Sorry - I should have mentioned that I haven't used Park's Biodome. I have, however, had great success using a similar seed-starting system from Gardner's Supply. They were on sale in late summer, but I'm not sure what the price is now. Good luck!
I just tried the link and it no longer showed the 35% off. The 15% code still worked, but it didn't show a place for the shipping code. Maybe I didn't go far enough for that. Hate that I missed the 35% off because I had been debating trying one of these. :(
Unfortunately, you can only use one code at a time. Just have to figure out which one saves more money, or if you would rather get it faster.
I didn't get the 35% off either, since the sale didn't include accessories.
Tabasco, I've used Park's bio-dome before. I had it in a sunny window sill and it kept growing toward the window. So, I had to turn the thing once or twice a week.. My only advice is that it comes in three growth sizes.. I used the middle size growth plug tray and the seedlings were already growing too big to keep the lid on. I think part of the problems was the seedlings stretching toward the light. So, if you're using a light system, you might not have that problem. I just got the large growth plug tray. Haven't tried that one yet..
I've used the bio dome with mixed success - some years it works out and some years not. (OMG That sounds just like my life!) The one thing I hate is the refills are 2x what it takes to fill the dome and they mold if you try to keep them too long - so there is always waste. Someone else has a "plug" dome that looks interesting.
Mine came in the mail the other day. The most immediate difference that I notice is the quality. The black seeds trays with the clear plastic covers are really thin and flimsy. The biodome is much thicker and more sturdy.
The "plugs" don't really seem to be soil at all. More like a sponge. You can pop them right out and they stay together.
The only thing that I am not sure about is the height of the dome. I know you are supposed to keep the lights a few inches above the plants, but the dome itself is like 8 or 9 inches tall. Does anyone know if that will make a difference?
tabasco, I have both types and the Home Depot type ones are much flimsier.. And that type it sits in the water (at least the ones I've gotten) so you have to be much more careful about watering.. Seeds seems to like damp but not water logged environment. The biodome is actually a hard plastic case and the "plugs" insert into a styrofoam type of holder that floats on top of the water. The water is "wicked" up to the seed. So the plug is not drenched but rather damp. The other sets I've gotten also have similar "plugs." So, I don't think the "plug" makes that much of a difference.. I can be wrong there though.. I never looked to closely at them..
jmcdowell, I don't know if you're referring to those growth lights.. I have those growth lights in my aerogarden systems and those things grows insanely fast. (secondary leaves were taking off by day 4) That might have to do with the extra air in the root zone though. I'm thinking that with the lights, once the plantlets get too big, you might want to take the top off. Humidity is good for seedlings but by the time it gets that big, it's like a small plant, no longer a small seedling that needs the extra protection.. Just a though.. In retrospect, guess I should have thought about that when my plants got too big.. But it was warm enough at the time for me to just transplant everything out then..
Could be the things you were trying to buy weren't eligible for free shipping--a lot of times when places have special deals like that it's only good on certain items but not on others. Or you have to spend a certain amount before you can get the deal, etc.
I received 3 Burpee self watering 72 cell Ultimate Garden systems last year for Christmas. They were half the price Burpee charges on its website now.
At that lower price, I give them a so-so rating-- if you never need to move the tray after setting it up. The trays are very light plastic. Try to move them and they'll bend in half with all the water spilling out. When I moved them, I had to empty the water and carefully, with both hands under it, remove the 72 cell tray , take off the self-watering mat, take out the stand the mat sits on, move the tray and then reassemble the system.
The potting mix contains a gel-like substance which is very good at keeping moisture in but if any cells pop up--as many in my trays did--you can't push the mix back down into the cell. In addition a few of the cells must have had holes on the side as the mix never hydrated.
The plus side is I left one tray outside for weeks after the plants should have gone in the dirt and they were still fine--the soiless mix kept the seedlings at the right moisture level and from becoming too tightly root bound.
Not going to buy any this year as I don't see them at ten bucks or under but if I did, I might.
I've seen those and they didn't look sturdy enough.. The biodome ones are very sturdy.. I've moved them around plenty of times.. I was wondering about the other set you posted. Those look a bit sturdier..
