Starting mediums for seeds

General Discussions
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Aeration, good point. Let’s see . . .

You mentioned leaf mold before. That’s partially decomposed fall leaves, right? Is that what it’s useful for, soil aeration? I was thinking it was just for nutrients. If it does two things at once, neat!

I’m sure I had some in my garden soil, since I buried all my autumn leaves in there last year, and quite a few grass clippings too, so hopefully that will be enough.

Water crystals are a permanent soil amendment that holds water, much like biochar does. When there’s too much water, they get large. When there’s too little water, they shrink down and let water gradually permeate into the soil. Miracle Grow sells them for keeping potted plants from being over or underwatered. I’ve started adding them to my garden beds, and I see the same benefits outdoors.

I imagine biochar is better because it’s all natural, but water crystals are nontoxic, and I’ve seen nothing but benefits with them, and I have access to free water crystals in the form of diaper fluff that I compost. I like using free resources I have on hand.

Oh, hey, it looks like coco coir is considered good for aeration! Great! Okay, so mixing it in with the soil was a good idea. Yay!

Question about the worms. Would it be a good idea for me to bury kitchen scraps in there, in order to feed them? (Or to provide more soil aeration?) Or will they be okay with whatever’s in there currently?

You mentioned before not adding water until it’s dry about an inch down. Is that also true when there are earthworms?

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If you’re talking about actual earthworms, yes. They will naturally migrate down to the level they find comfortable. Composting worms, such as red wiggles, I believe will do the same to an extent, but they prefer to be close to the surface. Earthworms can be as much as 30 feet down depending on the conditions.

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My ideal compost for starting seeds would be well rotted woodchip compost (composted for at least 18 months), mixed with some vermicasts and some well rotted local leaf litter if available.

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I have a wood stove and only use very well-seasoned firewood. So as not to bring in bugs I usually debark the wood before bringing it inside. I do that over a wheel cart and collect the dusty, rotted, bug poo, dead bugs that die from the cold after being rudely interrupted from their slumber, and other debris that falls out. It’s great stuff and apparently highly nutritious from a plant’s point of view. There isn’t enough of it to use by itself but generally I toss it in the mix as well.

The bugs are doomed anyway, it’s that or being incinerated in the stove, or squashed if they wake up and go marching across the floor.

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Switching to native soil is probably a good idea - but if you use potting soil, covering it with a thin layer of vermiculite keeps down the fungus gnats and stops damping off.

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I’ve been using native soil mixed in with the water crystals and coco coir, and I no longer see mold forming on top, so yay! That mold has not been welcome. I hope that means my plants will do well when they sprout. I’ve put some spare squash and bean seeds in with the banana seeds, on the theory that their health will tell me if the soil is working. So far, the squashes are thriving! I’ll likely pull them out when the bananas start sprouting.

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I use compost and worm castings or purchased compost and worm castings with my own castings added to it for seedlings – depends on how much effort I’m up for. Totally not sterilized! Damping off disappeared as soon as I started adding live compost/worm castings. It all works great. I also make sure my starts dry out a bunch – mostly from neglect on my part – ha! But I’ve noticed that if I’m on top of things and watering them like I’m “supposed” to, they do worse. Since they’re going out into an arid environment, I’ve decided to only water them enough to keep them from dying – it’s working.

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That sounds like a good idea. If it works better, and especially if they’re going into an arid environment (which is definitely true for me too – laugh), only watering if it seems absolutely necessary to keep them from dying sounds like a very good idea.

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Bumping this topic back up again as indoor/container soil continues to be one of my main expenses AND I feel weird about the ecological impacts of most commercial options

My go-to mix currently is a homebrew blend of coco coir and purchased compost (vermicompost or hot-composted manure+woodchips) with vermiculite. It works well but it’s pricey, and coconut coir is
highly questionable as a sustainable soil substrate in Canada.

When I tried using home compost in my seed starting mix I got an influx of large creepy crawlies and flying insects I dont really want to deal with indoors. I can only imagine leaf mold and soil would hold even more. Some fungi and bacteria, volunteer seeds, a few worms are more than welcome in my seed starting mix. Fungus gnats and aphids I accept as an inevitable annoyance - nothing soapy water spray, a few trips outside on warm days and in extreme cases neem oil cant fix. However, woodlice, centipedes, ants, wasps etc are a bit much for indoors.

If I had a greenhouse, I’d probably just use native soil, compost and leaf mold as all or most of my mix. Alas, I do not have space for a greenhouse. I start my seedlings on a shelving unit under lights…currently in my dining room.

Does somebody have intelligent way of treating leaf mold and local soil/compost to kill or scare off the big bugs without killing all traces of life and making a mess of my kitchen in the process?

Alternatively, my husband is a woodworker and my dog is a malamute mix. I have a steady supply of wood shavings and downy dog fluff. Currently I dump wood shavings and dog fluff on top of beds as mulch, but I keep thinking there must be a way to mix them with something high nitrogen (coffee grounds?urine?) to make some hot compost with low-to-no surprise wildlife residents.

