Hydrangeas are large, leafy, flowery plants. The color of the flowers on hydrangeas often depends on the acidity of the soil. In fact, the color of the blossoms can change over the course of a year as the PH of the soil it is planted in changes. Hydrangea flowers may be pink, purple, white and combinations of these colors. Painting hydrangeas is not necessarily difficult. Doing so with acrylic paint poses an advantage and disadvantage because the paint dries very quickly. While the fast drying time of acrylic paint will allow you to continually paint over old layers of paint without smearing or blending the colors together, this can be a disadvantage when trying to paint blossoms that represent a blend of two colors, like pink and blue. Blending colors with fast drying paint can be very difficult.
Select a picture of the Hydrangea you'd like to paint. This will help you get a sense of the size of the bush and the size of the flowers relative to the bush.
Paint the base coat of the leaves of the Hydrangeas. Thin green paint with a few drops of water and paint the base coat as a green blob on the canvas, in the shape and position where you want the bush to be. Give the base coat a minute to dry before proceeding to the next step. This will not take long -- acrylic paint dries in just minutes. Use a medium-size brush.
Paint several clusters of leaves using a darker or lighter green than you used in step 1. Position these clusters in random areas over the green blob you painted in step 1. Use a small detail brush.
Paint several clusters of flowers over the green blob in a manner similar to the way you painted clusters of leaves in step 2. These clusters of flowers should be either pink, purple or white. Don't worry about painting individual flowers -- simply paint the flowers as large irregular bulbs with somewhat jagged edges. Don't add details. If you have chosen to paint clusters of flowers that are a blend of two colors -- perhaps, pink with a hint of blue in some places -- then load your brush with the color that you see the most of one the bush. Thin it with a little water, then paint the clusters on the bush. Next, dip your paintbrush in the secondary color and thin it with a little water. Add dabs of that second color to the clusters. Do this quickly, before the paint on the canvas dries.
Repeat step 2, adding the appearance of more depth to your bush. Overlap some clusters of leaves.
Add a second layer of paint over the clusters of flowers you painted in step 3, especially if the paint was thin enough that you could see the green paint beneath through the layer of paint you applied for the flowers.
Painting hydrangeas from afar allows you to reduce the amount of detail that you paint in the flower clusters themselves. However, if you'd like to imply more detail, use a very small detail brush. Outline the edges of a few petals throughout the clusters of flowers with your detail brush, similar to the way that you painted clusters of leaves throughout the bush.