Growing lilacs in an outdoor plant box is possible, but it requires careful consideration of the plant's needs. Lilacs thrive in well-draining soil and full sunlight, so ensure your plant box meets these conditions. Choose a spacious container to accommodate the lilac's root system, as cramped spaces can stunt growth. Regular watering and occasional fertilizing will help your small lilac flourish. While lilacs typically prefer open ground, a well-maintained plant box can still yield beautiful blooms with proper care. Opt for dwarf lilac varieties for better adaptability to container life. Remember, lilacs may not reach their full potential in a box, but they can still add charm to your outdoor space.