally problematic. These thugs are the larger plants, shrubs and trees that, if left undisturbed, can spread into native habitat and crowd out native species.

Cotoneaster is a shrub in the Rosaceae family that grows enthusiastically in my neighborhood. The New Sunset Western Garden Book describes its growth habit as fountain-like with “graceful, arching branches.” Its summer sprays of small white flowers become red-orange berries in fall. Robins, cedar waxwings and other birds love them.

While cotoneaster is native to Eurasia, most of the cultivated varieties originated in China. They were introduced in California before 1900 but have only been reported as invasive in the last 20 years or so. With help from birds, they self-seed abundantly and can supplant native toyon (Heteromeles arbutifolia) in natural areas.

Another problem plant is the Himalayan blackberry or Armenian blackberry (Rubus armeniacus). Native to Armenia and Northern Iran, this plant was introduced to North America in 1885 as a fruit crop. It soon escaped into the wild and is considered invasive throughout temperate climates. While the berries are delicious, the plant is thorny and rambunctious. Canes can grow 30 feet long.

The plant propagates not only by seeds but also by “tip rooting” when the tip of the cane touches the ground and forms roots. If you ignore this plant for long, it creates a dense tangle of old brown growth and wicked, thorny green canes. It likes to grow among other shrubby plants, including the climbing roses and butterfly bushes (Buddleja) that screen my front bedroom windows from the street. Removing the blackberry vines that wander into that bed requires protective clothing as well as sharp pruners and a sturdy digging tool for prying out roots.

While the cotoneasters and blackberries probably invaded my property, another troublemaker—privet—was planted intentionally as a hedge. Three species of privet (Ligustrum spp.) are on the

California Invasive Plant Council's watch list, which means they have not yet been rated invasive in the state but are raising concerns. Those three are glossy privet, Japanese privet and California privet. Glossy privet (Ligustrum lucidum) is likely the one growing (and spreading) in my yard.

If kept trimmed, glossy privet makes a dense hedge. However, if left unclipped, it will reach tree height, bloom heavily in spring and produce a large crop of small black berries. The falling fruit can stain pavement and make a mess on parked cars. Birds attracted to the berries contribute to the mess and help spread the seeds, so new plants volunteer everywhere. After the fruit is gone, the fruiting clusters are unattractive. Sunset advises readers to consider the disadvantages of privet before planting it. I wish whoever planted it on my property had done so.

My property also has an abundant supply of ivy (Hedera helix, H.canariensis). Ivies are native to Eurasia and northern Africa but are now widespread. The California Invasive Plant Council lists ivy as being high in impact, invasiveness and distribution. I try not to let it climb into trees, and I pull it off the north side of the house, where it seems to like the micro climate. It infiltrated the overgrown hedges along the street and provided some screening where it grew densely on an old wire fence. I didn't think anything could kill ivy, although, after five years of drought, a small section in front of my house spontaneously died.

Once I was answering calls at the Master Gardener Help Desk when a client called to ask if we could help him figure out why his ivy had died. After doing some research, I was still stumped; this is a plant that does not succumb to pests or disease. I consulted a U.C. farm advisor specializing in weed science, and now we would both like to know why that ivy died. Finding an efficient way to control ivy in our forests and riparian areas would be a wonderful discovery. Meanwhile, in my yard, I whack it back from time to time in an effort to keep it from taking over.

All of these plants were brought to California intentionally because they had characteristics that seemed useful or attractive. Some of them are still sold in nurseries. But in our state's hospitable climate, the plants have escaped cultivation to become nuisances in wild areas as well as in some gardens.

For more information about invasive plants, check out the California Invasive Plant Council's website, CAL-IPC. The lesson here is to consider the unintended consequences of the things we do. After researching weeds for the past few weeks, I am vowing to be careful about the new plants I introduce into my garden.

Workshop: U. C. Master Gardeners of Napa County will conduct a workshop on “Rose Pruning and More” on Sunday, January 22, from 1 p.m. to 3 p.m., at the Yountville Community Center, 6516 Washington Street, Yountville. Learn 10 important facts about roses, rose pruning and rose care and maintenance. Registration is $12 per person, free to Yountville residents. Register with Yountville Parks & Recreation or call 707-944-8712.

Workshop: The Integrated Grape Team from the U. C. Master Gardeners of Napa County will host a workshop on “Home Vineyard 1” on Sunday, February 5, from 12:30 p.m. to 4:30 p.m., at White Rock Vineyards, 1115 Loma Vista Drive, Napa. Learn what to do, what to look for and what to plan for in the vineyard between February and August. This is an outdoor lecture so dress accordingly. Registration is $5 per person.Online registration (credit card only) Mail-in registration (check only or drop off cash payment)

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.edu/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.

