How to propagate dogwoods?

The Cornus genus, or dogwoods, is a vast botanical genus comprising bushes, trees and even a few rare perennials. Depending on the type or species of dogwood, the propagation technique will vary. Coloured-wood dogwoods are easy to propagate by propagation by cuttings or layering, while flowering dogwoods will require grafting or sowing, with plenty of patience. How can you easily propagate all these plants? We explain everything in our tutorial.

Flowering or decorative-wood dogwoods, they propagate very well!

By sowing

Sowing flowering dogwoods (Cornus kousa, Cornus florida, Cornus nutalii...) can be an option, but you'll need to be patient. Allow several months for germination and sometimes twenty years before you can admire the first flowers.

• Collect seeds from ripe fruits in October-November;
• Soak them for 24 hours in water;
• Sow in pots in a well-draining substrate (light compost);
• Leave the pots in cold frames and only take them out the following spring;
• Place your pots in partial shade and keep the substrate moist but not waterlogged;
• Transplant your young plants individually at the four-leaf stage, then plant them in the ground the following autumn.

Sowing Cornus controversa and Cornus alternifolia is unpredictable, as few seeds are fertile. Collect seeds from ripe fruits in October, soak them for 24 hours, then sow them in pots in a well-draining substrate. For the rest, the sowing technique is exactly the same as for flowering dogwoods.

Sowing fruit-bearing dogwoods, such as the Cornelian cherry, is done in March after cold stratification during winter (the seeds having been collected in autumn at ripeness). Sow the seeds in light compost (seed compost) at a depth of 2 centimetres. Keep the compost moist but not waterlogged. Germination can take weeks, so be patient. You can transplant the young plants in autumn if they are well developed.

For decorative-wood dogwoods, sowing is not worth considering, as propagation by cuttings and layering are so easy. But here too, the technique remains the same.

Cornus sericea, Cornus sanguinea and Cornus 'Alba Elegantissima'

By propagation by cuttings

Decorative-wood dogwoods

Propagation by cuttings is a quick and simple way to obtain many plants of decorative-wood dogwoods (Cornus alba, Cornus sericea, Cornus sanguinea...) from a single bush. For propagating cornus, the ideal method is semi-hardwood or semi-ripe propagation by cuttings, practised in July-August:

• Take propagation by cuttings from lateral shoots that have ripened (i.e., stems that are in the process of transforming from softwood to hardwood). At this stage of development, rooting of the taken stems is better for the success of the propagation by cuttings.
• Insert the propagation by cuttings into a mixture of sand and turf and place them at a temperature of 15 to 18°C.
• Repot in a mixture of soil and compost as soon as new leaves appear and overwinter in a frost-free place.
• Note that hardwood propagation by cuttings in November-December also give very good results.

Other dogwoods

Flowering dogwoods, layered dogwoods (Cornus controversa and Cornus alternifolia) and fruit-bearing dogwoods (Cornus mas and Cornus officinalis) can also be propagated by propagation by cuttings.

However, propagation by cuttings is not recommended for these dogwoods, as success is very unpredictable. If you want to try, take sections of ripened stems about 15 cm long in August, or even September. Remove the leaves and secondary shoots, but keep the last two leaves at the end of the cutting. In a shady spot, plant your propagation by cuttings in a mixture of garden soil (always non-calcareous) and river sand to lighten it, or in seed compost. And keep them covered.

When rooting is sufficient (approximately 2 to 3 months), transplant the propagation by cuttings carefully into buckets and overwinter them in a cold frame or another place where the temperature will not drop below 12°C. Keep the substrate moist but not waterlogged throughout the growing period. You can plant your successful propagation by cuttings in autumn of the following year only.

By layering

Simple layering is suitable for decorative-wood dogwoods, especially Cornus alba and Cornus sericea, whose lower branches often touch the ground and tend to take root when in contact with the soil. The layering technique involves inducing the appearance and then the development of roots on a portion of stem, temporarily buried, without being detached from the mother plant. In spring or early summer, bury long lower branches in a trench 20 cm deep until they root. Separate them in autumn or the following spring and grow them in pots for a year before planting.

By grafting

Horticultural professionals use grafting for flowering dogwoods, preferably by shield budding in July/August. The rootstock can be a Cornus kousa var. Chine sis for Cornus kousa and its hybrids or a Cornus florida of the species type for American flowering Cornus varieties. The rootstock will be a one-year-old scion.

For propagating cultivars of Cornus controversa and Cornus alternifolia, shield budding also gives good results, but is best practised in November.

Shield budding for dogwoods is called "dormant eye" budding, as growth will only start the following spring. How to perform this shield budding?:

• A few days before grafting, water the rootstock copiously so that its bark can be easily detached;
• At the time of grafting or a few days before, choose a well-ripened (hard and brown) current-year shoot with good eyes (wood buds) of the variety you wish to propagate. The taken shoot should be the diameter of a pencil;
• Immediately cut off the lamina of all the leaves while keeping the petiole to avoid dehydration of the buds;
• Soak the base of the shoot in a glass of water for a few hours before grafting;
• Choose a well-formed eye from the scion, preferably in the middle of the shoot, in the axil of a leaf or a leaf scar. With a grafting knife, make an incision about 1.5 cm below and above the eye, then slide the blade of the grafting knife under the bark, from top to bottom, without going too deep into the wood;
• Once the shield is taken, turn it over and remove the wood flap if necessary with the spatula of the grafting knife;
• On a clear area of a shoot of the rootstock, make a T-shaped incision quite shallow (down to the cambium). Gently peel back the bark on both sides with the spatula of the grafting knife;
• Slide the shield into the notch then trim the top part protruding from the T horizontally so that the edges of the respective barks are well applied against each other;
• Tie the graft with Flexibands or wet raffia so that the tissues are well applied against each other, but do not cover the bud;
• If the graft is successful, the petiole left on the scion falls off after 15 days;
• Remove the tie only when the scion has grown at least 5 to 10 cm;
• Wait until the scion's growth in spring reaches 30 cm to cut back the rootstock to 15 cm above the grafting point, then tie the shoot to this stub.

Grafting is recommended for flowering dogwoods

By collecting suckers or natural seedlings

Some dogwoods, such as the Cornus sanguinea or common dogwood, produce many suckers. This is an opportunity to get a new plant for free. You will separate the sucker from the mother plant with a sharp spade and transplant the young plant elsewhere in spring, or better, in autumn.

Some non-hybrid flowering dogwoods can, if circumstances allow, self-seed under trees. Here too, simply dig up the young plant and transfer it elsewhere in the ground or keep it in a pot for a year before final planting. The operation is best done in autumn.

Cornus sanguinea