Gadenin日本語Get the appWhy a flowering vine sets nothing
Akebia flowers are unisexual and both sexes appear on the same vine, arranged along a single hanging raceme: a few large female flowers near the base of the stalk, and a cluster of many smaller male flowers beyond them. So a lone vine has all the parts it needs, which is exactly why the failure is so confusing. The problem is not missing sexes. It is that akebia is self-incompatible, and pollen from a plant is rejected by the stigmas of that same plant.
That incompatibility extends to clones. Two plants raised from cuttings of one parent are one genotype, and they will pollinate each other as poorly as a single vine pollinates itself. Only genuinely different individuals, such as two seedlings or two plants from unrelated sources, cross successfully.
There is a second, quieter reason for failure even where two good plants stand side by side. The flowers are pollinated in the wild by small flies and beetles rather than by honeybees, they open in cool early-spring weather when insect traffic is thin, and the male and female flowers on a raceme are frequently not receptive at the same moment. In a garden, insect visits alone often set a handful of pods on a vine that could carry forty. Hand pollination is not a rescue for a sick plant; it is the normal way gardeners get a crop.
Telling the two flowers apart
Learn the difference once and you will read it across the vine in a glance. Both sexes are dull purple-brown to pale mauve, faintly scented of chocolate or vanilla on warm days, and hang in loose racemes from the leaf axils of last year's wood in mid spring, opening with or just after the new leaves.
| Feature | Female flower | Male flower |
|---|---|---|
| Position on the raceme | One to three at the base, nearest the stem | Many, clustered along and at the tip |
| Size | Larger, roughly one inch (2.5 cm) across | Smaller, about a third to half that width |
| Color | Usually deeper, darker purple-brown | Often paler, mauve to pinkish |
| Center of the flower | Three to nine thick, glossy, banana-shaped pistils | A tight bunch of small curved stamens |
| Surface when receptive | Pistil tips visibly wet and sticky | Stamens dry and dusty with pale pollen |
| Stalk | Longer, holding the flower clear | Shorter, flowers crowded together |
The sticky sheen on the pistils is the single most useful signal on the whole vine. Receptivity lasts only two or three days per flower, and a dry, dull pistil surface means you are either early or too late for that particular flower.
Hand pollinating, step by step
Do this on a dry morning after the dew has lifted, when temperatures are above about 55F (13C). Pollen is shed poorly in cold wet air and washes off in rain. The whole job on two garden vines takes ten to fifteen minutes, and you will repeat it two or three times across the ten days the vines are in flower, because flowers open in waves.
- Collect pollen from vine A Pick two or three whole male flower clusters from the first vine, or snap off a few individual male flowers and hold them by the stalk. Freshly opened flowers with dry, dusty stamens are what you want; flowers that opened three days ago are often spent.
- Find receptive females on vine B Work along the second vine and look at the base of each raceme. You are looking for the large flowers whose thick pistils are glossy and tacky. Ignore female flowers that are still tight, and ignore any whose pistils have gone brown at the tip.
- Transfer the pollen Either dab the male flower directly onto each pistil until you can see pale pollen grains on the sticky surface, or load a small soft artist's brush or cotton swab from the stamens and paint each pistil in turn. Touch every pistil in the flower, not just one; each unfertilised pistil is a pod you do not get.
- Reverse the direction Now take male flowers from vine B and pollinate the receptive females on vine A. Use a different brush or wipe the first one clean, so you are not carrying self pollen back onto the vine it came from. Doing both directions doubles the crop from the same walk.
- Come back in three or four days New flowers will have opened on both vines. Repeat the whole process. Two or three passes across the flowering period is usually enough to load both plants more heavily than they can ripen.
Reading the result and keeping notes
Within one to two weeks a successful female flower stops looking like a flower. The pistils swell, thicken and begin to stand out from the withering petals as small green sausages, and by early summer they are recognizable young pods. Unpollinated flowers simply yellow at the stalk and drop, usually within about ten days, so you get a clear verdict on the morning's work well before midsummer.
Some drop after apparent set is normal on a heavily pollinated vine, and if a stem is carrying more than about five or six developing pods it is worth thinning to the best ones so the rest reach full size.
The record that pays you back next year is short: the date the first female flower opened, the dates you pollinated, which vine gave pollen to which, and how many pods were hanging by midsummer against how many flowers you treated. After two seasons that data tells you your own vines' flowering window to within a few days, and whether one of your two plants is the weaker pollen source. Mark the position of each plant on a sketch too, because once the vines have tangled through one another you will not be able to tell whose flower is whose.