worm castings

ken1June 27, 2010

Does anybody reading these forums use straight worm castings to grow in? If that's overboard, what ratio of castings to soil do you use? Any good formulas out there?


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nygardener(z6 New York)

It's a great addition to potting soil (for container growing). Add at the start of the season and replenish in midsummer by top-dressing. I toss in some bone meal and a little greensand as well. For a 5-gallon container, I'd mix in about 6 cups of castings, 2 cups of bonemeal, and 1/2 cup of greensand. Top-dress at midseason with 1/3 of that and work as far as possible into the soil (up to 6 inches).

For growing in the ground, use like any rich compost. Mix or till in an inch in spring or fall.

    Bookmark   June 27, 2010 at 11:06AM
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tapla (mid-MI z5b-6a)

I doubt you could get anything to grow in worm, castings because it would compact so severely & likely drown your plants if you attempted to water properly.

If you're talking about growing in containers, I'd leave the castings out entirely. They add nothing that enhances container plantings that can't be had from a variety of fertilizers and/or micronutrient preparations that don't have a negative effect on drainage or aeration.


    Bookmark   June 27, 2010 at 11:08AM
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Straight castings is indeed overboard. Studies I have read recommend no more then 40%. Now for my lettuce grown indoors in pots I use 1 part sphagnum peat moss, 1/2 part vermiculite, 1/2 part Perlite, 1 part aged worm casting. Almost Mel's mix with worm poop instead of compost. It will grow 4-5 weeks with nothing but water then growth slows I then use MG weekly. I also used fish fert. but not to be used in the kitchen.(phew) This soil does hold a lot of water that's why I use it on lettuce. After 6-8 weeks the lettuce is harvested and the mix is composted. I have reused It over, but as Al said it is breaking down by then


    Bookmark   June 27, 2010 at 7:11PM
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Thanks all. I've used castings in the past but in small quantities, now I have a much larger quantity on hand to use.
I do know cantaloupe will grow quite well in straight castings, as I buried rinds and seeds in the beds last year and let the plants grow in the beds. I had melons everywhere. I just didn't really know what was "too much"
I think you have answered my question very well, including Al's comments about too much in container growing.
Thanks again

    Bookmark   June 28, 2010 at 1:23AM
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Worm castings shouldn't be confused with worm compost. Worm castings are just the worm poop and worm compost is the composted materials with worm castings in it. Mix only 20% worm castings in your potting soil mix. Use worm compost as you would regular compost. Worm castings are rich,but the low npk is misleading. The microbes in worm castings(and in compost as well) will slow release the nutrients for the plant to use. Chemical fertilizer has a high npk, but these are available all at the same time. Since plants can only uptake a certain amount, the rest is washed away. That's why chemical fertilizer can burn plants, whereas worm castings or compost does not.

Here is a link that might be useful: Worm Castings or Worm Compost

    Bookmark   January 24, 2011 at 2:27PM
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tapla (mid-MI z5b-6a)

My take: I honestly see no need for either in container culture. They're so fine (particle size) they're an assured impediment to aeration/drainage, and don't supply anything you can't get from either an organic or chemical product from a bottle, neither of which type would have any negative impact on the soil structure or physical properties.

BTW - soluble chemical fertilizers (like MG et al) have lots of different NPK %s and ratios. Some are more concentrated than others, but the dosage of ALL soluble fertilizers is determined by the dilution rate. In fact and in practice, it is much easier to maintain fertility levels in the adequate to luxury range, AND be certain that all the nutrients plants normally take from the soil are present, both at favorable o/a concentrations AND in a favorable ratio to each other, than it is to guess at what you MIGHT be supplying while waiting for what are technically soil amendments to be broken down into elemental forms so plants can access them.

Long live compost, worm castings, worm compost, and other forms or organic soil amendments in the gardens; but if a grower is results oriented and not limited by a certain ideology, it's much easier to ensure a plant's opportunity to grow nearest its genetic potential in containers by using a complete soluble fertilizer that contains all the essential elements in a favorable ratio (to each other).


    Bookmark   January 24, 2011 at 5:59PM
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Why would you want all castings or all leaf mold or all any thing in your garden.
That like growing only one plant of one type of vegetable.
Balance in all thinks.

    Bookmark   January 24, 2011 at 8:06PM
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Will earthworm castings harm phosphurus intolerant plants

    Bookmark   March 19, 2011 at 8:04PM
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feijoas(New Zealand)

I only use whatever vermicast is in my compost, but I was talking to a worm-farmer/seed-grower recently, and his plants apparently thrive in pretty much pure vermicast.
Sounds like major overkill, but works for him!
A bit OT, but could be useful to people: the guy was emphatic that what we over here usually call 'worm wee' is basically compost leachate from too much liquid in the bin and not desirable either in the bin or on the garden.
He considered castings to be really valuable, but any liquid in the bin a sign of less than ideal conditions.

    Bookmark   March 20, 2011 at 1:04AM
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Compost leachate is definitely not desirable, however it's a product of the process if you want to keep your worms happy. The contents of your vermisystem need to be nice and moist for the worms to thrive. The solution is to have a second drainage bin below your main bin, or use something like the Worm Inn, where all leachate naturally runs out of the bottom.

    Bookmark   March 21, 2011 at 10:09PM
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I raise 3 varieties of worms and find that properly managed bins have little leachate. Worms do better in wetter environments than normal (hot) composting but that does not mean swampy.

I have been using quite a bit of vermicompost in this year's planting and have had excellent results. I use about 25% vc.

    Bookmark   March 23, 2011 at 8:39PM
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You can use worm castings or worm compost full strength and it will not harm your plants but it would be quite wasteful for the "black gold" . I use it at a rate of 20% or less and I will also add liquid seaweed plus making worm tea from the vermicompost. Since I have been making my own for a year now I finally have enough to test on all my plants and garden and roses.

    Bookmark   March 25, 2014 at 8:50PM
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