'Mantequilla' means 'butter' in Spanish. This new hybrid is quite lovely, covering itself with scads of these 'yellowish' flowers in late April. The seed parent is R. 'Horizon Lakeside', adding big flowers plus excellent foliage genetics to this hybrid. The pollen parent is one of my own I call 'Golden Topaz', and has some genetics from the hybrid 'Naselle', plus some aspects of the large leaf rhododendron R. macabeanum. The large leaf rhododendron adds a heavy ribbed texture to the foliage, making it look 'bold'. The plant flowers very heavily, so is a knock out show in spring. Because of its A+ qualities, we are propagating as many as will root. Given the parents, I would guess that it is hardy to zone 7.