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Coffee grounds

  • Coffee grounds and coffee filters are good nitrogen sources ('greens') in a compost pile, so add as part of the greens in your compost pile.

    Coffee grounds can also be used as a mulch.  They are acidic and can be used as a mulch by themselves around evergreens, camellias, and other acid loving plants.

    If you have a worm bin of red wigglers, use coffee grounds as worm food. Worms love coffee grounds, and the grounds enhance the texture of the final compost.  Tea leaves, tea bags (be sure to remove staples) and coffee filters are also acceptable worm food. Earthworms love coffee grounds too, so using as a mulch and/or in the compost pile is attractive to them as well.

Compost vs Mulch

  • Many people are confused about the terms “compost” and “mulch;” frequently these terms are used interchangeably, but they are not really the same thing.   We hope the table below will help to clarify what is meant by these terms.

    DEFINITION Compost is the biologically active material that results from decomposition of organic matter under controlled circumstances. Mulch is any material, organic or inorganic, that is spread over garden soil to cover it.
    BENEFITS The main benefit of adding compost to soil is improvement of soil structure. Compost is considered a soil conditioner, rather than a fertilizer, but more importantly, it can retain and make existing nutrients more readily available to plants. Mulch can suppress weeds, moderate soil temperatures to help keep plant roots cool and moist; conserve water; maintain a porous surface and help prevent soil erosion. An organic mulch can improve soil structure as it decomposes over time.
    USES Compost can be mixed in with garden soil to amend soil prior to planting and also to amend potting soils. Compost can be spread on top of the soil and used as a mulch or top dressing in planted areas. Mulch is spread on top of the soil.
    TYPES Compost can be prepared at home in a bin composter or can be purchased in bulk or by the bag.

    A specialized form of compost results from worm composting (vermicomposting).

    Organic mulches: wood chips, grass clippings, leaves, straw. Most organic mulches consist of fairly large particles, although compost can also be used as an oranic mulch. The larger the particles, the longer it will take for the mulch to break down.

    Inorganic mulches : stones, gravel, landscape fabric, plastic,

Compost, common problems

  • Here's a guide to common problems with compost and how to solve them. 

    For more information on composting, view the videos on how to make a compost pile.

    Download and read the brochure on how to compost.

Have your soil tested

  • To determine the exact components of your soil, you can do the following:

    You can purchase a soil test kit at many retail garden centers and do the testing yourself
    Soil test kits range in cost from $10 to $50 for multiple tests.  A Technology & Product Report from the American Society of Horticultural Science assessed the accuracy of commercially available soil test kits, as compared to test results from an analytical laboratory:
           #1. La Motte Soil Test Kit (La Motte Co., Chesteron, MD)   94%
           #2. Rapidtest® (Luster Leaf Products, Woodstock, IL)    92%
           #3. Quick Soiltest (Hanna, Woonsocket, RI)      64%

    Source: HortTechnology 17:358-362 (2007) 

    Or you can send a soil sample to a testing laboratory
    Testing laboratories charge for soil analysis.  We suggest that you call the selected laboratory prior to submitting samples. Quite often samples must be taken, packaged, and sent in a particular manner in order to obtain the best possible diagnosis.  Soil testing laboratories in Southern California are:

    1. Associated Labs, Orange (714-771-6900)
    2. Waypoint Analytical, Inc., Anaheim (714-282-8777)
    (Name change from Soil and Plant Laboratory )
    3. Wallace Laboratories, El Segundo (800-473-3699)
    4. The PACE Turfgrass Research facility in Oceanside (760-272-9897) maintains a list of soil analytical laboratories. 

    5. Orange County Farm Supply in Orange (714) 978-6500.  Call to see how they want sample to be prepared.


How to improve soil

  • To improve your soil, you'll need to add six to eight inches of organic matter to the entire bed. Help figuring out how much that is.

    You can add any organic matter you choose. Spread your organic matter on top of the soil. Here's where the manual labor comes in. The organic matter needs to be mixed into the top six to twelve inches of soil. Digging it in and mixing it with a shovel is a great way to do this, as it moves a lot of earth without pulverizing the soil particles the way tilling can. However, if digging is just too hard on your back, using a tiller is a fine method.

