A roman shade or woven grass weave or woven wood shade hung between the sink and plants is your best bet. I would mount it as high as you can above the window so that when it is up it clears the top of the window. If it is a fabric shade then you will want to choose a durable fabric that will not water spot. A woven wood shade might be a better option. A solar shade is a functional option but would look better in a more contemporry styled kitchen. We had considered matchstick blinds under the soft roman shade in the eating area if the client needed additional sun control and still have the ability to see into the garden without dropping the fabric shade. You can definitely mix the two styles if the materials are complimentary. We also addressed the sun issue by building wood trellises on the back of the building and an arbor covered patio which helps shade the back of the house. The trellis holds vines that now shade the garden window in the heat of summer.

I would also suggest a roman shade mounted high above the window - that way when it is up all the way past the window frame it will look like a valance. I would use Sunbrella fabric - made to withstand sun and light - and comes in a crazy amount of patterns and styles.