converting ºC to ºF or ºF to ºC

Adam Fikso
Mon, 09 Feb 2009 14:36:18 PST
 °  David?  Isn't  the conversion formula  supposed to be 5/9ths or 9/5ths + 
or - 32--not 40.?  That's what I remember from Berkeley High School, and U 
of C.

----- Original Message ----- 
From: "David Ehrlich" <>
To: "Pacific Bulb Society" <>
Sent: Monday, February 09, 2009 4:05 PM
Subject: Re: [pbs] converting ºC to ºF or ºF to ºC

A little trick I learned in Hight School:
Add 40º
multiply by 5/9 or 9/5, depending upon which way you want to go
Subtract 40º

This rule is far easier to remember than any other.

From: "" 
Sent: Monday, February 9, 2009 9:59:50 AM
Subject: [pbs] seed sowing - timing of

I find the exchanges here are always fascinating for numerous reasons not 
the least of which to some degree or other we are all probably slightly mad, 
in the nicest possible way of course. It seems the parameters under which 
various people strive are often wide ranging, both bio-geographically as in 
plants orininating from Northern and Southern Hemispheres as well as 
Maritime, Continental and Montane climatic ecosystems and just to sow yet 
more self inflicted confusion, Arid versus Humid.

For what little worth or interest it may be, here at ABG I sow seed of some 
250 - 300 taxa annually. Of necessity the genera being worked with are from 
north temperate, boreal, alpine / arctic climatic types. However, in 
practical terms the local climate here is borderline maritime / continental 
[just] = roughly to USDA Zone 6 to 7 but an added aspect which I don't see 
referred to in any questions and answers in relation to seed sowing.timing 
and so forth is any awareness of latitude effects that definitely have a 
bearing on seed germination amongst many genera. I function here effectively 
at 58 degrees North which puts me in terms of lux levels = day length and 
intensity, modified by cloud cover percentages at a different level of 
influence than say somebody trying to work with temperate genera in what is 
effectively a Mediterranean climate to a huge extent in say California, [ 
central and southern coastal ] and the analogues with European Balkan and
 Apennine mountains and S
outhern Alps in terms of your mountain locations. In other words we have 
almost total daylight allowing me to read a newspaper at midnight at mid 
summer to very low lux levels in the winter when the world is either grey or 
white for a few hours dayly. Right now here in early February we are getting 
darkish at 4 pm, we had - 18 C last night preceeded by 60 cms of snow on top 
of a previous fall a few days previously.

I admire your collective courage but am staggered by the hurdles you often 
appear to inflict on yourselves in some of the plants you try so hard to 
work with when they clearly are not suited to natural processes in such 
areas in so many instances. I can't do the calculations any more converting 
from Centigrade to Fahrenheit as we left that behind long ago with the rest 
of the world and my memory is pretty rubbish anyway, however there is a 
crude rule of thumb for temperature clines which runs roughly as that for 
every 100 metres of altitude there is a drop of 1 degree Celsius with 
intuitive allowances for aspect, i.e. north versus south on a slope, the 
latter being moderately milder than the former. Presumably someone will have 
access to the conversion factor between Celsius and Fahrenheit. Mention 
Fahrenheit here in Europe and the rest of the world pretty much and they 
look at you as if you as if you have some sort of affliction so I don't know 
where to
 go to do so but good
old Google might well be of help.

In general terms, temperate and boreal species, e.g. amongst Iridaceae and 
Liliaceae are best grown by sowing the seeds as mother intended, i.e. 
immediately they are ripe because so many need to be vernalised before 
breaking dormancy or become dormant and if not they will lay for one or two 
years before germinating if left until the spring. Both are an evolutionary 
survival strategy however we can't all get our seed as soon as its fresh 
especially when coming from a different hemisphere. Two final aspects I 
haven't seen referred to but may well have missed are [a] the influence of 
light on germination, some seeds discriminate against lux levels of any sort 
and will be inhibited in germinating, other seeds positively discriminate in 
favour of the need for lux levels at the right amount over a specific period 
in order to germinate, indeed soem lily seeds will germinate inside a fridge 
in the dark !; and [b] the fact that as far as I am aware, every plant
 has an endogenous rhyt
hm, i.e. their seed will, as in the case of the plants leaving dormancy, 
initiate growth / germination in response to a heat sum which for example in 
many Temperate and Boreal trees and shrubs is, put very crudely, around 8 
degrees Celsius per day time 'x' days at 8 degrees an admittedly broad brush 
generalised statement qualified by research based per individual genera. 
From the work I am doing at the moment on Lilium it seems that this may also 
hold true but there is more to be done and I haven't yet had time to analyse 
the figures recorded so far.

To illustrate the above, from my silvicultural days, we grow here a north - 
south cline of Silver Birch - Betula pendula, starting with trees from the 
most northerly place in the world where arboreal trees grow, i.e. Nord Cape 
in Norway straight down through Europe to a southern population of the same 
species from just north of Madrid in Spain. It is fascinating in Spring 
watching the leaf burst progress along the line of these trees as the heat 
sum accumulates and in reverse along the line watching onset of senescense 
in the Autumn. I suspect some of the problems folk are coming up against may 
be due to not allowing for or being aware of these, several or various, 
parameters to germination of their seeds.

I hope one or two of the above points might through some light on the 
subject and be of some help to somebody. Iain

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