Searching for the ultimate tomato seedling container

Westbrook, CT(Zone 6a)

When I started growing tomatoes, I transplanted the seedlings into standard 6-pack cells when they got their first true leaves. This worked ok if they didn't stay there too long, but when I found that the plants did better if I waited an extra week after the last frost date to set them out, I found that they tended to become root-bound in the small containers.

I tried several alternatives. Paper cups (8 oz with holes punched in the bottom) gave the roots more room, but were a little wobbly and the bottoms tended to rot out when standing in a tray for bottom feeding. Some 2x2x6-inch hard plastic cells that held mail-order plants had plenty of room for roots, but it was difficult to extract the plants. Ronaash Root-trainers produced excellent root systems, and it was fun to open them and see how the roots developed, but they were spaced so close to each other that when the tomato plants reached a foot tall, their tops became so tangled that I sometimes broke the stems trying to separate them.

One day I was opening a 10-oz can of frozen orange juice, and happened to think that the empty container was just about the right size for a tomato seedling, so I started saving them, and this year when tomato planting time came, I had about 20 of the OJ containers. I punched holes in the metal bottom with an old ice pick, filled them with a good moistened grow mix, and transplanted the young seedlings into them, burying the stems as deep as possible. I put them into two trays, 10 apiece so as not to crowd the plants, and watered them from the bottom. When they got too big for my light frame, I moved them outside into a plastic pop-up planthouse.

A flurry of events caused me to postpone transplanting the tomatoes in the garden until May was half over and some of the tomato plants had reached 18 inches high. Nevertheless, they were all growing well, the sturdy OJ containers held them upright (only one flopped over), and when I set them out, by pulling at the spiral seam on the cardboard sides, the containers unpeeled easily, revealing a good deep root system which was better developed than the extra plants I plunked into 6-packs when I ran out of OJ containers.

If you are an orange juice drinker, I recommend that you try this yourself. I have already started saving the containers for next year. One oddity was that many of the cans developed tiny mushroom growths at the bottom rim where they sat in the watering tray. It didn't seem to affect the tomatoes. Sorry I didn't take a picture, but I was in a rush to get them set out and didn't think of it.

Stamford, CT(Zone 6b)

I start out with the largest cow pots or peat pots I can find (4 or 5 inches in diameter) with about an inch or less or potting mix after the seeds germinate we keep adding a bit of soil. As they continue to grow, we add more and more soil, and the seedlings get stronger. We take them out for a few hours to harden them off or keep them in one of the vans where they seem happy. When it is safe, we take them out for all day, and if it looks like it will get too cold, they go back into the van overnight till the frost threat is over.

Liberty Hill, TX(Zone 8a)

I have thought many times about trying those root trainers. Thank you for the heads up, I guess I don't need to bother.

Everett, WA(Zone 8a)

Hmmm, "10 ounce". How many inches deep is that?

I'm thinking that OJ containers are deeper and skinnier than an 8 ounce Dixie cup.

Westbrook, CT(Zone 6a)

Good guess! Frozen OJ and Lemonade containers are both about 4 5/8 inches high.

Dearborn, MI

I tried something new this year. I had been using plastic 16 oz cups from the dollar store but they were too tippy. I used the styrofoam soup cups from Gordons Food service. I could write the names in ink right on the containers, the bottoms pierced easily with an pencil, and they were much less tippy. I started with the 32 ouncers, but that took a lot of soil. I planted most in the 16 ounce size. Saved time of printing labels, and drilling out the bottoms. Figured there was a little insulation for the roots, too.

Saylorsburg, PA(Zone 6a)

I started my seedlings this year either on damp paper towels, toilet paper holders, or Burpee trays. Once they had the first leaf I transferred them to 16 oz clear or red cups from the Dollar store. I only filled the cup 1/3 to 1/2 full and kept adding coir and worm castings as they grew. The clear cups are great because you can see the root development. They all did great. The cups can be washed out and saved for next year. Much easier than using the larger pots I used to use since they required so much more soil. I also liked being able to write the names on the cup.

Everett, WA(Zone 8a)

I like the idea of tall and skinny pots, as long as I'm not potting up from one pot size to another too much.

And I agree that "tippy" drives me crazy. The only solution I found was to use relatively small cardboard trays with tallish sides, line them with plasitc bag, and avoid overwatering. If I pack them in tightly, and they JUST fit, the sidewalls keep them from tipping.

But then, remove a few cups, and they tip.

My counter to that was to repalce each removed cup with an empty cup (sometimes turned upside down).

And when I have several different sizes and shapes of pots, I can pack one tray tightly by using some of a different size to "chink" the holes.

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Everett, WA(Zone 8a)

I should say - these are not tomato seedlings, just random flowers early in my seed-starting c areer. Now I mostly use 72-cell 6-pack inserts, or 50-cell prop trays, or 128-cell prop trays.

But those all need to be potted faster than I get around to it!

For now, I pot up to 3" or 3.5" square, molded flimsy plastic pots, just becuase Home Depot and a local nursery threw lots away and let me take them home.

But Yogurt quarts are good for bigger plants.

This message was edited May 30, 2012 7:24 PM

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Richland, WA(Zone 7b)

Go to a garden shop and ask for empty flats that small cactus plants come in- the holes are perfect for the small dixie cups. I have several of them- no tipping!

Everett, WA(Zone 8a)

>> no tipping!

Great tip, bujt I had to read that twice. I thought you meant they gave you the used without your having to give the clerk a tip!

Richland, WA(Zone 7b)

LOL, corey- so far I haven't tipped any garden shop employees, but it could be a good idea! Our Lowe's people are just so helpful and nice to deal with--

Westbrook, CT(Zone 6a)

No tipping! That's a good tip.

Chico, CA

I put my seedlings in various size cups and to prevent tipping I get some cardboard 'vegetable' boxes from COSTCO and drill holes in them with a hole saw and have a tip-free place. another benefit is you can lift the box with all the cups in it and take it outside or whatever.

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Mackinaw, IL(Zone 5a)

Drkenai, I cracked up when I read your description about cutting holes in "vegetable boxes" and then opened the pic to see an M & M box. Those are my kind of vegetables! Though I love real vegetables just as much...

Carrollton, TX(Zone 8a)

Once I read someone’s post on DG saying that they used clear plastic cups for potting up their tomato seedlings. I thought that sounded like a good idea since I could then monitor how the root systems were doing and maybe that would give me some insights into things like when it was time to water them or even when to start hardening off the seedlings in preparation for planting them outside in my raised beds instead of going by the stem size and height of plant. So while at the grocery store this afternoon I purchased a package of 48 - 16 oz. clear plastic cups to try it out. The 16 oz. seemed to be the correct size since they are pretty deep and can accommodate an extensive root system but did seem to be sorta top heavy. So all the way home I was worrying and trying to figure out how to keep the cups from tipping over in the tray I will keep them in. Not to worry, all I had to do was read the latest posts on DG where the topic was being discussed.

Every year I discover little ways to tweak my system to make it a better but it never reaches perfection which of course is my goal. And I’d better hurry up and find that perfect system ‘cause I’m starting to run out of years. :)

Chico, CA

Booker - OOPS - now all the vegatarians and sugartarians are going to be upset with me. I thought most of them were from vegatables, and I think the ones in the second picture are. They are really very sturdy boxes and always plenty at COSTCO.

Snellville, GA(Zone 7b)

Has anyone tried the "Tomato Pot Makers" that you roll newspaper around it to make a pot. They are made of wood and look like a baker's small rolling pin. I'm half tempted to buy one (arounf $8-10) but would like to hear about their success or failures.

Richland, WA(Zone 7b)

I have tried just about all the gadgets in my 50 years of gardening, and found most to be more trouble that they were worth-including the newspaper deal. If you want to be crafty, save toilet paper rolls, and fold in one end to make a bottom, put a piece of tape to hold it and filla tray with those. The problem with things like that is that they become soggy and unstable after awhile. My favorite is 5oz. clear plastic cups from WalMart with 3 holes in the edge at the bottom- I use an old woodburner tool to make holes. You can see the roots as they grow. To hold the cups upright I scrounge the flats at garden shops that hold the littls cactus plants-the size is perfect.

Snellville, GA(Zone 7b)

I've been pretty fortunate in that I saved all those 4" plastic pots that my wife buys in flats of her posies over the years. Problem is that I got to clean all of them before reusing. And it seems that no matter how mannyi have I am always short one or two pots when it comes to transplanting. But the toilet paper rolls do work in a pinch.

Richland, WA(Zone 7b)

To me the 4" pots seem too big as a first pot size- I love the 50z cups.

Everett, WA(Zone 8a)

I saw some video (You-Tube, I think), where someone rolled newspaper pots using a soda bottle or yogurt cup as a form. She used an open end on the plastic form to fold the bottom "in". It seemed like a lot of excess paper as the bottom.

Then she pulled out the form, and squished and jammed the bottom flat from the top-inside of the pot.

I've never tried it. I haunt Home Depot around the end of the season, until they throw away / give away empty plastic pots, usually a lot of square 4" pots. Then I re-use those until I give them away. When two pots have big crocks, I nest them together with the cracks on opposite sides. Maybe I use a little duct tape also, but not usually. In principle, I would rather give seedlings away in my older pots.

I used to know a nursery where they discarded all pots in a plywood bin that customers could scrounge. I get some big pots there! Of course, all such pots need extra cleaning and disinfection.

Allen Park, MI(Zone 6a)

I also save any 4" pots that I come across.
I sterilize them in a 10% bleach solution to make sure that there are no fungus or bacteria present.

Everett, WA(Zone 8a)

I've been saving 20 ounce, 3" diameter "Sobe" bottles because the walls are straight and not wasp-waisted. There are only two shallow grooves visible and I thought I could cut the top one off and tap a root ball out past the bottom one. I would still have a pot 4 3/4" tall.

Unfortunately, when I cut the label off, I found three more deep, square-edged grooves that would mess up a root ball really badly.

So now I'm thinking that I will also cut a slit about 80% of the way down the bottles' wall so I can pull them apart apart like a clam shell when I want to pot up.

And I'll sit the 1 1/2" wide bottle cap on the bottom of the bottle, before filling it with soilless mix. Then I can use a pencil or dowel to push on the bottle cap like a plunger. That should eject the root ball in one piec e!

Mackinaw, IL(Zone 5a)

The plunger idea is really clever. Now you've got me thinking.

Everett, WA(Zone 8a)

For a while I thought I would add little wicks of cotton butcher's twine to some cells, and then be able to tug them out ... "root ball on a string". Instead i made better-draining soilless mix .

Richland, WA(Zone 7b)

Rick, I always get a chuckle from your posts- sounds to me you are trying to make a big job of this gardening thing! :-)

Everett, WA(Zone 8a)

I do like to fiddle.

If it was just "toss the seeds and watch them grow", I never would have started gardening.

Waaaay Down South, GA

I cut the top off 16 oz water bottles and start my seeds in those. When they get ready to repot, I slit it down on each side and gently remove it and place it in a 2 lt. bottle that the top has been cut off. I can write the names on them. I've been doing this for 3 years ... after trying several things, this works the best for me. At this, they're ready for the garden.

Oh, I forgot to mention, I do punch holes for bottom watering. The water bottles are easy to pierce, though.

No matter what you do, happy growin!

Richland, WA(Zone 7b)

I know exactly what you mean, Rick- I am always coming up with a new way of doing things too! It keeps it interesting!

SE Houston (Hobby), TX(Zone 9a)

Yep. Straight-sided drinking water bottles is the way to go, after starting multiple seeds in 4" seed pots, then, thinning the herd at potting up..

#1 My stash for this season (I only use the straightest sided bottles. Sam's Club and Costco drinking water bottles are the straightest!)
#2 "...a thousand words..."
#3 My trained co-workers' offerings to me, LOL! (I've gotten more car surprises than you could imagine!)


This message was edited Jan 17, 2013 11:38 AM

Thumbnail by Gymgirl Thumbnail by Gymgirl Thumbnail by Gymgirl
Everett, WA(Zone 8a)

>> I cut the top off 16 oz water bottles and start my seeds in those. When they get ready to repot, I slit it down on each side and gently remove it

My "Sobe" bottles have such rigid sides, with those deep grooves, that I think I'll b e OK PRE-slitting the sides.

How do you slit them without cutting the root ball? A cardboard cutter mostly retracted, or do you just have a steady hand? Or use scissors? I have a nice pair of tin snips.

SE Houston (Hobby), TX(Zone 9a)

You could use ALL of the above, with a steady hand...LOL!

I use a box cutter blade (mostly retracted).

Everett, WA(Zone 8a)

Thanks ... my hands are so far from steady, that my handwriting looks like I was driving over potholes.

Waaaay Down South, GA

Linda, that's what I use, also.

Hornell, NY(Zone 5a)

I've grown tomato plants in just about every junky container imaginable. Yogurt is my favorite one, but I also like the small cheese and margarine containers, too. Once I planted one in a giant 40 oz "Super Slurp" that already had baby tomatoes on it. My large extended family knows me well enough to "recycle" them to me as well. Maybe that's because I give them all nice transplants in mid-May..

Truth is - just about anything works.


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SE Houston (Hobby), TX(Zone 9a)

Those sure look good! Did you remove the lower branches on purpose, or did they fall off? Nice and neat for transplanting out with the lower branches already removed.

Nice touch!


Hornell, NY(Zone 5a)

I do trim them off somewhat more before planting, also they just look better when trimmed. This photo was for a school project about planting with recycled materials.

Thanks for the comment.


Nauvoo, AL(Zone 7a)

I like the 2 liter soft drink bottles. And I like it cause it is clear so you can watch the roots grow and tall and slender to bury deep. I always had a problem getting the soil to turn loose from the sides when it was time to transplant. but I recently came up with an idea for that based on someone elses idea but haven't put it to the test. First I want to explain how and why. Giant Pumpkin growers grow their pumpkin plants early in large 1 to 3 gallon pots but they have to get the plants out without disturbing the roots so they cut the pot down in half and tape it back together on the outside only with duct tape. When it comes time to transplant, they remove the tape and pull the the pot apart. I think the same can be done with the 2 liter bottles. Just a thought.

SE Houston (Hobby), TX(Zone 9a)

And, a very good thought at that!

After my first losing battle trying to extract a large seedling from a 3-liter bottle, I vowed not to do that again.

Plus, the bottles use an awful lot of Potting mix, and I don't need seedlings that large before transplanting out.

How big are your tomato seedlings at transplanting out?

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