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Greener Thumb
Posts: 1989
Joined: Sat Apr 16, 2011 8:48 pm
Location: Monterey, CA.

Seed starting up potting progression?


When doing your seed starts what size do you start in then what do you up pot to next?

I read somewhere that someone uses egg cartons as seed starting cells. For how long would you grow the plant here before you up pot to another size? And what size would be your next size?

I am looking for a progression from seed start all the way up to final pot size before you transplant to the ground.

If possible, would be helpful if you could post for things like tomatoes, peppers, herbs, flowers like marigolds, nasturtiums and sunflowers, and veggies.


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Super Green Thumb
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Joined: Sun Sep 26, 2010 1:10 pm
Location: ID/WA! border

Here's what I do. I am sure that there are many other approaches to this.

I start most everything in cookie boxes - you know, those clear plastic boxes you get cookies in at the bakery. The smaller ones for muffins, single-serving cake and sandwiches should be suitable for most gardeners. I've found that the bakery people are usually happy to sell these empty but I try to help them out by buying them full ;) . Just keep collecting them in a corner of the garage.

When the 2nd set of leaves (1st true leaves) show up on the seedling, it is usually about time for a larger container. Most things go in a 48-cell insert and a tray. Snapdragons and some smaller, slower-growing plants (like the perennial herbs) can go in 72-cell inserts.

Yes, I often transplant sunflowers. They start off in the 72-cell inserts, 1 seed in each. Cucurbits (squash, melons, cucumbers) go 1 seed each in 48-cell inserts. The idea is that I'm setting these plants out in the garden after just a few weeks. They grow quickly and do not transplant easily.

Tomatoes will be moved from the communal cookie box into 48-cell inserts and then, usually, into 4" square pots that can go 18/tray. Those pots are good until the plants are 8 to 10 weeks old altho' the final couple of weeks it would be best if they aren't packed so tight as 18/tray.

Hope that gives you some ideas.


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Super Green Thumb
Posts: 25279
Joined: Sun Feb 15, 2009 6:04 pm
Location: TN/GA 7b

I use the 10 x 20 trays:

with the 48 cell inserts:

The point of the trays (besides making the whole operation a lot less messy) is that you can bottom water. Just put a little water in the tray and let the potting soil soak it up. Avoids a lot of problems with damping off, etc.

For things with small/fine seeds, they are sown thickly in the little cells. For things like tomatoes and peppers, probably 2-3 seeds per cell, for squash one seed per cell.

All the plants that are grown crowded in the cells, will get transplanted to be one per cell. Then they are transplanted to 3.5" square pots, 18 to the tray:

The squash and other large seed plants that are started one per cell will go directly to the pots.

The reason for planting them crowded in the cells is that I have two heat mats. A lot of the stuff I grow germinates best on the heat mats, so I need to have as many seeds as I can on the two mats. I don't want to run any more, re the electricity use, so I use them efficiently. Once the seeds are well started, they are moved off the mats.

I don't usually pot up any more than the 3.5 in pots. After that, they go in the ground or the large container they will stay in. Any bigger and I wouldn't have enough room under my lights for all the plants.

If you scroll down to the bottom of this page:

there are pictures of my seed starting operation, showing the trays, pots, blue heat mats, lights etc. Those pictures were early in the season. Before the end of seed starting season, every square inch of space under all those lights will be filled with trays of plants.

I do get my supplies like this from greenhouse megastore. I have found them to be about the best price, high quality, fast service.

Green Thumb
Posts: 588
Joined: Thu Jul 14, 2011 5:19 pm
Location: Pacific NW

egg cartons dry out too fast and often you lose the plant. Anything large enough with drainage holes will work. I have used flats, commerial cells, 1/2 gallon milk cartons cut to yield a long planters, filled tp rolls cut in 1/2 and so forth.
Personally I don't like to move plants anymore than absolutely needed. Each move sets the plant back some and there are risks. Except for tomatoes, eggplant, peppers, I try to start the plants in the size container I am going to leave them in until I plant out. For most thing a 3" recycled nursery pot that has been cleaned works well.

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Green Thumb
Posts: 456
Joined: Tue Jun 21, 2011 11:42 am
Location: North Central Illinois

I like using the "jiffy" pellets. Just give them a good soak with warm water, You can see them expand. I then open the tops of the netting and lay it over the top. They are the best bet for germinating seeds. Water from the bottom and they soak up water fast. They are easy to handle and too seem to do well with transplanting to a larger pot. Just take off the netting before doing so, it's quickly done. When transplanting to a larger pot they seem to stay intact and don't fall apart leaving the plant and it's roots in your hand. They say they are digradable but I could not agree with that. If your roots grow too quickly just trim the netting down to the roots, do not pull the netting this will cause breakage to the plants roots.

They may be a bit pricey but give less trouble in the long run. When time to transplant just go with a suitable pot 1" larger than the seedling.

Super Green Thumb
Posts: 2437
Joined: Mon Nov 15, 2010 10:31 pm
Location: Latrobe Pa.

I also like watering from the bottom! My main problem was that I used 12 by 15 foam boxes to start all my seeds. I would thin them and leave 2 dozen in the boxes till may when I set them out! This year I have something different .
I bought summer things at the dollar store that they were getting rig of along with the seeds at 90% off. I bought 10 small hard plastic swimming pools for 80 cents each! They are about 4 foot in diameter and a foot deep. ! I will put about 3 inches of water in them and set my boxes in them. The swimming pools also hold more heat in them! It should work!

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Greener Thumb
Posts: 1855
Joined: Thu Jan 22, 2009 8:40 pm
Location: N. California

I start out with 200 cell trays, then move them to 72 cell trays. most of them go out from there when filled in but some things like tomatoes and peppers for sale and for warmer planting dates will go into something like a 4 inch pot. I don't like to start them early enough where they have to go up to a gallon pot. its a waste of space, time, energy, etc at that point for me.

bigger seeds need to be started in the 72 cell trays (beans, peas, nasturtiums, squash, stuff like that) they are usually started later though.

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