A high-speed blender is the best type of blender to use to make smoothies. Especially ones with leafy greens. High-speed blenders are able to blend all of the ingredients together so that you have no chunks or flecks of unblended spinach. If you don't have a high-speed blender like a Vitamix or a Blendtec then use a food processor or a regular blender. You will need to stop the blender scrape the edges with a spatula and blend some more until you get a smooth texture.