By David Walther, Butte County Master Gardener, March 1, 2013

Early spring is the perfect time to apply mulch to your garden. Mulch is any material that covers the ground and insulates it from sun, evaporation, and erosion. After you have finished your winter cleanup and pruning chores, but before the rains end is a great time to mulch, not only to provide the best environment for your plants, but also to help prevent the growth and development of weeds.

Mulch is good for the soil, and thus good for your plants for a number of reasons. It jump-starts the useful work done by microscopic organisms (this is often referred to as microbial activity); retains moisture, thus preventing plants’ roots from drying out; and deters weeds by providing a barrier between the soil and the sun.

Mulching is also a time-saver for the gardener – it takes a fraction of the time to put down mulch that it would take to weed later on. And using mulch to control weeds reduces the use of expensive herbicides.

Mulch can be composed of organic or inorganic materials. Organic mulches include manure, compost, grass clippings, shredded bark, shredded wood, and even newspaper sheets (more attractive when covered with compost so the newspaper doesn’t show). Pine needles can be used as mulch but they are very flammable, so it is best to chop or grind them up first. Shredded leaves from fall leaf drop make excellent mulch.  

Natural inorganic mulches include gravel, pebbles, and crushed stone. Other inorganic mulches are plastic, cardboard, and even pieces of old carpet. The mulch you use will depend upon the job you want the mulch to perform and how you want it to look.

Any ground that needs enrichment, such as flower or vegetable beds you will be planting later in the season, will benefit from an application of organic mulch. Mulching around shrubs, trees, annuals, and perennials will improve the soil that feeds their roots, as well as deter weeds. Large areas that you wish to keep weed-free are also candidates for a thick application of mulch.

Pile mulch six to eight inches deep, tapering down to three inches deep about 10 inches away from the stems or crowns of plants. Do not place mulch directly on top of plant crowns or too close to the trunk or stems of your plants, since a layer of mulch can cause the crown to rot. You can, however, apply mulch right on top of plants that do not have above-ground stems or crowns (such as bulbs, stoloniferous or rhizomatous plants).

To control annual weeds, apply four to six inches of mulch on top of the soil, or even on top of the weeds themselves. To control perennial weeds, an application of 12 to 16 inches of mulch is needed.

The reappearance of weeds in an area that has been mulched is an indication that the mulch has decomposed to such a degree that a new application of mulch is required.

While the benefits of applying mulch are many, mulch can also lead to an increase in mole activity because of the increase in the worms and grubs they feed on – the more alive your soil is, the more it becomes a habitat for other creatures.

Mulch can deplete the soil of nitrogen during the process of decomposition, so it is a good idea to supplement occasionally with applications of fertilizers rich in nitrogen such as manure, bloodmeal, feather meal (made from chicken feathers), or cottonseed meal.

Finally, different garden situations require different choices of mulching materials: for example, dryland garden plants (xeriscape plants) such as native California plants, cacti, and succulents, have evolved to flourish in dry conditions and poor soil. The moisture-retentive qualities of organic mulch could be detrimental to their vigor and growth while the use of stone or gravel mulch would be helpful in replicating their natural environment.

Your mulch choices can range from commercial mulches purchased at a landscape center, to bags of organic mulch available at nurseries and home improvement stores, to your own (free!) shredded leaves, grass clippings, and yesterday’s paper. The benefits of mulching far outweigh any negatives, so there is no reason not to mulch.

By Ken Hodge, Butte County Master Gardener, February 15, 2013

Growing your own fruit has become very popular, especially in these times of economic downturn.  And February and March are an excellent time to plant fruit trees bare-root, which can be a budget-friendly way of starting a home orchard.

It is not difficult to grow fruit trees, but with some help and planning, growing your own fruit can be even more rewarding.  Everyone has their favorite fruits to eat, and some fruit lovers may know which varieties they prefer (such as the Bing cherry, the O'Henry peach, the Freckle Face nectarine and the Dapple Dandy pluot), so your own preferences are a good place to start when planning your home orchard.