    When you're finished, your garden bed will be several inches higher than it was originally. It will settle some over the course of a season, but the soil structure will keep improving as microorganisms in the soil work to break down all of the organic matter you've added. The bed can be planted immediately, however. You'll be adding more organic matter on the top of the bed as a mulch once or twice a year. This will continue the process of improving soil structure and offset any settling that happens.

    Improve soil for established plants
    It is more difficult to improve soil around trees and other established plants than unplanted soil in, for example, a vegetable bed. To improve the fertility and the structure of the soil, consider using a thin (1 to 2 inch) layer of compost as mulch around the drip line of the tree or plant. Mulch is used on top of the existing soil surface.
    Be careful not to cultivate the soil (dig in) around the tree or plant, since many feeder roots are near the surface and cultivation can harm them. The compost mulch can be reapplied as needed.

How to reuse potting soil

  • Potting soil that has been used for one season to grow tomatoes, or for more than one or two seasons for growing other plants can be recycled. One good method is to add it to a compost pile.

    You can also refresh a pot by thoroughly mixing in about one-third by volume of new potting soil and adding fertilizer.

Looking for Worm Suppliers for Vermicomposting?

Manage clay soil

  • Managing Clay Soils in the Home Garden

    Soils that are predominantly clay also contain small amounts of silt and sand. Clay soils that crack excessively while drying are often called "adobe soils." If they are very low in organic matter, clay soils lose their structure and become cloddy and compact if plowed, stirred, walked on, or otherwise manipulated when they are too wet. Once a clay soil is badly puddled, it may take years of careful handling to restore good structure.

    Till with Care
    Tillage is commonly the first and most important step in preparing garden soil. Tilling helps to produce and maintain a good structure for seedling growth and rooting, control weeds, keep the soil permeable to water, and allow proper oxygen diffusion. Clay soils in particular must be handled with great care if favorable results are to be obtained from ordinary tillage practices.

    Use a Spading Fork
    When moist, clay soils should be dug with a spading fork rather than with a shovel or spade. As the soil is turned over, the large clods should be broken up with the side of the fork. The clods that remain should be exposed to the sun and air. After they have dried and crumbled somewhat, they can be wetted with a fine spray to soften them, and then raked when sufficiently dried again. The combination of air-drying, wetting, and raking will break up most of the clods. Although clay soils cannot be made ideal, they can be improved by any treatment which will cause the particles to form small granules and crumbs. The best treatment for this purpose is to incorporate large amounts of organic matter into the soil to promote better soil structure. The improved condition may remain long after organic matter has disappeared.

    Use Organic Materials
    Animal manures, green plant material, compost, and leaf mold are especially good for improving soil condition. Manure should be leached of the excessive salts to avoid injury to plants. Materials decaying very slowly, such as peat moss, straw, sawdust, rice hulls, and shredded bark, are somewhat less desirable because they do not aggregate the soil as well. These organic materials, when first incorporated into the soil, will compete with plants for the available nitrogen. It is advisable, therefore, to add extra nitrogen to the soil when using these materials. For example, to offset the competitive effect of a ton of straw, sawdust, or bark, it may be necessary to add an extra 30 to 50 pounds of elemental nitrogen; check label for nitrogen analysis in the fertilizer material purchased.

    These slowly decaying materials do not aid in bringing about good soil structure. They serve merely as fillers to increase the percentage of large pores and to improve the soil permeability.

    Large quantities of these materials are generally required to have value as a filler; as much as one-half by volume of soil could be needed for the treatment. Such additions may be economically feasible in garden areas or in preparing potting or bedding mixes. However, if only small amounts of good soil are required, as for potted plants, it would be better to import new soil rather than attempt to improve a tough clay soil.

    If organic materials that decompose slowly are used, cover the soil to a depth of about 4 inches. Incorporate this organic matter into the soil to a depth of about 8 inches. Watering should be done carefully to avoid excessive wetness below the 8-inch depth.

