Caring for Begonia Rex, also called royal begonia, requires special attention due to its specific needs. Here are some tips for taking good care of your Begonia Rex:

1. Light: Rex begonias prefer filtered light to direct sunlight. Place the plant in a bright location, but avoid direct exposure to sunlight, especially during the hottest hours of the day.

2. Temperature: Maintain a constant room temperature between 18 and 24°C. Rex begonias are sensitive to sudden changes in temperature, so avoid cold drafts.

3. Humidity: These plants like high humidity. You can increase the humidity around the plant by placing a tray of water nearby or using a humidifier.

4. Watering: Keep the substrate slightly moist but not soggy. Allow the surface of the soil to dry slightly between two waterings. Avoid excess water, as Rex begonia is susceptible to root rot.

5. Substrate: Use a light, well-aerated mixture rich in organic matter. Houseplant mixes with peat moss, perlite and vermiculite generally work well.

6. Fertilizer: Feed your Rex begonia with a diluted balanced fertilizer every 2 to 4 weeks during the growing period (spring and summer). Reduce doses during fall and winter.

7. Pruning: Pinch the ends of the stems to encourage compact, branched growth. Also remove wilted leaves to avoid mold problems.

8. Transplanting: Repot your Rex begonia once a year in spring. This helps renew the substrate and give more space to the roots.

9. Pest Protection: Watch for mealybugs, aphids and mites. If an infestation occurs, treat the plant with insecticide solutions or using natural methods like insecticidal soap.

By following these care tips, you should be able to keep a Rex begonia healthy and enjoy its beautiful, colorful leaves.