156 
JOURNAL  OF  HORTICULTURE  AND  COTTAGE  GARDENER. 
February  25,  1904. 
nightly  readings,  and  comparing  them  with  the  readings  of 
the  previous  evenings  can  one  gain  experience  in  forecast¬ 
ing  frosty  nights.  The  thennometer  should  be  hung  4ft  or 
5ft  above  the  ground,  and  should  be  fairly  exposed  to  the 
north  and  east  winds,  as  it  is  from  those  quarters,  especially 
the  latter,  that  most  of  our  spring  frosts  come. 
A  sufficiently  reliable  minimum  thermometer  can  be 
bought  for  two  shillings,  and  if  at  any  time  detached  drops 
of  the  spirit  get  into  the  upper  part  of  the  tube  they  can 
easily  be  made  to  rejoin  the  original  bulk  by  holding  the 
thermometer  in  the  hand,  bulb  downwards,  and  throwing 
the  hand  down  swiftly  and  stopping  with  a  jerk.  Those 
who  wish  to  go  into  the  matter  with  greater  nicety  will 
have  a  wet  bulb  thermometer  as  well  as  a  dry  bulb,  the 
forrner  having  the  bulb  either  immersed  in  water,  or  with 
a  piece  of  cloth  wrapped  round  it,  which  can  be  soaked  in 
water  when  it  is  desired  to  take  a  reading. 
The  two  thermometers  together  enable  one  to  find  out 
the  amount  of  moisture  in  the  air,  and  the  temperature  the 
air  must  fall  to  in  order  to  be  completely  saturated,  in 
other  words,  the  dew  point,  by  noticing  the  radiation  of 
temperature  by  evaporation,  and  referring  to  a  table  of 
temperatures  prepared  for  the  purpose.  The  greater  the 
difference  between  the  readings  of  the  dry  and  wet  bulbs  in 
a  given  temperature  of  the  air  the  greater  the  danger  of 
frost.  . 
Everyone  knows  that  if  the  sky  is  overcast  there  is  very 
little  chance  of  a  frost,  at  least  in  the  spring,  as  the  clouds 
prevent,  or  rather  lessen,  the  radiation  of  heat  from  the 
earth.  When  the  evening  is  still  and  the  sky  clear  the 
temperature  drops  rapidly  after  sundown  at  any  time  of  the 
year.  As  the  earth  gives  off- its  heat  the  stratum  of  air  in 
contact  with  the  earth,  and  the  vegetation  upon  it,  are 
rapidly  cooled,  and  the  air  may  be  many  degrees  cooler 
there  than  5ft  above  the  ground.  Hence  a  distinction  is 
always  made  between  readings  on  the  grass  and  5ft  above. 
This  has  very  important  effects  upon  the  fruit-grower  if 
he  is  in  a  low-lying  situation,  especially  if  near  rivers, 
swampy  meadows  or  sheets  of  water.  An  exception  to 
this  statement  must  be  made  in  the  case  of  vast  sheets  of 
water,  as  the  effect  of  the  proximity  of  such  is,  on  a  smaller 
scale,  like  that  of  nearness  to  the  sea,  namely,  that  it 
renders  the  climate  more  equable.  I  have  said  that  the 
air  close  to  the  ground  is  coldest.  Hence  all  over  the 
country  there  will  be  a  cold  stratum  of  air  near  the  ground, 
and  as  this  is  heavier  than  air  a  degree  or  two  warmer,  this 
colder  air  -will  seek  its  own  level  like  so  much  water,  that 
from  the  high  ground  sliding  dowm  into  the  valley  and  dis¬ 
placing  the  warmer  air  which  is  there  immediately  above 
the  cold  stratum. 