    Use Chemicals - Sometimes
    Gypsum is often recommended to improve clay soil. It is beneficial for sodic (alkali) soils, which often have poor structure. Although gypsum is seldom beneficial to garden soils it may be tried, at the rate of 1 pound per 5 square feet. The benefits obtained, if any, will be temporary, since irrigation water will gradually dissolve the gypsum out of the soil. In areas of high rainfall, lime may improve soil structure. However, most clay soils in California already contain sufficient lime. Lime should not be used for structure problems unless the soil is excessively acid.

    Use Mulch
    A surface mulch or thin layers of organic matter may eliminate the necessity for frequent cultivations and reduce evaporation. Organic mulch reduces the formation of soil crust, which impedes water entry into the soil. A good layer of mulch also prevents water droplets from eroding the soil.

    Planted Areas
    Lawns planted on poor clay soils are often hard to water and may develop shallow rooted ground cover. To improve lawns on these soils, an aerification program may be followed. Select aerifiers that remove soil cores 3 to 4 inches deep. The holes should be filled with chopped organic or other appropriate material. Repeating this procedure several times will improve the soil gradually. Gardeners who use time clocks should split water application into several intervals to avoid runoff and improve depth of water penetration.

    by Falih K. Aljibury, Area Irrigation Specialist, Parlier, CA
    University of California, Vegetable Research and Information Center

Mulch and leaf litter

  • Leaf litter gets mixed together in the mulch. Should it be turned into the soil or removed and replaced?

    Leaf litter acts as a very nice mulch and will decompose along with other types of organic mulch over time. It can be left in place when you replenish your mulch; this is generally done on a yearly basis or as needed.

Mulch, how often to add

  • Mulch slowly decomposes over time, and new mulch is needed to fill in gaps and build the mulch layer back up to about 2 to 4 inches. It is generally recommended that fresh mulch be added on about a yearly basis.

    When adding new mulch, it is best to leave the existing mulch in place and add the new mulch to the top. Mulch decomposes over time and adds to the fertility of the soil.

Mulch, what is it

  • Mulch is any material spread over the garden soil to cover it.  Mulch can improve water penetration, regulate soil temperature, and help to prevent soil erosion.  During the warm summer months, mulch reduces water loss and keeps soil cooler for plant roots.

    There is no one answer for ‘the best mulch’ to use.  Factors involved in making your choice will depend not only on what kind of garden area (vegetable garden, succulent landscape, around trees, etc.) you would like to mulch, but also your personal preference for the appearance of the mulch.

    There are two classes of mulch:
    • Organic mulches -- Organic mulches can conserve moisture, prevent surface crusting, improve water penetration, and cool the soil.  Organic mulches include compost, very fine wood chips, grass clippings, sawdust, leaves, clippings, chipped and shredded prunings, wood products, and hardwood or softwood bark chips or nuggets.  Gorilla Hair is a stringy redwood & cedar bark that forms a long lasting mat.  However, it is sharp enough to puncture the skin; it is also very pricey, something you may want to consider since you will probably be renewing your mulch on an annual basis.  Other organic mulches that are good are redwood and cedar mulches.  In time, organic mulches decay, providing nutrients and improving the soil texture at the same time, which is especially helpful for heavy clay soils.  Plan to replenish landscape mulches periodically because of decomposition, movement, or settling. 
     Inorganic mulches -- Natural inorganic mulches include sand, gravel, and pebbles. They do not provide organic matter for soil, but do conserve moisture. If using rocks as mulch, consider placing a landscape fabric underneath to create a layer between the mulch and the soil and to prevent rock pieces from sinking into the soil.  Black plastic has been used as a mulch to improve weed control, but it restricts air and water movement. Synthetic mulches, which are manufactured materials that are called geotextile or landscape fabrics, have been developed to replace black plastic in the landscape. Geotextiles are porous and allow water and air to pass through them, overcoming the major disadvantage of black plastic.

    Apply mulch to a weed-free area of soil to a depth between 2 to 4 inches.  Applying mulch at depths of greater than 4 inches may injure plants by keeping the soil too wet and limiting oxygen to the plant's roots. However, lesser depths may have less weed control benefits. Disease incidence may increase when deep mulches are maintained.