I bought the Bio-Dome with the 40 Jumbo inserts and it worked well. I had also bought the heating pad of the same size as we keep our house at 58 degrees and it would be a little chilly for germination. Now that I have expanded my garden and adding to varieties I just ordered a 64 cell Bio Dome and the medium heating pad from Park Seeds.
Needless to say I am quite happy with this product especially as a lot of the other products are too flimsy.
I have used the Park Biodome to start tomatoes, peppers, and pak choy and have had 100% germination under lights. It is sturdy and easy to use. The quality is far superior to the flimsy Jiffy and Burpee systems.
I don't know if anyone can answer this question or not. Do you have to use their plugs in the bio-dome I'd rather not have to buy the plugs yearly. Has anyone tried using regular pottting mix for seedlings in them. I just received two wasn't exactly what I thought. The plug holes are really small. Thinking about ordering the 40 cell block. Will appreciate any comments.
I always use the generic, flimsy black "1020" thermopastic trays. At $1 to $1.40 before shipping, I can double them up if I want to.
Then I have a wide choice of tear-apart "inserts" to put into the trays, also around $1 to $1.50:
72 cells per tray (12 6-packs)
48 cells per tray (12 4-packs or 8 6-packs)
36 cells 6 6-packs
32 cells 8 4-packs
24 cells, 18 cells, 12 cells etc.
I re-use the inserts and trays for several years, taping the inserts back together with tiny strips of Gorilla tape or duct tape, if needed.
"Flimsy" just means you can't move them without some support like thin plywood or wood panelling or a doubled tray under the insert. And I would never try to move them with water in the tray: I always avoid standing water so as not to drown any roots.
You can use "propagation trays" instead of the flimsy inserts. Prop trays are sturdier and don;t even need the 1020 tray under them, except to catch runoff water, or for bottom-watering. Prop trays can be had with medium to tiny cells: 38, 50, 72, 98, 128, 200, or even 288 cells per tray! Cells can had in round, square, star or "vented" shapes. They might not have been designed for seed-starting, but can be used that way.
I like this online vendor for price and availability of "Hobby Packs" like 10 of each tray, instead of 100s per case.
>> Has anyone tried using regular pottting mix for seedlings in them.
Never! I did try commerical seed-starting mix, but it was mostly powedered peat and held FAR too much water and let in FAR too little air. Drianage was zilch. As soon as I overwatered it once, aeration was zilch and roots drowned even before damping off set in.
Just make sure that whatever you buy says "seed starting" not "potting".
And it must say "mix" or soilless mix", not "soil".
It should say "sterile", but my experience is that "clean and fast-draining" counts for more than "sterile".
Whatever you buy, unless it is really for professional nurseries, is likely to be too fine and hold FAR too much water.
Water will never drain out, it will "perch" in the bottom inch or so of the cell and drown the roots. There will be no open pores, channels or voids for air to circulate through. The surface will stay damp and encourage damping-off.
Almost anything commercial will benfit greatly from adding lots of coarse stuff to improve its drainage. I guess people skilled at underwatering can get around that, but for me it is a total necessity.
coarse perlite (as coarse as you can find)
chicken grit or turkey grit (coarser is better: 2-4 mm or even 5 mm)
double-screened crushed stone (avoid rock dust, powder, or anything with fine sandy texture)
coarse fibrous coir or small coir chips, NOT coir powder. Avoid salty coir.
screened pine bark shreds and chips from medium mulch (see below)
I vote against sand because you can never find truly coarse sand without 50-80% of it being much finer than you want. Technically, "sand" with grains coarser than 2 mm should be called "fine gravel" but I never see that for sale either. The other thing wrong with sand is that grains are rounded or spherical instead of jagged and irregular. You need drainage! Sand can even be salty or dirty - if it has any place, that is in outdoor soil to make clay more friable.
Vermiculite breaks down very quickly into fine powder. And it holds water more than it improves drainage. It is especially bad sprinkled on top, because it holds water against the seedling stem and encouarages fungus, algae and damping off. NG! Seeds usually need more air, not more water.