By Gayle Nelson, U.C. Master Gardener of Napa County

Armed with a little knowledge and time, any homeowner can prune his or her own fruit trees. Here's a multi-point primer to get you started, beginning with some actions to take well before you prune.

Keep fruit trees under six feet in height. Train the tree in the first few years to create a strong scaffold and branch structure. This balanced, open structure and short stature will make future care easier and minimize the potential of a ladder mishap.

Thin fruit early so that remaining fruits are five to six inches apart. Discarding fruit may seem wasteful, but thinning allows the remaining fruit to develop to full size and reduces the risk of disease transmission and broken limbs.

Prune regularly. Begin right after new trees are planted and continue pruning thoughtfully throughout the tree's life. Pruning establishes a sound structure, promotes air circulation, balances shade and sun and encourages fruit production. Numerous books and online resources can advise you on how to prune each type of fruit tree correctly. Typing “UC fruit tree pruning” into your search engine will yield University of California-sanctioned publications, articles and videos for guidance.

Understand the difference between dormant pruning and summer pruning. Dormant pruning takes place in winter when the tree's leaves have fallen and you can see the branch structure clearly. Pruning during dormancy helps manage fruit production and guide the structure. It invigorates the tree, spurring growth the following spring.

Summer pruning manages the size of the tree. You can prune any time from spring through summer to train young trees, reduce tree height and improve sunlight access.

Learn some tree anatomy. Mastering such terms as scaffold branch, lateral branch, node, fruiting wood and fruit spur, water sprout and branch collar will help you understand your tree's growth cycle.

A scaffold branch is a main structural limb. Lateral branches emerge from the scaffold branches but are not as strong or upright. A node is where a leaf attaches to the shoot. Fruit spurs are short branches that produce the flowers and fruit on most trees. Water sprouts are vigorous vertical shoots that emerge from a tree's trunk or branches. They rarely produce fruit. The branch collar is the enlarged woody tissue where the branch attaches to the trunk.

Tackle some pruning vocabulary. A leader is a dormant, upright stem that usually becomes the main trunk in a tree trained to a central leader or modified central leader. “Open center” is a method of training in which three to five primary scaffold branches are developed low in the tree and the center of the tree is kept open. A thinning cut—removing a branch or cutting it back to a lateral branch—improves light penetration. Thinning, in contrast, is selective pruning done to improve branch spacing, direct growth, eliminate weak or defective branches and reduce the end weight of branches.

Assemble the right tools. Bypass hand pruners and loppers do essentially the same job but on different-size branches. A pruning saw is handy for removing larger limbs. Wearing gloves and personal protection equipment such as safety glasses is good practice.

Keep tools clean, oiled and sharp. If the tree is diseased, sanitize tools between cuts to keep the condition from spreading.

Allow plenty of time for pruning. Gather your tools and sanitizer. Now take a long look at the tree. Are there any dead or broken branches, crossing limbs or vertical water sprouts? Does the tree seem lopsided? Begin at the back of the tree or near the bottom to get a feel for the process.

Work from the inside out. Never leave a stub. When heading, cut back to an out-facing bud. When thinning, cut outside the branch collar and don't seal or paint the cut. Downward bending branches eventually lose vigor and stop producing fruit. Cut off the downward-hanging part.

Learn where your tree produces its fruit. Apples and pears bear differently than peaches and nectarines.

Do most of the pruning in the top of the tree so the lower branches are exposed to sunlight. Sun-exposed wood remains fruitful and produces the largest fruit. Shaded branches eventually stop fruiting and will never produce again without drastic topping. Balance is the key, and practice helps you get it right.

Take time to inform yourself, and you can readily manage your own fruit trees, relying on the research and recommendations of the University of California Cooperative Extension.

Workshop: SORRY The “Fruit Tree Pruning and Grafting” on Saturday, January 21, 2017 is full please see our website calendar for other workshops at http://ucanr.edu/ucmgnapa

There will be another Fruit Tree Workshop covering "10 Thing to Know about Fruit Trees" held in Yountville on Sunday, February 12, 2017, 1-3 pm.  Contact Yountville Recreation, Adult Programs for details.

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.edu/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.

By Pat Hitchcock, U. C. Master Gardener of Napa County

This winter seems to be a promising one; it's raining regularly. But along with the filling reservoirs and green hills come a multitude of weeds.

