Tiny seeds pose many problems that are not encountered with larger seeds that are easy to see and easy to handle.
Tiny seeds generally need light for germination, so they cannot be covered with soil to keep them in place while they germinate and establish enough root system to anchor them in place. They also require constant moisture to start the germination process.
Heavy watering ( even heavy misting we have found ) can wash the seeds into the soil, or forgetting to keep soil surface misted for only a day can allow the top of the soil to dry out in hot weather, killing the germination process. And yes, heavy winds can actually blow seeds from the surface of the soil ( after one heavy storm a few years ago, we noticed very poor germination with our sedum seeds, only to find them germinating quite well in other test trays nearby ).
Pelleted seeds make handling and seeing small seeds much easier and many gardeners are more successful with pelleted seeds, but they too have a drawback, when the inert material melts away from the seed, it can create a tiny crater in the soil, which can cover the seed with soil the next time it is watered.
We have worked on this problem in our greenhouses for years, and have come up with a solution that has worked very well for us in tests conducted over a two year period.
We created a product we named VG07 SeedcoverTM. We started with vermiculite as a base for the product. Vermiculite has been used for nurseries for decades as a seed cover. The drawback to vermiculite is that it moves around very easily on the surface of the soil and can be displaced by heavy watering or wind. It allows light to get to the seeds, if the cover is even and consistent, but this is sometimes difficult to maintain.
What is vermiculite? Vermiculite is the mineralogical name given to hydrated laminar magnesium-aluminum-ironsilicate which resembles mica in appearance. Vermiculite is found in various parts of the world. Locations of the predominant commercial mines are in Australia, Brazil, China, Kenya, South Africa, USA and Zimbabwe.
Vermiculite mines are surface operations where ore is separated from other minerals, and then screened or classified into several basic particle sizes.
When subjected to heat vermiculite has the unusual property of exfoliating or expanding into worm-like pieces (the name vermiculite is derived from the Latin 'vermiculare' - to breed worms).
This characteristic of exfoliation, the basis for commercial use of the mineral, is the result of the mechanical separation of the layers by the rapid conversion of contained water to steam.
Vermiculite's many uses and beneficial properties include: Inorganic, and sterile, no known toxicity or fire hazard, high water holding capacity, non-abrasive and non-irritant, absorbs excess nutrients, facilitates re-wetting, low alkalinity, high cation-exchange capacity, does not deteriorate in storage (if kept dry), free from disease, weeds and insects (very important for our use ), good air holding capacity and insulates and minimizes soil temperature fluctuations.
As you can see, vermiculite is an excellent material for seed germination, but the commercial form has the drawbacks we have noted, it is easily displaced by wind and watering and though it is small, it still can easily be applied too thickly for tiny seed coverage. So we started milling commercial grade vermiculite down the the perfect size for our needs, this took a lot of experimenting, milling and sieving to get the exact size we needed for our base.
We then developed a procees to hold it in place and also to keep the constant moisture against the seed without holding too much moisture, which would rot the seed in place. We accomplished this by adding a powdered water absorbing polymer ( our Powdered Plant Gel ) to the milled vermiculite and after many, many attempts, obtained the perfect formula that provided consistent results.
The Plant Gel reacts to moisture and turns into a jelly like substance on it's own. When mixed with the milled vermiculite and sprinkled onto wet soil that has tiny seeds on the surface, it envelopes the seeds with a blanket of vermiculite and moisture that anchors to the soil, and yet allows light to penetrate enough for germination.
This protective blanket will withstand wind and light watering, protecting and holding the seed in place. After several days, it will start to dissipate into the soil, having allowed the new seedlings time to establish roots in the soil below.
We further enhanced this blend with a mild water soluble plant food mix that will gently feed the new seedlings to insure they start off healthy. We then finished the formula with a tiny amount of GA3 Gibberellic Acid-3. The purpose of the GA3 is not to stimulate germination as it is known for with many seed varieties, rather we use it to soften the seed coat to allow quicker germination. Many tiny seeds actually have a rather hard seed coat that must be softened before germination can begin. If a seed does not need the GA3 for this, the GA3 does no harm to the seed and naturally dissipates into the soil.
We packaged this product in a 3.5 ounce ( volume ) plastic spice bottle that has a sifter top on it. It contains 2 ounces ( weight ) of VG07 Seedcover. This bottle will hold enough VG07 Seedcover to cover about 50 seed packets, as it takes very little to cover the seeds. It will keep for years if stored in a dry location.
To use the VG07 Seedcover, follow these easy steps:
1. First, use a good seed starting mix that drains well and does not become "packy" when wet, then make sure the soil is wet as possible by throughly soaking the soil before sowing seeds. This is very important as the VG07 Seedcover needs to interact with the moisture in the soil.
2. Sprinkle the tiny ( or pelleted ) seeds onto the surface of the soil, spacing the seeds as you prefer.
3. Remove the top from the VG07 Seedcover bottle, turn the bottle upside down over the seeds and lightly tap the bottom, which will release a cloud of VG07 Seedcover directly onto the seeds. Tap the bottom of the bottle and apply VG07 Seedcover until the surface of the soil is covered ( i.e. you cannot tell the color of the soil through the VG07 Seedcover ).
4. You will notice the VG07 Seedcover immediately interacting with the wet surface of the soil and starting to form a "blanket" over the seeds, enveloping them inside the VG07 Seedcover.
5. Simply mist the top of the VG07 Seedcover daily to maintain moisture in the soil. Once seedlings appear, you can begin to water more heavily.
The VG07 Seedcover will break down into the soil as the seedlings grow.