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Capsule Drying and Seed Preparation
 
 
Dry Seed Preparation vs. "Greencapping"

Our preference is for the capsules to mature on the plant, keep a close eye on them and when they just start to split, harvest the caps rather than to remove green capsules early. "Greencapping" is a common practice, with the primary reason for doing it being that the unopened caps will have uncontaminated seed inside, but unfortunately that isn't always true. Just because the cap is closed does NOT mean that the contents haven't been exposed to bacteria or fungus that has penetrated the plant tissue. So, the best practice in the lab is to disinfect even green seed, but if the seed is too young it will be harmed by the disinfecting process. Also, green seed is reported to pass on virus to the offspring, while mature, dry seed does not. Virus may not be killed by disinfection. Also, unless prepared properly and shipped and used immediately a greencap can spoil. Additionally, a greencap must all be sown at once, leaving no opportunity to hold back and seed in case a second attempt is needed.

There are some species that need to be greencapped because mature seed is difficult to germinate. In these cases greencapping may be essential for success, and, in our opinion, greencapping is best only used in these cases.

 Seed Harvest and Drying

When a capsule is nearing maturity you need to keep a close eye out for splitting. Caps usually (but not always) split near the column end first. If you can't check daily then you should tie a coffee filter or some such thing over the near-ripe capsule to help catch seed and to help keep airborne contaminants out. You might consider moving a plant with near-ripe capsules out of the greenhouse to a less humid, less pathogen-rich environment, perhaps your house.

Split Capsule
A Capsule that has just split - note the gaps on the column end

When a capsule splits, sometimes it takes days but sometimes only hours for it to open completely. If you remove a split capsule from the plant and lay it on a coffee filter and then cut the column off with a sterile razor blade, the cap will likely spring open a bit and seed will drop out immediately.

Cut Capsule
Same capsule after cutting off column end with a sterile blade - note how it has sprung open and seed has immediately fallen out

Size permitting, you can staple the stem to the upper edge of the coffee filter. Huge capsules will need to be suspended with appropriate ingenuity on your part.

Stapled to Filter Paper
Capsule is stapled to edge of coffee filter to dangle while drying and opening further

Protect it from blowing air by slipping it into a jar or other container, but DON'T put a lid on the jar as the seed may mold from the humidity from the moisture in the meaty capsule walls.

Paper in Jar
The filter is tucked into the jar to allow free drying and protect from breezes that would carry away the seed.

Once the capsule is fairly dry (a few days) the good seed will fall out by tapping it lightly. Scraping usually isn't needed, and if done unnecessarily it just adds useless material that complicates the disinfection process.

Dry Capsule
After two days, in this case, the carpels have dried, and seed has fallen out. Only tapping was needed to get the best of the seed.

Remove the capsule remains, fold up the coffee filter so that seed can't spill, and secure it shut with a little tape or a couple of staples so that we will be able to open it without spilling seed and label it. Good things to put on the label are genus & species of parent(s), whether it is a selfing, outcross, or other, pollination date, harvest date, number of capsules contained, and any identifying number assigned by you or us.

If there is a lot of seed from a huge capsule, further drying may be appropriate, and if so, once the meaty carpels have been removed, the packet can be place in a closed jar with a very active desiccant such as calcium chloride. A passive desiccant such as silica gel does not have a sufficient uptake rate and will cause problems, unless the seed is dry already. This finishing drying should be done at room temperature still, since drying is retarded if it is placed in a refrigerator.

It is usually best to only put the contents of one capsule in each paper packet even though they are from the same plant and pollen parent. This is because we examine the seed under a microscope and often we find that one cap may have seeds with no embryos or with mold mycelia while another may be good seed... and to mix them together would be a shame.

After the dry seed is out of the cap, it should be sent to us immediately, or if you are keeping it, when fully dry only it should be stored in the refrigerator in a jar with a humidity-controlling mixture. A good one is equal parts by volume of calcium chloride pellets and water, such as a tablespoon of each, in a small open container inside the jar.

 
 

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