University of California Agriculture and Natural Resources publishes “Weed Pest Identification and Monitoring Cards” (Publication 3541) that identify nearly 50 different broadleaf and grassy weeds common in California. The cards have pictures of the plants at different stages of growth, as well as information on how they spread, where they grow and how to control them. Alas, most of them grow well on my property.

Weeds can't grow without water. Once the rains begin, they sprout from seeds or emerge from their dry-season dormancy. I was curious as to where they originated and why so many thrive here, so I began researching. It is daunting to discover that the weeds in my backyard come from all over the world.

Take dandelions (Taraxacum officinale). There are native American versions, but the more widespread dandelion was imported from Europe as an edible and medicinal plant. Today, most of us consider it a weed, although some people still enjoy it as a cooked green or salad.

Another common edible weed is purslane (Portulaca oleracea), a succulent summer annual with small yellow flowers. Purslane has been eaten throughout Europe, Asia and the Middle East since prehistoric times, but when it arrived in the New World is unclear. It makes a lemony addition to salads.

Several annual grasses thrive in Napa Valley winters, including Italian ryegrass (Lolum multiflorum), wild oat (Avena fatua) and ripgut brome (Bromus diandrus). These appear to have originated in the temperate regions of Europe but are widespread in our grasslands, parks and farmland. Besides taking over cultivated soil and crowding out garden plants, some have troublesome seeds that catch on pet fur or clothing and work their way into flesh. Pet owners know what misery these so-called “foxtails” can cause dogs and cats.  

One of the most persistent weeds in my garden is field bindweed (Convolvulus arvensis). This perennial plant originated in Europe and Asia and most likely arrived with crop seeds in the 1700s. It quickly became invasive. Roots can grow as deep as 10 feet and prefer moist, fertile soil. That pretty much describes my vegetable beds; no wonder I am constantly pulling and digging this plant out.

Redstem fillaree (Erodium cicutarium) is a plant I loved as a child. I liked to pick off the drying seed head and watch it coil when separated from its flower. Now, as a gardener, I find its ability to stick to clothing, especially socks, truly annoying. Native to the Mediterranean basin, this plant is edible, but the leaves are best eaten young.

Mustard (Sinapsis arvensis) is another weed originating in the Mediterranean basin. Legend has it that the Spanish padres deliberately sowed mustard along El Camino Real to mark the way. More likely, this plant arrived in North America accidentally like so many others.

Wild radish (Raphanus raphanistrum) is related to mustard.Native to Asia, it has spread all over the world. According to the weed I.D. cards, it is similar to Raphanus sativus, the common radish, and hybridizes easily with it. Both have four-petal flowers that may be white, yellow or pale purplish-pink. They bloom in early spring and continue as late as July, producing a lot of seeds over several months. Seeds can remain viable in the soil for 30 years, so preventing seed production is one key to controlling the weed.

Redroot pigweed (Amaranthus retroflexus) is another apparently edible weed in our region. It is native to the tropical Americas but has naturalized all over the world. An annual plant, it spreads by seed that can live up to 40 years.

Prickly lettuce (Lactuca serriola) is an unattractive plant with prickly leaves and stems and bitter sap. Who would guess that it is the nearest wild relative of our common garden lettuces? It appears to have originated in Europe, Asia and North Africa, and ancient Greeks and Egyptians used it.

Some say that a weed is any plant in the wrong place. The weeds I researched thrive all over the world due to their ability to out-compete other plants for water, sunlight and nutrients. Controlling weeds is important both in cultivated gardens like my vegetable patch and in natural areas where they can crowd out native plants.

As the I.D. cards suggest, the best way to control most weeds is by manually removing them before they can bloom and produce seed. Another word for that is weeding. Winter is a good time to get out there and enjoy, I mean control, your weeds.

Workshop: U. C. Master Gardeners of Napa County will hold a workshop on “Fruit Tree Pruning and Grafting” on Saturday, January 21, from 9 a.m. to 2 p.m., at the University of California Cooperative Extension office, 1710 Soscol Avenue, Napa. The dormant season is the best time to prune your deciduous fruit trees to increase vigor. Join the Master Gardeners fruit-tree team for this workshop showing techniques to develop healthy and productive fruit trees. A local expert grafter will give a grafting demonstration. The afternoon field trip offers home gardeners the opportunity for a hands-on experience. Dress for seasonal outdoor weather and bring your pruners. Online registration (credit card only); Mail-in registration (check only or drop off cash payment)

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.edu/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.