If you look at the edges of a seed, you'll notice that there's a seam all the way around, and that it's more pronounced on one side - like a ridge. This ridge comes off quite easily and then allows the seeds to pop right out of their shells with ease.
Grip the seed between your thumb and forefinger with the ridge side up, then using the sharp edge of a small pocket-knife or paring knife, very gently scrape at a 90 degree angle across the ridge and you'll see it come right off, exposing a slight opening along the edge of the seed.
Take extra care not to squeeze the seed at all, but spin it around to finish scraping the other end of the ridge (on the same side)
Seeds can take anywhere between 12 hours and 3 weeks to germinate. Most seeds that do not germinate under good germination/grow conditions are considered non-viable seeds. The 4 main reasons why a seed is not viable is as follows.
1. Seed has been damaged.
2. Seed is immature.
3. Seed is too old.
4. Seed can not absorb water.
Sometime 3 and 4 go hand in hand. If a seed does not pop, then most people chuck the seed. Here is method to help you germinate seeds that may still be viable but are having trouble germinating. The process is called Scuffing.
Dig up your seeds that have not germinated (wait at least 3 weeks).
Get a small box (match box is good)
Put sand paper into the box.
Put seeds into the box.
Shake around for 30 seconds to 1 minute.
The sand paper will wear down the seedcoat, making it easier for the seedcoat to absorb water and split open.
Then put the seed into a small container of room temperature filtered/distilled water without any additives for about 18-24 hours.
Next gently transfer your pre-soaked seeds to a pair of wet paper towels (pre-warmed to room temp), maybe in a large tupperware-like covered container.
Misting the paper towels daily so it stays nice and damp (but without any standing water puddles in the folds of the towels).
Don't let the towels get too cold, because the wet paper towels will always get chilly fast, so they must be kept in a constantly warm area (but dark). A heating pad may be required to maintain 25C to 26C throughout germination.
I use a regular heating pad set on low, covered with a light towel to buffer the heat, and on a timer, set to go on and off every half-hour. Make sure they are kept in a very temp stable area. I use a digital temp gauge, the kind that cost about €10 and have a probe on the end of a wire, so you can place the probe right into the wet paper towels.
[editor’s note: place seeds on top of the fridge if you don’t have a rootmat]
Seeds should sprout within a few days; when they do, they must be transferred to the medium with great care when the taproot has come out about 0,5cm to 1cm. I find that a 1cm tap root seems to be the best. When it's much shorter, they tend to get shocked and die easier, and if it's much longer, there's more risk of damage.
They are very delicate at this stage; sprouted seeds can be killed by rough handling, damaging the tap root, or if the soil or medium they're put into has not been properly prepared in advance to the right moisture and temp.
If you're using a soil mix, I usually add about 25% perlite and 25% vermiculite to 50% pre-sterilized Supersoil. Using a pencil or something to prepare a hole for your seedling, and lower it in with the taproot down first and the seed end up. Gently pack or fill in the hole fairly loosely around the taproot, covering the top of the seed by about 0,5cm, and I water them with an eyedropper or a spray bottle set on mist.
Now you'll want to place them under fluorescent lighting about 10cm to 15cm away and mist them down daily. Continue to ensure they are kept warm enough, because when the wet medium cools off at night down toward 15C it can shock and slow them down or possibly even kill them.