It's also good idea to look at a ripening chart to see when different fruit varieties ripen.  Choosing species and varieties that spread out ripening dates can provide tree-ripened fruit throughout the year. It is possible to have some type of fruit ripe in your little orchard every season of the year, especially if you include winter- and spring-ripening citrus, such as Washington navel oranges and Clementine or Pixie mandarins.

Another consideration in variety selection is flavor and sweetness. White peaches and nectarines tend to be sweeter than yellow-fleshed peaches and nectarines because they have lower acid content.  Since even a small fruit orchard is a long-term project, it's important to read a good description of each variety before selecting your fruit trees.

With plums, many people object to the tartness of the fruit, especially in the skin and around the pit. But in Pluots, plumcots and Apriums (a plum x apricot hybrid), the tartness is replaced by more sweetness.

Many varieties of cherries, pears, Asian pears, plums and pluots need to be pollinized by another variety. For instance a Santa Rosa plum is fine by itself, but a Flavor Supreme pluot needs the Santa Rosa plum or another pluot that blooms at the same time, in order to pollinate it and set fruit.

Likewise a Stella cherry is fine by itself, but a Bing cherry requires the Stella or a Black Tartarian cherry for pollination. Pollination is not overly complicated, but it is important to get it right. Fortunately fruit growing is so popular in Butte County that one of your neighbors may have a tree that fulfills your pollination needs, so you might ask your neighbors what kind of fruit trees they have growing already.

The site you select for growing trees can be a designated orchard area or the trees can be spread out throughout your landscape. Many trees such as persimmons also make good shade trees and they have nice fall color.  Citrus trees or shrubs are evergreen, so they can be used to create a good barrier, similar to a hedge of Photina or privet, but with the added benefit of edible fruit, fruit trees are a practical landscape ingredient that can serve both aesthetics and food production.

Generally fruit trees need full sun to be the most productive, but even a half day's sunlight may suffice although fruit production will be reduced.  If partially shaded trees stretch for sunlight, more pruning may be required to keep the trees bushier.

Growing your own fruit can be very rewarding and you'll be surprised how many friends you have when your fruits are ripe.  But seek good advice and check out your options before planting, since even a mini fruit orchard is a long term project that you’ll want to get right from the beginning.

By Brett McGhie, Butte County Master Gardener, February 1, 2013

Integrated Pest Management (IPM) is a science-based pest management process which focuses on the long-term prevention of pests and their damage by managing the ecosystem.  The University of California Division of Agriculture and Natural Resources has developed an IPM program dedicated to helping Californians “prevent and solve pest problems with the least unintended impacts on people and their environment.”  For the home gardener, a guiding principle of IPM is to understand why your landscape favors particular pests, and help you enact changes which will make that environment less attractive to those pests.

The first steps in the IPM process involve identifying what pests are present and then monitoring their numbers and the extent of the damage they are causing.  At this point, it can be determined whether the pest can be tolerated, or if further actions need to be taken.  The guiding principal with IPM is to use the least harmful control method(s) that will be effective in managing a particular pest.  These methods include one or more of the following: cultural controls, biological controls, mechanical and physical controls, and chemical controls.

Cultural control involves creating an environment that prevents and/or reduces pest populations.  Practices such as careful site selection, sanitation (removing garden debris), water management and fertilization are examples of cultural control.  Many pests overwinter in garden debris left lying on the ground.  If plants are stressed because of poor growing conditions, they are more susceptible to insect attack.  Fungal diseases can be encouraged if too much water or fertilizer is applied to the garden.  Controlling pest damage might also be as simple as selecting plants that are disease- or pest- resistant. In the long run, good cultural practices often eliminate the need for other pest control measures.

