Well-Drained Soil

• Clematis hate wet roots. Never plant them where water remains puddled hours after a heavy rain. To test your soil's drainage, dig a hole roughly 24 inches deep and 36 inches wide on the proposed planting spot. Fill it with water. If the water readily drains within an hour or so, the spot is suitable for planting clematis.
  
  

The Right pH

• Clematis needs soil as close to neutral as possible. Neutral soil has a pH of 7.0. If you have grown many plants in the spot before, it's likely that clematis will grow well there too. Purchase a soil pH testing kit from your local garden center and test the soil. This test is important if the soil is virgin and no ornamental plants ever grew there before.
  
  

Keep the Soil Cool

• Clematis needs cool roots. Add a 2-inch layer of organic or inorganic mulch. Pine needles, bark chips, stones and even pavers do the job. Refreshing organic mulch periodically keeps it at a 2-inch depth. For a more permanent cooling effect, plant low shrubs or thick-growing plants near clematis. Their foliage casts shadows over clematis' roots and keep them cool. Don't plant anything tall enough that casts a heavy shadow over much of the clematis' foliage. That stunts its growth and leaves it susceptible to disease.
  
  

Amend the Soil

• Clematis needs nutritious soil. Test the soil to determine its nutritional content. Even nutritious soil sites benefit from soil amendments. Proper amendments add much-needed nutrients and improve drainage. The Ohio State University Extension recommends incorporating soil amendments at a depth of 24 inches in a 3-foot wide area. Use the test drainage hole you created. Mix the excavated soil with 1/3 compost or well-rotted manure by volume. While mixing, add any fertilizers recommended by your soil test. When done, add the amended soil to the hole as you plant your clematis.