plant collecting

Robin Leech robinl at CONNECT.AB.CA
Tue Oct 12 18:03:29 CDT 1999

Don't be too carried away with "Rule of Thumb".  This comes from The Old
English Law,  which states that a man may beat his wife with a stick no
thicker than his thumb.  Things have changed, eh.  Just for your info.
Robin Leech

----- Original Message -----
From: Adolf Ceska <aceska at VICTORIA.TC.CA>
Sent: Tuesday, October 12, 1999 8:53 AM
Subject: Re: plant collecting

> David Wagner published his "Rule of thumb" in Oregon Flora On-line
> Newsletter and elsewhere. This is a version from BEN (Botanical Electronic
> News) # 180 (Dec. 12, 1997):
> From: Dr. David H. Wagner <103132.2716 at>
>     originally published in the Oregon Flora On-Line Newsletter
>     Volume 1 Number 3 - Oregon State University - July 1995
> There have apparently been instances in  the  past  where  well-
> meaning  botanists have destroyed plant populations through over
> zealous collecting. The case most familiar to me concerns one of
> the world's rarest  ferns,  the  pumice  grape-fern,  Botrychium
> pumicola.  A  student  searching  for  new  sites  found two in-
> dividuals of this species on Oregon's Tumalo  Mountain  in  1954
> which  he  collected  to  make  herbarium specimens. In the late
> 1970s I searched the top of Tumalo  Mountain  with  friends.  We
> were  experienced  fern  hunters,  but we found no Botrychium. I
> strongly suspect that the two plants removed in 1954  eliminated
> the  population  at  this  location.  Today  we  would hope that
> botanists finding only one or two plants at a site  would  docu-
> ment   their   discovery   with   photographs  and  notes.  Good
> photographs and careful field notes are increasingly  acceptable
> for recording plant discoveries.
> Nevertheless,  from time to time, a field worker may encounter a
> small population of a plant and feel it is necessary to  collect
> a  bit  of it for positive identification and documentation. The
> Native Plant Society of Oregon's Guidelines  and  Ethical  Codes
> for  botanists  urges  that  a  collector use good judgement and
> rules of thumb when deciding whether or not to collect.  But  in
> this  case,  what  is  a  good rule of thumb? During the past 10
> years, I have been using what I call the "1-in-20 Rule."
> The 1-in-20 Rule dictates that a  botanist  never  collect  more
> than one out of twenty plants. It means NOT collecting ONE plant
> UNTIL  you  have found at least TWENTY. Only if twenty are found
> should you consider collecting one plant. And  forty  should  be
> present  before  two  are  taken, and so on. The rule applies to
> parts of plants, also: remove no more than  five  percent  (one-
> twentieth) of a shrub, one fern frond from a clump of twenty, 5%
> of  a patch of moss, 5% of seeds from a plant. I use the 1-in-20
> Rule whether I am collecting  voucher  specimens  for  the  her-
> barium,  doing  rare plant work, or gathering common species for
> classroom use.
> The 1-in-20 Rule does not obviate the need for  good  judgement.
> Only  when  a  botanist has the knowledge to assess whether col-
> lecting is both ecologically  justified  and  legally  permitted
> should a specimen be taken. Any pertinent factor relating to the
> survival of a population needs to be superimposed on the 1-in-20
> Rule. The main value of this rule of thumb is to provide a clear
> point of reference from which to begin assessing a situation. It
> helps  a botanist determine how much time should be spent inven-
> torying before sampling is appropriate. I  suggest  the  1-in-20
> Rule  as  a  minimal  criterion to be met before any taking of a
> plant be considered.
> There is at least a modicum  of  scientific  logic  behind  this
> rule.  Statistically,  a  population  sample  of nineteen is not
> significantly different from a sample of twenty. One  population
> geneticist  I consulted advised me that contemporary statistical
> theory would support the  1-in-20  Rule.  Another  pointed  out,
> however,  that  repeated  collecting  would tend to reduce every
> population to  nineteen  individuals.  This  caution  serves  to
> emphasize  that  the  1-in-20  Rule  is  a  rule of thumb, not a
> license to ravage.
> An interesting line of argument in support of the  1-in-20  rule
> has  developed  since I first published the idea in the Bulletin
> of the Native Plant Society of Oregon in 1991. First, I received
> a letter from James Grimes of  the  New  York  Botanical  Garden
> querying  whether or not I had picked up the idea from a similar
> article he and others had published in  the  newsletter  of  the
> Idaho Native Plant Society a few years before. I honestly cannot
> recall  seeing  their note. Then, last year, four botanists from
> Australia and New Zealand published an article in  the  interna-
> tional journal, Taxon, which made essentially the same recommen-
> dation. Thus, three botanists or groups of botanists, deliberat-
> ing  independently,  have arrived at the same standard. I submit
> that  this  concurrence  from  three  separate  sources   speaks
> strongly for the sensibility of the 1-in-20 Rule.
> ------
> Regards,
> Adolf Ceska
> -----------------------------------------------------------------
> Adolf Ceska, P.O.Box 8546, Victoria, B.C., Canada V8W 3S2
> e-mail: aceska at
> Phone: 250-356-7855 (work), 250-477-1211 (home)
> Fax: 250-387-2733 (work)
> .................................................................
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