The  consequence  will  be  that  the  air  being  so  cold  for 
perhaps  several  feet  above  the  ground  in  the  valleys,  the 
radiation  of  heat  from  the  ground  will  go  on  all  the  faster, 
and  hence  it  will  freeze  in  all  the  valleys  before  it  freezes  on 
the  higher  lands,  as  a  cup  of  tea  will  give  off  its  heat  faster  in 
a  frosty  air  than  it  will  if  set  in  the  fender  with  the 
warm  air  above  it.  Hence,  w'e  see  how  it  is  that  in  low- 
lying  situations  there  is  more  frost,  or  at  least  what  may  be 
called  the  dewy  frosts  of  spring,  than  on  higher  ground. 
This'  statement  needs  this  amount  of  modification,  that, 
after  a  certain  elevation  the  advantage  is  counteracted  by 
the  greater  dryness  and  rarity  of  the  air  inducing  more 
rapid  radiation. 
Fruit-growers  attach  much  importance  to  having  fruit 
land  where  there  is  atmospheric  drainage,  that  is,  land  so 
situated  that  the  cold  air  can  run  off  and  slide  down  to 
some  lower  lands.  A  remarkable  instance  of  this  was  seen 
in  the  spring  of  19U2.  In  a  garden  situated  in  close 
proximity  to  river  meadows  there  were  on  May  14,  lOdeg  or 
12deg  of  frost,  which  cut  off  nearly  all  fruit  that  w’as  not 
protected.  In  another  garden,  three-quarters  of  a  mile 
aw’ay,  but  on  higher  ground,  only  4deg  or  5deg  of  frost  were 
experienced,  and  the  owner  had  a  very  good  fruit  year. 
Many  will  have  noticed  when  cycling  or  driving  on  a  still 
spring  or  summer  evening  how  in  going  down  a  hill  one 
generally  enters  a  cooler  atmosphere.  Where  there  are 
no  valleys  for  the  cool  air  to  run  down  into,  in  other  w’ords 
w'here  the  country  is  perfectly  flat,  there  is  almost  certain 
to  be  a  good  deal  of  frost,  the  Fen  district  being  an 
extreme  case  in  point. 
Thus  we  see  the  necessity  for  a  fairly  still  night  for  a 
spring  frost,  for  if  there  is  wind  the  air  of  all  places  is 
mixed  together — the  low'er  stratum  of  air  with  that  above 
it,  the  air  of  the  valleys  with  that  of  the  high  ground— thus 
maintaining  a  fairly  uniform  temperature,  and  instead  of 
lOdeg  of  frost  in  the  valley  and  3deg  or  4deg  on  the  higher 
ground  there  may  be  only  4deg  or  5deg  everywhere  alike. 
April,  1903,  was  a  remarkable  exception  to  the  statement 
about  still  nights  and  frost,  and  is  the  only  time  we  remember 
of  sharp  frost  and  strong  wind  together  so  late  in  the 
spring,  and  high  and  low  lands  felt  it  Avith  about  equal 
severity. 
The  above  statement  of  elementary  facts  will  be  familiar 
to  most  gardeners,  but  was  necessary  to  make  clear  what 
is  to  be  said.  Those  who  have  not  studied  the  matter 
before  wdll  see  that  we  can  generally  know  when  there  is  a 
likelihood  of  frost.  Of  course,  the  sky  will  sometimes 
clear  and  the  stars  come  out  towards  morning,  the  minimum 
temperature  usually  being  at  sunrise  ;  but  if  it  does  not 
clear  till  nine  or  ten  in  the  evening  in  April  or  May,  when 
the  temperature  is  above  40deg,  there  is  not  likely  to  be 
enough  frost  to  injure  fruit  blossom.  If  it  is  dry  most  fruit 
blossom  will  stand  odeg  or  6deg  of  frost  wdthout  injury, 
sometimes  even  more. 
