Ashikaga Flower Park holds a number of illumination shows throughout the year. I visited their 'Flower Fantasy Illumination' event when I was there in February.
If you decide to visit I would allow most part of a day as travel time can vary depending on what mode of transport you use. The train station is a short walk to the park once you arrive.
Prices vary depending what time of year you decide to visit. Winter tends to be the cheapest (500-900 yen), whereas spring is the most expensive (900-2200 yen). Opening times also vary, so it is best to check the website.
There is a large shop selling lots of flowers, unique snacks (strawberry crisps or lemon crisps to mention a few). There was also Studio Ghibli merchandise to buy and there are restaurants and cafes on site.
The park runs many events throughout the year so it is best to visit the website that is in the link below. When they have their wisteria in full bloom, this tends to be one of the most popular times to visit during the spring.
WEBSITE:
www.ashikaga.co.jp/english/in...