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Seed-starting supplies

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I've been at this seed-starting thing for a good many years now, and am always on the lookout for materials and gadgets that make things just a littler better, easier, or more efficient. On this page, I list a few of the things I've tried, along with the sources for some of my supplies.

Germination supplies

Since I germinate most of my seeds in baggies, that's where I'll start. For me, the 3" tall by 2" wide ziplock baggies work best. That way, my folded filter paper fits right in. You can buy these baggies for about a buck per hundred at Walmart, for the kind which are just plain clear plastic. Those work fine, but they require a sharpie marker for writing species name, dates of stratification, etc on the baggy, and the writing rubs off easily. Not a big problem, but I somewhat prefer baggies with white writing strips, which can be marked with a regular ballpoint pen. These aren't quite as easy to find (i.e., Walmart doesn't reliably stock them), but you can find them readily from many mail-order sources. I got a shipment of 1000 of them from Papermart, for less than a penny per baggy, so I won't be needing any more anytime soon.

Then there's the filters. I'm not picky - I get the cheapest pleated round coffee filters I can get. A large bag of them lasts forever. I only use one half of a filter per seed variety.

Gibberellic acid GA-3. This plant growth regulation hormone has been researched quite a bit, and can increase germination success in certain hard-to-germinate species. I purchased a small supply of the stuff from JL Hudson once and dabbled with it, but not enough to have definitive results. Still, JLH is a reasonable source if you'd like to try yourself.

Gel starter kits. There are a few outfits on the market that sell kits where you germinate your seeds suspended in a gelatinous clear liquid. I tried them a few times, and found that easy-to-germinate seeds did just fine in the gel, whereas more difficult ones rotted before they had a chance to germinate. I gave up on this approach, since it was more time-consuming, took more space, and didn't have any clear benefits. But it was cool to see the little guys growing in the clear gel.

Soils and such

For starting seeds directly into pots, and for potting the newly germinated seedlings from baggies, I use only potting mixture specifically labeled for seed-starting or similar duty. I tried some of the expensive small bags from Scott's, Jiffy, and such. I also tried mixing my own from milled peat moss, perlite, and vermiculite. But for my money, by far the best solution has been PRO-MIX PGX, a product based on finely milled peat moss and vermiculite. I have very few mold problems with this mix (although algae will grow on top if it's left moist for too many days at a stretch), and it's real easy to work with. The only problem is - I've found no local retail source for this. Worse yet, my erstwhile mail-order source, Mellingers, has gone out of business. So I finally broke down, and armed with my brand new nursery license (Pennsylvania made me get one when they learned about my annual plant sale) I opened an account with a distributor of Pro-Mix products. The rub: the minimum order was $300, so I had a rather larger stash of the stuff than I really needed. Luckily, I found several like-minded gardeners over the next six months, and was able to share the wealth. I'm down to my last bale now, so I may do the same thing this fall. If I do, I will once again be happy to part with a bale or two at close to my cost. In which case I'll post an update here.

For potting established seedlings into larger containers, I use a cheaper potting soil. Those seedlings are sturdy enough to handle a few mold spores, but I still shy away from real cheap potting soil. I often use PRO-MIX BX, which, unlike the PGX, I can sometimes find locally. Since it comes in a big bag, it's relatively economical. If I can't find the PRO-MIX I'll settle for one of the other name brands offered at my local DIY store. Those are usually pricier, and come with fertilizer mixed in, which is fine for seedlings at that stage.

Procedures for seeds started in pots often call for grit - a granular material offering good drainage, used as a top-dressing. Although I've not had much use for it so far, I did track down local sources for grit, and secured some for myself. The easiest is to go to your local supermarket's pet aisle, and buy some in the bird section. It's not the cheapest that way, but if you use only a little, what the heck. I needed more (as a soil amendment for a rock garden I was putting together), and pulled my hair out trying to find a good source until I finally found an agricultural feed store in a rural part of my area. Around here, these places don't advertise in any channels non-agricultural folks are likely to read, so I just happened upon it. You may have to ask around to find the equivalent place around your area.

Amendments - I hardly ever mix anything else into my soil. At one time, I had fairly good success mixing in some drywall spackle dust into a mix I used for growing on dianthus seedlings (since they like slightly more alkaline conditions), but I don't know if my amendment had anything to do with it. Forget I even mentioned it...

Pots and pans

And where shall we house these green things while they're waiting for garden placement?

Nearly all of my baggy-started seedlings first meet soil in the cell of a small six-cell-pack. Twelve of these packs fit into a standard 11x22 flat. I reuse these packs extensively, but when I need new ones, they're easy to find; most of the larger mail-order seed companies carry them, as well as replacement trays. The trays do develop leaks after a while (especially if they get used outside for a while for hardening off duty), so I keep a stash of replacements on hand.

