FRUIT SEED CONTINUED: Before we begin talking about seeds produced in pods or capsules, I wanted to clarify a couple of points from my last lecture. As you may remember, I mentioned that some professional propagators treat certain species of plant seeds with an acid solution to help remove the stubborn oils that inhibit germination. This may give you the mistaken impression that this is the main reason that acid is used. Actually, the concept of using acid, usually sulfuric, to treat seeds with, evolved from trying to duplicate the effect of stomach acids on seeds. As we discussed before, many of the plants that produce fruit, have evolved along with animals that subsist on the fruit. As the fruit passes through the digestive tract of the fruit eater, the amino acids present not only clean the seed coat of any chemical germination inhibitors, but also assist in softening, or abrading it, aiding in the speedy germination of the seed. While present research findings disagree with the notion that most fruit seeds need this for water to reach the interior of the seed, there are those that still use acid solutions for treating all fruit seeds. There may be some seeds that do need this to be cultivated by artificial means.Remember, I'm a perennial nursery owner, and have only limited first hand knowledge of starting tree seeds, where most of this behavior is reported to be found. I'm only reporting what I've read.
In summary, the following is recommended for collected fruit seeds. - Remove the seeds from the fruit pulp as soon as possible after collection, using one of the methods we discussed, or one of your own making.
- Clean the seeds thoroughly in clear water to remove the remaining pulp that clings to the seeds. It is OK to use a little elbow grease, or even a scouring pad on larger seeds.
- Give any seeds that have the slightest oily feel left to them a gentle scrubbing with a grease removing detergent. a) It is a good idea to continue rinsing the seed daily in fresh water for at least one week. (I add a little lemon juice to the water). Some seeds benefit from a longer rinsing cycle. The exception to this rule is the seeds encased in a gelatin like substance or the seeds of annual vegetables. If you continue to rinse seeds of this type, germination may begin prematurely. b) In general, at this point, if the seed is from an annual or tropical plant, you may either sow the seeds at room temperature immediately, or spread them out, allow them to dry, and store them until you are ready to sow them.
- Again, as a general rule of thumb, place the seeds of temperate zone plants into cold storage for, at least, 3 months (90 days), and then move them to room temp. (about 70F). If germination does not occur within that period, repeat the cold and warm cycles until it does.
For purchased fruit seeds, or seeds that have been dry stored, assuming that the pulp has already been removed, (this isn't always the case, I've received seeds that has been stored in dried fruit) begin with step 3 above and treat like fresh seed. Seed that has been dry stored may not be viable, or may take a lot longer to germinate than fresh seed. This is not a hard and fast rule, but before you waste your time, it might be a good idea to open a couple and check them for life signs.
Keep in mind that these are only general guidelines. They won't work for everything. If they fail, try something else. We'll discuss some other germination tricks in a bit. I use these methods because I'm an impatient propagator. I want to see quick results. Remember that each species has evolved it's own methods of survival and germination of it's seed. You can always throw the seeds in a pot, set it outdoors, and hope for the best.
SEEDS FROM PODS/CAPSULES: (This very general category, includes any of the many seeds that are not encased in a fleshy fruit, but in a thin walled, usually dry and papery capsule or pod.) Unfortunately, the rules are even less specific with these type of seeds. I hope I don't totally confuse you, but I'll try and give some basic guidelines for collecting, storing and germinating these seeds. First of all, collect them when the pods begin to open. This indicates that they are ripe. Second, clean as much excess material (chaff) from the seeds as possible before sowing or storing. Disposition and storage are another matter.
As you may have surmised from our talk on fruit seed, how a seed is dealt with after collection is quite important. Some seeds in this category do not tolerate being dry stored any more than many of the fruit seeds, and if they are, they may die, or go into deep dormancy. And this time I do mean the word dormancy. Conversely, there are other seeds that will not germinate well unless they are dry stored for a period of time before sowing. Yet others have impervious seed coats that must be corrupted before water can enter and germination begin. There are some that germinate immediately if sown in warmth. There are some that germinate in cold temperatures only. There are some that germinate in warmth, but need a cold period first. And there are some that need a warm period followed by a cold period. There are even quite a few that need warm day temperatures and cool nights to condition them. And if that isn't enough, some require light, and a few need darkness. And you thought fruit seed was complicated *Grin*.
