Answer: Mandevillas require plenty of sunshine, an acidic, very rich soil and ample moisture during the growing season to bloom their best; they bloom heaviest when in active, vigorous growth. Fertilizer alone would not be sufficient for good blooming performance over time. It is possible that they need to be repotted into fresh soil or into larger pots, especially if they have grown a lot or if the soil has become compacted and depleted over time as most soils do; a late winter trim can also help stimulate new growth and lusher blooming. Good luck with your mendevillas.
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