Re: Flowering time : latitudinal relationships?

Dear Chris,

I have several books that are basically collections of flowering times for
a given area.  One for Boston, written by Mable Sedgwick in 1907.  She lists
plants only for the months of March-September and dates are early,
middle or
late for any given month.  In the preface, she writes "the season about
 New York is, generally speaking, ten days earlier.  A rough and ready 
calculation allows six days' difference to every degree of latitude"
Joseph Hudak compiled a similar book in 1976, which has since be reprinted
by Timber Press.  He is also in Boston, butclaims 3-4 days for each degree
of latitude.  Both of these books deal primarily with perennials. 

 My favorite, however, is Elizabeth Lawrence's "A Southern Garden",
 originally published in 1942. Miss Lawrence kept incredibly detailed records,
not only of the plants in her garden, but of the plantin her neighborhood.
She lists both the earliest recorded date of first bloom and the latest
recorded date.  She also did something which, as far as I can tell, the
other authors did not do.  She compared her records with those of
gardeners in other parts of the country.  She had Mrs. Sedgwick's book,
and used it.  Miss Lawrence has this to say  

"From dates for the North we are told to subtract according to our
position 
in the path of spring.  Here we are said to be about a month ahead of
New England.  
But records show that plants do not fall in as neatly with this mathematical
 maneuvering as we have been led to believe.  ........While it is true
that 
many plants do bloom just a month earlier with methere may be ten weeks 
difference in some, and practically none in others.  Here the tawny
day-lily 
blooms a month in advance of Mrs. Sedgwick's date, and the very early day-lilies
 a month to the day, but the golden day lily blooms here in mid April
and 
there in July.  Here Iris reticulata, recorde for the middle of March in 
Boston, rarely blooms more thatn two weeks ahead of that date."

(E Lawrence, "A Southern Garden"  UNC Press, 1991)


Don listed some of the other factors (besides latitude) and I would
include the heat bubble effect of urban areas and the altitude.


Incidently, if you would like to crosscheck some recent data, the MO
Botanical Garden, www.MoBot.org  ,  has posted plants in bloom, by week
for several years. 


If you ever decide to publish your records, I'll be in line to buy
a copy

Lisa


> 
> Does anyone know if any work has been done to establish a relationship
> between degrees of latitude and and flowering times?
> 
> I have lots of documented flowering times for the Chicagoland area, but I'd
> like to make this extensible to just about anywhere.   For example,
> Champaign-Urbana is about two weeks ahead of Chicago for most everything.
> Can I then assume that for each degree of latitude (approx. 69 miles, or
> 111 km) the flowering time will change by one week?
> 
> I'd say the answer is no since solar angles, etc. come into play for
> different seasons.  But there's also no doubt in my mind that someone's
> already put a lot more thought into this than I have.  :)
> 
> So please, any references or pointers would really be appreciated...
> 
> Thanks,
> 
> Chris

-- 
Lisa Flaum
Waterloo,  SW Illinois, USA
Temp range -10F-105F (-24C-40C),  clay soil,
Winter wet, unreliable snow cover;  Summer dry, punctuated by downpours
Member NARGS, AHS, RHS, AGS, SRGC, IBS, APS, ACS (I like seed exchanges)

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