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Container Gardening: Why not add pine bark to soggy dense seed-starting mix?

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RickCorey_WA

RickCorey_WA
Everett, WA
(Zone 8a)

February 8, 2011
5:42 PM

Post #8361631

Mainly I'm asking if anyone knows a reason why finely shredded pine bark should NOT be used for starting seeds, or winter sowing. I made up 30 pots of WS seeds, THEN someone told me that they never used pine bark with seeds ... but for no stated reason.

??

I was trying to increase air and drainage by adding fine bark chunks (like 1/16" - 1/8", anyway under 1/4".
I could have used less bark if it had been chipped or chunked instead of shredded, but the stuff on display didn't match the contents of the (opaque) bag. It was fibrous instead of chunky or chips. So I used a higher percentage of the fibrous "fine pine mulch" than I had planned.

I started with a conventional seed starting mix from 'what I had on hand' or bought.
- 4 Qts of Jiffy-Mix plus
- 8 Qts of "Orchid Mix, screened to 1/4".
Both of those were very fine, nearly powder.
- 4 Qts coarse perlite and
- 4 Qts coarse vermiculite.

(The last two volumes are very approximate.)

Because I wanted it to drain faster, stay less soggy, and hold some air (and I "just don't like" Perlite), I kept adding screened, shredded pine bark until it seemed "light" enough. The pine bark is now more than half of the mix.
All by itself, it was almost the right consistency. If I had had an 1/8th inch screen, i would have tried to exclude as much "fine bark fiber" as I could.

If I had had time to drive around looking for chick grit, I would have used that - maybe medium grit. Naybe next year I'll use more pelite, but for some reason I just don't like it.

But I was pretty happy with the result as it seemed airy. Any idea whether bark will kill my seeds for me?

Corey
pirl
(Arlene) Southold, NY
(Zone 7a)

February 8, 2011
6:54 PM

Post #8361736

Seems like the ideal question for Tapla. Why not send him a link and invite him to join the thread?
Carolyn22
Athens, PA
(Zone 5b)

February 9, 2011
8:05 AM

Post #8362404

Corey

Wondering why you don't like Perlite - I tend to use quite a bit of it myself.

Sharp sand would add drainage. Not sure about the pine bark. I would be concerned about pine bark adding acidity to the soil, however I don't know that that would happen either.

Let us know what you find out.

RickCorey_WA

RickCorey_WA
Everett, WA
(Zone 8a)

February 9, 2011
10:20 AM

Post #8362682

>> Seems like the ideal question for Tapla. Why not send him a link

I agree, getting his thoughts was why I posted a germination question on the4 Container forum. I'll Dmail the link to him.

The other reason I posted here is that starting seeds in small, shallow pots or even smaller cells is the ultimate "container" problem. A "container" a few inches across and a few inches deep is (I assume) almost all "perched layer".


I'm not sure why I don't like Perlite. No very good reason, I guess.

Each particle is just a big void wasted space, except for water that might cling to the surface - it's not porous to any depth, is it?

It looks artificial and conspicuous, especially when mixed into in my beds, where I think it tends to float to the surface. ("Ugly", but that's subjective.)

They are almost perfect spheres - the 2nd-worst shape for improving aeration & drainage.

Somewhat expensive. Probably energy-intensive to make (compared to sand, anyway!)

Dusty.

Probably most of all: baseless prejudice.

Corey
Carolyn22
Athens, PA
(Zone 5b)

February 9, 2011
10:39 AM

Post #8362711

Hmmmm... do you have any baseless prejudice towards vermiculite? that would work too.

RickCorey_WA

RickCorey_WA
Everett, WA
(Zone 8a)

February 9, 2011
11:14 AM

Post #8362765

Don't know why, but I like vermiculite, except for the price, which is OK for starting seeds, not so much for potting up. This is my second year of mixing fine vermiculite into the top layer of seed-starting cells, and covering seeds witth it.

I bought about 12 quarts of coarse vermiculite this year and have been using it in the sedling mix. It tends to float also, but at least it doesn't look like bright white beads in the garden.

I wish I knew why no one uses fine pine bark (shredded or chunked) for starting seeds: all by itself, it has about the texture I'm looking for. It holds water, but not too much (as peat and vermiculite do). It can be coarse enough to let air in. It's stable enough to hold a plant in place, and not float to the surface and wash around like perlite.

It's cheap! It's certainly renewable, and appears to be a waste product of forestry and lumbering.

I think nurseries use a lot of it when potting up, and that's quite a recomendation.

