Worm castings are very fine in texture and clog valuable macropores in container soils. They add nothing that can't be had by using a fertilizer with ALL the minor elements (Foliage-Pro 9-3-6 is a fertilizer I just discovered. It has ALL the minor elements and the secondary macronutrients, Ca & Mg, in a liquid, easy to use blend. It should be a wonderful fertilizer for houseplants.) or a micronutrient supplement like STEM or MicroBlast.

Al

Sherry, I've never used worm castings, but I've read positive results from people who do. homeharvest.com, a place I sometimes shop, sells worm castings....
Here is what they say: castings are not only organic, but do not burn roots like some chemical fertilizers.
They also state, tests have shown castings have 5 times more Nitrogen, 7 times more phosphate, 11 times more Potash and 3 times more Magnesium..
For potted plants/seeds/seed flats, mix 1 part castings to 3 parts mix..
For established potted plants, window boxes and hanging baskets, 1-2" of castings on top of soil..Mix in, with care, so as not to damage shallow roots. Water, repeat every 2 months..sounds easy enough..Since you have access to the castings, you might as well use them.
You can also make a tea, (for plants, lol) from castings..Soak 1 part castings to 3 parts water, let sit 12-24 hours..Stir well and water as usual. Casting tea is excellent for fruiting, flowering or hard to access potted plants..
If you use the castings, will you add additional fertilizers? I'd go to Home Harvest, send an email, asking about the castings..inquire if additional fertilizer is neccesary if you use castings. You don't want to overdo it. Perhaps another organic ferlizer can be used, like Fish Emulsion, but ask first..Good luck, Toni

Not to mention, someday you might find a few of them dried up on your carpet!

Billy Rae

I vermicompost, too, and when it's done I let it get rather dry (slightly moist, actually) and store it in old plastic jugs. Some gets mixed into potting soil (10% max by volume), but I also sprinkle 2 Tablespoons or so over the tops of houseplants this time of year, when they're showing that they want to grow but it's not time for potting up. I use even more in summer, to rejuvenate containers of petunias, etc, when they exhaust themselves with heavy blooms. It's more of a tonic than a fertilizer, I think, but great stuff in moderation. High salt content is the main problem, yet another reason to flush containers at least twice a year.

Here is a link that might be useful: my website

BC, where are your plants? LOL..I went to your site but didn't see your plants...
Bc, so you're saying you use castings on your plants...do you add additional fertilizer? Toni

Toni, thanks for all the great information! That's awesome, with the measurements of castings:soil ratio.
I'm thinking that fertilizing would need to be done at a minimum, if at all, if using castings. I'll look into that, and let you know.

Billy Rae, yeah, I'll definitely look for the little squirmies on the carpet. They won't last long in the plants and flowerpots because there's no dead rotting stuff to feed off.

I'm wondering why the salt content would be so particularly high, Barb. They aren't fed anything with salt...I rinse off anything that might have had a salty sauce etc, before feeding.

Sherry

All animal manures are high in salts compared to soil, which is fine in nature, where the worms (and other manure producers) are spread out rather than living shoulder to shoulder. The concentrated stuff we get from our bins has a lot of sodium in it, but plants and soil know what to do about that if you use amounts that might occur naturally in outdoor sites with lots of earthworms. From university research projects to grade school science fair experiments, research shows that 10-15% vermicompost by volume is the point to hit when using it to amend potting soil.

I do use fertilizer to support plants that are actively growing, which all indoor plants tend to start doing this time of year. I'm confessin': One of the few not-organic products I use is a mix-with-water synthetic fertilizer, (there are several excellent national brands). I use it from late winter to early spring, when the windows stay closed all the time. As soon as open-window days return, I switch to a fish/seaweed fertilizer. I've tried lots of brands, and even the ones that don't smell much are too aromatic to use indoors when the windows are closed, by my standards at least.

Another good use for castings is to rejuvenate used potting soil. In my experience, worm castings won't restore strong enough structure to make old potting soil good enough for indoor plants, but I've never seen a basket of petunias complain about a cocktail of old soil, some new potting soil, and a 10% kicker of vermicompost.

Here is a link that might be useful: my website

I used worm castings a number of yrs. ago (maybe 10), when I first became involved w/ my local plant society. Someone was invited in to give a talk on them & I bought a bag. I used a teaspoon or 2 in a 4" or 5" pot & they seemed to act as tonic, my plants seemed perkier afterwards. At the time I was growing mostly 'Houseplanty" plants, not succulents.

At the time I think I quit fertilizing those same plants, feeling like the castings acted as fertilizer, but only for one season.

