Techniques for Seed Collecting and Storage
Locating Material For
Techniques for Seed Collecting and Storage
Locating Material For Collection
Look for seed spikes with calyxes that persist after turning brown and papery dry. Unfertilized calyxes usually fall off quickly. A sign of fertilization is the opening of the calyx mouth. Look down the tube to see if there are one to four ripe nutlets. These will be black or dark brown if ripe, and should be collected within a couple days before they fall out. You can tell if a green calyx is developing viable seed by pinching it at the base. It will be thicker and harder than calyxes that have aborted fertilization. You can confirm this by pinching open the mouth of the calyx to observe the green growing nutlets.
Collecting fully grown green seeds is an expedient, done only if necessary. An example is a one-time visit during a plant collecting trip. If you must collect unripe seed, its seed coat should at least be losing its green color. The development of the enzyme systems needed for a successful germination correspond to the development of the dark pigments in the seed coat.
For an illustration of what a fertilized versus an unfertilized seed looks like, go to the Seed Development section of the Salvia Floral Structures page.
Drying The Collected Seed Heads
First, label the seed lot with the name, date, collecting site, and your collection number. This can be a plant label dropped in with the lot, or the container itself can be marked. Also, record the info in a log book or data base. It is very easy to misplace this information. Don’t rely on your memory. It helps to drop in a few whole flowers while collecting to jog your memory later.
The container should allow the seed lot to dry out and to allow insects to migrate away. A tray or a large paper sack work well. For the same reason, do not pack the lot tightly. Look for small weevils. Their larvae will enter the seeds near their point of attachment and eat out the seed from the inside out, leaving a hollow husk. There will be telltale signs if this is the case, because the calyx will also have a hole at its base.
After the seed lot is dry, strip off the calyxes from the stems between your fingers, being careful to avoid scattering the emerging seeds. You may have to rub the freed calyxes to loosen the remaining seeds. If the lot is still damp, dry it further.
Releasing The Seed From The Chaff
For small quantities, you will need a few trays, a set of screens, funnels, envelopes and/or vials. Larger lots may require specialized equipment, some of it home made.
Start off by using screens to remove the fines (mold spores, dirt, etc.) and coarse chaff, then go to the specialized cleaning techniques. Since I usually work with mint family plants, these techniques are most useful for round to oblong seeds.
I generally rub the fully dried flower heads between my palms for the small amount of seed I collect. I don't use wet methods for cleaning seeds of Salvias because the glutinous seed coat will swell and stick to the rest of the material, including mold spores.
It is important to collect Salvia seed that is ripe, meaning that it is at least brown, preferably black, AND has not been moistened after ripening - this will cause it to pick up mold. Seed lots contaminated with remoistened seed will damp out on germination, leaving the sower with a lot of moldy, dead seedlings.
Isolating The Seed From The Chaff
The first stem is the removal of the coarser material from the seed. Doing this will release a lot of dust, so do these operations in a garage or in a kitchen. Start with coarse screens that let the seed pass through. Follow this with a de-dusting using the finer screens.
The next step is sorting out residual chaff and substandard seed, using trays and bowls. If you have an air tower separator for large lots, all the better.
I started with a 16 x 16 screen from window screen, and a 40 x 40 screen from the brass hardware cloth supplied for use as a water filter at hardware stores. My frames were made from number one 1 x 4" pressure treated pine cut to make a 12 x 12" frame. I ripped off a 3/4" piece off the sides to make the trim that held the screen on the rest of the frame.
Next, I invested in some inexpensive special size screens from Burrows Equipment Company. I got sizes (10 x 10, 14 x 14, 24 x 24, 32 x 32) that were not available from common sources. Made with wood rims that can be stacked, they cost $11 apiece in 1979.
Later, I made 14 x 18, 18 x 18, 36 x 36, 42 x 42, 48 x 48, and 60 x 60 screens from samples given to me from hardware cloth used in the factory for dust control equipment. The factory I referred to is the production facility of Lorillard Tobacco, where I used to work.
Gilson, amongst others, supplies lab screens, but these are expensive ($25 for 3" to $80 for 12" apiece), depending on the diameter, depth, and construction (brass or stainless steel). These are the screens one most often sees in academic or industrial labs.
Trays And Bowls
Trays can be used to separate seed from the chaff that can’t be removed by screens. Much seed is denser and usually round or oblong. By taking a cardboard beer flat or similarly sized plastic tray and laying down a half-inch wide row at one end and shaking the tray with a regular motion at just the right angle, one can induce the more desirable seed to separate first and roll to the bottom. The intermediate material can be sent back to the top by lightly blowing on it for a second or third chance. The art is in picking the right angle, motion, and load for the seed variety.
