To maintain the beauty of your arrangement of 25 white Ohara roses in a glass vase, follow these care instructions:

1. **Watering**: Fill the vase with clean, room temperature water and trim the stems at an angle before placing them in the vase. Change the water every two days to keep it fresh and clear.

2. **Placement**: Display the arrangement in a cool location away from direct sunlight and heat sources. Avoid placing it near drafts or heaters, as extreme temperatures can cause the flowers to wilt prematurely.

3. **Trimming**: Trim the stems of the Ohara roses every few days to maintain water absorption. Remove any foliage that will be submerged in water to prevent bacterial growth.

4. **Ethylene Exposure**: Keep the arrangement away from ethylene-producing fruits and vegetables, as they can accelerate the aging process of the roses.

5. **Misting**: Lightly mist the roses with water to keep them hydrated, especially in dry environments. This helps prolong the freshness of the blooms and prevents them from drying out.

6. **Enjoyment**: Remove any wilted or spent flowers promptly to encourage the remaining roses to last longer. Take time to appreciate the beauty of your arrangement.

By following these care tips, you can ensure that your arrangement of 25 white Ohara roses in a glass vase remains vibrant and beautiful for an extended period.