So if you don't know which is which, how do you figure it out? I will not pretend to have all the answers. I can, in fact, guarantee you I do not, and not even an expert like Norman Deno does, although his books are of tremendous benefit here. But there is always an answer, and the answer can be usually be determined by observing the plants natural habits, or using the information that you have or can find about a purchased or traded seed to make an educated guess. If you have the plant, note when it sets seed. This will give you some clues.
I divide the seeds into three basic categories, those to sow immediately, those that need to be dried out before sowing, and those that have impervious seed coats. Here are some basic guidelines to get you started.
SEEDS THAT SHOULD BE SOWN IMMEDIATELY: Many plants can be sown immediately, but seeds of these plants will be difficult and on rare occasions impossible to germinate if they are not.
Spring ephemera's is the first type falling into this category. These are normally woodland or understory perennials, often bulbs, that put up foliage very early in the spring, and bloom before the average air temperature hits 70F. Many of the seeds of these plants need to be sown fresh, or alternatively stored in a moist cool environment until time to sow them. If seed of these plants is allowed to dry out before sowing, germination may take 3 or 4 times as long, and some few may never germinate. After cleaning these seeds, I wrap them in a moist paper towel, place them in a baggy, and store them at room temperature until early fall when they are sown into seedling pans and placed out of doors in a cold frame. Many of them will germinate with the onset of cool nights and warm days. Others germinate the following spring. Alternatively, you could place the seeds in your refrigerator each evening, and germinate them in the towels. Some examples of these plants are Trillium species, Dicentra (Bleeding Hearts and Dutchman's Breeches), Delphinium tricorne (Wild Larkspur), Corydalis species (Fumitory), Sanguinaria canadensis (Bloodroot), and Eranthis (Winter Aconite).
The other seeds that fall into this category are those woodland species that set seed in early to late fall. Often these seeds fall to the ground and germinate immediately. The tiny seedlings then overwinter in the ground, and begin growing with the onset of warm weather. The classic examples of these plants are Aconitum (Wolf's Bane), Cyclamen, and late blooming Helleborus sp. (Christmas Rose) and Arisaema species (these can also be considered a fruit). I place these seeds immediately into seedling pans, and follow the cool night, warm day pattern that is used for the spring species. You may of course also sow them into towels.
Sometimes, the only way to obtain these plants is to buy seed. If you obtain seed of one of these plants that has been dry stored, sow them into towels in the refrigerator, and alternate cold and warm cycles until germination begins. I find it helpful to start with a cold cycle, then after 3 months remove the seeds from the refrigerator every second day and allow them to come to room temperature. They are then returned to the refrigerator. This is of course to imitate the warming up cycle in spring. I keep this up for about a month, leaving the seeds out for increasingly longer periods of time. If germination doesn't begin within 3 months after the seeds are kept constantly at room temperature, try giving them another cold treatment. I use this treatment though for just about all of my seeds that I sow in the refrigerator, not just the ephemera's.
SEEDS THAT NEED TO BE DRY STORED BEFORE SOWING: Many, many seeds respond well to being dried out before sowing. The theory is that either they don't have mature embryos when they leave the plant, or that there are chemical inhibitors that break down as the seed ages. According to Norm Deno, with these seeds, there is an optimum storage time. Seeds sown fresh often won't germinate at all, but if they are stored for a few months, they will germinate easily. If they are kept in storage too long, they will eventually use up all their stored food and die. Norm suggests that they be stored for approximately 6 months, but I never really pay much attention to storage time. I collect seeds as they are ripe, dry them by leaving them in thin layers in a old butter carton, then clean, package and store them until I'm ready to sow. If I collected them in early summer they probably do get six months storage, but any later and I'm sure they get less. This general rule applies to nearly all of the popular sun-loving garden plants and grasses. For clues, look at the plant. Does it hold it's pods upright, or retain it's seeds for a long time after the capsules are open? If so, it probably will respond favorably to dry storage. The seed of all the common garden vegetables, most herbs, and probably 90% of the annual flowers fall into this category.
