A heat mat is generally not essential for indoor plumerias, especially with temperatures consistently around 65°F or higher. Plumeria plants are tropical in nature and prefer warm conditions, but they are quite adaptable. Here are some considerations to help you decide whether you need a heat mat:

Factors to Consider

1. Temperature Range: Plumerias typically thrive in temperatures between 65°F to 80°F. Additional heating may be unnecessary if your indoor environment consistently stays within or above this lower range.
2. Growth Stage:
   • Seed Germination: If you are germinating seeds, a heat mat can be beneficial as it can provide the consistent warmth needed for optimal germination.
   • Mature Plants: As long as the temperatures don’t drop significantly below 65°F, established plants should be fine without additional heat.
3. Seasonal Variations: Plumerias go dormant in the winter. During this period, they can tolerate cooler temperatures (down to about 50°F). If your indoor temperature is consistently above this, a heat mat is not required.
4. Lighting Conditions: Adequate lighting is crucial. If they are receiving plenty of sunlight or artificial grow light, this can also help maintain an adequate temperature range.
5. Humidity Levels: Indoor environments, especially in winter, can be dry. While a heat mat isn’t directly related to humidity, consider using a humidifier or other methods to maintain adequate humidity levels for your plumerias.

Alternatives to Heat Mats

If you find the temperature is slightly lower than ideal or you want to encourage more vigorous growth, here are some alternatives to using a heat mat:

• Position Near Heat Source: Placing plants near a heat vent or in a naturally warmer area of your home can help.
• Increase Light Exposure: More light, particularly grow lights, can raise the temperature in the immediate vicinity of the plants.
• Insulate the Pot: Using pot insulators or placing the pot on a rug or mat can help retain heat.

Conclusion

In summary, for indoor plumerias in your described environment, a heat mat is not a necessity. Focus on providing sufficient light, monitoring the humidity, and ensuring a stable environment and your plumerias should thrive. Heat mats are more of a tool for specific scenarios, such as seed germination or if you need to create a significantly warmer microclimate for your plants.