Answer:
田 DEN, ta - rice field
古 KO, furu(i) - old
化 KA, KE, ba(keru) - transform
何 KA, nan, nani - what, which, how many
成 SEI, JO, na(ru), na(su) - become, consist, form
Adding the "flower" radical (艹 kusakanmuri) makes them all into different characters!
苗 BYOU, nae, nawa - seedling, sapling
苦 KU, kuru(shimu), niga(i) - suffer, bitter
花 KA, hana(su), - flower
荷 KA, ni - load, cargo, baggage
荿 MO, shige(ru) - grass