Master Gardeners are obliged to dispense home gardening advice that is based on valid, reliable research performed by unbiased and reputable organizations.  Since we are an arm of the University of California Cooperative Extension, the information we pass on to the public is university-researched and not based on a specific company's possible economic benefits from product use.  Therefore, this column is aimed at debunking some garden myths that have floated around for many years.  Research done by the University shows that most of these practices have no value whatsoever and in some cases, are even bad for your plants.  Dr. Robert Raabe, Professor Emeritus and UC Plant Pathologist, as well as Cindy Fake, Horticulture & Small Farm Advisor from Placer and Nevada Counties, are frequent speakers at Master Gardener meetings, and following are some excerpts from their talks on garden lore:    

Vitamin B1 on plants:  Using vitamin B1 to prevent transplant shock has shown no benefit whatsoever after multiple experiments, both in a laboratory setting and in the field, on a variety of plant species.  Using B1 may make the gardener feel good and certainly the manufacturer, but your plants will be totally indifferent to it.

Putting gravel, pebbles or broken pottery in plant containers:  This one not only doesn't help your container plants, it can actually lead to their demise.  This practice creates a situation that leads to root rot because it causes poor drainage rather than promoting it.  Water moves through planting medium to eventually result in the formation of a saturation zone at the bottom of a pot.  This will occur slower from fine-textured soil (like your potting mix) to larger-textured medium (like gravel, etc.) than if the soil is uniform.  Therefore, the act of filling the bottom of a pot with anything but potting mix decreases the volume of the soil column, leading to the saturation zone occurring in a plant's root zone with rot possibly resulting.  The only things you should put in a container is potting mix and the plant.  If you still persist in believing that "junk" at the bottom of a pot helps drainage, remove a plant from a 5-gallon container and smell the bottom of it; it will invariably have a rotten odor which is not a good thing. 

Peonies need ants to help open their blossoms:  This myth has been around forever.  In reality, if you see ants on your peonies, they are merely feeding on the sticky sap produced by the buds.  Ants may also help attack natural enemies of peonies that come to feed on the nectar and pollen.  What does make a difference in whether or not peonies bloom is planting them at the right depth and making sure they are in a location that gets sun exposure . . . peonies are not shade plants. 

Painting pruning wounds hastens healing:  First, tree wounds don't heal, they seal over.  Painting them actually may harm a tree because some wood-rotting organisms may already be on the cut surface and if you paint over them, you're just sealing these harmful organisms into a warm, moist environment where they can grow and multiply.  Prune at the proper time for a plant or tree and leave the pruning wounds alone. 

Adding gypsum will help "loosen" clay soils:  True, but only if your clay soil is sodic which is not the case for most of our clay soils in the foothills (sodic clay is present when sodium instead of calcium or magnesium saturates the clay).  Gypsum does not improve soil drainage problems caused by compaction or "loosen" heavy clay soils which are low in organic matter, the usual situation for most foothill gardeners. Therefore, adding lots of organic matter to your clay soil instead of gypsum is the best solution. 

Bigger does not mean better:  Research shows that planting a 1-gallon size plant or tree will catch up to (and often surpass) a 5-gallon size within one to two years.  Planting a smaller-sized ornamental or tree also is less expensive to buy and easier to dig a hole for.

Advice that is passed down through time is hard to ignore, especially that which you probably hear time and time again, but gardening practices are ever-changing and really should be based on hard research.  To assess the validity of garden information, you should first consider the source.  Then, go on to ask questions.  Is it unbiased and not based on economic benefit?  Can results be replicated by other researchers in other locations with similar results?  What data support the conclusions?  If there are only testimonials and no data, beware.  Last, make sure the data are relevant to our climate, soil and ecological conditions.

There is no Master Gardener class tomorrow, but next Saturday, August 5, we are offering a free class on planting and harvesting Fall & Winter Vegetables.  It will begin at 9 a.m. in the Ag Extension Office at 311 Fair Lane in Placerville and will last until approximately noon.  If you can't attend, but have questions on this or other home gardening topics, call our office at 621-5512 Monday through Friday, 9 a.m. to noon.  We also welcome walk-ins at the above address.