Dry stored seed is usually dried for a week or so in the open air. I've heard some people recommend that you leave them out the sun, but I don't. I simply spread them out in thin layers and allow them to air dry in a room with good air circulation. They are then cleaned and packaged into paper envelopes (properly labeled and dated of course) and placed in a seed collection box. If I have leftover seed after I get done sowing the seed in winter, or early spring, the remainder are moved to cold storage, to maintain as much viability as possible. I place the packets in ziploc bags and put them in the refrigerator. Do not try to force all of the air out of the bag, as the seeds need to have air, and the air will keep you from crushing them with a milk carton.
Now do I sow them at room temperature, or do I start them in the refrigerator. By far, the largest number of popular garden plants can be started easily in warmth. There is, however, no easy way to tell which ones need a cold period. If I simply have no idea, I try to make a guess as to the time of the year the plant sets seeds (assuming I don't know). If it sets seed early on in the late spring or summer, it is probable that the seed won't be harmed by warm temps, and will probably germinate in warmth, so I start them at 70F. If the plant sets seed later on, it is likely that either the plant needs a cold period first, or will at least not germinate readily at room temperature. Sometimes it can be harmful to sow seeds warm. If the plant's seeds would not fall on warm soil in nature, don't try starting them that way. Try the cold period first. In general, if I don't know, and the seed is valuable I always start with a cold period. You are less likely to kill the seed this way.
IMPERVIOUS SEED COATS: These are most often found in seeds of the pea family (Fabacaea), but may be found elsewhere on occasion, especially in plants that evolved on prairies where they would be subjected to annual fires. These seeds are usually dry stored prior to sowing, but it doesn't really seem to matter. On the whole, these seeds are longer lived than most of the other types. I've germinated seeds of the Golden Chain tree (Laburnum) that; were 12 years old.
Usually, the only trick to germinating this type of seed is to corrupt the seed coat enough so that water can get in, without tearing up the seed. (There are a couple of exceptions, one is Opuntia, and the other Leucocrinum, both natives of the Western US, there maybe others as well. These seeds also need a cold treatment.) With large seeds, like morning glories, it is a simple procedure to clip off a piece of the seed coat with a pair of nail clippers, or make a small pinprick with an exacto knife. Smaller seeds can be rubbed against some sandpaper glued to a board. Both of these methods will work, although I don't use the sandpaper one. The seeds are often too damaged to live. If you dampen a towel and then sprinkle the seeds you've treated in it and hold for a couple of hours, the ones that are ready to absorb water will begin to swell. Here are a couple of other tips. I haven't tried all of them.
- Tie the seeds up in a stocking and place them in running water (a dripping faucet) for several days. When they start to swell up, plant them.
- Soak them in a cola product until the coats are softened. I've not tried this one, just read about it the other day.
- Place them in a small jar with some sandblasting (silica) sand, and shake them vigorously, or put the whole mix in a rock tumbler without the water and tumble for an hour. This one I've tried, and it is great for really small seeds like Astragalus and Sphaeralcea.
- Rub the seeds against a whetting stone instead of sandpaper. You are less likely to damage them than if you use sandpaper.
- Pour almost boiling water over them, and let stand overnight before sowing.
GENERAL SOWING INSTRUCTIONS: I use two different methods for sowing seed, either paper towels or seedling pots (commonly referred to as pans).
PAPER TOWEL METHOD: I got this method from Norm Deno, who says he got it from someone else. This is very easy. Take white paper towels. Fold them in half three times. Label the towel with the variety, date and any other information, like oscillate temps before bringing to warmth. Dampen the towels, squeezing out most of the water. It should be well dampened, but you shouldn't be able to squeeze more than a couple of drops out of it. Open the towel open two folds. Sow the seeds inside. Fold back up, and place in a thin, non-ziploc bag.