By  looking  at  the  thermometer  in  the  evening  one  gets 
to  know  just  what  to  expect.  If  the  gardener  is  the  only 
person  to  cover  up  trees,  and  he  is  not  accessible  after  five 
or  six,  the  trees  must  be  covered  up  more  often  than  when 
there  is  someone  handy  to  do  the  work  if  need  be  as  late 
as  nine  or  ten  o’clock  if  the  temperature  is  seen  to  be 
rapidly  falling,  consequent  upon  a  sudden  clearing  of  the 
sky.  If  the  man  on  duty  comes  round  at  nine  or  ten  o’clock 
to  make  up  the  fires  he  could  make  it  a  rule  to  look  at  the 
temperature,  and.  if  necessary,  cover  up  or  protect  trees 
w’ith  the  aid  of  a  lantern.  It  need  not  be  a  long  operation, 
if  the  necessary  things  are  kept  ready  for  an  emergency  and 
are  properly  contrived.  The  essential  point  is  to  have 
everything  ready  Avhen  wanted,  so  that  it  is  known  just 
which  things  to  use  for  each  particular  tree.  If  the  spring 
goes  on  and  they  are  not  wanted — a  rare  thing — all  the 
better,  for  it  will  be  a  marvellous  fruit  year. 
It  goes  without  saying  that  the  trees  need  much  more 
protection  when  in  blossom  than  after  the  fruit  is  set, 
for  not  only  will  the  fruit  stand  more  frost  than  the  blossom, 
but  there  is  generally  foliage  to  protect  it.  Some  gardeners, 
after  covering  up  wall  trees  when  necessary  during 
blossoming  time  cease  to  do  so  after  the  fruit  is  set,  put 
long  fishing  nets  in  front  of  the  wall,  which  as  a  rule  will 
sufficiently  moderate  any  frosts,  to  spve  the  fruit. 
As  stated  above,  it  is  Apricots  and  Peaches,  and  in  a 
less  degree  Plums,  which  need  to  be  w'atched  for  such  a 
long  time.  A  frost  so  often  comes  when  the  young  Plums 
are  just  forming,  when  there  is  no  foliage  worth  speaking 
of,  and  the  embryo  Plums  are  blackened.  Some  are  w’orse 
than  others.  Green  Gage  being  especially  bad,  often  shed¬ 
ding  all  its  fruit  during  continued  cold  w^eather,  even  if 
there  is  little  or  no  frost.  With  d^varf  Pears  the  protection 
is  a  small  matter,  but  they  seldom  get  it,  which  is  all  the 
greater  pity  ;  as  just  the  throwing  of  some  light  covering 
over  the  bushes  or  pyramids,  perhaps  only  once  about  the 
end  of  April  or  beginning  of  May,  may  make  all  the  differ¬ 
ence  between  a  good  crop  and  none  at  all.  With  Apples 
it  is  a  still  smaller  matter,  as  we  rai’ely  get  more  than  one 
damaging  frost  while  they  are  in  bloom,  and  seldom  or 
never  after  it  is  over. 
One  knows  it  seems  most  futile  labour  covering  up  trees 
at  night  and  uncovering  them  in  the  morning,  but  one  is 
well  rewarded  in  the  summer  by  seeing  the  fruit  develop, 
and  knowing  that  it  was  one’s  own  efforts  which  saved  it 
from  destruction.  In  1903  we  had  the  gratification  of  seeing 
a  good  crop  of  Peaches  and  Apricots  on  our  trees 
through  having  protected  the  trees  in  the  spring, 
a  gratification  which  was  not  lessened  by  seeing 
trees  in  other  gardens  quite  devoid  of  any  fruit  through  the 
neglect  of  adopting  this  simple  precaution. — A.  Pktts. 
Beetuoot  C.'ultivation  in  Greenock. — The  directors  of  Berry- 
yards  Sugar  Refinery,  Greenock,  gave  to  their  employes  a  little 
over  a  year  ago  a  plot  of  ground  and  qlubhouse.  At  that  time 
they  suggested  tha,t  the  amateur  gardeners,  in  conjunction  with 
the  plot-holders  of  the  Lyudoch  Allotment  Gardens,  go  in. for 
the  cultivation  of  sugar  Beetroot.  This  has  been  going  on  for 
some  time,  and  excellent  results  are  being  obtained. 