I always make my own seed-starting mix (or start with "whatever" and add 80% - 90% amendments). In truth, the coarse components are what create the airy structure: even 15-20% fine stuff like milled peat will clog up the open spaces and turn your mix back into a non-draining root-drowner.
Consider making your mix the way my Dad made his martini: first put in all the good coarse stuff like medium bark, medium coir, coarse grit and very coarse Perlite. Then take the bag of milled-peat Jiffy-Mix (vermouth) and add just a little tiny pinch, visualizing roots drowning and seedlings damping off as you do it. Don't over-do it!
I have not read about many other people using shredded, screened pine bark for starting seeds, but I swear by it.
There is no need to use more than 5% - 10% FINE pine bark: seedling roots need more air than water and medium bark shreds will hold plenty of water, especially if you spritz them every few days, or bottom-water weekly or less often. And bark doesn't dry out th3 way peat does: no problem re-hydrating it.
And bark wicks just fine, if you bottom-water.
Since I started using pine bark for seed-starting, I have lost zero seedlings to damping off, and my germination rates went WAY up. (I do tend to over-water, and fast-draining bark-based mix shrugs off excess water and maintains a semi-dry surface like a charm.)
And bark is super-cheap, unless you buy orchid bark. I buy the best grade of "medium beauty mulch" I can find. $7-8 gets me two cubic feet: enough to start seeds for years.
I screen it with 1/2" screen and turn the coarse parts into top-dress mulch for my raised beds. (The intended use for "mulch".)
Then I screen it again to pull out as much of the "finest stuff" as I can. If it goes through a 1/4" screen too easily, it is powder and I don't want it in my seed-starting trays. These bark fines or powder I mix into heavy clay soil outdoors, and the clay likes that.
The middle-coarser grade of bark makes a great potting mix .
The middle-finer grade makes my seed-starting mix.
I mix in a little grit, Perlite, vermiculite and/or coir just to feel consciencious, but the bark and the air it brings with it are most of what my seedling roots need.
So far, I have also added in some commercial peat-based mix, as if to be traditional, but I tend to regret that. The bark doesnt need any help wicking or holding water. If I really needed peat, I should have screened some UN-milled sphagum peat.
Since the bark has no nutrients, water with 1/2 strength or 1/4 strength soluble fertilizer a week or three sooner than than you might have with commercial mix.
I used the bio dome for the first time last year. As always, once the seedlings were well up, I took the top off, or moved the containers out into regular trays and started another batch in the bio dome. Natural light is enough for germination, (although I've found a heat pad can make a huge difference). By the time the seedlings start stretching toward the light, it's time to give them some air.
I never used the insert that came with it, but did use the smaller ones with the spongy plugs. I had mixed results. Germination was fine, but growing on was problematic. For one thing, they say to pot up when the seedlings have 4 sets of leaves, but the plugs are longer than cell-packs are deep, so what to put them in that won't eat up too much space?! Also, this fall, pulling up gone-by annuals, I found many plugs still attached to the stems. Because of this I don't plan to use them with perennials. I did try regular potting mix, wrapping the bottom with a paper towel and elastic bands so the mix didn't fall out. That worked fairly well until the paper towel fell apart. This year I'll try coffee filters or gauze.
Also this year, I'm thinking to try germinating squash, beans, nasturtiums and others that don't like moving in the large biodome insert. That will give them an earlier start in case of a cold spring like last year, and it won't matter that the plugs don't break down.
I agree that the biodome is nice and sturdy, and I like the adjustable vents. It's also a convenient size for city window-sill gardening, which is what I have to do until we open the CT house in the spring.
[quote="RickCorey_WA"]>> Has anyone tried using regular pottting mix for seedlings in them.
... on using Bark nuggets ...
Thanks for the tips. My wife started using a similar mix for indoor plants. It was a combination of pine bark, chicken grit (fine granite) and Turface.
I just setup my Parks Bio-Dome and for this year I plan to use the supplied sponges but would prefer to use something else more economical next season. When you replied to a bio-dome question are you using this mix in a Parks bio-dome or a homemade one ? I ask because I would like to know what you do to try and keep the plug together when you pull it out of its container (in this case the Styrofoam trays) ? I assume that it being so coarse that if I try to push it out it will fall apart.
