Plug Trays - Anyone using these?

Central, TX(Zone 8b)

I start herb and vegetable seeds using 50 cell packs or community pots to germinate them until I can bump them up to 4" containers for growing on.

I'm curious if anyone is using 128, 144, 288, 520 cell packs for starting seeds, if so, what seeds are started in which size cell pack? Whenever I visit greenhouse/nurseries that start their own seeds I see numerous small cell packs with hundreds of plants started this way before being bumped up. Makes sense that an individual plug can be easily lifted and popped into a larger container however placing seeds into each cell by hand will be a daunting task!

My seed starting arrangement consist of a 5 shelf metro rack equipped with 2, 4' shop light fixtures per shelf and seedling heat mats with thermostat to control bottom heat. If it's possible for me to use the same space to produce more seedlings without the hassle of "picking them out" of community pots, I'd like to give it a try. Nothing speaks like the voice of experience though - please chime in?

Oh, the web site where I saw these is:

Thanks a bunch!

(Pam) Warren, CT(Zone 5b)

I cluster sow many seeds in 4" pots, then prick out the seedlings when they are still quite small and the roots are not yet tangled. I also germinate quite a lot of seeds with the Deno, or baggy method. I put the seeds on a dampened paper towel, then in a Ziplock bag, and plant them as they germinate. I use this method on many annuals and perennials, especially on seeds that need to be chilled to break dormancy. It's also good for moring glories (after soaking) and Sweet Peas.


Galesburg, IL

I use 128 flats for growing my onion transplants. Been doing this for about 4 years now with great success. I don't step the onions up to larger pots, once they have 3-4 leaves they have a large enough root mass for transplanting in the field. You do need to watch watering with the smaller cells and make sure you have a fine enough soil-less mix to completely fill the cells. I've also used them for sowing native grasses.

I wouldn't use them unless you are sowing a large number of one type of plant. Differential germination of different species makes using them a nightmare. I would also only recommend them for species with high germination so you can sow singles and not have to worry about thinning plants out of the closely spaced flats. I don't like sowing multiple seeds per cell unless you know you have very low germination tests. I would rather have empty cells with no germination than have to thin every cell in a flat (whether it is a 128 or a 32) Personally, I only use them when both of these conditions are met.

A couple of years I used them to sow several different species of native wild flowers. I was just getting my prairie started and wanted to have some cheap transplants in addition to my field sowing. I mixed species in flats and it was a problem with differential germ times. I did it because I was germinating >25 species and didn't want to have that many pots to keep track of while they were being stratified outside over winter. Wouldn't do that again.

I would never use anything with smaller cells than the 128. Smaller cells in those flats require a higher level of management, are almost impossible to properly seed without a vacuum seeder and are a real pain to transplant.

I'd also point out that you can not "easily" lift the plugs to step them up to larger pots. Seedlings that are small like that don't have the size or mass to be able to lift them. They need to be pushed up from the bottom with as large a dowel as you can fit in the center drainage hole - one by one, one cell at a time! Growers who are using plug trays have equipment that will push all cells up at once for transplanting.

Plug trays can be a great space saver, but you need to think about how you might want to use them. If you are planning to try them to increase the number of seedlings you will grow, you also need to plan for where to grow the increased number of seedlings when they need to be stepped up and they still need to be under lights or are too small to be moved outside.

I don't mean to be totally negative about the flats, they can be a valuable tool for the small grower/homeowner in starting plants, but they will not work for all plants in all systems.

Calgary, Canada

The 128 cell plug trays are useful for just sprouting seeds before
transplanting outside. I have done dwarf marigolds that way.
They are not useful for anything to be kept for a long time.
I would not use anything smaller than a 128 cell tray.

Everett, WA(Zone 8a)

I use a 128-cell tray when I have a lot of seeds to start. Salvia, Delphinium, Petunia. My downfall is being to busy to pot them up when they're ready, and lettin g them get rootbound.

You do have to water or mist them fairly often.

I cut mine up into 4 or 5 batches of 3 or 4 or rows. Those are stable enough that they don't tip over. And they are small enough that each batch can have the same variety or species of plant. Thus they germinate and are ready pot up around the same time. My main reason for cutting up the big prop trays is that I can tilt them over while pushing them from the bottom.

I recently found a DEEP prop tray of 50 cells (5x10 rows). These are 4 1/4" or 4 3/8" deep! I don't worry as much about a little water perched in the bottom, or sowing a seed 1/2-3/4 deep and "wasting" half the dpeth of a cell.

Baltimore, MD(Zone 7a)

In one of my earlier garden-related jobs, I worked for a big, wholesale grower for a year and a half.

They had a mechanical seeder that placed one seed in one plug hole in large plug trays (more than 128).
These trays were all laid on low tables in the "transplanting Greenhouse".
They were watered with a regular fine, shower-type hose. Huge numbers of these germinating trays filled half the G-House.

I was hired to transplant the plugs into market packs. The pressed paper kind--not cell packs.
We worked right off a wagon-full of their own made, and sterilized potting mix. There were 3 of us.

I am telling you all this because the small, germinated and growing seedlings (less than 1" tall) were easy to remove
by hand from the plug trays. No poking from below was ever done.
We would just pull them out by their tops and pot them, 6 to a market pack, in finger-holes and send it on
to be watered in on a conveyor belt. Each "flat" held 10 market packs. We were paid 70 cents for each flat we filled.

I stayed on there after the seed transplanting and worked caring for, and watering 5 of their greenhouses.
Also--taking cuttings and propagating plants
That was enough--I had to get out of there after a year and a half.
I felt like I was an extension to the hose....:o). But I loved plants and took very good care of them.
Not everyone has the chance to work for a grower--where there is so much to learn. I sure did!


Central, TX(Zone 8b)

Thanks everyone for sharing! I've picked up great pointers for managing 128s which seem to be the best size for me.

Gita...I particularly enjoyed your "hose" comment. I've toured more than my share of big name greenhouses and have seen nursery workers hurriedly performing repetitive task. Despite automation a GH still needs people to get those thousands of plants out the door!

Kiowa, CO(Zone 5b)

I have been using various sized flats for seeding annual and perenns for years and just love them. Most were retreived from a nursery who recycles pots. Have pix but post a pix is not showing let me try again.

Kiowa, CO(Zone 5b)

I have been growing most of my plants to fill my English Cottage Style borders with seedlings (45ftwide x 100ft long), and let me tell ya it takes vast amounts of plants! Good luck!

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