Some seedlings grow so slowly, they never outgrow their tiny cells. But most of them will need a bigger home before it's time to set them out in the garden. I have a few different approaches to this:

  • Bigger cell-packs. These are what you commonly buy annual and vegetable starts in at garden centers, but I found they were surprisingly hard to find for purchase. I finally tracked down a good resource for various sizes of these larger packs: Novosel, a mail-order outfit. They were extremely helpful in getting me just what I needed, and I highly recommend them. Reasonable prices, too. I use two sizes:
    • "Slim jims", which are the same length, only slightly wider, and a good bit taller than the small cellpacks, meaning about double the root volume for hardly any more area under my lights. They are meant to be used in their own 8x22 flats, but I found that creative arranging in a standard flat works just about as well.
    • "Market packs" are larger, and therefore take up more space. I use them when I think a seedling really needs to spread out. Eight of these fit in a standard tray.
    Click here for pictures of the various sixpacks
  • Deep square pots. I really like these little pots. They are only 2½ inch square, but 3½ inch tall. That means a LOT more root space, but still an acceptable footprint that doesn't hog all the space under my lights. They can be reused many times, which means that my current supply, from various orders placed at Mellinger's, is only slowly dwindling. But now that Mellingers is gone, I'll have to hunt for a different source.
  • 3" square cut-pots. These inexpensive pots come 18 to a sheet, and must be carefully teased apart to prevent the flimsy plastic from tearing. Or, if you have a stack of sheets, you can break a whole bunch of pots off in one go, with no danger of ripping (much easier!). They make fine all-purpose containers, and I reuse them extensively. All of the seeds I start directly in pots go into these containers. That includes pots that get set outside in the winter for stratification in place, pots that get a warm stratification before being set outside, and seeds that are so fine that directly sowing works better than the baggy method. In all cases, the pot will wind up with several or many seedlings, which will have to be transplanted to (smaller) pots or directly into the garden nursery bed at some point.

What about plug trays? These are sturdy, heavy plastic construction multi-cell contraptions. In most cases, each cell is quite a bit smaller than the cells in the small 6-packs described above. They are meant only for germinating seedlings, which are then potted up. I own two of such trays, and used them a few years - but they just weren't right for me. They are best for starting a lot of seeds of the same variety, while my modus operandi is to start a few seedlings of many many varieties. Also, their longer, narrower size didn't fit in well with my other trays. But lots of people swear by them, so this is just a reflection of my personal experience. If you stop in at my plant sale, I'd be happy to sell 'm to you at a good price.

Recycling pots and packs

I'm a stingy Dutchman, and a closet environmentalist to boot - so I don't like to waste resources. Most of my plasticwares (cellpacks, pots, etc.) find their way back into the cycle after they've served me for a season. As a matter of fact, I cajole others into recycling their leftovers to me by offering a discount at my plant sale. For just about any established plant, containers can be reused without any significant cleaning - so pots one quart and up just get stacked in my shed, and reused as needed. Smaller pots often house seedlings, which can be a little finnickier. So cellpacks and pots smaller than 4 inch get a little wash job. Most tips on

Max loves to help with the cleaning operation
seed-starting will tell you that to reuse containers, you should wash them in a dilute bleach solution, to kill all the disease organisms. Well - with many hundreds of containers to wash, I can't deal with the bleach thing. My alternative method is as follows: throughout spring, I collect all containers, and set them aside. Then, on a hot and sunny day in summer, I get them all out to my back yard. I also grab my wheelbarrow (and give it a cursory cleaning if it's filthy) and my hose-end triggered spray nozzle. Now all of the containers get dunked in the water-filled wheelbarrow; as I clean them, I add more, so that I've always got a good batch soaking. One by one, I take out the containers, give them a quick spritz inside and out with the nozzle, and then toss them as far as I can into the yard. The act of tossing flings off most of the water, and the hot sun on the black-plastic containers finishes off the drying process. I like to think that this method is fairly effective in dispensing with disease carriers, but I'm not going to pretend the containers come out squeaky clean. So for the seed varieties that I expect, by notoriety or personal experience, to be especially prone to fungal attack, I just use newly acquired containers - even with the recycling, I always have to restock to make up for broken/crushed containers, or those that left during my plant sale or with plants donated to the HPS/MAG sale.

Let there be light

Perhaps the most essential ingredient to plant life that's missing from the natural state of my basement is light (the natural state of my basement contains plenty of water - long live sump pumps!). Most seed-starting gurus agree that special growlights are not necessary for growing healthy seedlings - regular fluorescent light contains all the wavelengths needed to support the little ones. Cheap shoplights available from places like Walmart or Home Depot do the trick. A few spins on this strategy are sometimes mentioned:

  • Supercharging shoplights as a way to get more light output from a standard 40W fluorescent bulb.
  • Mixing cool and warm spectrum fluorescent bulbs (one of each in a fixture) to get a broader slice of the light spectrum.
  • Replacing bulbs every year to maintain maximum light output.

All of these sound reasonable. I don't heed any of them (call me a rebel). I use whatever bulbs come in cheap packs, wouldn't dare mess with shoplight circuitry, and use bulbs for as long as they shine light on my seedlings (or at least until their flickering becomes unbearable). I don't claim to provide perfect conditions for my greenlings, but my results aren't shabby, and I'm known to stick to my ways...

I arrange my shoplights in two parallel rows, suspended along the lengths of my seedling tables. Flats go in perpendicular to the lights, so that the front half of each flat gets light from one fixture, and the back from the other fixture. Four flats fit side by side underneath two fixtures (confused? look at some photos). I used to have another row of fixtures in between, but my basement circuit breaker started glowing one day after I added yet another set of lights, so I removed the middle ones, and the seedlings still grow.

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Last modified: March 24, 2010
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