Slow-release fertilizers, like Excalibur, are formulated to release nutrients gradually over time and are generally less likely to cause fertilizer burn compared to quick-release formulas. This characteristic makes them safer to use, as they reduce the risk of overwhelming plants with a sudden influx of nutrients. However, there are still considerations to keep in mind, especially regarding dormant plumeria:

1. Reduced Nutrient Uptake During Dormancy: Plumeria, like many plants, significantly reduces its nutrient uptake during dormancy. Since they are not actively growing, their need for nutrients decreases.
2. Risk of Fertilizer Burn: Although slow-release fertilizers are less likely to cause burn due to their gradual nutrient release, applying any fertilizer during dormancy can still be risky. The plant might not use the nutrients and could potentially accumulate in the soil, leading to an overly concentrated nutrient environment. This could be harmful once the plant exits dormancy and resumes active growth.
3. Application Timing: It’s generally recommended to apply fertilizers like Excalibur during the growing season when plumeria are actively growing and can utilize the nutrients effectively. Fertilizing just before or during dormancy might not be beneficial and could pose a risk to the plant.
4. Soil Health: Continuous use of any fertilizer, including slow-release types, should be balanced with measures to maintain soil health. Over time, even slow-release fertilizers can alter soil pH or lead to nutrient imbalances if not managed properly.
5. Environmental Conditions: The effectiveness and rate of release of slow-release fertilizers can be influenced by environmental factors such as temperature and soil moisture. Cooler temperatures during dormancy can slow down the release rate even further.

In summary, while slow-release fertilizers like Excalibur are less likely to cause immediate fertilizer burn, avoiding fertilizing dormant plumeria is still advisable. The best practice is to apply fertilizers during the active growing season when the plant can utilize the nutrients effectively. This approach helps ensure that your plumeria receives the right amount of nutrients at the right time, reducing the risk of potential issues associated with dormancy fertilization.