By Brent McGhie, Butte County Master Gardener, August 14, 2015

At this time of the year, it is not uncommon for large branches to suddenly drop from oak trees without warning.  Although this phenomenon is not limited to oaks, the sheer size of their branches makes summer branch drop (also known as “sudden limb failure”) in oaks much more hazardous for life and property than branch drop by other tree species.  Dr. Richard Harris, Professor of Landscape Horticulture at UC Davis, published an article on the topic in the Journal of Arboriculture in April 1983 describing this condition and its possible causes, and suggested steps that tree owners can take to reduce the hazard of summer branch drop.

Summer branch drop is not related to wind and often occurs in the afternoon on hot, calm days.  Unlike most breaks due to wind, which occur where a branch attaches to the trunk, a break due to summer branch drop usually occurs 3 to 12 feet away from the trunk, along the length of the branch. The branches that break are usually long and horizontal, as opposed to upright, frequently extending to or beyond the average tree canopy.  While some limbs that drop show evidence of wounds or decay, many of these failed limbs appear to be quite sound.  Older, less vigorous trees seem to be more prone to this problem.  Once a tree has lost a limb due to summer branch drop, it is more likely to lose another.

Drought stress may somehow contribute to summer branch drop, but at this time, there is no generally accepted hypothesis that explains this occurrence.  In California this type of limb failure occurs on both native and planted trees as well as in irrigated and un-irrigated landscapes.  One possibility is that drought stress during a hot calm afternoon reduces the flow of water in the branch, causing the branch temperature and the concentration of ethylene to increase.  Ethylene, a gaseous hormone found in all plants, is known to promote the process of cell aging. Elevated levels of ethylene may weaken the cell wall cementation which when coupled with reduced transpiration and increased root pressure, increases internal sap pressure, moisture content of branches, and limb weight, resulting in branch failure.  Old wounds and decay hidden inside a limb (possibly resulting from improper pruning) occasionally contribute to branch drop, but this does not account for the majority of summer branch drop failures.  Pruning that encourages uneven growth at the end of a limb can put tremendous stress on the limb due to the added weight of the new growth.

Although there is no guaranteed way to prevent summer branch drop, several things can be done to mitigate this hazard in oaks and other commonly affected tree species such as eucalyptus, elm, and ash.  On mature trees, shorten and lighten long horizontal branches and open up the tree by thinning to healthy lateral branches to reduce branch weight.  Inspect the tree for externally visible defects and prune out damaged or sickly low-vigor limbs that have decay or cavities.  Although watering is required to keep most ornamental trees healthy in our hot summer climate, don't forget that summer moisture can encourage oak root fungus and other oak pathogens that can kill oaks when the summer-watered area is within 10 feet of the trunk.  Finally, do not park cars or place play structures, benches, or picnic tables beneath older, susceptible trees.  Falling limbs can't harm people (or property) if they aren't under the tree. 

By Billie Parish, Butte County Master Gardener, July 31, 2015

Each year, the U.S. throws away between 30% and 40% of the food produced for human consumption (over $162 billion worth). Roughly 20% of the total volume of waste sent to landfills is food. If you have tended a vegetable garden, then you are probably well aware of the amount of water, labor and money that is required to produce your food. And, while it is certainly commendable to compost your food and plant scraps, reducing the waste is even better.

All too often, vegetable plants are harvested for just one of their many plant parts- whether it be the leaves (e.g. lettuce), the roots (e.g. carrots), the flowers (e.g. broccoli), or the seeds (e.g. beans). But many plants have more than one edible plant part.  Grape vines and beetroots are perhaps the best-known examples of such multi-use plants, as the leaves of both are useful edibles.

But grapes and beets are by no means the only crops with edible leaves. The leaves of both immature pumpkins and fava beans can be sautéed in place of any green; carrot tops can be substituted for parsley or made into a fresh-tasting pesto, and broccoli leaves can be roasted like kale chips. Even okra leaves have something to offer, acting as a thickener when added to soups and stews. 

Often times, a recipe will leave you with a heaping pile of scraps. And while you can continually freeze these scraps until you have enough to make a rich broth, this isn't the only option. Apple peels and cores can be simmered with water in order to create home-made pectin.  If you are stumped as to how to use the tough ribs of Swiss chard, try making a gratin, or steam and puree the ribs with lemon and tahini for a refreshing middle-eastern style hummus. For a richer snack, leftover potato peels can be fried in bacon grease.

Another useful peel, the citrus rind, offers endless possibilities in the flavoring of foods. Use citrus rinds to infuse teas, oils, and liqueurs for extra zest; or dehydrate them and then infuse salt with their citrus flavor.