Corey
pirl
(Arlene) Southold, NY
(Zone 7a)

February 9, 2011
1:59 PM

Post #8363009

Potting up just might be a totally different issue than raising seeds. I hope Tapla posts so we'll get his expert advice. He is one amazing guy.

tapla

tapla
Bay City, MI
(Zone 6a)

February 9, 2011
5:11 PM

Post #8363341

The most important properties for media for starting seeds to have is that it isn't phytotoxic (poison to plants) to the seedlings, followed closely by the idea that it should have ample but not excess moisture, and LOTS of air. Roots grow best and thrive in damp but not wet media, so our job is to provide it. We can do that through VERY careful watering of media that has the POTENTIAL to become waterlogged (fine, peat-based starting mixes, e.g.) or by starting seeds in a coarse mix that has less potential to become waterlogged.

Since either the seed endosperm or the cotyledons themselves serve as organs for energy storage, the seeds will do fine without supplemental nutrition until the first true leaves appear.

Not all pine bark is created (packaged) equal. Bark stored in tall/wide heaps or windrows can become toxic and low in pH if it's not turned regularly. The anaerobic conditions promote the formation of organic acids, nitrates, and other bio-compounds that act like hormones or interfere with hormonal activity. This is one of the reasons that soils that support significant amounts of perched water (anaerobic conditions) can inhibit growth.

You can usually detect any 'issue' by smelling the bark - it will smell 'sour', and it's pH will usually below - under 4.0. Even if the pH of the bark actually WAS as low as 3.5, you could still bring it up with dolomite, but that doesn't mean it will eliminate any toxins. You might need to moisten and compost/turn any problem bark for a few weeks, turning every few days if there is a problem arising from anaerobic conditions during storage. Sorry - no way to tell from here, so if you're using bark, allow yourself enough time to do a little test run.

There are some 'tricks' you can employ to help you maintain that moist but not soggy level, like employing wicks to help drain excess water from your starter containers. Tipping flats at a steep angle after watering can drain almost ALL the excess water from flats. Often, setting cell packs on a towel after watering will 'pull' excess water from containers ...

Basically, if you keep 'damp, not wet' and 'lots of air in the media' in mind whenever you're starting seeds, you can't go too far wrong. Most seeds also like about 70* until they germinate, then they appreciate it if you turn off the bottom heat if you're using it.

Al
pirl
(Arlene) Southold, NY
(Zone 7a)

February 9, 2011
5:23 PM

Post #8363368

Thank you, Al.

Both the wicks and the tipping of large pots, outdoors, worked very well for me last year.

Who said you can't teach an old dog new tricks?

tapla

tapla
Bay City, MI
(Zone 6a)

February 9, 2011
7:38 PM

Post #8363671

Oh - I forgot to mention ... I don't particularly like vermiculite for much of anything. I think it holds too much water and it breaks down in ... oh ... about 10 minutes! ;o)

I should thank YOU guys for the vote of confidence. I really appreciate it. ;o)

Thanks for inviting me over, Cory!



Al

Thumbnail by tapla
Click the image for an enlarged view.

pirl
(Arlene) Southold, NY
(Zone 7a)

February 10, 2011
5:31 AM

Post #8363986

What you may not realize, Al, is that I, for one, copy some parts of your post as they apply to plants in general. I sent the portion about "Roots grow best and thrive in damp but not wet media...", to someone new to clematis. Often people drown them in the hopes of keeping them "wet enough" but they suffocate the roots by doing so and then wonder why the plants don't thrive.

Thanks, again, Al.
pollyk
Hannibal, NY
(Zone 6a)

February 10, 2011
8:24 AM

Post #8364281

Since Tapla has given such great information, I am just going to give my experience.

In my nursery I normally use Metro Mix 510 for potting plants. A couple of times when I have not had seed starter mix and wanted to start seeds that day I have used the Metro Mix and had good results. Metro mix is a bark based mix of about 40% pine bark. I did keep in mind not to over water it due to that.

RickCorey_WA

RickCorey_WA
Everett, WA
(Zone 8a)

February 10, 2011
9:59 AM

Post #8364459

Thanks very much, Al and all.

>> I should thank YOU guys for the vote of confidence. I really appreciate it. ;o)

I appreciate that you always give reasons, not rules. That lets me apply your advice to various circumstances, and gauge relative relevance and criticality. And, what you say alwyas makes sense!

Thanks for mentioning anerobic/anoxic/hypoxic metabolic by-products!
I always thought "drowned roots" died purely becuase of low pO2.

Do you think flushing is likely to remove many toxins? The bark is bound to hold water and hence flush slowly, but at least there are plenty of pores and channels! Hopefully, the WS environnment will provide time and oxygen for aerobic microbes to digest some of the anaerobic waste products, before the seeds actually sprout and are poisoned.

I will try watering in some powdered lime to counteract the pH (can't hurt, right?)


>> The anaerobic conditions promote the formation of organic acids, nitrates, and other bio-compounds that act like hormones or interfere with hormonal activity. This is one of the reasons that soils that support significant amounts of perched water (anaerobic conditions) can inhibit growth.

