Can I plant a clematis now? What would be the best time for zone 5-6?

Answer 1

Pot-grown clematis can be planted anytime of year. The ideal time for planting is spring and early fall. Plant in well-drained soil.

In colder climates where temperatures drop below 0°F (-20°C) foundation planting and mulch are required to ensure a long life. High light and long days can be ideal growing conditions for clematis if a little care is taken when planting. Most varieties will survive and flourish. Double flowering varieties are usually not recommended in colder zones.
http://www.homeofclematis.net/html/pl_01.htm

In hardiness Z5 or below, be sure you plant the crown of your clematis at least 2" below ground.
you can actually bury your clematis up to its lowest leaf node -- even if there's a foot of vine before the first leaf! Your reward: a bigger beefier plant that will undoubtedly have more than one stem, which is the final, ultimate, hidden key to the perfect clematis vine.
http://www.npr.org/programs/talkingplants/features/2002/clematis/plantingtips.html

Deep planting encourages large-flowered cultivars to develop a healthy basal root crown of buds below the soil level as a precaution against sud­den wilting. When the plant is in position, fill the area around the root ball with equal parts of good soil and potting com­post mixed with the recommended amount of any gen­eral-purpose fertilizer. Gently firm the mixture around the root ball. Cover the base of the plant with additional organic matter used at the base of the planting hole, tak­ing care to keep it away from the stems or vines. When mounded, it serves as a mulch to prevent excessive loss of moisture. Water the plant well, allowing at least 1 gallon of water per plant.
http://www.clematis.com/HTML-Docs/Guide_001.html

Plant a low-growing perennial or shrub close to the newly planted clematis to provide some shade for the plant's root system & to prevent excessive loss of moisture.
Good luck! Hope this was helpful.

Answer 2

Fall is a pretty good time to plant perennials. The rate of success is lower than spring planting but I have many beautiful plants that I planted in September and October the first year I moved into my home.

I also lost a few, so be prepared, it may or may not survive. Reality check though, I have lost a few perennials over the winter that were spring planted too. You just never know.