>> It was a combination of pine bark, chicken grit (fine granite) and Turface.
Nice! Now the root hairs in that mix will never drown or suffocate! Nice drainage and aeration!
I have 8 mknths of rain per year, and heavy, heavy clay with almost no "perk". I obses about drainage and waterlogging even indoors.
>> are you using this mix in a Parks bio-dome or a homemade one ?
Homemade in the sense that I use 4-5 generic plastic "1020" trays to catch the runoff water,
2 plastic humidity domes or a bunch of 18" wide "Saran Wrap" or 'food film' to retain humidity,
some cotton flannel as a capillary wicking sheet,
and a spray bottle and mustard bottle and ketsup bottle to water gently.
The only part of the Bio-Dome system that I really wish i had were the extra-deep cells.
I try to compensate by using a capilary mat to draw excess water out of each cell: to fight the dread "perched water" that alwyas used to drown my roots when I overwatered.
I still overwater, but now more of my seedlings survive. My goal is to make a seed mix that drains as fast as i can over-water.
I put my bark-grit-perlite-whatever mix into "propagation trays", also called "cells" or "plugs".
Or I use "6-packs" also called tear-apart plastic inserts.
When I have to pot up before planting out, I used to use 2 sizes of Dixie cups (Solo cups), but they tend to fall over.
Now I use 3.5" square plastic pots, much lower than Dixie cups and wider.
I am still experimenting, but I tend to use plug trays with 50, 98 or 128 cells.
When using the "inserts", I usually use the trays that hold 72 cells (12 packs of 6 cells each).
You see that I start seeds in pretty small cells.
>> I ask because I would like to know what you do to try and keep the plug together when you pull it out of its container
I use the small cells so that they approach being root-bound pretty fast.
The roots themselves hold the soil mix together if the root ball is healthy.
Other than that, I try to support the soil ball from three sides with my hand or a fork with bent times and one time cut off.
Then I rest the soil ball on a clean 'Sharphooter' spade and slide it into a prepared hole as gently as I can (squatting and kneeling are two things I can't do if I wnat to get up again without help).
Pine bark can be pretty fibrous if you have not removed all the fines, and that TENDS to hold together if the roots help it somewhat.
But 90% of my answer is: I let them get almost root-bound in a very small cell.
My biggest cell (the 50-cell prop tray) is 1" across at the bottom, less than 2" at the top (round-conical 2.4" deep).
I don;t use the 98-cell tray any more becuase they are only 1.5" deep (round, 1.4" at the top and 1" at the bottom).
I don;t have the ones I use most handy to measure, but the 72-cell 6-pack (inverted Vee) is pretty common, for vegetables or fast-starting things like Zinnias or marigolds.
I use the tiny 128-cell prop tray for small perennials like salvia, and petunias. Small slow-growing things that I wnat to give every possible chance to become root-bound so i don;t tear the root ball to shreds.
These are much sturdier than the tear-apart 6-pack inserts. But then i cut them up into sections of 3 or 4 rows each, so i can invert 20-30 at once, and poke the root balls out with the blunt end of a pencil .
Sorry about the previous post but I wrote a rather lengthy reply to Rick and whenever I tried to send it my browser just spun and spun each time I tried.
Thanks Rick for the insight and the links. This is my first time starting seeds indoors (seriously that is). Half of the seeds I will plant this year are from last years crops so this should be an adventure. :-)
After my initial sowing I will give your mix a shot and see how it goes. You made me realize that I still need some transplant containers. I may have flats from last years purchases but I will still need a few more. Once I transplant out I will see what I can sow.
One more question, is your definition of grit the same as mine (chicken grit / fine granite ?)
>> is your definition of grit the same as mine (chicken grit / fine granite ?)
The grit I was able to buy was indeed crushed, washed granite sold as "#2 Chicken Grit".
But I think almost naything is "grit" if it is coarser than coarse sand, and finer than fine gravel.
Say around 2 mm - but is that the long dimension or the thinnest dimension?
Personally, I call it "grit" if the long dimension is around 1 mm - 3 mm ... 1/25th inch - 1/8th inch.
