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Cornus (Flowering) - Growing Guide
Cornus florida, from the USA, will tolerate all acidic soils up to as high a pH as 6. Cornus kousa, from Japan and China, will also thrive on neutral soils with a pH of up to around 7.
Within these limitations cornus are relatively unfussy about soil types and conditions but a little more demanding in terms of climate and exposure. Cornus can tolerate heat, cold and frost but react badly to drought and waterlogging.
Cornus florida needs to be planted in full sun to ensure good bract and flower production which will reduce markedly in shade. Cornus kousa will however still flower equally well in sun or dappled shade. Those varieties of both species which have white or yellow variegation in their leaves are best planted in a little more shade to avoid scorching in hotter periods.
Some shelter or wind protection will avoid branches snapping off in the wind. All flowering dogwoods produce spectacular autumn colours, Cornus florida in particular. This is another reason for providing some shelter so that you can enjoy the show.
If your soil is heavy or very light it can readily be improved by adding manure, peat, or organic compost in quantity into the planting pit or bed.
To ensure moisture retention around the roots of young plants it is advisable to apply a mulch of bark or, better still, well rotted compost.
Cornus react badly to the use of granular fertiliser which can cause leaf scorch in hot periods after rain. Your plants will get all the nutrition that they need from the compost and do not need additional feeding.
Most cornus are grafted plants. Make absolutely sure when planting that neither the soil nor any compost on top of it in any way touches the graft. This may well introduce rot and cause the graft to fail.
Staking of any grafted plant is important until it is well established. Remove any side shoots which appear from below the graft.
Maintenance - Video Tip
Cornus florida and Cornus kousa varieties are normally grafted by specialist growers onto rootstock of Cornus kousa var chinensis which is relatively easy to grow from seed and has a natural resistance to powdery mildew.
Cornus seeds within the ‘strawberry like’ fruits are generally difficult to germinate unless treated correctly. When the ‘strawberries’ have turned red and slightly mushy and they are clearly ripe enough to attract squirrels and birds, then you can collect them. Remove the individual seeds from the pulp of the fruit and store them over winter in a layer of moist sand. They should only be removed from the sand and planted in seed trays in the second spring after a full year’s storage in the sand. Therefore growing these cornus species from seed is a lengthy business within which it is easy to make a mistake of have a problem.
We have a detailed article on how to collect, store and plant seeds if you wish to try it this.
Cornus capitata seed collection - Video Tip
Powdery mildew can be a problem in areas of high rainfall when damp conditions can result in some of the younger leaves and growths being covered in a white mildew. This is sometimes an issue with C. florida varieties here in the nursery especially when watered with irrigation systems. It is less likely to be a problem in southern and eastern counties of England. While one can spray with a fungicide or with ground garlic to control the problem we have found that it is seldom a serious issue that the plant cannot grow through perfectly well when conditions are drier.
There are no other specific pests or diseases to worry about.
Finest flowering dogwoods
Our selection of the three finest flowering dogwoods:
A vigorous growing C. florida hybrid with enormous white bracts from a young age
('Royal Red') – its branches are covered with inflorescences which are a vivid and brilliant red.
Cornus capitata - Video Tip
Cornus kousa 'Satomi' - Video Tip