Those dreaded words "damping-off disease" instill fear in the heart of every gardener who starts seeds. It is a fungal disease, and there are several things besides sterility and cleanliness that can help mitigate the problem. Chick (starter) grit is one of them. Chick grit is crushed granite, and available in sizes "starter" and "grower", from somewhat fine to much larger grit. It does a great job of covering the seeds, much better than using the same soil, or soilless mix, used beneath the seeds. It's really cheap ($6-$7 for 50 pounds), and all farm stores carry it. You might also find it in small bags (for caged birds like parakeets) in a pet store... but I looked at PetSmart today when I went to buy cat food, and they didn't have any.
Use the finest grade of chick grit (which might be oyster shell powder instead of granite dust, which I've heard it's not good for chickens) for any really tiny seeds, and a slightly coarser grade for bigger seeds, more like the size of sand grains.
If you are starting medium to large seeds, you could probably use the grade of grit for mature chickens (grower grade, shown above), which is all my feed store had in stock this year. Last year I put the extra (unused) granite dust to my garden as a source of potassium and trace minerals. It’s a great soil conditioner for clay based soils. I need to drive over to the quarry and see if I can get a couple of pounds of somewhat finer rock powder since my feed store was out of starter grit.
edited to add: Phooey, the quarry was closed on Saturday, so you'll just have to take my word on the chick starter grit size...
The amount to use as covering varies; it depends on the seed size, but usually a covering 3 times thicker than the size of the seed. Best to follow the directions on the seed package. The advantage of using grit is that it breathes, and doesn't mat or cake up like other seed coverings (vermiculite, sphagnum, etc.) can.
I use a small, fine strainer to distribute the fine grade of grit over tiny seeds, bumping the strainer against my hand to get just a light dusting. Kinda like dusting powdered sugar on a cupcake. I use a regular strainer for larger size grit over most seeds, mainly so I can control the amount of covering. Once they are large enough to be transplanted to regular pots, I just add the grit by hand.
Fungi (major cause of damping-off) LOVE wet conditions. Using chick grit, and care in watering, is the best prevention for damping-off (if the seeds have been planted in a sterile container and medium). That means it's best not to water from the top! Set your pots or trays in a larger container with some tepid water in it. Leave them just long enough for the top layer of chick grit to get fully moistened. Let the seed pots/trays dry out before watering again, but not so dry as dust (the seedlings wilt)! Wilting is very stressful for seedlings, or any plant for that matter. I water my seed starter mix well and let it drain thoroughly before I put any seeds into it. Then I add my seeds, and cover with fine grit, or sometimes a mix of fine grit and sterile mix, depending on the seed size. All subsequent watering is done from the bottom.
I do mist my seedlings usually twice a day, as my house is always very dry from our winter heating system. I found a nifty 1500mL pressure sprayer with an adjustable brass nozzle at a big box store for under $8. I use bottled water (not tap water which contains chlorine, nor distilled water) for my seedlings and house plants, both for watering and for misting. My inexpensive pressure sprayer doesn't hold pressure for more than a few minutes, but it pumps up quickly and easily and sprays a fine mist.
Soilless seed starter mix usually contains no fertilizer, as the seed itself contains enough nutrition to get the seed started and survive until it gets a first set of true leaves.
After my seedlings get their first set (or sometimes their second set) of true leaves, I transplant them to individual small pots, and again use grit to cover the soil. From that point on, I add about a 1/4 teaspoon or less of a liquid general fertilizer per gallon of water to feed them every time I water. I just mix it up in a large plastic tote, set each tray in the water until thoroughly moistened, and make sure to stir up the water/fertilizer mix well between dunking trays. Throw any water not taken up by the trays out over the garden; don't try to save it.
ps... a couple more tips:
Sow seeds thinly to allow space for air to circulate between the seedlings. Provide constant some slight air movement 24/7 but not directly aimed at the seedlings. If you do everything else right but do not provide plenty of air circulation, you may still get damping-off!