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Sorry Lee no answers to that.
I use sand to economize my starter soil, which is just a mix of commercially acquired universal garden soil suited for biological gardening. I use that from the same shop for a while and i’m hesitant to change, the results are to my liking. I mix it in with a third builders sand and plant out in balcony trays. I found germination rates higher that way for small seeds. And the higher than usual sand concentration makes water go down where my roots go. I like them to go down and be long to replant deep. They’re a bit bigger for replanting that way, so less snail kill and deeper roots provides for better resistance against drought.

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Personnally I am still stuck with organic garden soil I buy in a farming cooperative + N and P organic inputs (which helps with vegetation, so to say without K elements which promote flowering that I don’t want until my plants are in the soil, otherwise they exhaust themselves early in the season…), and so using 4x4cm soil blockers, then transplant into 8x8cm plastic things, eventually in the soil. This for all solanaceae, and big transplants like that (ball head cabbages and so on).

That costs some money (lot of money…) + takes a lot of time., early in the seaon. My transplants are now nearly perfect, but every year I have problems with mice or snails on my hotbeds… who storm the greenhouse in a ay or another… For example this year, I thought I would lose one third of my eggplants and peppers after mice took these to create a nest… When I saw it I went into rescue mode for about 150 plants… without roots! Eventually it worked: all are fine now -i.e.e with roots!- but it has been awful seeing that… Worse: I lost 90% of nearly à 1000 tomato transplants, using many material sent from everywhere, with a huge work preparing it, with plans as you can imagine (about 150 references…): finished sowing at 2am in the morning, put them on my hotbeds, covered them nicely, went on a tour with a friend… came back 3 or 4 days later, nearly 100% had sprouted but 90% of them had been eaten by mice… So I have resown what I could in soil blockers since 2 times using what was left + buying new stuff to replace… in the process, I lost some material from breeders… feeling awful. That was a bit more than 1 month ago.

Anyway, it is not to ramble: it is why I want to convert most or all of these to direct seeding. So I don’t think I will spend too much effort trying to convert this system into home made starting medium, so to say I will spend much efforts into converting plants into direct seeding, notably 95-99% of cucurbits this year on a 600 square meter patch, but also selective trials of some solanaceae with @JesseI’s seeds + mine.

On the other side I will follow this topic because I believe I will always (??) have to sow early a few things like luffas, probably some peppers… A friend of mine made some trials with home made compost from a wood pile last year. I will ask him for infos.

PS: starting in soil blockers using these inputs sounds 100% contradictory with our trajectory of local adaptation, everything endophytes related: so you create artificial nutrition, then transplant into a normal soil with no inputs. So to say you don’t rely on endophytic mediation first, and then 100%. It is contradictory. At first stages of breeding, and as long as the main thing you want is CROSSES, to get back vigor, why not then, but later you should go towards direct seeding, Or should I say “I”? That is what I am intending to do with mosts, as my diverse populations are from 1 to 3 years old, time to go so soil without any prior artificial nutrition…

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I think we should move to seeding by hand but always be careful to keep extras cause it’s all but sure it works as we like! I’m moving to chaos gardening. It’s complicated to achieve now, but i’m confident i’ll get there in time.
Yes i’m confused by people’s super duper starting mixes. I reuse a lot of my sandy soil mixes. But yeah maybe we should try more with local soil, but then there’s weeds.

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Suggestion for reducing weeds in native soil-- use forest soil, ideally an oak-like forest and not conifer (plants seem happier). Then you get all the fungal gifts but not the weeds.

I suggest it holds less because it’s more carbon based/not high in nitrogen. Especially if it’s finely sifted. I know I keep saying this, and I probably will always-- but high N is what attracts all those little beasties!

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I too have had experience with more insect life in my indoor utility room than I was expecting. Thankfully it came into balance with minimal intervention by me but I might have appreciated fewer insects.

I have found myself still thinking it would be pretty handy if I had a solar oven that could handle about a cubic foot of soil. I could heat it up to 180-200 degrees fahrenheit, and then re-inoculate with some compost tea, etc. to start to restore at least a bit of microbial life.

I wouldn’t necessarily bake all soil that I use for starting, but I think it would be great to have the option without too much hassle.

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I’m going to push back gently against the concept that collectively we “should” want to move away from starting seeds indoors, or for that matter even aim for a zero input system. Those may be goals for many here and they’re absolutely valid, but ultimately the beauty of adaptation gardening is that each gardener can work on adapting plants to their own situation and preferences. A landrace of tomatoes that yields from direct seeding in short seasons is a valid pursuit, but so is a landrace of winter tomatoes grown fully indoors in an aquaponic system, or started indoors but selected to hit the ground running and start yielding tomatoes 2 weeks after transplant for the earliest fresh tomatoes.

I would like to use more local, affordable and less packaged materials in my indoor mixes, but I have no interest in moving away from starting plants indoors.

