Clematis flowers come in an enormous range of shapes and colors, from pink blooms that span 6 inches across to drooping blue bells to starry white flowers. They've grown in popularity in recent years, so many nurseries offer dozens of varieties to choose from. When you decide which cultivar to buy, take the color, shape, potential side and sun requirements into account. Clematis often take several years to flower, so look for a potted plant that's already a year or two old. Here are the most common clematis cultivars:   Nelly Moser: Has large, pink flowers and is one of the most common types of clematis. It's hardy and easy to establish.  Ernest Markham: Has stunning magenta flowers and grows vigorously on trellises and arbors. This variety blooms last, from late spring to fall.  Niobe: Has red flowers and is a suitable choice for growing in a pot, since it doesn't get very large.  Princess Diana: Has pale pink, bell-shaped flowers and does particularly well in very hot climates.  Jackmanii: Has deep purple blooms and grows vigorously; a widely available favorite.  Venosa Violacea: Has abundant blue-violet blooms and vines that climb vigorously.  Apple Blossom: Has small white blooms; grows as an evergreen. Clematis may come in an amazing range of shapes and sizes, but they have similar needs when it comes to sun and temperature. They are hardy plants that require at least 6 hours of full sun per day.  Clematis are hardy from growing zone 3 to zone 9.  A few varieties of clematis will grow in partial shade, but they won't reach their full potential unless they have full sun for 6 hours per day. Look for a spot with low-growing perennials and groundcover that will shade the roots of the clematis but allow it to grow into full sun about 3 or 4 inches off of the ground. Clematis need cool roots and full sun on the vine and flowers. If you can't find a spot with groundcover, you can plant it later or mulch 4 in (10.2 cm) deep around the clematis to keep the roots cool. You can also plant clematis near the base of a shrub or small tree. The clematis will grow up the branches without harming the "companion" shrub or tree. The location shouldn't be so dry that it doesn't retain moisture, but it should drain well enough that standing water doesn't sit around the roots of the clematis. To test whether the soil in an area drains well, dig a hole and fill it with water. If the water drains immediately, the soil is on the sandy side. If the water stands in the hole, the soil has too much clay, and doesn't drain fast enough. If the water slowly but steadily seeps into the soil, it's just right for clematis. Clematis prefer the soil to be neutral or alkaline over acidic. If you conduct a test and determine that the pH is a little too acidic, sweeten the soil by mixing in limestone or wood ash. Dig a hole several inches deeper than the pot the clematis came in, so that when you plant it the soil comes right up to the first set of leaves. Before you plant the clematis, amend the soil by working in compost and granular organic fertilizer. This will ensure that the plant has enough nutrients to establish itself in the first few months after planting. If you're working with soil that tends to be clay heavy (slow to drain), dig the hole a few inches deeper than you normally would. If your soil is sandy (quick to drain), a slightly shallower hole will be better for the plant's roots, so they're close enough to the surface to get plenty of water. Very gently remove the clematis from the pot it came in, taking care not to rip or break the fragile roots and shoots. Set the root ball into the hole, about 3-5 in (7.6-12.7 cm) below the surface of the dirt, and pat the soil around its base stem. The soil should come up to the first set of leaves; if it doesn't, lift out the root ball and dig the hole a bit deeper. Leave the stake in place so that the young clematis has something to grow against for the first year. Place 4 inches of straw or another type of mulch around the base of the clematis to keep the roots cool. You can also plant or encourage the growth of low-growing perennials whose leaves will shade the roots of the clematis throughout the summer.

Summary:
Pick a clematis cultivar. Choose a sunny location. Choose a spot with well-draining soil. Test the soil for its pH level. Dig a hole and enrich the soil. Plant the clematis. Mulch around the roots.