Bring a medium saucepan of salted water to a boil. Add the sweet peas and cook until bright green, about 30 seconds. Remove to a colander using a slotted spoon and run under cold water until cool. Blot dry with paper towels. Return the saucepan of water to a boil and repeat with the sugar snap peas; remove, run under cold water until cool and blot dry.
Preheat the broiler. Pulse all but 2 tablespoons of the sweet peas in a food processor with the ricotta, parmesan, 2 tablespoons olive oil, the lemon zest, a large pinch of salt and a few grinds of pepper until smooth.
Arrange the ciabatta on a baking sheet and broil until toasted and charred around the edges, 1 to 2 minutes per side. Spread the ricotta mixture on the toasts.
Combine the reserved sweet peas with the sugar snap peas, pea shoots, lemon juice and the remaining 1 tablespoon olive oil in a bowl. Toss well and season with salt and pepper. Divide the pea mixture among the crostini and top with edible flowers.
Edible flowers are often sold as an assortment. Taste each bloom individually to see if you like it -- some are more peppery than others.
Make sure your flowers are labeled as edible when you buy them.