    Whenever you apply mulch, be careful to leave some space around the plant crown or tree base. If you pile any kind of mulch up against the crown, you may cause the stem/trunk to rot, so keep the mulch material at least 1 to 2 inches away from the stem or base of the plant.

    We hope this helps you to make a decision on the mulch you would like to use.  Most importantly, you are considering the use of mulch in your garden – good for it and good for the environment!

Poor draining soil

  • Poor drainage usually means that the soil particles are small and compacted. Clay soils have very fine particles and retain water. Compacted soils have poor structure with little air in the soil and so the water cannot penetrate.

    The remedy for poor drainage in soil is to amend the soil to improve its texture. Add organic matter such as compost and mix in to a depth of about 4 to 6 inches. This is an ongoing process, and it will take time and repeated applications of organic matter.

Soil Amendments

  • There are many factors to consider when choosing a soil amendment. Here is a summary article from Colorado State University Extension that has many useful ideas and good information.


Soil pH and drainage

  • Soils in California typically range from pH 5 (acidic) to 8.5 (alkalline).  Most plants do best when the soil pH is slightly acidic to neutral (pH 5.5 to 7.5) because absorption of minerals can occur in this pH range. At higher and lower pH some nutrients are not soluble, and therefore not available to the plant roots.

    Soil pH affects the availabililty of essential nutrients and also of toxic mineral elements.

    Very acidic soils (low pH) may contain inadequate levels of plant-available nitrogen, phosphorus, potassium, sulfur, calcium, magnesium, molybdinum and may contain toxic levels of aluminum and manganese.

    Very alkaline soils (high pH) are deficient in plant-available nitrogen, phosphorus, iron, and manganese but also may contain excessive concentrations of soluble salts or sodium, both of which are detrimental or toxic to plant growth.

    Low levels of calcium, magnesium and potassium in the soil can lead to low soil pH. Low soil pH can be adjusted by addiiton of lime (calcium carbonate, for example). High soil pH can be adjusted with additions of sulfur. These materials need to be incorporated into the root zone of the soil, and the process can take some time, especially for sulfur treatments.

    A saline soil is a soil that has excessive soluble salts and (usually) a high pH in the root zone inhibiting plant growth.  Saline soils can develop in the arid climates of California because evaporation of water vapor from the soil surface occurs more often than leaching, leaving the salts behind in the root zone. Saline soils develop a surface crust of whitish material (salts).

    Plants tend to show wilt when growing in saline soils. Saline soils should be irrigated depply to flush away the excess salts. Mulch on the soil surface helps prevent surface water evaporation, reducing the accumulation of salts in the root zone.

    A sodic soil is a soil that has a high pH (greater than 8.5) because of sodium accumulation alone without the presence of excessive concentrations of other salts.  High sodium levels are toxic to plants.

    Some soils are both sodic and saline.

    Gypsum (calcium sulfate) and sulfur are used to reclaim sodic soils. A common misconception is that gypsum lowers soil pH, but its major effect is to improve water infiltration of sodic soils or high-sodium irrigation water. Large amounts of water must be added to gypsum-treated sodic soils to leach away sodium displaced by gypsum. If excessive sodium is not present, adding gypsum will not improve water infiltration (drainage).

    Review information on testing your soil pH.

Soil, quick squeeze test

  • Here's a quick way to tell what kind of soil you have using the squeeze test. To determine your soil type, take a handful of moist (but not wet) soil from your garden, and give it a firm squeeze. Then, open your hand. One of three things will happen:

    Loam soil
    1. It will hold its shape, and when you give it a light poke, it crumbles. This means luxurious loam!

    Clay soil
    2. It will hold its shape, and, when poked, sits stubbornly in your hand. This means you have clay soil.

    Sandy soil
    3. It will fall apart as soon as you open your hand. This means you have sandy soil.

What is sterile soil?

  • Sterile soil is soil that has been steam sterilized to kill soil pathogens. It is best to use sterile soil for starting seeds.

Worm composting, common problems