Many of the flowers you may find in your garden are edible. Pansies, marigolds (especially Tagetes tenuifolia), roses, anise hyssop (Agastache foeniculum), tuberous begonias, and pineapple guava flowers all make beautiful and tasty complements to salads, ice cubes, and butter. Even the pesky dandelions in your yard can be of value: both the leaves and flowers can be eaten raw or cooked (or, for a true culinary adventure, try making dandelion wine!). Elderflowers (the flowers of elderberries) can also be used to make wine, as well as infused vinegars and liqueurs. 

Both the leaves and flowers of nasturtiums add a peppery punch to any dish, but perhaps the most impressive use of the nasturtium is the pickling of young seeds in order to make “poor man's capers.”

The seeds of many plants can be useful as well. Instead of ripping out your celery after it has bolted, allow it to flower and collect the dried seed, which can be used medicinally or culinarily. The same can be done with cilantro – its seeds are known as coriander. Not only are the leaves and seeds of cilantro edible, but the roots also pack plenty of flavor, and are often used in Asian cooking. With the right preparation, such as leaching or boiling away the poisonous tannins, acorns can be turned into a substitute for flour.

While many plants have multiple edible parts, do keep in mind that not every part of every plant is edible. Always consult a reliable source before eating anything unknown. And remember, when life gives you lemons… don't throw away the peel!

Butte County Master Gardener Program Recruiting Volunteers, July 31, 2015

Do you like to garden? Would you like to volunteer in your community and teach others about gardening? The Butte County Master Gardeners are holding free orientations for people interested in joining the Master Gardener Program.

Master Gardeners provide home gardeners with University of California research-based information. We reach and teach hundreds of people each year through our garden hotline, educational workshops, and community outreach activities.

Orientations are scheduled at the Chico branch of the Butte County Public Library, 1108 Sherman Avenue, on Wednesday, August 26, 2015 from 12:30-1:30 PM and from 6:00-7:00 PM. A second set of orientations will be held at the Oroville branch of the Butte County Public Library, 1820 Mitchell Avenue, on Monday, August 31, 2015 from 11:00 AM-12:00 PM and from 6:00-7:00 PM.  More information can be found on our website.

By Brent McGhie, Butte County Master Gardener, July 17, 2015

Blue oaks (Quercus douglasii) are found naturally only in California.  Their habitat includes the lower slopes of the Coast Ranges and the western foothills of the Sierra Nevada mountain range, forming a ring around the Central Valley.  Here in Butte County, blue oaks grow in the lower foothills below 2,000 feet.  They get their common name from the blue-gray color on the upper surface of their leaves, which are yellow-green underneath.  The leaves are one to three inches long and one-and one-half to two inches wide, with lobed margins.  Mature blue oaks are typically about 30 feet tall and can live from 175 to 450 years. 

On good sites with deeper soils and available moisture, blue oaks can't compete with other trees, such as live oaks. They are, however, superbly adapted to the shallow, rocky soils of the hot, dry foothills, where other oaks would struggle to survive.  These trees can tolerate temperatures above 100° for several weeks at a time.  In addition to an extensive system of lateral feeder roots, which are fairly shallow, blue oaks develop deep sinker roots, which can grow through cracks in rocks to as deep as 80 feet in pursuit of groundwater.

The upper surface of blue oak leaves have a thick, waxy coating, which reduces evaporation and gives the leaves their characteristic bluish hue.  Also the canopy of these trees is fairly open, so blue oaks have fewer leaves relative to less drought-tolerant species.  This means they have less leaf surface from which water can evaporate. These trees also have complex anatomical and physiological adaptations that help them withstand internal stresses imposed by dehydration.

Normally blue oaks are winter-deciduous, dropping their leaves in the fall.  However, when water becomes too scarce, even for blue oaks, they become drought-deciduous and simply drop their leaves and remain dormant until the following spring.  Drought dormancy is common among desert and chaparral plants, but is a rare feature for oaks and for trees in general.    

For homeowners who are lucky enough to have blue oaks growing on their land, this means “fall” may come as early as July or August in dry years.  In fact, it has been noted that this year the leaves of some blue oaks in the Butte County foothills are already beginning to turn brown.  These trees may look like they are dying or dead, but don't be fooled into cutting them down.  They will normally produce a fall crop of acorns from stored food and then follow up with new leaves in the spring.  

A tree owner may be tempted to water drought-stressed oaks, but should avoid doing so.  Summer irrigation will encourage “oak root rot” and other soil pathogens and could very likely do far more harm than good.  Our blue oaks have survived many droughts before this one.  Keep in mind that the key to living with oaks is to disturb them as little as possible.