Whether you are placing them in the fridge, or not, you need to open them up at least once a week to check for germination and allow air to circulate around the seeds briefly. When germination begins, I move the germinated seeds with tweezers to a seedling pot. If I know the variety well enough to predict it's behavior, I don't wait for more than one or two seedlings to germinate before moving them all to pots. Some seeds, with erratic germination, have to be moved as they germinate. These are the main ones I sow in towels. If you sow seeds with erratic germination in pots, the ones that germinate first will crowd out the later ones, and if you try to prick them out one at a time, you may end up burying the others. I also sow very rare and valuable seeds into towels, as overall there is a better success rate. The only other ones I sow in towels are those needing alternating cycles of warmth and cold. Germination is faster this way.
You can place several towels into each bag, although you should be careful to place seeds that actually need light to germinate in bags by themselves. (There actually aren't very many that do. Most of the ones that light is recommended for actually don't require it, but are very small and just shouldn't be sown too deep or they won't be able to break the surface). Make sure you do not put the bags in the sun, as they will overheat. I place mine on the end of the same shelf the seedling pots are on. Norm Deno uses a separate method for seeds that require light to germinate, sowing the seeds on top of the towels. I don't, I've found that they get plenty of light to germinate through a white paper towel.
If the towels begin to break down, or get really moldy, just transfer the seeds to a clean towel. You will often have a little mold growing on the towel, or internally infected seeds. Remove the bad seeds, but don't worry too much about the mold growing on the towel. After three years experience with this method, I can say for certain that I've only had one case of seeds being killed by the mold in a towel, and that was some I left in the fridge over the busy spring season without remembering to ever check them.
Lastly, use this method of sowing only if it's necessary, or you have the time to transplant the sprouted seeds. It is a time consuming process. And don't use this method on dust like seeds. You can never get them loose from the towels as the ultra fine radicles root immediately to the towel.
SEEDLING POTS: Even with a nursery, I still only use seedling pots. If the variety is very popular, I might sow two or three, but rarely do I need them all. I use a sterile soil mix for the medium, mixed with 1/4 to 1/2 part coarse grit or perlite. Rock garden plants get more grit. The pots are cleaned in hot water and filled full to the rim. I then dampen the pots with a fine spray from the hose. (Some people use a boiling water bath to insure sterility). The seeds are sown directly on to the surface of the soil. I do not make little holes for each one. Most professional propagators don't. We'd never get finished. The seeds are then covered with granite grit. Rarely more than 1/4", and just a very fine layer over seeds that are small or need light. Place a plastic label in the pot, or use a folder label, and stick one to the pot. Put the pots either out of doors in a cold frame, or indoors under lights. I don't use my greenhouse for starting because it tends to overheat, but if you have one that has fairly even temperatures, you could. Indoors, I mist the surface of the pots daily with a fine mister, and water about twice a month. You'll soon be able to tell which ones need water just by the weight of the pot when you lift it. Keep the seed pots evenly moist, but not constantly soaked.
Sprouted seeds moved to pots from the towels are treated the same way. There is no need to go about making a tiny hole for each radicle. Just lay them on the soil. They'll find the way down.
I do not feed seedlings in seedling pots. When the seedlings are big enough, they are moved to individual pots, or seedling flats. Transplant them before they become over crowded. I don't wait very long. Usually if they are big enough for me to hold on to, and have the first set of true leaves, I move them. I begin feeding a mild organic fertilizer after they are established in their new homes. You'll have to make your own choices there. I have no suggestions as far as chemical fertilizers are concerned. I don't use them.
Above all when beginning don't expect everything to work like clockwork. Don't give up. If at first you don't succeed with a particular variety, try it again next year. I get better at it every year. You will too.
I know that I didn't cover everything, but that's most of it. I wish I could cover the plants individually, but this is supposed to be a lecture, not a book. I do recommend that you buy one to aid you in seed germination, and Norm Deno's Seed Germination book is the very best for garden seeds. I'll be happy to answer questions about individual species as my time and knowledge allows. E-mail me at jadare@accessus.net with questions. It may take me awhile, but I'll get you an answer if I can find one.
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