My feeling is that seed-starting cells and potting soil need things as coarse as grit or fine gravel, but clay soil benifts from almost anything coarser than clay - even sand. It may not iommediatly impriove drianage unless you add LOTS of coasrse stuff, but snad seems to make hard clay more friable. And it seems to make pine bark shreds more effective, as if by holding shreds apart instead of gluing them together.
The only time I ever impressed a nearby, very experienced gardener was when I bought a cubic yard of nice crushed rock: mostly 1/32 - 3/16th inch. She OHHHed and AHHHed and ran her hands through it the same way i admire her flowers. I offerd some, but she didn't need it.
I do not have a sunny window where I can leave a bio-dome etc., but I have though about getting one and putting it outside as a kind of mini greenhouse. Was hoping this would let me start seed just a little earlier than I would direct sow and improve my germination rate. Any thoughts?
I just guessing that you might need to vent it, especially on a sunny day.
Sun + clear plastic dome = a lot of "greenhouse" heating.
If you're gone all day, or can't check it, I would be afraid of 'cooking' seedlings. Giving it early morning sun ought to "chase away the chill". Late aternoon partial sun ought to warm it up to give it a better chance of making it through the night without too much chill.
But wouldn't direct noon sun cook it? A small dome like that doesn;t have the thrermal inertia of a greenhouse or a cold frmae, and it might have huge temperature swings.
But I'm just guessing. That's why I'm nervous about a low hoop tunnel / cold frame even in cloudy coastal WA. If the sun came out while I was at work, I'm thniking that any greens would be steamed before I came home to vent it.
Last year was my first to use the 60 cell bio Dome from Parks. This past summer I purchased the 18 cell block which is interchangeable with the 60 cell block and refills to use for large seed types. Yesterday I received my second Bio Dome 60 cell kit and a bag of refills. I will use this for seeds with different germination rates. Now I have three blocks to be used alternately between two Bio Domes.
I germinate on heat mats under grow lights. As soon as about 90% or so of the seeds have germinated the dome is removed during the day and the grow light is set about 1/2 to 1" above the plants. The dome goes back on at night on the heat mat as the temp in winter in the grow room runs between 50 -60 degrees.
I always had problems of over watering with Jiffy pellets, but never with the Bio Dome. The trick with starting seeds in a 60 cell block is to get all the seed in the cells being used to germinate at the time. I plant tomato seed and pepper seed separately because pepper usually take longer to germinate than tomato seed. Thats why I bought a second dome.
>> pepper usually take longer to germinate than tomato seed. Thats why I bought a second dome.
When I germinate in tearable inserts ("cells" or "6-packs") , I can remove one or two 6-packs at a time, from the dome, as the sprouts emerge. Each pack gets only one kind of seed, which also makes them easier to label and keep straight.
When I germinate in prop tarys, each ROW gets one kind of seed, or usually 2-4 adjacent rows. When that kind of seed has mostly emerged, I cut those rows apart from the rest of the tray and move it out from under the humidity dome.
I always fear damping off if I leave emerged seedlings under a humidity dome even for a few days.
>> I always had problems of over watering with Jiffy pellets, but never with the Bio Dome
That's why I gave up on Jiffy-Mix or other commercial seed mixes based on what looks to me like POWDERED peat. It held too much water. Maybe the trick is to never give peat as much water as it will hold, but I switched over to home-made screened pine bark mulch mix and became a happy germinator instead of a mass murderer of seeds.
I've been using my biodome over a heat mat to germinate all my 'warm' varieties, both annuals and perennials. For most I cluster sow in 2" pots, then transplant to cellpacks once they're up. Then I put the packs on a self-watering tray under lights. I like using this method better than the standard greenhouse covers that come with regular 1020trays. I can start just as many varieties at the same time in a smaller space, and 'duds' and slow starters take up very little room unless and until they germinate. Also, I can remove seedlings from the greenhouse as soon as they're ready, no matter what the next pot is doing.
I bought, and keep thinking about using, a tray insert that has 20 very narrow rows. But I fear that once things sprout, I would have to prick them out RIGHT THAT DAY or the roots would grow out the slit at the botom of the row and break off when I tried to pull them.
