Homegrown seed starting mix?

[Gato Moteado]

Hey All

I am planning on starting heirlooms from seed in the next week or so.

Down here in Costa Rica, it's hard to find premade potting mix for seeds, and if you do find it, it's expensive. I'd like to make my own. I have access to limitless supplies of pulverized coconut fiber, rice hulls (which seem to be really useful when burned), and lombri-compost (worm compost). I can also find vermiculite. Are these materials suitable to mix a great seed starting mix, and if so, what ratio would be best? Are there other materials I can find down here in the third world that would be better?

Thanks,
mike

[RebelRidin]

Mike...

As far as starting seeds to get a couple leaves for potting up... almost anything can do. Some people use straight peat all the time.

It's the grow out that matters. I have used reclaimed flower mix from old pots that I sterilized in the oven and then rejuvinated with some house plant food. Your worm compost soumds promising. It should contain the magic the otherwise and relatively barren materials you mention may lack. If I had to take a stab....

3 parts coconut fibers (chopped up)
1 part rice hulls
1/2 part worm compost
1/4 part vermiculite.

The charring or the rice hulls you mention may well make some carbon more available. Once it's all mixed you should be able to pour/shake it from a container. If you can then you probably have the coconut fiber chopped fine enough. Be sure to premoisten it before putting into your containers.

I wouldn't wait around till you need it though. Try it with some "seed o plenty" right away so you will know what you've got.

Keep us posted... and best of luck!

[Gato Moteado]

Originally Posted by RebelRidin

Mike...

As far as starting seeds to get a couple leaves for potting up... almost anything can do. Some people use straight peat all the time.
...
Keep us posted... and best of luck!

Thanks, Rebel! That sounds like an easy mix to make. I'll definitely char the rice hulls first.

[dice]

The coconut fiber needs to be thoroughly washed to remove salts. I got
some commercial coir and it was fine, no apparent saltiness and pH
6.5-6.7. I sprouted the seeds in pure coir, then potted up into 3" pots
with 5 parts coir, 2 parts worm castings, and 1 part perlite after they had
a set of true leaves (so about 1/4 worm castings).

You could probably substitute rice hulls for the perlite and have basically
the same mix.

If you can spread the coconut fiber out on a screen or in a wide, shallow
container with drainage and let a few weeks of tropical rainfall wash
through it, that would probably wash out most of any salt in it. You could
also put it in a mesh bag of some kind and submerge it in one of your
freshwater streams for a couple of weeks before using it.

[Gato Moteado]

Originally Posted by dice

The coconut fiber needs to be thoroughly washed to remove salts.

Is that only a problem with coconuts grown right on the coast or even coconuts grown well inland from the ocean?

[dice]

Is that only a problem with coconuts grown right on the coast or even coconuts grown well inland from the ocean?

When someone gets it in bulk, they probably do not know where the
coconuts came from exactly, and saltiness in packaged coir has been
reported by some growers. Who knows how it got there. Reputable
packagers wash it themselves and actually test it before packaging it
for the growing media supply chain, but you do not really know if you
are buying a product from that kind of company until after you get it.

Rice hulls break down slow, like coir and peat. I would not expect them
to affect pH or nutrient balance in a potting mix that you are going to
grow seedlings in to plant in the ground that same year. They just add
drainage and air space that will not decay to silt in a season.

[laspasturas]

We use a mix of coir, worm castings and vermiculite in a 3:2:1 ratio. I've heard of others having the salt issue, but I've used three or four different brands without any problems.

I've also used a straight mix of 1:1 coir and castings, which I really liked and hope to go back to when we have enough worms to produce that much compost.

[dice]

I started out using 1/6th worm castings in seedling mix, but I potted up
a few of the seedlings in 1/4 castings, and those seedlings were more
robust, faster growing plants.

I always run out of worm castings before I run out of coir and perlite
or other potting mix in the spring, so I usually end up potting up a few
seedlings at the end with a pinch of slow-release organic fertilizer in
a 3" pot instead of the worm castings. The plants still grow, they are
simply "not as perfect" to my eye as the plants grown with worm castings.

[dice]

Some research on use of rice hulls in greenhouse media (growing marigold
and salvia seedlings; 10-20% aged hulls worked best):
http://hortsci.ashspublications.org/...736.3.abstract

[Cole_Robbie]

I can get rice hulls cheaper than any other media and I was thinking about using a lot of them to blend into the pro mix I buy, but I'm growing container tomato and cuke plants and I don't want to give myself ph problems. That article said 10-20% was optimum in their experiment. I guess I will just use about that much???

[dice]

I went up to 1/2 worm castings, 1/2 coir+perlite last year,
and it seemed like it lost too much air space. It was like
mixing 1/2 seed-starting mix with 1/2 fine-textured dirt
that becomes mud when wet.

Worm castings as a fertilizer have great balance, but large
pore air space in the seed-starting mix is still important to
rooting seedlings.

[dice]

Rice hulls will eventually change ph in the media. Whether it will do it
fast enough to effect seedlings I do not know. (I doubt it, given how
slowly rice hulls decay.)

[Cole_Robbie]

What about container plants grown to completion? They would be in the rice hull media for 2-3 months.

[PaulF]

Costa Rica may be a different place altogether, but for me seed starting and potting up medium is cheaper and easier than homemade. Besides that, it is more uniform and does a very good job. It is fun to play around with what you can find and make you own, though.

I have gotten to the point where I do not want to spend the time and money on media I am not sure of. If you like making your own, have fun with it. That is my take on soilless mix.