Biological control uses natural enemies, such as predators like ladybeetles, lacewings, or praying mantis, to control pests.  Natural enemies also include parasites and pathogens (diseases that attack the pest).  For example, several tiny wasp species parasitize garden caterpillars, and the pathogen Bacillus thuringiensis, is a commercially-available bacterium that attacks caterpillars, but is nontoxic to other organisms.

Mechanical and physical controls either kill a pest directly or exclude it from an area.  A gopher trap is an example of mechanical control.  Physical control includes mulching, cultivation, or mowing to eliminate weeds, and the use of nets and screens to exclude insects and birds.

Chemical control is the use of pesticides.  With IPM, pesticides are used as a last resort and in combination with the other control methods mentioned above.  If pesticides are deemed necessary, it is important to use them as selectively as possible and to take into consideration how safe a pesticide is for other organisms, including the natural enemies of the targeted pest.

The Butte County Master Gardeners, along with Master Gardeners statewide, have been trained in the UC Agriculture and Natural Resources IPM program and are ready to support local gardeners who are interested in utilizing this approach to pest management. If you want to know more about IPM, you can call the Butte County Master Gardeners at (530) 538-7201.  You can also read more about IPM by visiting the UC Davis IPM website: www.ipm.ucdavis.edu.

By Brent McGhie, Butte County Master Gardener,January 18, 2013

Plum leaf curl is indicated by tightly curled, deformed leaves, which are usually near the ends of new plum shoots in the spring. Unlike leaf curl in peaches and nectarines, which is caused by a fungus, leaf curl in plums is caused by an infestation of the leaf curl plum aphid, Brachycaudus helichrysi. This insect sucks tree fluids from plum leaves, causing them to curl.  Colonies of these aphids will mass inside the curled leaves on which they are feeding. 

The leaf curl plum aphid is shiny and can vary in color from yellowish green to brownish yellow.  While doing their damage, they secrete large amounts of honeydew, which can attract ants and encourage the growth of sooty mold fungus on the leaves as well. Although this mold is unsightly, it does not harm plum leaves directly.  However, it can interfere with photosynthesis by partially blocking the sunlight that reaches the leaves.  Heavy infestations of aphids can also slow tree growth, reduce fruit size and reduce fruit sugar content.  

The leaf curl plum aphid overwinters as eggs deposited near the base of buds. In spring, the eggs hatch and the aphid population builds rapidly on newly opened leaves. In May, the aphids migrate from their plum tree host to summer host plants in the daisy family (Asteraceae).  In the fall, leaf curl plum aphids return to plum trees to lay their eggs and the cycle begins again.

There are several natural enemies of the leaf curl plum aphid. These include lady beetles, green lacewings, brown lacewings and soldier beetles. Although these insect predators can often lead to natural control of aphid populations, any damage that the aphids have already caused cannot be undone. Curled leaves will remain curled and fruit size may still be reduced after the aphids are suppressed. If leaf curl plum aphids are a chronic problem, two treatments of horticultural oil just as buds are swelling can be effective. Hard blasts of water can remove the aphids from trees if this is done early in the growing season before they have been able to shelter inside curled leaves. Additionally, limiting the amount of nitrogen fertilizer applied to the plum tree leads to less new shoot tip growth, thus depriving the aphids of their favorite plant parts. Pyrethrins or insecticidal soap can kill aphids during the growing season, but are usually ineffective because the aphids are protected inside their curled-leaf home.  Whenever a pesticide is used it is important to read and follow all label instructions and to consider its impact on natural enemies and pollinators such as honey bees.  Treatment of trees later in the summer will have no impact on the aphids because they will not be present; they have moved on to their summer host plants.

Information in this article is based on an entry found in UC Pest Management Guidelines, “Leaf Curl Plum Aphid” at UC IPM Online. For more information on managing the leaf curl plum aphid and other pests, visit the UC IPM website at:  www.ipm.ucdavis.edu

Photo: Leaf Curl Plum Aphids