Collecting and 'Finishing' Hosta Seed Pods with Sugar Water
When hosta seed pods are ripe they will split open. This usually happens later in September or October in North America. The trick is to pick the pods before the seeds start falling out. If you can't be sure about getting out there in time to catch the opening event, you can tie a cloth bag over your seed pod stalk. Just make sure that the cloth allows plenty of air movement to prevent damaging fungus and mold from destroying the stalk.
As a rule, the longer you leave the pods on the plant to grow, the better. If you can wait until the last (top) seed pod on the stalk has dark seeds in it, then you can be fairly sure that the other pods lower down (and therefore earlier) pods are ripe as well. Most people tell you to wait until the pods are dried out, while this is great if you have the opportunity to let mother nature do her thing but people have reported successful seed germination even if the pods are still somewhat fleshy, or green (or whatever color they may be such as purple, maroon or even striped).
If you have to harvest your pods early, you can try finishing the pods in sugar water. The ratio of sugar to water roughly 1 teaspoon of sugar to 4 ounces of water. People have even reported success with cutting the flower scape off and saving them in sugar water while they bloom. They pollinate the blooms and ripen the pods indoors, and leave the scapes in the sugar water for a few months while the seeds ripen. The thing you have to watch out for is mold growing in the sugar water. It helps if you mix sugar into rapidly boiling water to help sterilize everything then use the solution after it has cooled off. Also adding a few drops of bleach can help slow down the growth of harmful molds and bacteria in your sugar solution.
Once you have your pods, if they are not already split open you'll need to carefully open the outer case to remove the seeds. You can use whatever sharp or pointy tool that suits you, just be careful not to dig too deep because you may rip one of the papery seeds inside. It's usually best to do your pod opening over a large bowl or clean counter top as seeds may scatter while you try getting them out of their tight pod.
If you plan on storing you seeds it's a good idea to dry them out. A very simple way to do that is to leave them in a shallow paper plate, bowl, or on a paper towel for a couple of days. Move them around every so often so that they dry out evenly. Using paper under the seeds will help draw the moisture out. Once you have dry seeds storing them is as simple as putting them in a paper envelope, then inside a freezer-proof zip lock bag and popping them into your refrigerator. Make sure you label your envelopes too, if you plan on tracking seedling parentage at all.
Some hosta breeders report getting better germination from seeds that have been stratified (kept cold for a certain period of time). In general seed dormancy is usually overcome by the seed spending time in the ground through a winter period and having its hard seed coat softened up by frost and weathering action. This is a natural form of "cold stratification" or pretreatment. It is believed that the cold moist period triggers the seed's embryo. The embryo's growth and subsequent expansion eventually break through the softened seed coat in its search for sun and nutrients. In its most basic form, when the cold stratification process is controlled, the stratifying process amounts to nothing more than subjecting the seed to storage in a cool (ideally +1° to +3°C; not freezing) and moist environment for a period found to be sufficient for the species in question. This period of time may vary from one to three months. To accomplish this you merely place the seeds in a sealed plastic bag with moistened vermiculite (or sand or even a moistened paper towel) and refrigerate it. Use three times the amount of vermiculite as seeds. It is important to only slightly dampen the vermiculite, as excessive moisture can cause the seeds to grow mouldy in the bag, so err on the side of drier rather than wetter. To give an idea, it should not be possible to squeeze any dripping water out of the vermiculite.
An added precaution might be a good idea if you plan on keeping your seeds in cold storage for more than a few months. You can double bag your seeds or put the zip lock bag in a mason jar and then put it into the freezer. Hybridizers have reported success after having stored their seeds a number of years in the freezer! Remember that the Hosta's native habitat ranges from China, to Japan to Korea so knowing where your hosta originated can help you figure out how long it can handle being in frozen stasis.
When you are ready to plant your hosta seeds, just sprinkle them over the top of moist seed-starting medium. Care should be taken to use sterilized medium as young hosta are susceptible to molds, fungus and seedling die-off. There is debate over whether it's best to cover the seeds with seed starting medium or to just sow the seeds on top of the medium. While in nature it's probably more the case where seeds lay on top of the soil, which method you choose will depend on your own experiences and preferences.
Hosta seeds do not need light to germinate. You should see some germination action sometime around the 2 to 4 week mark. The thing that hosta seeds do need to germinate is a reliable temperature of around 70 degrees Fahrenheit. So if you plan on starting your seeds indoors just make sure you've got some way to keep the temperature regulated.