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Park's Biodome: Anyone tried it?

Cincinnati (Anderson, OH(Zone 6a)

Hi, All,

I saw the Park's Biodome on sale for 35% Off and wondered if anyone on DG used it and had success with it? Would appreciate any comments.

By the way, Park's is having a very nice sale on Seeds 'n Such for just a few days....35% off plus a enter 15PRKCPN in the coupon code when you check out and get another 15% off. Pretty good....

Long Island, NY(Zone 7a)

Thanks for the tip about the 15% off code. I used it to buy some bulbs that were already on sale.

Ozark, AL(Zone 8a)

I haven't used it, but just out of curiousity I ordered it using the code you listed. We'll see how well it works. I got the one with the 80 jumbo cells.

Another code that still works is "SHIPFAST", which upgrades you to Express Shipping for the same price as regular.

Long Island, NY(Zone 7a)


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!

Cincinnati (Anderson, OH(Zone 6a)

Ooooh...maybe if the codes still work I'll send one to my sis for Christmas!

Gilmer, TX

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. :(

Ozark, AL(Zone 8a)

Hey Catlady,
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.

Gilmer, TX

Boo Hoo, guess I'll try the 15% coupon #.

Pawling, NY(Zone 5b)

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..

Fairfield County, CT(Zone 6b)

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.

Pawling, NY(Zone 5b)

YankeeCat, try using a bit of H2O2.. That's kept the mold and algae to a minimum in mine.. Had problems too before..

Cincinnati (Anderson, OH(Zone 6a)

Thanks for all the good comments. Very helpful.

But a couple more questions, if you don't mind---

How are the Park's Bio domes different from the black seed trays with clear plastic covers that you can buy at Home Depot?

Is it that the 'plugs' have extra good soil mixture in them? Or the vents in the top?

Thanks for your help!

Ozark, AL(Zone 8a)

Good Morning,
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?

Pawling, NY(Zone 5b)

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..

Cincinnati (Anderson, OH(Zone 6a)

Thanks again for the tips on the Biodome. Sounds like they work rather well. I can't wait to get one going this winter!

Pawling, NY(Zone 5b)

no problem tobasco.. :)

Ozark, AL(Zone 8a)

Just to let you guys know. Those codes expired in November. The new express shipping code is DECSHIP, not sure if there is a new % off code.

Monticello, MN(Zone 4b)

I tried the free shipping code but a message came up: not qualified but code was valid. How does one qualify to get this/

Dublin, CA(Zone 9a)

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.

Long Island, NY(Zone 7a)

Just curious: Where are you guys learning about these codes? Are they advertised somewhere?

Dublin, CA(Zone 9a)

I think they probably send them to people who are on their email list. I don't subscribe to Park's but I do on some other sites and that's how I always get discount codes, notices of sales, etc.

Long Island, NY(Zone 7a)

A-ha. That makes sense. I remove my Email from mailing lists because my inbox becomes so cluttered. In the case of gardening, perhaps unwise...


Cincinnati (Anderson, OH(Zone 6a)

Sometimes there's a code on the back of the catalogs and sometimes I read about them on the DG threads, too.

But there are a lot of good sales scoops coming throught the various on line 'news letters'! Clutters up the inbox, but so good to know about!

Clinton, CT(Zone 6b) a sale notice from Charlie's Greenhouse the other day. The deals end Dec 31st:

The self-watering tray with 18 three and a half inch pots looks good. Anyone ever use them?

Pawling, NY(Zone 5b)

Not me but I was thinking of getting another germination set (yet again) so if anyone gets it, please post your eval.. :)

Clinton, CT(Zone 6b)

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.

Pawling, NY(Zone 5b)

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..

Yorktown Heights, NY(Zone 6b)

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.

Gold Canyon, AZ(Zone 9a)

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.

Morgantown, WV

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.

Everett, WA(Zone 8a)

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.

Greenhouse mega store


Everett, WA(Zone 8a)

>> 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've become a total bark zealot.



(Pam) Warren, CT(Zone 5b)

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.

Hope this helps!


Crisfield, MD

Quote from 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.

Any and all suggestions are welcome.


Everett, WA(Zone 8a)

>> 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.

Thumbnail by RickCorey_WA
Everett, WA(Zone 8a)

There are some pictures of propagation trays (plug trays) here:

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 .

These are the typical flimsy "inserts": easy to invert 6 at a time and flex the bottom so the root ball pops out intact.:

The "hobby pack" is just ten of one size tray, more affordable than the case of 100! Usually $10 - $13 per 10, PLUS shipping. You might as well buy a lifetime supply, and just pay the shipping once.

P.S. The name for the "72-cell-per-tray insert 6-packs" is "1206": one tray equals 12 6-packs.

Crisfield, MD

ignore ... checking to see if I can post again ...

Crisfield, MD

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 ?)

thanks and stay dry up there !

Everett, WA(Zone 8a)

>> 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.

North Augusta, SC

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?

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