66 COMMON WEEDS 



occasionally very troublesome in arable land. Only 

 last summer (1909) a friend wrote to the author from 

 Lincolnshire : lt I never saw Pepperwort here until a 

 few years ago ; it appeared in a field on the site of 

 an old stackyard, now all arable. I hoe it, pull it, 

 and this year I have mown 50 square yards, corn 

 and weeds together. It seems to spread awfully, 

 and is appearing at other points. I am sowing the 

 field down to four years' ley, and trust it will not come 

 after." 1 The taking of a root crop, or if necessary two 

 root crops in succession, should reduce it considerably. 

 As the plant is only produced from seed, seeding must 

 be prevented by tillage operations or by hand pulling. 



Another Pepperwort (Lepidium Draba L.) is occa- 

 sionally troublesome on land near the sea, as on warp 

 land, chiefly in the south of England. Although an 

 " alien " in Britain, it is a common weed of roadsides 

 and fields on the Continent. It is a perennial, branched, 

 downy plant, i to 3 feet high. The leaves are oblong, the 

 lower being stalked, while the upper have an arrow- 

 headed base which clasps the stem. The flowers are 

 white, | inch in diameter, in short corymbose clusters. 

 The pods are nearly heart-shaped, and constricted in 

 the centre. Flowering occurs from May to June. If 

 allowed to seed, this weed may spread rapidly and 

 become a pest. It is therefore necessary to prevent 

 seeding entirely for a year or two by thorough tillage 

 operations and the use of hoed crops. 



Penny Cress or Mithridate Mustard ( Thlaspi arvense 

 L.) is an erect annual with simple stem, i to 2 feet high. 

 The leaves on the stem are somewhat oblong, arrow- 

 shaped, and toothed ; the white flowers are only \ inch 

 across, while the round flat pods are two or three times 

 this diameter, broadly winged, with a deep notch at the 



1 W. C. Brown. See p. 241. 