I woulds like to read one or more of those studies about 10-15% castings as an objective point. While it may be fine to add 10-15% worm castings to a new and sturdy, well aerated soil, it could just as easily be a death sentence when used to "rejuvenate" a used soil, already in a state of collapse.

There is no denying that fine particulates like castings reduce aeration and increase water retention in soils. My opinion re. castings in container soils is: Use them in new soils if you absolutely feel you have to, but do not use them with other aeration destroying ingredients and limit their presence to less than 10%. There are other chemical and organic micronutrient supplements that deliver the nutrients predictably and more reliably w/o impacting soil structure adversely.

"They also state, tests have shown castings have 5 times more Nitrogen, 7 times more phosphate, 11 times more Potash and 3 times more Magnesium." Than what? Who .... 'they'? Someone selling worm castings?

I can also assure that this mix: "For potted plants/seeds/seed flats, mix 1 part castings to 3 parts mix.." for combining 3 parts out-of-the-bag potting soil with 1 part worm castings is a recipe that sentences plants to a soil that will very quickly compact, and virtually assures a reduction in vitality.

C'mon guys. Look at your plants that are struggling and declining. Look at the soil. Is it light and fluffy, full of air? NO! Of course it isn't. It's probably hard and crusty and holding soo much water that you have to water in sips or risk root rot. Do you REALLY believe that adding more very vine particulates to this soil, even when new, will improve it? It will not - no mater what small level of nutrients it contains.

Worm castings are not a panacea, and there are better ways, both organic and inorganic, of reliably delivering all the minor elements in the right proportions w/o negatively impacting soil structure.

Al

You're right, Al. Vermicompost is gummy stuff, and a 25% portion in a potting soil is well past the point of diminishing returns. But there is another angle to bring in on the fine points, because vermicompost recycles kitchen waste into fertilizer, without leaving your house and sometimes without leaving your kitchen. So, when you look at the circle of life going on in your home, using the vermicompost you make in a bin brings a poetic beauty to things. And the worms are so cool!

Anyway, as you say, it is not a panacea, but it is a fertilizer/tonic/amendment/whatever that helps plants when used appropriately. Outdoor containers that get leached by rain are the best place to use it, but little bites to houseplants are great when their "sap starts rising" in the spring. If they were still in the rain forest, maybe an earthworm or two would have already tunneled through their roots, sliming them with humic acids and other mysterious substances.

Here is a link that might be useful: my website

My point was, and continues to be, that worm castings in any appreciable volume in container soils, and especially in soils for houseplants, are going to have a negative effect on both drainage and aeration, and that there are other, better alternatives for supplying the minor elements.

I would also point to the fact that containers are much different than gardens, and we are not talking about plants in rain forests. Additionally, we are not trying to establish an intricate relationship between soil flora/fauna and plants in containers. If so, if we were, to what effect - a rapid collapse in soil structure as a result of the increased microorganism activity? That is extremely counterproductive and we cannot afford to allow it.

I believe wholeheartedly in the philosophy of 'feeding the soil' in my gardens and beds, and I rarely add anything other than organic matter, but in container culture it serves the grower well to very carefully guard soil aeration and drainage by judiciously selecting the ingredients used to amend soils. This is ESPECIALLY so in houseplant soils because so many tend to keep plants in the same soil/container far longer than appropriate.

We can easily control and adjust water, light, temperature, and nutrition, but there is virtually nothing we can do about aeration . . . to 'uncollapse' a soil or repair a soil with clogged macropores; and worm castings do unnecessarily clog macropores.

I'm pretty certain we can still enhance the circle of life and enjoy the poetic beauty of that circle by withholding castings from our containers and using them in our gardens, so while that argument is compelling from an eco-perspective, it loses traction because it isn't convincing enough to make me wish to rush to add something to the soil that will rob it of air while only adding something we can provide more efficiently from either organic or chemical sources.

Al

After reading the commentary on this worm castings topic and other conversations about potting soil in general, I find myself befuddled. I should also mention that I'm not a scientist, this isn't my only hobby, and I have spent days and hours researching the topic just to find that opinions are all over the spectrum. If I only have a few indoor plants (think dracaena) that are supposed to do well in low light, my storage space is limited and I would like to be able to create a reasonably healthy potting medium to make my plants "reasonably" happy, are there some general and simple rules I can utilize to meet this goal? Aeration is obviously important and I find all commercial potting mixes too "soggy and mushy". I really need to be able to do this with products readily available where I don't have to buy large quantities of materials or physically search extensively to buy something to mix in my soil. I've read about worm castings, coir, perlite, vermiculite, sand, aquarium rocks, pumice rocks etc. Starting with a good organic potting soil what should I use in what increments as a start (⅓ potting soil and then what else)? I know there isn't one answer. Different plants have different needs. I have some generic houseplants that are hating ANY expensive commercial potting soil I buy. As someone starting out trying to make a few plants happier, where do I begin? I have the fertilization, water and light down. I do agree aeration is an issue. I hate the soil (it's stays too wet for too long) and I don't think the plants like it too much either. I do use clay and ceramic pots.

