Dear Gardeners, In our garden at a commercial site in Etobicoke, Zone 5, we planted a number of the above named shrubs for winter colour and also because it was mentioned that it would be “compact in stature” unlike the huge ones I have planted elsewhere.As well the colour promised to be Vibrant Dark Red. The soil was pure clay, which I have amended over the years with trailer loads of sand and peat moss/compost to a considerable depth, which has improved the water absorption.My problem is as follows: each fall, when we are looking forward to the gorgeous red twigs, the leaves will not drop off the shrubs, which produces a winter long nasty look. As well 2 of the shrubs must be a different variety because they grew well above the other ones which we bought at the same time.(that must be a matter of mistaken identity/tag switch). Looking forward to your answer/suggestions.
Thank you for your inquiry. I will comment on your last note about the two different shrubs; you are likely very right that there was a tag switch or mistaken identity. When shrubs are small, in 1 gallon pots, and especially dormant, they can be mistaken for another cultivar or even different species. If they are bothersome, they can be relocated and new shrubs of the same cultivar planted in their place. Just to be sure, if these are Arctic Fire dogwood (Cornus stolonifera “Farrow”), their leaves should be dark green during the growing season and turn a deep red in the fall. The reddening of the twigs come as the shrub goes dormant.
Your amendment of the soil for the shrubs was the right response; dogwood (Cornus sp.) prefer lighter soils than clay. Further care would be mulching the root zone, proper watering and low nitrogen fertilizer.
To tackle your leaf drop, or rather non-leaf drop problem, is more complicated. Some species, like Beech (Fagus grandifolia) or Black Cherry (Prunus serotina) often keep their leaves throughout the winter; it’s a natural part of their growth cycle. For other species, it’s sometimes the weather, a slowly cooling fall might keep the leaves a bit longer. Sometimes it’s stress related, too little/too much water, drought conditions, even a pathological reason.
To determine what it could be, you have to answer yourself some questions. You don’t say if they are a new or established planting. If they’ve been planted only a season or two, it may be that they are still “finding their feet”, and not yet behaving normally. A key observation would be are the taller shrubs behaving the same way? Either way, they need time to establish. That also means, as these are dogwoods, they do have a preference for not only lighter soil, but moister soil. It may be they’ve been stressed because they don’t have enough water. Newly planted shrubs need at least a deep watering once a week, especially before freeze up.
If this is a well established shrub garden, it could be ready for a late winter/early spring renewal pruning. Most dogwoods benefit from this. Older twigs go a brownish colour and lose that wonderful red glow. Approximately 20 to 30% of the older twigs can be pruned out of the shrub, at the base, to allow new growth. This new growth will have the bright red twigs.
Even so, another season of observation might be needed if none of these possibilities are the case. As hardy as dogwood shrubs are, there could be a pathological reason. If this is an expensive mass planting, then it might be worthwhile for an arbourist to have a look during the growing season. In addition to looking at how they are planted, soil structure and watering requirements, he will look for other issues such as leaf spotting during the growing season, and cankers formed on or below the bark.