This section is from the book "A Manual Of Weeds", by Ada E. Georgia. Also available from Amazon: A Manual Of Weeds.
Introduced. Annual or biennial. Propagates by seeds.
Time of bloom: June to September.
Seed-time: July to October.
Range: New Brunswick to Ontario, southward to Rhode Island, Pennsylvania and Ohio. Also in British Columbia.
Habitat: Fields and waste places.
Root slender, not swollen and fleshy like the garden radish. Stem fifteen to thirty inches tall, erect, branching, sparsely set with fine stiff hairs, or often entirely smooth. Basal and root leaves deeply pinnatifid, with terminal lobe large, and four to six pairs of lateral lobes, decreasing in size toward the •petiole, which is short; upper leaves small and oblong, but all are toothed and scalloped. Flowers about a half-inch broad or sometimes larger, the four spreading petals pale yellow with purple veins, fading to white as they wither; calyx-lobes drawn close together, instead of spreading like those of Wild Mustard. Pods indehiscent siliques one to two inches long, constricted between the seeds, faintly grooved lengthwise but without partitions, being stuffed with a spongy substance between the seeds, which are larger than Mustard seed and brown. Because its rather thick-textured leaves are so nearly smooth, this weed is more resistant to injury from sprays than other wild Mustards and it must be fought in other ways. (Fig. 127.)
Fig. 127. - Wild Radish (Raphanus Raphanistrum). X 1/4.
Cut the tufted leaves of autumn plants from their roots with hoe or spud, the latter tool being preferable in grain fields. Spring seedlings may be raked from the fields with a weeding harrow when the grain is but a few inches tall. Plants that spud, hoe, and harrow have missed, should be hand-pulled in their first bloom rather than be allowed to foul the ground with their long-lived seeds. Where seed has entered the soil, give stubbles surface cultivation after harvest, in order to stimulate germination, and then disk the ground about once in two weeks, so as to kill the weeds while they are tender.