I'm not sure how coarse desert sand is, my climate is about as opposite from desert as one could be. The chick grit is more coarse than most sand and applied sparingly it will allow some light to the seeds. You don't want lobelia cardinalis deprived of light, they should be on the surface or only very barely covered. Sowing very fine seed like lobelia, I'll top the pot lightly with grit or aquarium gravel then add the seed, giving the top a spray of water so the seed finds its way down and makes soil contact.

I wonder why the problem, mine always self sowed - although I have none here at this house. Do you have enough seed to try some with your horticultural sand and do a couple of pots later with grit? I've used the parakeet gravel available (small boxes) in the pet aisle of the grocery store when I haven't made a stop at a feed store for chick grit.

Thank You Morz8 for getting back to me:
I got an estimate of 3,000 seeds w/out counting what the package says. I don't know why I have not been able to get them to germinate, I tried from all seed companies and used various containers via WSing. What I thought sprouted turned out to be Lobelia spicata 'blue'. The nursery only had desert sand. I should of shopped earlier waited until Christmas when they put all the plant stuff away. The local agricultural store went out of business so we are directed to go to the local horse shop. They had bird grit for 9.99.

So let me get this correct the topmost layer will be of bird grit substrate or sand substrate, then the potting soil substrate next. Do you mix the seeds with the top substrate or just sprinkle on top of substrate?

I don't mix the seeds. I prepare the pot with the potting soil/medium and wet it down. Larger seeds I will sow next then cover with the grit or fine aquarium gravel.

If the seeds are very very fine, I prepare the pot with the soil, water it, add the grit as a final topping, then sprinkle the fine seed, washing it down with another (soft) spray of water so it slips into the crevices created by the grit and makes soil contact.

That's why I was wondering about the coarseness of your sand. If not too 'gritty', you may want to use it on top the seeds in a very light layer and not adding any depth with it. The lobelia will want some light. They don't have to be totally bare exposed, but you don't want them covered to any depth at all.

That's a shame your horse shop doesn't sell chick grit by the pound, a pound or two goes a long way and I don't pay anywhere close to $10. Pet supplies will often sell fine aquarium gravel by the pound if they sell tank fish, works much the same.

Thank You Morz8. I will let you know how I worked with it. I am very determined to get the Lobelia Cardinalis to germ.

Sincerely,
Avis M.