Make sure you are fertilizing your clematis. Decrease in flower size occurs over the growing season since each successive bloom requires more and more nutrients in the soil. Most clematis do not require dividing to bloom with larger blooms. Nutritional needs are often the cause of decreasing flower size. Generally speaking, organic fertilizers are best since they are timed released and do not supply the plants with a large shot of nitrogen at one time. This can be supplied via time released synthetic fertizers or with organics such as blood meal, compost, composted cow manure, alfalfa pellets, compost tea, or even grass clippings or many other types of organic fertilizers. Keeping the plant supplied with ample moisture during the heat of the summer will also help with nutrient uptake.

It could just be the time of year - in spring, clematis usually put out normal/average sized blooms but then later in the summer, some of them can have another blooming period (and even a third period) but the flowers tend to be much smaller the second (or third) time around. As an example, I have Will Goodwin whose earlier spring blooms are about 6 or so inches across, but right now it's in bloom for the second time this season and it has lots of puny little 2" blooms. Sometimes, these second blooms can even look nothing like the springtime blooms! So, I wouldn't worry for now. Next spring, if the blooms are still really small (but should be big) it might need some pruning to spruce it up or maybe a more srtict fertilizing schedule. Hope this helps :)

nckvilledudes and jameslb,

Cheers for the help. I have been busy driving my guests around the province that I barely have time to attend to my garden. I should pay more attention to their needs next year. There are two new clematis that need planting. Any advice on this? Thanks again for your advice.