To become larger
increase, expand, swell, wax, pullulate, thrive, gain, enlarge, swell in substance, augment, advance, dilate, stretch, mount, build, burst forth, spread, burgeon, amplify, germinate, multiply, develop, abound, accumulate, mature, jump up, flourish, luxuriate, grow up, rise, sprout, shoot up, start up, spring up, spread like wildfire*, pop up*, jump up*, branch out*, fill out*, puff out.
Antonyms lessen*, shrink, wither.
To change slowly
become, develop, alter, tend, pass, evolve, flower, shift, flow, progress, advance, get, wax, turn into, work up, turn, improve, mellow, age, better, ripen, ripen into, blossom, assume the form of, open out, resolve itself into, mature.
Antonyms continue*, regress, preserve.
To cultivate
raise, nurture, tend, nurse, foster, produce, plant, breed, market.
Antonyms harm*, impede, neglect.
To begin
originate, start, arise; see begin 2.
To become
develop into, grow to be, change to; see become 1.