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Most of the plants I grow from seed are perennials and wildflowers which can be somewhat difficult to germinate. I was just reading through some comments found in the plant files about a specific vine and one person said, he soaks the seeds before planting. He throws out the seeds that float to the top and only plants the seeds that do not float to the top of the soaking water/solution. Is this something that everyone knows to do but me? Is this correct? If so, does it apply to most seeds and is this generally a valid rule to follow?
No it is not valid. If it makes you feel good and you have seeds to throw away go ahead and do it. There are many things which can make seeds float including microscopic air bubbles on seed coat and even under seed coat. In some seed species, the seed coat may not shrink as much as the germ leaving air space and causing seeds to float. Additionally, there are some seeds that have evolved to float as a dispersal mechanism.
There is no advantage to doing this before sowing seeds unless you are trying to equate one seed to one pot to one plant which is not realistic unless you have 100% germination which very few things in nature do.
For the perennials and wildflowers, pay close attention to methods of breaking dormancy and don't cheat on stratification times for those that need this. Also be aware that even after applying treatments to help break dormancy germination times can be greatly elongated especially for many wildflowers. Another thing to pay close attention to is age of seed that you are obtaining. Some wildflowers will only germinate from seed sown very shortly after seed maturity is reached. Even seeds that are 6 months old will not germinate regardless of treatments applied.
Thank you trc! Your answer is thorough and interesting and much appreciated. If I had the option, i'd go to the nursery to buy a plant, but the nurseries here in Mexico don't have the plants i want. i have sure tried all the methods and have come to the conclusion that many of these seeds will germinate when they very well please no matter what i do to them. Often when i've given up on some seeds and am tired of looking at the pot, i'll dump the nice potting soil out in the garden somewhere and maybe 3 or 6 months later something will pop up. Just goes to show you who is in charge here...and good lessons in patience. At any rate, i won't be tossing out the floaters.
I've found that seeds which floated when first added to water (warm>hot depending on the seeds) and left for a period of time (again depends on the seeds) usually sink! It means the seed has absorbed enough moisture to begin the germination process so I don't worry about them at all. Those that don't sink, I don't worry about picking them out.
If the seed is large enough and has a hard seed coat I slightly rough the coat by rubbing them between 2 pieces of sandpaper (ever so lightly) then soak them in water.
Those that germinate freely, I just plant in soil and let nature take it's course.
Thank you for the good advice Sassy. You and trc are making perfect sense to me. I am just now trying peat pellets. I didn't like peat pots but i'm loving these little pellets. Sandpaper will work well for me with the tiny seeds especially so i will add that to my list of things to try and i haven't tried the water/hydrogen peroxide solution for soaking yet. Altogether, gardening is a fascinating process, yes? I have gardened in the state of Washington and now over 4 years in the tropics. There is a big difference and the same rules do not always apply so it is a little bit like starting over. But where ever the garden, it is always an adventure in learning with lots of surprises too.
If you like peat pellets, you might try "paper pots"! I bury bad news that way!!! Google "paper pot maker" or visit YouTube for video instructions. They last about 5-6 weeks and the whole pot is planted along with the seedling - be sure to bury the paper pot rim in the soil or peel back, otherwise it acts like a wick. After a few weeks in the soil the newspaper disintegrates. Most newspapers now days use soy ink for the black and white sections, avoid glossy or color printed pages.
I make enough to stand them up in a standard flat tray or you can stand them up in cell packs that are large enough to hold them. You do have to pay attention to moisture or they can dry out...