Short answer: YES!

Long answer: Yes, because:

• They were pretty much the most beautiful greenhouses I ever visited. (I liked them over Kew Gardens)
• They’re only open for public for three weeks a year, when the flowers are at their most beautiful.
• Awesome flowers.
• It’s easily accessible (by car or bus)
• Entrance fee is very low (2,50 EUR in 2015)

Downsides:

• It was really crowded when we arrived at the Royal Greenhouses. REALLY crowed. It felt like an overpopulated tour in a flower factory.
• The Greenhouses could use some fresh paint. From the outside they look a bit dilapidated, but the insides make up for it. (The Greenhouses are being renovated as we speak.)