24 TREES AND SHRUBS 



shortened back after flowering, and if on a wall they 

 should be spurred in. 



Chionanthus. — See Cercis. 



CiSTUS. — Those which are hardy of this genus 

 should be cut back each spring while in a young 

 state, but when they have attained a flowering size no 

 pruning is required. The cutting back of young 

 plants induces a bushy habit, and also keeps them 

 from weakening themselves by blooming and seeding. 



Clematis. — The garden forms of this genus are 

 divided into two sections, of which C. Jackmani, 

 C. lanuginosa, C. Viticella, and C. aromatica (C. cmrulea 

 odorata) are the types of those which flower on the 

 young wood, and which require cutting back close 

 to the old wood in the winter ; while C. florida, 

 C. patens, and C. montana are the types of those 

 which flower on the ripened wood of the previous 

 year, and merely require a thinning out of weakly or 

 unnecessary growth. Of species other than those 

 mentioned above, C, Flammula, C. paniadata, and 

 C. Vitalba flower on the young wood ; and the re- 

 maining species are either herbaceous or flower on 

 the old wood. 



Clethra. — These practically require no pruning, 

 but long shoots may be shortened and weakly ones 

 cut away with advantage. 



CoLUTEA. — These make better plants and flower 

 later if they are cut back every winter. C. istria (a 

 rare species) should not be cut down if flowers are 

 desired. 



CORNUS. — The strong-growing shrubby Cornus, 