This bag of bark came from a good nursery, but came from a pallet - tall stack - of 2-cubic-foot heavy plastic bags. I'm sure it wasn't turned, and must have been compressed during storage and shipping. Too bad I didn't sniff it as soon as I opened the bag! I'll look and see if the bag had holes, but even if it did, I should assume the bag had anoxic or hypoxic conditions for days, weeks or months. If I do luck out, it will probably be becuase the bag was near the top of the stack, or it was heaped, packed, shipped and sold rapidly.

- -
>> Roots grow best and thrive in damp but not wet media, so our job is to provide it. We can do that through VERY careful watering of media that has the POTENTIAL to become waterlogged (fine, peat-based starting mixes, e.g.)

I have never mastered the "liught hand" when wtaering - rather the opposite.

>> or by starting seeds in a coarse mix that has less potential to become waterlogged.

That's what I'm trying to accomplish. I haven't found Turface, and it seems VERY coarse. I don't like Perlite, but started adding 10-20% of it anyway. Last year, I added lots of sand, but I think I usded too fine a grade and it did not create much aeration. Also, Tom Clothier doesn't seem to like sand for starting seeds (maybe just because it tends to be dirty and non-sterile?)

If not shredded/chipped bark, maybe chick grit and medium granite grit. (If I find oyster-shell-grit, that would tend to counteract acidity.) So far, every seed-start mix I've bought has seemed 80-90% powdered peat moss, or were pure heavy junk.

>> There are some 'tricks' you can employ to help you maintain that moist but not soggy level, like employing wicks to help drain excess water from your starter containers.

I'm thinking of investing in "capillary watering mats" so i can bottom water very sparingly and still trust that each cell will get SOME water. Then put a big label on my spray bottle "DON'T DROWN THOSE SEEDLINGS!!"

The thought of threading polyester wicks into each of 20-30 3.5" pots is annoying, but so is losing all my seeds.

>> Often, setting cell packs on a towel after watering will 'pull' excess water from containers ...

And I thougt bottom watering was a messy hassle! Oh, well, whatever it takes. Maybe just keeping a watering mat between them and the tray bottoms will pull water from trays with a turkey batser will serve the same purpose.


pirl
(Arlene) Southold, NY
(Zone 7a)

February 10, 2011
10:37 AM

Post #8364510

Why are you using a spray bottle, Rick?

tapla

tapla
Bay City, MI
(Zone 6a)

February 10, 2011
11:53 AM

Post #8364664

Pirl - yes ... that 'over-nurturing' of a new plant, especially by new or inexperienced growers, can sort of end up being like 'killing them with kindness'. Most of you that know me, know I think that how well your soil is aerated when you established a planting, and how long you can depend on that soil to remain well-aerated, are the most important considerations when establishing a conventional container planting.

Thanks, Rick. I try to qualify what I say as I go. There are plenty of 'one size fits all' statements we CAN make, but there are lots more commonly made that need qualification. I find that most arguments arise when one person says something without qualifying the information - someone notices and corrects or qualifies - then we're off to the races because some one's ego got bruised. ;o)

I'll try to follow your post with my comments, so you might need to scroll back & forth to see what part of your post my comments are directed to.

If you're unsure of the pH, don't just guess that it's low. Add your 1 tbsp of lime per gallon, or 1/2 cup/cu ft as a starting point. A pH too low is probably better in containers than one too high. More on that if you need it.

If there are any issues with a bark product, flushing will remove some of the toxins, but composting & turning will do the job faster. Personally, I've never run across a problem with a conifer bark product, but I do know that entities that make their own soils occasionally reject loads of bark for the reasons I mentioned. I just wanted you to be aware of the issue in case you mix up a bark media & find it lacking. The natural tendency would be to blame method rather than the influence of toxins. Like Polly, I've started lots of mainly cuttings in bark-based soils (and the gritty mix) with great results. I'm not big into seeds, but there's not much difference - both cuttings and seeds love a coarse medium with lots & lots of air in it.

If the bark you have is going to have a problem, I would expect it to be wet - maybe turning black where it's wet. Dry (in the bag or when you receive it) bark is very unlikely to present problems. Try not to make too much of an issue that probably isn't there.

Watering technique is a very important part of container culture - much more important when the containers are shallow or the soil is heavy. The margin for error increases dramatically as the soils PWT approaches 0 or is 0. Ideally, you want to be able to water copiously enough that 10-15% of the water you apply exits the drain hole ... every time you water. If you cannot do this w/o risking a negative impact on root function/metabolism, you're leaving potential growth/vitality behind, often a very significant amount. The air:water relationship of soils, including the accumulation of soluble salts is very often, if not usually, more responsible for decline/death of houseplants than lack of light.