But my theory was a litle like your practice: start 20 different varieties in one tray.
Instead I use a 128-cell prop tray (16 rows of 8 cells per row). I sow 1-3 rows in each variety, and can get 6-10 varieties per tray, even though I only get 8-24 plants of each variety.
The advantage is that, if I get busy for a week or two, they just get root-bound, not root-decapitated.
Someone pointed out that GHMS (greenhousemegastore) has a real bargain on 2.5" TLC Square Form / Black Form Pots. The great thing is that they are 3.5" deep!
Yes, those are the ones I use. Once they sprout, I get them out of the Biodome and under lights, but I don't have to prick them out right away. As long as I move them before the roots get too tangled up together they are fine. I also use the 2" pots for perennials and larger annuals.
I bought several Bio-Domes for the 2013-2014 winter season, planning for retirement and a MUCH larger garden. They were sale-priced at the end of the 2013 season, so I was trying all of the sizes and also the refill sponges. The trays and inserts are well-made and easy to move around. The system of watering from below and having the inserts float upward to keep the roots from getting overwatered seems quite logical. It works pretty well, except that some of the sponges are hard to get hydrated when first inserted.
So far, I'm impressed with how reliably seeds germinate in them -- and unimpressed with how many of them grow afterward.
Some plants, particularly nicotiana, have robust roots and just fight their way through the sponges. Others, like lisianthus and matthiola, want to give up and die. I've started most of my later seeds in regular plastic packs and have transplanted the lisianthus after prying open the sponges until I can see a root and then packing potting mix into the gap. (Not sure how that's going to work.)
The sponges are very resistant to breaking down, which is nice for getting them out of the holes, but looks as if it will be a problem in the garden.
Has anyone had success with using a different seed-starting medium in these?
I bought Park's Bio Dome Pro's this spring and am using Miracle Grow potting soil in them. I am just about ready to start potting up my broccoli, cauliflower and Brussels sprouts.
Today I felt the need to remove the domes as there seemed to be the start of a mold fuzz developing and suspicions of damping off make me uneasy. I put a fan on them too to strengthen their little stems. The mold appears to have started on the capillary mat which strikes me as peculiar as they are new.
I have fennel, basil, celery, parsley, cilantro planted in the domes too.
Tomorrow I will thin seedlings and I will post pix when I start transplanting, I am curious about the root formation.
My practice is the same as all the advice that I have read:
as soon as a seedling emerges from the soil, it does better with low-humidity air. Take off the humidity dome as soon as a few seedlings emerge. That will reduce mold and damping off. Your seedlings must be very healthy and vigorous to avoid damping off INSIDE a humidity dome!
Usually seedlings also like much cooler air than the warm soil that germinating seeds like best. And moving air (fan). And as much light as they can get (fluorescent tubes within 1-2 inches of the seedlings' leaves.)
The only purposes the humidity dome served were to keep the soil moist and hold more heat from the heating mats in the soil.
If some of the rows have emerged and some have not, you could gently mist the slow rows a few times per days to keep their surfaces moist. Or use some Saran Wrap to cover the slow rows.
P.S. I cut plastic mini-blind slats in half to make skinny labels for small cells. They also serve as "tent poles" to support plastic film humidity covers.
I use plastic "insert" trays and "plug trays" also called propagation trays. I cut both of them up into "slices", each slice perhaps 1/4 of a 1020 tray.
I cut up a 200-cell tray into 10 blocks, each 5x4=20 cells.
I cut up 72-cell plug trays into 4 slices of 18 cells each (3x6), or 8 blocks of 9 cells each (3x3)
That way, I can make each slice or block of cells all one species or variety of vegetable. That way, they emerge close to the same time, and I can move that whole slice or block of cells to a tray with no humidity cover.
>> The mold appears to have started on the capillary mat which strikes me as peculiar as they are new.
I don't think that "old" favors mold, unless "old" means dirty. Mold will grow anywhere there is humidity and nutrients. Seedlings are probably better off unfertilized, or VERY lightly fertilized, for several weeks.
Maybe your seedling soil mix has some organic components, or some built-in fertilizer (especially organic fertilizer)?
