I planted two Clematises Jackmanii Superba this spring. They started growing well and more than a meter high now and it seems that they will bloom, but both show some yellow spotty leaves on the bottom of the plant. One has more yellow leaves than the other, and that one has direct sun for only an hour per day. I planted them with standard compost. I wonder if this is some disease, or this is due to the lack of light. I had read that Clematis Jackmanii (not Superba) can thrive on north facing walls. This is an east facing wall, but the shade from the house also affects it. Thank you very much for your support.
Thank you for contacting Toronto Master Gardeners. You made a great choice as Clematis ‘Jackmanii’ are vigorous, compact vines with spectacular flowers.
Abnormal yellowing of leaves is called chlorosis, caused by a lack of the green pigment chlorophyll. Possible causes of chlorosis include poor drainage, damaged roots, compacted roots, high soil pH, and nutrient deficiencies (magnesium or iron). Refer to a previous post from a gardener with the same concern: Chlorotic clematis.
Cultural items to consider:
- You mentioned only an hour per day of direct sun. Most varieties of clematis require 6 hours of full sun to reach their peak potential.
- Did you plant the roots deep enough? Planting depth: top of the root ball should be 5 – 7.5 cm under the soil surface.
- Clematis require fertile, moist but well-draining soil. Avoid planting in a waterlogged area. Ensure that you are not overwatering as this a common cause of yellow leaves
- Clematis plants like to have their “heads in the sun and their feet in the shade”. Keep the roots in light shade – consider shading roots with other plantings or mulch.
More information that may be helpful, including tips on pruning, can be found at: Clematis care
Hope this is helpful, and you have many years of beautiful blooms from your new Clematis ‘Jackmanii’.