Wim - This may help. Here is a North Tisbury nakaharai hybrid called 'Late Love' in flower here now. It's about a week to ten days earlier than normal, the colour is a bit more reddish than shown. It stands only 30cm high x 1 meter wide after 25 years. Also the foliage of another NT hybrid called 'Michael Hill'; it flowered 2 weeks early and is completely prostrate. The latter's foliage is typical of nakaharai.
A few of my own nakaharai hybrids are still to flower and nakaharai itself will be the last.
johnw