A variation of this is swirling in a bowl. With the right amount of seed, very often the best material will collect in the center, and the chaff on the outside. It is important not to overload the bowl. You should have only one layer of seed for effectiveness. The best quality seed collects in the center of the bowl because it is both larger and denser. A deep stainless steel bowl (3" deep, 4" wide) works best for me.
If you want to blow harder, you can remove the chaff entirely. This is a messy but highly effective process.
SAFETY WARNING: I once scratched my cornea pretty good blowing chaff out of a bowl of seed that I was cleaning, so wear protective glasses.
Sometimes electrostatic forces will interfere with seed cleaning, especially with small seed. The way to remove this is to use an electrostatic field generator. I have a Zerostat 3, made in England for Discwasher. This gun-shaped device produces a charge by squeezing a piezoelectric crystal. One charge is produced by light squeezing, and the opposite by releasing the trigger. This should discharge the particles, allowing them to flow freely. I got my gun at a stereo center or an electronics supply store. It is designed to remove dust from CDs and LPs.
Air Separator Tower
Burrows also had a tower with air blown upwards through a sample with carefully controlled air flow. This would allow lighter chaff to be blown out first, leaving the usually heavier, viable seed at the bottom. By slowly increasing the air flow, more of the chaff and lighter, immature seed could be removed.
Working such a tower is an art. One needs to know how much material to load into the tower, what air flow to use, and how many tower sections to add to get an effective separation. It should be possible for a gifted handy man to make one starting with an old vacuum cleaner. The process is similar to distillation of organic compounds using a fractionation column. Separation is based on the density and shape of the objects in the stream.
The best method is supposed to be in paper envelopes. I prefer to store seed in glass vials. It would be best to keep the seed in a 40 degree refrigerator. Paper envelopes breath and will release condensed moisture. If you store seed in vials, make sure you have removed all dampness. This is more important if the vials are refrigerated.
Germinating Difficult Seed
The publication “Seed Germination Theory and Practice” is $20.00 (postpaid anywhere in the world), is available from Norman Deno, 139 Lenor Drive, State College, PA 00016 (Phone: 814-238-8770). The author is professor emeritus of chemistry in the Eberly College of Science, Penn State University. This labor of love is a classic work much loved by rock gardeners and others who work with hard to germinate seed.
Besides techniques for germination, results for various species are listed. Methods included generally do not involve chemicals like gibberellic acid treatment. Stratification is a common method involving alternate cooling and warming from sub freezing to room temperatures. Dr. Deno merely applied various organic chemical principals and techniques to the problem of seed germination.
I have found that the gibberellic acid treatment for Salvia sonomensis seed gemination to be generally applicable to other arid area Salvia and other Labiatae seed that have dormancies. A 100 ppm solution of GA3 is prepared in distilled water, and added to the seed placed in a small vial with a secure cap, using a three to five volume ratio of solution to seed. The seed vials are shaken gently for 30 minutes on a shaker table. This device is normally used for swirling cultures in microbiological labs. Alternately, the vials could be fixed to a slow-moving wheel run by a small motor (from an Erector set, for example), or attached to an old electromagnetically pulsed pendulum like those used for old counter displays.
Treated seed should be promptly sowed. Excess GA3 solution should be refrigerated and will be good for only a few weeks because of microbiological degradation.
Testing Seed For Viability
You may need to determine the percent germination of seed, especially if it will be sold commercially. Your best tools are germination test paper and a stain that indicates the presence of reducing enzymes.
Germination Test Paper
Burrows also supplied Kimpak Germination Paper in boxes of 100 sheets (about $18/box in1979) in various sizes. The paper is sterile, has no injurious chemicals, and holds 16 times its weight of water. It works for both small and large seeds. A chamber for controlling humidity is very helpful, as is bottom heat and grow lights to control light and heat. Collected data will be meaningful only if you have controlled conditions that are recorded with the percent germination. It is useful for Dr. Deno’s methods.
If alternate paper is to be used, it should be free of salts and other soluble materials, which will interfere with germination.
Reducing Enzyme Stains
These are various tetrazolium compounds. In the presence of a reducing enzyme and a reducing agent in a viable seed, the exposed seed tissue will develop a blue or purple stain. A set number of sees are sliced in half and exposed for a while to the stain, and a ratio based on the count of stained half-segments to total segments taken.
Addresses for Sources
Seed screens and other equipment:
Information on seed germination:
Reference book source:
A list of scientists who specialize in seed research.
A company that does seed testing. They may be able to provide leads for sources.
Staining as a means of testing germination:
Protocols for seed testing:
Links to Other World of Salvia Pages: