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Foam Rubber as a growing medium? Newbie Questions!

Posted by amylama Iowa (My Page) on
Mon, May 24, 04 at 16:15

Has anyone ever used/had success with using "craft store" foam rubber to start seeds?

I have NO stores in my area that sell hydroponic supplies. And I'm having a hard time visualizing the products to be able to make the choices that would work for me. So before I run off and buy a bunch of stuff online, I would love to know of things that you can buy "anywhere" that will work as substitutes.

The "foam rubber" idea (which may not be original) came because I think I would like to try the "oasis foam cubes" to start seeds with. But what are they, other than a square of foam with a pencil size hole cut in them? Can't I just make my own? Or is there something I'm missing?

Is there anything wrong with buying a PH test from the pet store (aquarium supplies)? And ph-up or ph-down from there? That last question (up/down) is a guess if they sell such a thing?

I have already found the WONDERFUL website made by Ed Varona (Thank You Ed for creating it and thank you forum members for posting it!). I plan on using his simple bubbler system that I will create out of a styrofoam cooler and stryrofoam cups. (I saw styrofoam coolers with lids at the "Everythings $1.00" store a few days ago, WHAT A DEAL!)

But any AND all buy "anywhere" items that anyone could suggest would be awesome!

I think the nutrients I will have to order no matter what, I do realize there are recipes, but as a beginner I think that would be more hassle than it would worth. BUT I STILL NEED HELP HERE TOO! THERE ARE JUST WAY TO DARN MANY TO CHOOSE FROM! Any suggestions? Something all-purpose?

I'm planning on growing fruits and veggies.... ALL OF THEM!!! Well..... I'll start with the easiest ones..... Then work my way up to the tators and watermelons ;o)

BUT I would prefer to start from seeds at the beginning. I'm already suffering from information-overload and will figure out cloneing/cuttings later.

Here is a link that might be useful: Ed Varona's site for future readers!

Follow-Up Postings:

RE: Foam Rubber as a growing medium? Newbie Questions!

I could be wrong, but I would guess you shouldn't try to get seeds started in plain foam rubber. I don't think roots are going to push into that stuff very well. Also it probably doesn't absorb water very well and won't stay wet unless you submerged it into water. I think if you tried it the seeds may germinate (sprout), but then that's about it. Perhaps there's a more porous open celled foam (polyurethane) type of block that could work.

RE: Foam Rubber as a growing medium? Newbie Questions!

Are these the only problems you for-see with the foam? I was anxious to get started so I already purchased a piece of foam. (I just got back home). Not a big deal, I just want to start!

And does that mean I am safe in assuming there is nothing "special" added to oasis foam other than the type of foam itself? Nutrients or anything?

My foam is 2" x 12" x 24". I was planning on cutting the foam into 2" x 2" x 2" cubes and THEN I was going to cut a slit "almost" all the way thru the middle of each cube, like a taco shell <---I can't think of a better thing to compare it to, so you understand what I mean. I am planning on standing my "taco shells" on an open edge, so that the the 1 solid edge that is left on the foam cube will be on the side, NOT the top or bottom.

Do you think the seedlings still couldn't push thru foam?

And thank you for the reply, please don't take my above questions as if I don't appreciate your help or think you are wrong. I just don't know if you thought I was planning on using the foam as a solid cube. Maybe the seedling can't push the closed "taco shell" apart to get both ends out?

I just figured if they could push thru dirt that foam would be a piece of cake for them.

Maybe cutting the cubes down to 1" x 1" x 1" would be better? Then there would be less "pushing" distance.

I do plan on using lava rock (<---buy anywhere) for my main growing medium. But I wasn't going to remove the foam (if it worked). My original plan was after the seedlings had the first true leaves, I was going to place the seedling, foam and all, into its growing cup and fill with the lava rock. I figured the foam would serve as padding/protection from the lava rock.

I am just looking for the easiest way to get to the first true leaves. I have read about the paper towel method, but I just don't think I could get the seedlings to stand up in lava rock without smushing them!

As far as keeping it wet, I work from home and am excited about this project, so I don't think there is any risk of them drying out. I grow MANY things already in "soil" with very good luck, the only things I have bad luck with are cacti... And that's because I won't leave them alone! SO... I really mean it when I say... "I don't think there is any risk of them drying out" ;o)

RE: Foam Rubber as a growing medium? Newbie Questions!

Dear Amylama,
Thank you for the kind words. It's a pleasure to be of service. It might be of interest to you to know that I took my MA degree in educational technology from the University of Iowa in Iowa City. That was in 1969. That's a long time ago. One of the skills I learned there is how to make technical information more understandable. My website is an off shoot of the desire to make technical information more available.
Thanks again and regards.

RE: Foam Rubber as a growing medium? Newbie Questions!

It's a small world, Ed! I'm in Sioux City, but I have been to Iowa City. Although it was an unpleasant trip. My husband was life-flighted there after a serious injury about 5 years ago. He is fine now. But I have to admit, I was amazed at the size of the hospital/university that spanned several city blocks! I don't know if that's where you attended or if they had even more buildings elsewhere for non-medical classes.

Anyway, I must tell you that I have an associates degree in Computer Programming. I graduated with a 3.7 GPA and I currently work as a freelance (by choice) C++ programmer, so I am no dummy. BUT, I am what my instructors used to call a "visual" learner, meaning that it is harder for me to grasp how things work without seeing them in action... Now I was having a very hard time understanding the setup for most of the hydroponic systems, even after scouring the internet and reading the limited amount of books that my local library carried... UNTIL I found your site, and suddenly the light bulb went on! Not just for the bubbler, but for all of the instructions you have posted there! So when you say you learned "how to make technical information more understandable", You did an EXCELLENT job!

OK OK I'm done sucking up, ;o) but I just wanted you to understand "how well" you did at clearing up many things that where still a little fuzzy to me!

Have a good one!

RE: RE: Foam Rubber as a growing medium? Newbie Questions!

After re-reading my post, I'm wondering if I gave the wrong impression by calling it "foam rubber". I should have just said "foam". You know... The soft, mushy kind that is used to stuff things. ;o)

RE: Foam Rubber as a growing medium? Newbie Questions!

Yeah, if you mean a more open-cell foam, I really don't know for sure as I have never considered trying that stuff. You'd just have to try it I suppose.
The foam rubber (what I was thinking about) is usually used to help dampen vibration (well the other foam is as well), although the foam rubber does it just a bit better as long as it isn't compressed too much.

RE: Foam Rubber as a growing medium? Newbie Questions!

Improvise with one of those long tube things for your swimming pool made of foam rubber. If looks dont matter, just cut them how you need them.

RE: Foam Rubber as a growing medium? Newbie Questions!

My wife found some foam and asked me if I could use it.
I cut the foam into 3/4" cubes and popped a hole thru with a pencil. Then I used tweasers to set the pansy seeds in the middle of the cube. The sprout should come out one side and the root out the other. I should be able to dip them and shake the water off and put them back in the grow tray.
When they sprout I'll stick them in the hydro. I did this just yesterday so a little time will tell. I'll post again after they sprout.

RE: Foam Rubber as a growing medium? Newbie Questions!

The foam will probably work, but, it may actually be too wet for the seedlings to thrive. But hey, it's paid for and seeds are cheap, go ahead and try it. In the meantime, go to a garden center and buy a bag of perlite. Go to the grocery store and buy some small plastgic cups, the kind you put int hose bathroom dispensers.

Drill at least 4 1/4" holes in the bottoms of the cups. Fill the cups with perlite. Put the seeds on the perlite (lettuce on the surface) or push them in a bit if the seeds need to be covered. Water thoroughly until water comes out the bottom. Put the cup in a container with 1/2 inch of water. Water daily.

Perlite is a perfect seeding medium because it holds just the right amount of moisture. You can put the cup into some systems as is.

RE: Foam Rubber as a growing medium? Newbie Questions!

AdrianaG. Thanks for the thunbs up on the perlite. My wife bought a bag and today I planted a lot of seeds. I did'nt use the cups though. After thinking it over I bought a small tote, 8"x16"x4" tall and peppered the bottom with holes. I took the lid which is 1/2" deep rim, set the little tote on top of the lid and poured 3" of perlite, soaked it down and ferrowed in the seeds.
I planted 2 rows of Delphinium, 3 rows of Lobelia and 4 rows of Pansy's. The perlite was easier then I though to work with. I tryied to sink some in a glass of water and after 30 minuts, would not sink, but after watering down 3" of mass it becomes quite heavy and dose'nt float in 1/2" of water. I am hoping that when the plants get 3" tall I'll be able to pull then out and put them in the hydro ( did you see my pic's?)
Can you pull them out of the perlite and rinse or do you rinse the prelite off as if they were in soil. I mean should I dig them out and rinse them off? My system will only take 3" seedlings.

RE: Foam Rubber as a growing medium? Newbie Questions!

I read you're talking about planting seeds, here's a place to go to.

Here is a link that might be useful: STARTING SEEDLINGS

RE: Foam Rubber as a growing medium? Newbie Questions!

Edurink. Thanks for the link. Very usefull. I'll have to try planting them like that but I was in a rush to get them in. the flowers I planted take weeks to germinate and I wanted to get them going. Now I got time to find some planting cups that will fit into the grow cups. thanks again.

RE: Foam Rubber as a growing medium? Newbie Questions!

For: pepperbox

You are most welcome. I am beginner myself. The ideas in my website are just a synthesis of what I observed and learned from various sources.
Wish you the best in you undertaking!


RE: Foam Rubber as a growing medium? Newbie Questions!

There's no need to rinse off the perlite. I actually recommend that you keep some perlite in your system in case of an interruption in flow (power outage, plugged emitter, etc...)
The perlite will provide a reservoir of nutruients and water until flow is restored.

If you wanted to grow bare-root NFT then you could, if you wnated to swidh the roots gently in water to remove most of the perlite.

I didn't see your pictures, where are they?

RE: Foam Rubber as a growing medium? Newbie Questions!

Thanks for the tip on the perlite. The foam rubber did not work. The seedlings died after ten days. I checked by ripping opening one of the squares. The perlite flat I made is germinating in only five days. My pictures are in the (new hydro pic's thread). Thanks again Joe

RE: Foam Rubber as a growing medium? Newbie Questions!

OK, I see your pictures. With that diameter pipe you are going to be restricted in what you grow. I recommend herbs and lettuces.

You might try growing an assortment of different greens densely seeded in the cups to make up a mesclun salad that is harvested at the 2-3" size. By densely seeded I mean 3-4 seeds per inch. Yes, per inch :>). You can buy a premixed seed mix to begin with, such as Johnny's Seeds All Greens mix below. You can pair it up with some lettuce. If you do this I would recommend their All Star Gourmet Lettuce Mix Gourmet Lettuce Mix&cat_id=407&topcatid=1&subcatid=27&subcatid2=407&subcatid3=0&search_keywords=mesclun&ct=hg&pagename=resultdetails.html

Start the lettuce one week ahead of the grens and they will all be ready to harvest after about 3-4 weeks. You can "cut and come agian) 2 or 3 times, then you need to tear out and reseed. Even quicker and sturdier than lettuce, and you would never know it isn't lettuce in a mix, is their Tokyo Bekana cabbage.

Bon Appetit!

Here is a link that might be useful: All greens mix.

RE: Foam Rubber as a growing medium? Newbie Questions!

AdrianaG The all green mix looks very interesting. The only thing is I made the garden for my wife for flowers that she drys and presses for her crafts. Most of the flowers that she uses are the smaller ones. I guess that what your saying in your last post is that large plants with lage root systems will choke the flow of the nutes? The largest plant we'll be growing will be delphinums in the bottom row in every other hole. The spacing will be 11". I am hoping the roots will stay small.

RE: Foam Rubber as a growing medium? Newbie Questions!

Yes, things like tomato plants will definitely plug the entire channel. Growers have chased the roots 20 feet down the lengths of their drains.

Aren't delphiniums fairly tall plants? You will need to work up a trellis or some sort of anchor - I have no idea of the root mass of these either, so you may be in for possible plugging there too.

RE: Foam Rubber as a growing medium? Newbie Questions!

  • Posted by amar z5 IA (My Page) on
    Thu, Oct 28, 04 at 1:50

Hello Amylama

I live in Iowa as well. I'm in Ames right now and I am attending Iowa State University. I guess you aren't too far away from here. I know a couple of guys in my class who are from Sioux City.

You have some interesting questions and I hope I can be of some help. I am not sure what you are referring to when you said Oasis foam. Are you talking about rockwool or those "rubber dirt" plugs? Because they are quite different but they both work fine.

I understand your problems here in Iowa there is not a single hydroponics store. This has been a big problem for me and shipping is incredibly expensive for most things. I hate to bring you bad news but you should know that hydroponic nutrients are very expensive and you go through the container very fast. I bought some fert on sale for a very good price only to find out that a bottle (quart) lasts for less than a month. It is very costly so I suggest learning how to mix your own as soon as possible. I am going to do this when my bottles are all gone.

I am lucky because my brother lives in Chicago and when he visits me I have him bring whatever I need and it saves me money on shipping.

I like lava rock, perlite, vermiculite, and anything else I can buy locally. I found a great mix consisting of equal parts perlite, vermiculite, and lava rock. But the lava rock in this mix was very small even smaller than pea sized it was very fine (Can't think of anything to compare the size to but believe me it was tiny). Anyways this mix was great and it supported the plants better than soil and it drained well.

I suppose you could use a similar type of mix and use recycled containers with a simple drip system on a timer. This type of setup is not too expensive and the medium is reusable for a while. I haven't seen the setup for the bubbler system on your link but if it is cheapest then go for it.

I like the method I just talked about because the plants can be supported very well and it is simple. Drip irrigation is pretty cheap if you shop wisely. I found a water pump on ebay for 5 or 6 bucks and a digital programmable timer for 7 bucks (I got the kind you can set 14 on/off settings per day). So far not too bad, the rest is cheap (tubeing, drip emmiters, stakes, etc.) and you can get it from an online source and shop around. Don't buy pumps or timers from hydro stores they are really expensive. Play the ebay game and don't give up thats how I saved money.

Have you checked your pH yet? I don't know how well the aquarium pH testers work but I assume they should be fine as long as you can tell what pH you have. Check to see how accuarate it is by looking at the intervals of measurement. A tester that goes 5 to 6 to 7 to 8 is not as good as 5.5 to 6 to 6.5 to 7 makes sense. I have a digital handheld pH tester and it works great but it cost me 70 bucks. It is very crucial to test your pH often when you are new to hydro. In my opinion it was one of the most challenging aspects. It just isn't consistent and it was never predictable. Sometimes it jumps up or down for no apparent reason. I have become more comfortable with pH but it still is strange.

I have a great system for cuttings/clones and it is very cheap and simple and it works great. I will post with that system next time because this post is very very long already. Hope this rambling has been helpful.

Good Luck.

RE: Foam Rubber as a growing medium? Newbie Questions!

I use a good old kitchen sponge - not cellulose, but cheap sponges from the dollar store, cut into 2" squares, to start seeds and cuttings. I wet the sponges with fertilizer water, place the seed or cutting in the sponge cube and place the whole thing in a gallon jar and a well-lighted window. My method works great! When the seeds sprout and unfurl the first leaves, I pot the whole shebang in a 4" pot and treat as usual. The cuttings root very well (and fast), and I just am amazed at how quickly everything 'does it's thing'!

RE: Foam Rubber as a growing medium? Newbie Questions!

Hydroponics is not about a cool store with gadgets. It is thousands of years old, and intuitive when you think about it. You do not need coir bricks or rockwool cubes (*even though both are great). Get a bag of coarse sand from the hardware store, bbq briquettes (*lava NOT charcoal), wood chips (*orchid mix), gravel, rice hulls, compost, untreated saw dust. Heck you can even ditch the medium if you want.

While rubber on its own isnt all that, recycled automobile rubber is called Malpita in Holland, and its use is growing.

Sponge as propagating medium


I happened to notice your post on using sponges (but not cellulose) as a growing medium. I've used cellulose sponges (those ones that come dried and flattened) to 1) root a Christmas cactus 'leaf', and 2) warm stratify some Grancy Graybeard seeds (took seven months before they germinated, but it worked!). I'm thinking I'd like to test this more seriously, but I was wondering why you specifically mention not using cellulose sponges. Are they simply more expensive (I got mine in a big bag at a local dollar store)? Or do they not work as well?

Thanks! It's great to hear that someone else has positive experiences with sponge as propagating medium!

RE: Foam Rubber as a growing medium? Newbie Questions!

For dontsleep,

You are absolutely correct. Hydroponics is growing plants without soil. Whatever medium one uses is merely to support the plant. True hydroponics does not need any medium at all. You can even use a lowly rustproof paper clip to hold the plant above the nutrient solution. The true challenge to the hydroponics enthusiast is to do it this way. The sponge e.g. in the DWC or bubbler is wrapped around the stem of the plant to hold it in place. So, the roots don't grow into the sponge. What inspires me most is to see plants with thick dense roots growing in nothing but the nutrient solution in a system

RE: Foam Rubber as a growing medium? Newbie Questions!

Hi Amylama,

If you want to get serious about growing vegetables hydroponically, please have a look at my Australian web site, below.

As for the question of using foam rubber as a growing medium ... forget it. The accelerator residues in foam rubber are derivatives of Mercaptobenzothiazole which is not nice to taste, even at 1 part per million. Then there is the residue from Sodium silico fluoride that sets the foam up before it is vulcanized. These chemicals are not kind to seeds trying to germinate.

If you save each page of my web site, as its own name, to your computer, all in the one directory, then you will be able to navigate from page tp page in a flash when you are off-line.

The site shows how to make a simple system using sand as a medium, how to make your own nutrients and adjust them, hints for success, an FAQ page and links to other hydroponic web sites (none of which appear to use sand).


Here is a link that might be useful: Simple Sand Hydroponics

RE: Foam Rubber as a growing medium? Newbie Questions!

I have an aero garden too and I am also trying to start seeds

Have anyone used the car wash sponge as grow sponge in aero
garden ? I just read some of the responses , there are people
using diffenent type of sponge ( from craft store or kitchen
sponge) , but I am wondering if anyone used sponge for car
wash, they are very light weight with big holes should absorb water and maintain moist real good.

If anybody has tried them , please give me some feedback !!

RE: Foam Rubber as a growing medium? Newbie Questions!

Kind of an old thread to jump into there.

I don't know about car wash sponge.

I've started seeds on very easy every day items like paper towel or cotton balls. No need to buy an extra special item for the purpose.

Oh, and as far as not having specialty hydro store media you can buy. I've used wood chip mulch as media in systems before.

foam cups work but instead of buying new ones for the purpose, I re-use old yogurt cups. Heck, I've already bought them and they would be getting tossed in the garbage as they are not recyclable here.

Here is a link that might be useful: My hydro page

RE: cut up carpet pad under plants.

We are in Okla experiencing a terrible drought. Replacing our carpet and wondered how the foam pad would work buried under plants. Anyone ever do this??

RE: Foam Rubber as a growing medium? Newbie Questions!

I use polyurethane (low density) cubes for lettuce. I score the top of each sheet in a grid pattern using a circular sewing pattern knife (looks like a pizza cutter).

I put the foam in a flat storage tote containing an inch water that has been sitting out overnight to de-gas the chlorine. I squeeze the air out the foam to get it thoroughly wet, sprinkle the seeds on top, then cover the tote with it's white translucent lid to keep the seeds moist. Every 24 hrs I open the lid, mist the seeds, close the lid again. For lettuce,I also leave a daylight CFL lamp shining on the lid to help it germinate.

After 3 days I open the lid and remove the excess standing water. By now the foam retains about 50% of it's maximum capacity, plenty for the lettuce seedling once the roots penetrate that far down (by this point all the seeds have germinated)

I continue misting once a day for 4 more days. By then the roots have reached the bottom of the cube, the cotyledons are fully open, and I move the seedling to the half strength recirculating hydo solution tray, which has about 1/2" of solution continuously flowing through it. A week later and the roots are hanging an inch or more out the foam, the first real leaves have opened, and it's ready for transplanting.

Different plants will require longer to sprout, and/or may prefer less moisture while germinating. Some need heat, some may need to be kept dark. Lettuce likes it cool, moist, light and airy. The fun is figuring each one out!

RE: Foam Rubber as a growing medium? Newbie Questions!

I have been planing to try the polyurethane foam as well. I have looked around for the sponges, but cant find them the right price. Carpet foam may be a bit to dense, but they come in all types of materials. Though as Thaihydrofarmer mentioned you want to use a low density foam to get good aeration to the roots. I haven't yet went down to talk to them but they use those type of polyurethane foam sheets in furniture repair, so that was my next place to look. I basically plan to use it as described by Thaihydrofarmer for the mass sprouting like the green onions I plan, but also want to use it for smaller scale sprouting as well on others seeds. I have been meaning to try cotton balls also, just to see how it works because I already have a bunch. But I already know it will be important to make sure they don't become waterlogged one way or another. But their cheep and readily available, so it's worth trying out.

RE: Foam Rubber as a growing medium? Newbie Questions!

Are you anywhere near Des Moines, IA? If so check out Infinite Season.

Here is a link that might be useful: Infinite Season

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