A river cruise can be the ultimate way to slow down and stop and smell the flowers — and we mean that literally. Choose your cruise wisely and you can wander amid vibrant tulips and hyacinths in late March and April, take in the aroma of roses in June, and spot the bold beauty of chrysanthemums and dahlias well into September. Here are 10 don’t-miss European river ports for botanically inclined cruisers — including the best time to see them in bloom.