Introduction - Raised Bed Gardening - page 10

Life Span of Material - Untreated wood will probably last 10 years in my cold dry climate,
but may not last but a few years in warm and wet climates like found in the Southern U.S.
Pressure Treated Woodis supposed to last for20years. Used railroad ties have already been
discarded but will last for many more years. Concrete blocks should last for a long time, but
some are brittle and will easily break if they are not filled with soil or mortared in place. I
have also seen some landscape or garden blocks that have totally deteriorated from freezing
and thawing in about 10 years.
Hold soil only and/or provide place to sit or walk - AnewtrendinlandscapingistheSeat
Wall. Why not build a raised bed that looks and sits like a seat wall? A typical 2x12 board
does a good job of holding soil inside the raised bed, but on edge, a single board makes a
poorseat.Additional lumbercouldbeattached tothetopsoftheraisedbedtocreate abetter
seat. Most true seat walls are made of stone, concrete or garden blocks.
Organic Requirements - Manypeoplethatstartraisedbedgardeningdosowiththeideaof
growingsomeoftheirownfoodthathaslittle ornopesticides. Ifthegardenissprayed,they
knowwhatkind,howmuchspraywasusedandwhenitwaslastused.Theymayormaynot
buy into the whole "Organic" idea.
I am not going to get into all the details here, but I know it is possible to have Arsenic
treatedwoodincontactwithsoil,foodoranimalsandstillbeCertifiedOrganicbytheFeder-
al Government. I like the idea of knowing where my food comes from and that it has not
been poisoned and does not have additives I don't want. But since the Federal Government
is in charge of the Organic Program, it works like everything else the Federal Government
touches. I am not convinced we are getting what we pay for or have been led to believe.
If you are interested in following the Organic Program, you need to be aware that some
building materials that could be used for raised beds may leach chemicals into the soil or
water. For more information see USDA Organic Certification Program .
Does the Material Leach chemicals or affect soil pH? - Read my take on using pressure
treated wood in the garden here: Chapter IV; Section 1 .
• Thepressuretreatedwoodavailableatmostbuildingsupplystoreswillleachcopper
into the soil. Copper is not a big deal in soil and not a big problem to people, but it
is a big problem in aquatic systems.
• WoodtreatedwithArsenicisstillavailableforagriculturalpurposesleachesarsenic
into the soil.
• Soil in contact with concrete will have elevated pH because of the lime in the con-
crete. This is good for some plants, but is not good for plants that prefer low pH.
• Metal materials can leach metals into the soil especially at pH 5.5 or lower - fortu-
nately, most plants prefer pH above 5.5.