Yes, you should continue to water your plumeria even while they are under a light, especially if they are showing signs of doing well. However, the watering needs of plumeria during periods of indoor growth, particularly under artificial lighting, are different from their needs outdoors or during their active growing season. Here are some guidelines:

Watering Plumeria Indoors

1. Reduced Watering: Plumeria typically requires less water when they are not in their active growing season. This is particularly true if they are indoors and in a less intense light environment than outdoors.
2. Check the Soil: Before watering, check the top inch or so of the soil. If it feels dry, it’s time to water. If it still feels moist, wait a bit longer.
3. Water Thoroughly: When you water, ensure that the water reaches the roots by watering thoroughly. However, make sure there is good drainage to prevent any standing water in the pot, which can lead to root rot.
4. Avoid Over-Watering: Over-watering is a common mistake and can be more detrimental than under-watering, especially in a controlled indoor environment.
5. Monitor Plant Health: Look for signs of both over- and under-watering. Drooping leaves or yellowing can indicate watering issues.

Other Considerations

• Humidity: Plumeria likes some humidity, but not wet leaves or soil. If your indoor air is very dry, consider using a humidity tray or a room humidifier, but don’t mist the leaves directly.
• Lighting: Ensure that your artificial light setup is adequate for plumeria, providing a good balance of light without being too intense or too far from the plants.
• Temperature: Keep them in a warm environment, as cold temperatures can also affect their water needs and overall health.

Conclusion

Consistent but moderate watering, tailored to the indoor conditions and the plant’s cues, is key to keeping your plumeria healthy under artificial light. Remember that every indoor environment is different, so it’s important to observe your plants and adjust care routines accordingly.