Seedlings will "drown" if they stay in a soggy medium... the roots need oxygen. If you accidentally over-water seedlings (or any plant), just over-water them again (really!) with a mix of water and hydrogen peroxide and let them drain well.
Misting with water mixed with either chamomile tea or clove tea is said to help prevent damping-off. So is a ONE TIME light dusting of powdered cinnamon or powdered charcoal on the soil surface. I haven't tried either...
Use the finest grade of chick grit (which might be oyster shell powder instead of granite dust, which I've heard it's not good for chickens) for any really tiny seeds, and a slightly coarser grade for bigger seeds, more like the size of sand grains.
If you are starting medium to large seeds, you could probably use the grade of grit for mature chickens (grower grade, shown above), which is all my feed store had in stock this year. Last year I put the extra (unused) granite dust to my garden as a source of potassium and trace minerals. It’s a great soil conditioner for clay based soils. I need to drive over to the quarry and see if I can get a couple of pounds of somewhat finer rock powder since my feed store was out of starter grit.
edited to add: Phooey, the quarry was closed on Saturday, so you'll just have to take my word on the chick starter grit size...
The amount to use as covering varies; it depends on the seed size, but usually a covering 3 times thicker than the size of the seed. Best to follow the directions on the seed package. The advantage of using grit is that it breathes, and doesn't mat or cake up like other seed coverings (vermiculite, sphagnum, etc.) can.
I use a small, fine strainer to distribute the fine grade of grit over tiny seeds, bumping the strainer against my hand to get just a light dusting. Kinda like dusting powdered sugar on a cupcake. I use a regular strainer for larger size grit over most seeds, mainly so I can control the amount of covering. Once they are large enough to be transplanted to regular pots, I just add the grit by hand.
Fungi (major cause of damping-off) LOVE wet conditions. Using chick grit, and care in watering, is the best prevention for damping-off (if the seeds have been planted in a sterile container and medium). That means it's best not to water from the top! Set your pots or trays in a larger container with some tepid water in it. Leave them just long enough for the top layer of chick grit to get fully moistened. Let the seed pots/trays dry out before watering again, but not so dry as dust (the seedlings wilt)! Wilting is very stressful for seedlings, or any plant for that matter. I water my seed starter mix well and let it drain thoroughly before I put any seeds into it. Then I add my seeds, and cover with fine grit, or sometimes a mix of fine grit and sterile mix, depending on the seed size. All subsequent watering is done from the bottom.
I do mist my seedlings usually twice a day, as my house is always very dry from our winter heating system. I found a nifty 1500mL pressure sprayer with an adjustable brass nozzle at a big box store for under $8. I use bottled water (not tap water which contains chlorine, nor distilled water) for my seedlings and house plants, both for watering and for misting. My inexpensive pressure sprayer doesn't hold pressure for more than a few minutes, but it pumps up quickly and easily and sprays a fine mist.
Soilless seed starter mix usually contains no fertilizer, as the seed itself contains enough nutrition to get the seed started and survive until it gets a first set of true leaves.
After my seedlings get their first set (or sometimes their second set) of true leaves, I transplant them to individual small pots, and again use grit to cover the soil. From that point on, I add about a 1/4 teaspoon or less of a liquid general fertilizer per gallon of water to feed them every time I water. I just mix it up in a large plastic tote, set each tray in the water until thoroughly moistened, and make sure to stir up the water/fertilizer mix well between dunking trays. Throw any water not taken up by the trays out over the garden; don't try to save it.
ps... a couple more tips:
Sow seeds thinly to allow space for air to circulate between the seedlings. Provide constant some slight air movement 24/7 but not directly aimed at the seedlings. If you do everything else right but do not provide plenty of air circulation, you may still get damping-off!
Seedlings will "drown" if they stay in a soggy medium... the roots need oxygen. If you accidentally over-water seedlings (or any plant), just over-water them again (really!) with a mix of water and hydrogen peroxide and let them drain well.
Misting with water mixed with either chamomile tea or clove tea is said to help prevent damping-off. So is a ONE TIME light dusting of powdered cinnamon or powdered charcoal on the soil surface. I haven't tried either...
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