Well, I didn't lose even one seedling to damping off or anything else for that matter. It was peculiar though, when I went to transplant the seedlings, I found two toadstools growing on the capillary mat. Just plain weird. My brassicas are now ready to go out to the cold frame, yeah!.
I have never had issues with Miracle Grow potting soil and yes, sometimes I cut it with peat as I think it has too much fertilizer in it.
I have decided to be more discriminatory about what seeds I plant in the Park's Bio domes, they really need to have about the same growth rates. Brassicas should be kept in separate domes from slower sprouting plants as in celery and parsley. And Lisianthus will always get it's own from here on in!
My celery sprouting was pretty lacking in uniformity (different brands?) and I will use an icing spatula instead of the little prongs shove up from the bottom as their root systems seem to be finer.
I always use capillary mats for self-watering, which means I grow my seedlings on the wet side. I've had to use Miracle Grow, as that's all the local places carry. A sprinkle of cinnamon on top of the soil keeps things smelling fresh and keeps the gnats away, and a little peroxide in the water seems to prevent problems too. I also make sure I have adequate heat and light. With these precautions, I never, ever have damping off any more.
I've also learned to keep each variety that I plant in separate containers. When I get large multi-celled trays, I cut them into smaller sections. Even within one packet of seeds, germination doesn't happen all at the same time. With different varieties, it becomes impossible to give each type the conditions it needs.
Also, about the Park Start sponges... I used them one year, and thought they were great for annuals. The second year I had some left over and used them... Apparently you can't do that. The few things that germinated grew poorly. When I moved them to regular cells, their roots were miniscule, almost looked burned. Maybe a fungus got in there? I don't know, but never again. On top of that, a couple of years later I'm still finding the sponges in my garden, hard little dried up things.
The biggest problem, and that's only with certain tricky perennials, is that the mix gets soggy. For germination, I add lots more vermiculite to lighten the MG Seed Starting mix. And this year for the first time I've mail-ordered a special Self-Watering Container Mix from Gardener's Supply, which is working very well for Lupines, Dianthus, Campanulas and others which require better drainage.
I'm still using MG for all the annuals and veggies, in my experience it's just fine for that.
I have used Park's Biodomes for many years. When the trays and domes were newer they worked well for larger seeds like tomatoes and peppers and fairly well for basil, salvia and other easy to manage seed. As they aged, sterilization became more critical. I let my domes and trays soak in a Clorox solution for quite a while, rinsed them then added fresh plugs. Alas, they were still prone to some damping off that had not happened to my seed starts when the domes were newer. The plastic yellowed over time and UV exposure.
I also was trying more difficult plants to germinate: columbine and bell flower come to mind. They take so long to germinate that I needed to leave the domes on too long, which promoted damping off. It was a experiment with mixed results.
The plugs really work well-I find them scattered throughout the garden years later, as they don't break down. Air gets to the roots of seedlings because the holes are round and the plugs are elongated trapezoidal solids. All in all I think they are a pretty good system for starting annual plants but perhaps not so great for perennials or slow-starting seed.
On another slightly different topic, this spring I tried starting some scarlet gillia. I had good luck using a coarse cactus mix placed in a small plastic tub. The tub came from a packaged spring mix from the grocery store. I punched holes in the bottom & the lid, planted the seeds, including some penstemon seed, placed the box in a cold frame, lightly watered them and waited. The penstemon seeds never sprouted but I have a dozen very small but healthy gillia seedlings now. The lid was removed when the first sprout appeared. I am going to be very careful about keeping them just damp and not too wet. This variety is pink and called Fairy Trumpet.
Is it possible to use the Biodome with a heating pad and regular seedling mix?
I'm thinking about buying it to use indoors. I've had absolutely no luck with seed germination indoors. I did tackle the damping off problem for seeds sown outdoors by watering them with water mixed with copper fungicide.
I use mine all the time for germinating, but sow in regular cell packs, or cluster sow in 4" pots, with seed starting mix. As soon as I see sprouts, I take them out. If it starts smelling musty in there, I sprinkle a little cinnamon around to freshen it up. I've had no damping off problems.