Mix butter with petals from 2 marigolds and set aside.
Heat a large frying pan (not nonstick) or wok over high heat. Coat green onions with 1 tbsp. oil, season with salt and pepper, and add to pan. Cook, turning often, until browned on all sides, about 4 minutes, then transfer to a plate to cool. Add lime or lemon, cut side down, and cook until charred, 45 seconds to 1 minute. Once green onions cool, slice thinly and set aside. Fluff chilled rice with a fork, breaking up clumps.
Heat same pan over medium-high heat. Swirl in remaining 2 tbsp. oil. Add ginger, peas, and corn and cook, stirring so ginger doesn’t burn, until vegetables are heated through, 2 minutes. Add green onions and cook 2 minutes more.
Push vegetables to side of pan, pour in eggs, and scram- ble quickly with a wooden spoon. Once eggs are firmly set, stir into vegetables.
Add chilled rice and soy sauce and stir-fry, drizzling in a little more oil if rice sticks to pan, until completely heated through. Taste and add salt and pepper if you like. Stir in marigold butter.
Turn rice into a bowl and add charred citrus half. Sprinkle with remaining marigold petals, along with nasturtium petals and pea shoots.
*To chill the rice well, spread on a rimmed baking sheet, cover with plastic wrap, and chill until very cold and hard (preferably overnight).