IRISH GARDENING. 



69 



late frosts. A good example of the ameliorating 

 influence of a large water area is furnished by the 

 Peach belt, several miles wide, on the southern 

 shore of Lake Ontario. 



As the air over a lake is cooler by day than the 

 air over the land, the vegetation around the 

 lake and for a short distance inland will be 

 retarded in spring, and thus the danger from 

 late frosts is still further lessened over this 

 area. 



There are many large lakes in Ireland where 

 this influence ought to be felt, particularly 

 round the shores of Lough Neagh. How far the 

 influence of the lake extends inwards I am unable 

 to say, but it is noteworthy that there is a 

 good deal of fruit grown in that neighbour- 

 hood. 



So much for general considerations. It now 

 remains to refer to some of the figures recorded 

 from different localities, but the following facts 

 should be borne in mind : — (1) The figures refer 

 to shade temperatures, and, as is well known, the 

 actual temperature on the grass where the 

 thermometer is fully exposed is several degrees 

 lower than the shade temperature. From the 

 gardener's point of view the grass temperature 

 is much the more important of the two, as it 

 represents the actual amount of cold which the 

 plants have to bear unless protected in some 

 way. (2) The temperature of a place on the 

 sea coast is usually higher than that of a region 

 further inland owing to the sea being warmer 

 than the land in winter. (3) The temperature 

 of a town is usually considerably higher than 

 that of the country in the immediate neighbour- 

 hood, owing to the heat given off by numerous 

 chimneys, and also to the smoke hanging like 

 a cloud over the town. 



April Frosts. — As the result of a laree series 

 of observations in different places, it ma_\ be said 

 that frosts are liable to occur during this month 

 in all parts of Ireland. In view of what has beeu 

 said above, it will be evident that an inland 

 locality will be moie liable to frost than one near 

 the sea. If we select Birr Castle as typical of 

 inland localities generally, frosts have occurred 

 there in April every year during the period 

 1900-1911. The numbei of frosty nights during 

 the month varied from 1 in 1900 to 9 in 1906 and 

 9 in. 1908. and the lowest temperature recorded 

 in April during these 12 years was 23° in 1908 

 and again in 1911. 



May Frosts. — During the years 1886-1910 

 the lowest May temperatuie recorded for Malin 

 Head was 35° and for Blacksod Point 34°. 

 During the years 1876-1910 the lowest May 

 temperature recorded was 34° for Valentia. 35° 

 for Roche's Point, 28° for Birr Castle. 33° for 

 Donaghadee. 



Records of frosts in various places in Ireland 



during the month of May from 1882 onwards 

 are as follows : — 



1882, 30.9° at Killamev. 



1883, 29.1° 



1884, none. 



1885, 27.5° at Killarney. 



1886, none. 



1887, 30.2° at Killarney. 



1888, 1889. 1890, 1891, none. 



1892, 29° at Killamev. 



1893, none. 



1891, 31.3° at Ardgillan (Co. Dublin). 



1895, 32° at Killarney. 



1896, 28.5° 



1897, 30° 



1898, 30.8° 



1899, 30.6° ., 30° at Cahir. 



1900, 190], none. 



1902. 31.3° at Enniskillen. 



1903, 31° at Cahir. 



1901, 1905. 1906. none. 



1907, 30.2° at Cahir. 



1908, none. 



1909, 30.6° at Ardgillan, 30.2° at Cahir. 



1910, 1911, none. 



The full list of May frosts at Birr in 1909 was 

 as follows :— 2nd May, 30° ; 13th May, 32° ; 

 14th May, 29° ; 15th May, 29° ; 18th May, 32°. 



It will be evident from the above figures that 

 places on the sea coast are practically free from 

 May frosts. The figures also show that during 

 the 30 years from 1882 till 1911 May frosts 

 have occurred during 15 separate years in some 

 part of Ireland. 



The date of the last frost varies very con- 

 siderably in different years. The following are 

 the figures for seven years at Dublin : — 



1843, 13th April. 

 1841. 18th May. 



1845, 10th 



1846, 18th 



1847, 15th April. 



1848, 29th 



1849, 20th 



Lastly, it is worthy of note that a tempeiature 

 of 32° occurred at Birr Castle in June, 1881. 



Note. — It is very important in making 

 observations on temperature that the ther- 

 mometers used should be compared with a. 

 standard instrument. A minimum thermo- 

 meter which I purchased from a well known 

 firm invariably reads as much as 5° too high. 



Potentilla Vilmoriniana. 



By a printer's error in our last issue the illustra- 

 tion on page' 49 of Potentilla Vilmoriniana 

 appeared as P. Kilmoriniana. Several years ago 

 this beautiful shrub was introduced from China 

 by Mons. Maurice de Vilmorin, and it is proving 

 hardy, free-growing, and free-flowering in this 

 country, but requires full sunshine to bring out 

 its silvery foliage. In habit it is similar to 

 P. fruticosa, our native shrubby Cinquefoil, 

 forming a bush three to four feet h gh ; but the 

 flowers are a pale sulphur-yellow, with a deeper 

 coloured base. 



