It seems there might be a slight misunderstanding. Orchids are typically not grown from bulbs; they are cultivated from specialized structures like pseudobulbs or rhizomes. Cymbidium orchids are popular and beautiful orchids that produce spectacular, long-lasting blooms. If you're referring to Cymbidium orchids with yellow flowers, here are some general care guidelines:

Cymbidium Orchid Care:

1. Light: Provide bright, indirect light for Cymbidium orchids. They thrive in filtered sunlight but can tolerate some direct morning sunlight.

2. Temperature: Cymbidium orchids prefer cooler temperatures, especially during the night. Daytime temperatures between 70-80°F (21-27°C) and nighttime temperatures between 50-65°F (10-18°C) are suitable.

3. Watering: Allow the top inch of the growing medium to dry out before watering. Water thoroughly when needed, and avoid letting the plant sit in standing water. Reduce watering during the winter months.

4. Humidity: Cymbidium orchids appreciate high humidity, but they can tolerate average indoor levels. Increase humidity by placing a tray of water with pebbles near the orchid or using a humidifier.

5. Potting Medium: Use a well-draining orchid mix. Cymbidiums are often grown in a mix of bark, perlite, and sometimes sphagnum moss.

6. Fertilization: Feed Cymbidium orchids with a balanced orchid fertilizer during the growing season (spring and summer). Dilute the fertilizer and apply it every 2-4 weeks. Reduce or stop fertilizing during the winter.

7. Potting: Repot Cymbidium orchids every 2-3 years or when the growing medium breaks down. Repotting is typically done after flowering.

8. Air Circulation: Ensure good air circulation around the orchid. Proper ventilation helps prevent fungal issues.

9. Flowering: Cymbidium orchids often bloom in winter or early spring. After flowering, they enter a period of rest. Provide slightly cooler temperatures during this time.

Remember that specific care requirements can vary based on the exact Cymbidium hybrid and the conditions in your growing environment. If you have a specific Cymbidium hybrid named "Yellow Star," additional care information specific to that hybrid would be beneficial for precise care instructions.