Turface isn't coarse enough for seed starting unless you screen it. It holds too much water when unscreened. Perlite the size of BBs (or larger) is a good medium for seeds & cuttings. I don't like sand in soils unless it's at least half the size of a BB - more like fine gravel. Think 'aeration'.

Capillary watering is ok for the short term in the right soils, but promotes a build-up of solubles over the long term. I like to top-water seeds & seedlings to 'moisten' the soil. Then use a wick & tilting the container to drain any excess water (from the PWT).

If you do use a spritzer - try not to wet foliage. Many fungi need a period of wet/moist conditions, or conditions of near 100% humidity for incubation. The period needed varies by fungi - but don't give any of them what they need to get a hold. Spritz soil - not leaves.

Al







Thumbnail by tapla
Click the image for an enlarged view.

RickCorey_WA

RickCorey_WA
Everett, WA
(Zone 8a)

February 10, 2011
11:58 AM

Post #8364680

Pirl,

Partly so that I don't disturb the soil surface. Mostly because I still have trouble curbing my over-watering tendency, yet hate to see the top layer of soil get dry ... which in past years has also made it tough or crusty.

Corey

RickCorey_WA

RickCorey_WA
Everett, WA
(Zone 8a)

February 10, 2011
12:41 PM

Post #8364750

>> If the bark you have is going to have a problem, I would expect it to be wet - maybe turning black where it's wet. Dry (in the bag or when you receive it) bark is very unlikely to present problems.

Great news - it was dry, so I'll only worry about the pH.

>> Capillary watering is ok for the short term in the right soils, but promotes a build-up of solubles over the long term. I like to top-water seeds & seedlings to 'moisten' the soil. Then use a wick & tilting the container to drain any excess water (from the PWT).

That makes sense: flush salts out. Furthermore, if water floods the pores and then drains out, it guarantees 100% exchange of air.

I might use a mat only until 1-2 pairs of true leaves emerge: with water only, no fertilizer. Right now my seeds are in 3.5" square pots, Dixie cups, or "6-pack" cells like 72-per-tray. Sometimes I start them 1-2 per cell in 128-cells-per-tray or 98, or 50.

I don't know about putting little wicks into dozens or hundreds of cells - that seems like a huge amount of effort. I think I'll keep pursuing the Holy Grail of well-draining soil.

>> Turface isn't coarse enough for seed starting unless you screen it. It holds too much water when unscreened. Perlite the size of BBs (or larger) is a good medium for seeds & cuttings. I don't like sand in soils unless it's at least half the size of a BB - more like fine gravel. Think 'aeration'.

I didn't realize Turface was so small! I've seen 1/2" - 1" brisk-colored pellets in outdoor planters. I'll keep looking. There's a nursery wholesaler 30-60 minutes away that I've been wanting to check out.

I guess I should overcome my dislike of Perlite, at least for seedling mix, until I find an alternative.

I agree about the size of sand. I tried "medium coarse" and that is much too fine for pots. It seems barely OK for raised beds, it improves friability and seems to improve drainage. I don't know about aeration.

I finally bought a cubic yard of coarser sand and love that (for raised beds). Maybe I should sift it to find the coarser fractions, wash it, try to sterilize it, and use it with seedling mixes.

Now I'm looking for "grit" ... say 2-3-4 mm grain size. Some call that "fine gravel", but to me, "gravel" is what hurts my feet if I walk on it (1/2" or bigger, and sharp)! There's a feed store near that nursery wholesaler. The Everett Grange Co-op is closer, but has prices and selections that seem aimed at yuppies, not farmers.

Thanks for the thoughtful reply!

Corey





>> 1 tbsp of lime per gallon

I always thought that, no matter how much you added, Dolomite lime would only raise the pH to its own buffering level, pH 7.4? 7.8? But I guess that might be too basic for some seeds. I'll go gently! And maybe finally invest in a pH meter, since I can't find the pH sticks I had many years ago. (I used to grow plants in 4 gallon tubs with soluble fertilizer, mixing 4 gallon batches iof 16X fertilizer, and neturalized the batches using hydrated lime and pH sticks that re4ad down to 0.2 pH units. I always worried that I might be precipitating some nutirents, storing them at 16X strength around pH 6.8

I won't use any hydrated lime on WS seeds!

>> . Ideally, you want to be able to water copiously enough that 10-15% of the water you apply exits the drain hole ... every time you water. If you cannot do this w/o risking a negative impact

YES! I've always thought that, and yet never succeeded in making my pot soil drain that well. If I'm adding salts IN, I want to be able to flush salts OUT.



pollyk
Hannibal, NY
(Zone 6a)

February 10, 2011
2:27 PM

Post #8364930

Great discussion. I've learned a lot also.

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