We've had a few open garden days during the past two weeks and we are winding down. Usually during these tours, everybody seems to ask about a particular plant and it will always be one you least expect. This time there wasn't one particular plant that elicited questions but several kept coming up again and again.    Peony 'Doreen' - Many of the peonies had already bloomed but this one opened at just the right time.   Rose 'Michelangelo' - The roses are really fabulous at the moment but the one that everyone asked about was this hybrid tea which is an upright growing variety, about 6 feet tall.   Acer campestre 'Carnival' is a hedge maple with variegated leaves. Currently this one is green and white but shades of pink appear on new leaves. Teucrium fruiticans 'Azureum' (Germander) - I brought this home last year on a whim and it has turned out to be a great doer and always seems to have blooms. Silene uniflora 'Druett's Variegated