My personal preference is for starting indoors in almost all circumstances and I’m not really trying to get away from external inputs either. Im not trying to change that, or apologize for it. I have a bunch of reasons for this preference. Here’s a non-exhaustive list:

  1. One of my goals is to spread out my harvest season While I live somewhere I could feasibly grow many things to maturity from direct seeding with some moderate-strong selection pressure, in the best case I would only get mature tomatoes, peppers, eggplant etc in a short harvest window for a few weeks before freezing temps killed them off. By starting indoors quite early, and hardening off in a protected climate before the technical last frost date, I am able to get my first fresh outdoor garden tomatoes in June most years, when volunteer tomatoes only have a couple of leaves, a full 2 months before I could reasonably hope for any direct seeded tomatoes to be producing. Fresh tomatoes in June are such a treat.

  2. I (personally, this is a me thing) have literally orders of magnitude better success with starting seeds indoors- even with seeds usually recommended to direct seed. My ADHD makes me immediately forget where I planted things so I forget to water, or overseed with something else, or mistake my own seedlings for weeds and weed them out. Some chaos gardening is refreshing but me direct seeding is a disaster. At home under bright lights on a heatmat with humidity domes, I get nearly 100% germination and nice strong seedlings across the board. They’re all neatly lined up like with like in trays in a big cabinets brightly lit up to remind me to check on my plants. Then I can get my chaos fix mixing them up as I wish in my garden beds in between volunteers and overwintered stuff and flower seeds sprinkled willy nilly to get my chaos fix

  3. Living somewhere with a longish darkish winter, I love having plants growing at home. My “houseplants” are mostly warmer climate food plants and my seedlings. They cheer me up in winter.

  4. Living in an urban environment, space is a sharply limited resource. I want to make the most of my space Starting in trays unlocks timestacking - I get the next crop started while a bed is still occupied, and transplant plants with several weeks of growth. Other inputs are not very limited for me at all - grass clippings, wood shavings, forestry woodchips, coffeeshop coffee grounds, autumn leaves and municipal are locally available to me free of charge. While urban, Im near prime agricultural land and can also easily get composted manure and organic hay at a very low price. These inputs help me maximize production and minimize watering/weeding while keeping my gardens looking relatively neat and presentable (important as my gardens are all either very visible from the street at my own house, or on borrowed land I commit to improving)

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3 posts were split to a new topic: How to deal with gardening despite ADHD (and also ADHD is an asset)

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Appreciating this thread, I did split it for additional discussion on that topic :slight_smile:

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This post in this thread has a great idea for a pot growing medium: pure compost that was made by your municipal locally. It should be sustainable, and it will probably be very cheap. Do you think that would work for your seed-starting needs?

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I appreciate the points Lee is making; transplants can make better use of space (in small gardens) time (in short growing seasons, not necessarily in gardening hours) and water (in dry climates, trying to keep an outdoor bed moist enough for germination is a real pain.)

If I had a big garden, I think I would go over to all direct seeding. But for my small home garden, transplants are very useful.

Currently, I’m purchasing inputs to blend my own mixes: peat, compost, sand, and perlite. I want to get away from this. So I am going to try a “hybrid” approach: a seed bed. Basically, a raised bed (on my patio) with a few inches of enriched soil in it, and the ability to use a plastic cover and heating wire/mat to keep it warm. When the plants are ready to be moved out, the soil would be cut up like “brownies”. (Eliot Coleman used this method for some of his plants before he started doing soil bricks. I’ve been doing soil bricks, but they seem to depend on purchased inputs to get the mix just right, and they are fragile; if they get rained on, they can dissolve into sludge and destroy the plants.)

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I make my own potting medium. I wouldn’t want to call it soil, which is specifically the soil that is underneath my feet. Potting mediums consist of other things. My mix sometimes contain soil or other things in contact with soil (leaf mould).

My standard mix is 70% coco coir, 20% compost and 10% perlite. For plants that need better drainage, I add more perlite. The compost is not entirely organic and also contains some sand, so generally my mix drains pretty well.

My observation with damping off and similar problems of starting seed in trays is that people who have these problems also have very compact potting mediums. They don’t drain well. I see many gardeners who use 100% compost. Not only is that a lot of nutrients, but those mediums tend to not drain so well. Compost is also very varied. There’s not consensus on what compost even is …

In practice I vary my mixes depending on what’s available. I re-use potting medium a lot. I don’t mind taking material that’s been sitting outside for months or years and blend it in.

I start seeds on the assumption that they actually need very little nutrients to begin. Those nutrients are contained in the seed itself. I mostly just want the seed to get started and then either plant it out or pot it up in a larger container, that does contain some more nutrients. By then, the plant is healthy enough that it won’t have problems with damping off.

My mixes always contain these elements:

  • 50-75% solids (to hold on to water and nutrients)
  • 25-50% bulking agent (which adds porosity, e.g. sand, perlite, bark)
  • Possibly some nutrients. I use granulated Vicia faba, which is easy to sprinkle over pots, and I buy from a local producer.