Obviously, we don't need worm castings from the POV of soil structure, because they are very fine and reduce aeration/drainage. Micro-organisms in container media aren't necessary for healthy plants, and their populations are notably influenced by other cultural factors to the point where they are often boom or bust. So, lets look at them from a nutritional POV, and leave lots of room for any discussions that might not agree with what I say.

I think it would be a good idea to first define what our goal is when we provide supplemental nutrition to our plants. I've thought about that, and this is what I came up with and saved for use in conversations like this:

Whenever we discuss what is or isn't an appropriate part of the methodology we use to make certain our containerized plants get all the nutrients essential to growth and good health, we would probably first want to be sure our objectives are on target. It's difficult to argue with the idea that our focus in supplying supplemental nutrition to our plants should be on ensuring all the nutrients plants normally assimilate from the soil are A) IN the soil and available for uptake at all times, B) in the soil in a favorable ratio - that is to say in a ratio that mimics the ratio at which the plant actually uses the nutrient, C) at a concentration high enough to ensure no nutritional deficiencies, yet still low enough to ensure the plant's ability to take up water, and the nutrients dissolved in that water won't be impeded (by a high concentration of solubles in the soil solution).

At this point, you (used collectively) can accept these premises as worthy goals or argue against them. If accepted, we should then necessarily examine our efforts at supplementation in the light of whether or not our efforts bring us closer to or limit our ability to see the goals implemented. YMMV, but I'd be interested in how to improve on what I said.

What's in worm castings? What nutrients? The fact is, we don't know. We have no idea what they supply, or how much of any particular nutrient they supply. Their contribution to any increases in soil biota populations would only serve to break down the soil faster than it would normally break down w/o them. How then, do we know if we are limiting our ability to reach our goal. We need control over what we supply, and plants are best served when the ratio of nutrients in the soil are matched as closely as possible to the ratio at which plants actually use those nutrients. IOW, WCs don't supply anything you can't get from a well-made fertilizer that provides all the essential nutrients in a favorable ratio. The fact is, in light of the goal, they have as much or more potential to be limiting than beneficial.

Changing topics ....... I think if you rearrange your thinking about your starting point for building a better soil so it's more like: Start with a ______ (fill in the blank with a coarse material or materials that ensure you can actually amend what you start with). If you start with potting soil, how can you amend it? You'll need to add well over 50% of other coarse materials (like pine bark) to get it to a point where you can water correctly. If you have more than 50% bark, didn't you actually 'start' with bark; or, maybe the better question is, wouldn't it then be a bark-based soil instead of a soil based on whatever potting mix you're using as the filler?

I suggested a goal for nutritional supplementation, so how about a goal for the quality of your soil? From my perspective, an appropriate medium is a medium that allows us to water to beyond the point of saturation, at will, so we're flushing the dissolved solids (salts) that are present in tapwater and fertilizer solutions; this, w/o the plant having to pay the penalty of reduced root function, or perhaps wrecked root health, due to those prolonged periods of soil saturation after watering correctly. All the dissolved solids in tapwater and fertilizer solutions are left behind and accumulate in soils whenever we're forced to water in sips, which is commonly employed as a strategy to help avoid the sogginess that limits root function and wrecks root health. It's important to realize that a healthy plant is not possible w/o a healthy root system. If you have established goals that include healthy and attractive plants, it's critical that you have a plan to avoid the limitations imposed by over-watering and an accumulation of dissolved solids (salts) in the soil solution.

Not every grower fully understands the dilemmic issues associated with
inappropriate soils that force the plant to pay a vitality tax resultant of an unhealthy amount of water being retained for extended periods when we water correctly – which is to say, when we flush the soil to limit salt build-up. On one hand, we have the potential for over-watering, and when we act to avoid it by offering dribs and drabs of water here and there, we have high salt levels to deal with. It's easy to see how we all might benefit from use of a soil that allows us to water so we're flushing away excess salts without limiting our plant's vitality via waterlogged soils.

You can see that getting to the point where you can water correctly w/o problems is a worthy goal. I should also say, there are ways to get you to that point w/o a lot of difficulty, just by employing some simple methods/arrangements that force excess water from the soil.

Al