I have a 6 yr old (approx) Smoke Bush that has never smoked. It has red leaves, is in full sun and has not been pruned for 18 month. Our soil is largely clay. This year it had many flower blooms that lasted for a long time but did not smoke before they fell off. It is now quite ratty looking and needs pruning. What should I do???
The most common Smoke Tree/Bush used in gardens in and around the Toronto area is Cotinus coggygria, with “Notcutt’s Variety” and “Royal Purple” being the two most popular varieties. Both of these are hardy to zone 5, are relatively undemanding plants, will grow in most soil types and exposures (N, S, E or W and in full sun or partial shade).
That being said, there may be a few reasons your particular bush has never “smoked”.
Firstly, your plant is still fairly young at 6 years old. Sometimes it just takes time for a woody bush to settle into its environment after the shock of being transplanted, which means it takes longer to reach maturity, so I would encourage patience.
Secondly, you state that your soil is largely clay. This soil structure may be retaining too much water within it and may be swamping the bush roots. Generally, a moist well drained soil is ideal so adding organic matter such as compost or manure will allow for better drainage with the added advantage of feeding the plant too. A 2-4 inch layer can be applied in the spring making sure to keep it a few inches away from the plant trunk/stems. Also, access your watering schedule/time/duration and cutting it back during wetter weather periods is advisable.
Lastly, any major pruning should be done in late winter or very early spring while the plant is still dormant. At that time you can take out not more than 25% of the branches, cutting them back down to almost ground level making sure to leave 2 good node buds per stem intact so that new growth can sprout from below. If you do this for the next four years, you will rejuvenate the shrub entirely. In the meantime, you can do a little trimming now – take out any branches that are dead, diseased, crossing over each other or are dangerous/unwieldy and this should help the ratty appearance for the winter. Pruners should be sharp and cleaned/sterilized between cuts.
The main disease that threatens these bushes is Verticillium Wilt which would cause major leaf drop which doesn’t seem to be the case here. Needless, clean up and remove any leaf litter debris from around the base of your shrub and dispose of it in your municipal compost/green garbage collection.