My last application of granular fertilizer was on Sept. 15th. Although it is a 90 day fertilizer, the majority of the mineral salts have dissolved in the first 60 days. Dr Frank Brown in his book Florida's Beautiful Crotons 1960 on page 55 states " A fertilizer high in nitrogen content should be used for applications up until about the first of September". As suggested by Judy Glock, I supplement with a foliar feeding of soluble fertilizer. This is readily absorbed and the residual benefits last for 10 - 14 days. By ceasing the foliar feedings and with the granular fertilizer nearly depleted, the available nitrogen to my plants diminshed. This is important going into our winter cycle. Nitogen promotes new leaf grown that will not get a chance to harden off for our cold days. Research has been done on nitrogen derived from urea (soluble). This research was done in reference to Palms: When soils drop below 60 F, this type of nitrogen provides no benefit and actually becomes toxic to the plant. If this is true for crotons, I do not know but I will not gamble and will assume it is parallel with crotons as well. To aid our plants to harden off, I recommend an application of K-Mag (Potassium / Magnesium). As Dr. Frank Brown stated again in his book on page 55: "After that Time (September), a fertilizer with a high content of potash is recommended." Potassium and Magnesium work hand in hand. If not applied together, you may lock up the absorbtion of these importnt minerals. Plants that have recieved a K-Mag supplement have proven to suffer less cols damage and an increased survival rate when we we get wacked by "severe cold". What is your fertilzer schedule?