6 FLOWERING PERIOD [CH. 



extent on external circumstances such as we term, in the 

 aggregate, season, climate, and weather. 



Some herbaceous plants will flower a few weeks after 

 sowing, and repeated crops may be obtained in one year. 

 At the other extreme are trees which do not flower until 

 they are fifty or sixty years old, and then die. Many of 

 our ordinary shrubs only commence to bear flowers after 

 from two or three to eight or ten years ; while trees are 

 usually much older before they bear flowers capable of 

 yielding seed. 



The following list gives the approximate age of flower- 

 ing in certain of our common trees : 



Ash, 20 to 25, or even 40 years. 



White Poplar, 10 years. 



Aspen, 10 to 20, or even 25 years. 



Lime, 15 to 20, or even 30 years. 



Sycamore, 10 to 25, or even 30 years. 



Norway Maple, 10 to 15 or 20, or even 40 years. 



Horse-chestnut, 15 to 20 years. 



Beech, 40 to 50, or even 60 to 80 years. 



Chestnut, 6 to 10, up to 20 or 30, or even 40 to 60 years. 



Oak, 20 to 50 or 60, or even 80 to 100 years. 



Holme Oak, 8 to 10 years. 



Cork Oak, 15 to 30 years. 



Hazel, 5 to 10 years, or even earlier. 



Hornbeam, 15 to 20 years. 



Birch, 8 to 10, up to 20, or even 30 years. 



Alder, 12 to 20, up to 35, or even 40 years. 



Spruce, 15 or less, up to 50, or even 70 years. 



Cedar, 30 to 40 years. 



Scots Pine, 15 to 20, up to 30 or 40, or even 70 to 80 years. 



Mountain Pine, 6 to 10 years. 



Austrian Pine, 15 to 30 years. 



Cluster Pine, 15 to 20 years. 



Arolla Pine, 25 to 50, or even 60 years. 



Weymouth Pine, 25 to 50 years. 



Stone Pine, 20 to 40, or even 60 years. 



