Rhododendron Horizon Monarch.

Large Flowered Hybrid Rhododendrons are unsurpassed for the beauty of their large flower trusses, produced in ever increasing numbers each year as the plants develop making these plants a solid long-term investment. If space allows, they are at their best when planted in bold groups and with a mix of varieties it is possible to have flowers in succession from March until early June. They also go well with deciduous and evergreen Azaleas.
Although often seen planted in the dappled shade of a woodland setting, these tough plants will succeed in full sun. Rhododendron Horizon Monarch are ericaceous plants and so they should have acid soil that is well prepared and free draining. (Check to see if they are growing in nearby gardens if you aren’t sure about your soil). If your soil is alkaline, they can still be enjoyed in your garden if grown in large containers or raised beds filled with Ericaceous compost.
Hybrid Rhododendrons dislike cultivation immediately around them (their roots are very close to the surface) but they do benefit from a light mulch each Spring to conserve moisture. This will also discourage weeds making these plant both beautiful, and very low maintenance.