As their coarse, foot wide basal clumps of foliage turn yellow and start to die down, the solitary two foot tall stalks of money plant, Lunaria annua, develop open clusters of flat, inch wide seedpods that resemble coins. The thin outer casing and seeds within fall away as soon as these coins ripen, leaving tan, tissue paper thin discs that are ideal for dried flower arrangements. Seeds self sow reliably enough to naturalize where conditions are right, but not aggressively enough to be noxiously weedy. Money plant does not need good soil, and wants only a bit more water than related mustard and wild radish. Their small, purple or white flowers that bloom in spring look like radish or mustard flowers but are not as colorful.