Propagating Chinese Milk Vetch: Saving Seed, Letting It Self Sow and Keeping the Bacteria

Seed is the way

Milk vetch is a winter annual that completes its life in a single cool season, so it is propagated from seed. There is no practical way to keep plants alive through summer or to grow them from cuttings, and no reason to try: it sets seed freely, and the seed is easy to collect.

Saving your own seed has a particular advantage with this plant. Seed is not always easy to find from US or UK suppliers, and a patch that has grown well in your garden is already adapted to your conditions.

Collecting the seed

After flowering, each cluster turns into a small group of pods that darken as they ripen. Ripe pods turn black or dark brown and dry, and they split easily, so collect them as they color rather than waiting for the whole plant to finish.

1. Leave a strip uncut When you turn in the rest of the stand, leave a strip of healthy, vigorous plants to ripen.
2. Watch the pods darken Pods are ready when they turn dark and dry, and the seed inside is hard.
3. Cut and dry Cut the stems with ripe pods into a paper bag or onto a sheet and dry them in an airy place out of the rain.
4. Thresh and clean Rub or tread the dry pods to release the seed, then winnow away the chaff.
5. Store cool and dry Keep the seed in a labeled paper envelope inside an airtight jar in a cool place until autumn.

Store only fully dry seed. Damp seed molds quickly in a sealed container.

Letting it self sow

In mild-winter gardens, milk vetch often sows itself. Pods left on the plants split and drop seed, which sits through summer and germinates as the weather cools in autumn. A patch can return year after year this way with very little effort, which is how it persisted in paddy fields between deliberate sowings.

Self-sown plants come up where the seed fell, so they suit a cover crop or wildflower patch better than a defined border. If it spreads where you do not want it, cut the plants before the pods ripen.

Keeping the bacteria

Once milk vetch has nodulated well in a bed, the specific rhizobium it needs tends to remain in that soil, so later sowings in the same place often do not need fresh inoculant. Sowing into a new bed is a different matter: the bacteria are not there yet, so inoculate again, or move a little soil from the old patch to the new one.

Hard seed is common in legumes, and some milk vetch seed may not germinate in its first season. Lightly rubbing seed between sheets of sandpaper before sowing can improve germination if a batch comes up poorly.