In case you are unable to find these flowers you are also able to “grow” these flowers by using Floral Fertilizer. By default this can be crafted with 1 Bone Meal and 2 Yellow Dye and 2 Red Dye (Vanilla Dyes), these dyes can be any colour (recipe may vary between mod packs). This can also be made with 4 Botania Dyes which are made by crafting a Pestle and Mortar which can then be combined with Botania Petals within a crafting grid. Botania Dyes act like Vanilla Minecraft Dyes. Mushrooms can only be turned into dyes.
With the Fertilizer in hand, right-click the ground and up to 4 different Botania flowers will spawn. This will only work on Grass and Dirt and will not work underground.
Petals can also be used to grow 2 block high flowers, with a petal in hand right-click a block of grass. This will plant the petal and cause a shimmer effect on the ground. This shimmer effect can be right-clicked with Bone Meal, this will cause 2 high flowers of the colour of the petal to appear.
Remember these can only be picked up with Shears!