Cornus kousa Japanese Dogwood
Japanese Dogwood is a deciduous tree growing up to 10 metres tall and 6 metres wide. It is very ornamental, especially when in flower in early summer, but also when heavily laden with fruit and when it colours up in the autumn. It belongs to a genus that contains many species that produce tasty fruits, though this species is by far the nicest according to my taste-buds.
An easily grown plant, it prefers a rich well-drained loamy soil and a position that is at least partially sunny. However, it will succeed in any soil of good or moderate fertility, ranging from acid to slightly alkaline though it dislikes shallow chalky soils. It grows well in heavy clay soils. It is hardy to about -20°c and so should succeed in most parts of the country. The plant is fairly resistant to honey fungus and so can be grown in land where these fungi have killed other trees.
Plants are slow-growing when young, they speed up somewhat after a few years but then soon slow down again. The sub-species C. kousa chinensis grows more freely, flowering and fruiting better in Britain though it barely differs in appearance from the species.
The fruit, which is about 2cm in diameter, is absolutely delicious and can be eaten raw or cooked. The skin is rather tough and unpleasant with a bitter flavour, but the pulp inside has an exquisite flavour that has a hint of banana and a custard-like texture - this is far and away one of our favourite late summer fruits. We find the best way of eating it is to take a small bite out of the skin and spit this out. Then you suck out the inner flesh and just enjoy it. There are quite a few moderately sized seeds in the flesh, though we do not find that they detract in any way from the pleasure of eating this fruit.
Propagation can be a bit slow. Try to obtain fresh seed and so it immediately in a cold frame - it should then germinate in the spring. Be sure to wash all the fruit flesh off the seed since it contains germination inhibitors. Stored seed should be cold stratified
for 3 - 4 months (soak it in warm water for 24 hours, then put it in a plastic bag with some compost and store it in the salad compartment of the fridge) and sown as early as possible in the year. Scarification (removing some of the woody seed case so that water can reach the seed more easily) may also help as may storing the soaked and bagged up seed for a few weeks in a warm position before the cold stratification. Germination, especially of stored seed, can be very slow often taking 18 months or more. Prick out the seedlings into individual pots as soon as they are large enough to handle and grow the plants on for their first winter in a greenhouse, planting out in the spring after the last expected frosts.
The plant can also be propagated by cuttings, though these are not as vigorous as seedlings. However, if you know of a particularly good fruiting form then cuttings are the best way of increase. Half-ripe side shoots 10 - 15cm long and preferably with a heel can be taken in July or August. Put them in a sandy compost and place them in a lightly shaded place in a greenhouse or polytunnel. It is important to keep the shoots in a fairly humid atmosphere and preferably with some bottom heat to encourage rooting. Rooting should take place within a few weeks, though we usually get quite poor results. We get a much better take with hardwood cuttings in late autumn once the leaves have fallen. These should be 15 - 20cm long of the current years growth and preferably with a heel. We put them straight into the ground in a polytunnel and usually get good results.
The database has more details on these plants: Cornus kousa.