Hello everyone. My question is regarding the 72 plug propagation trays and starting seeds in them. I have started several wave series petunias, impatiens, and alyssum in these trays for planting around my home once spring arrives. I'm growing in my basement with heat mats and lights and everything is beginning to germinate. I'm trying to figure out if I will need to pot up these plants or if they will survive in these 72 cells until spring arrives. We are usually safe from freezes around April 1st so we have about 9 weeks to go from today. Last year I started my seeds in one container and seperated them after germination into used 6 oz plastic yogurt containers. This was tedious but it worked. This year I have purchased 1020 trays and the 72 cell propagation cells to make things easier, as I plan on planting several hundred annuals and border plants. They are listed as having 2.68 cu in. per cell. These will be planted directly around my home and in hanging baskets. Thank you for any advice that you can offer.

You are most likely going to need to re-pot them. 72 cells are very small and in 9 weeks time your plants would be root bound, which is not good.

Thank you for the quick answer. What size do you feel would get me to spring and how long should I keep them in the 72 cell ? I'm trying to plan ahead with containers.

Your yogurt cups should be a nice size to pot up to, David. Start saving those puppies!

Petunias particularly take quite a while to get big. You might get away with leaving them in the 72-cell. I've never started Impatiens from seed so no idea, and alyssum never really get to be huge plants anyway. I'd play it by ear on the sizes and only pot up those that look like they're getting too big for the cell pack.

Thank you Elaine for the response. I did save last year containers and have already bleached and cleaned them just in case !! My children eat lots of yogurt so I have hundreds of those little cups. I suppose every plant will be a little different so I will do as you say and keep an eye on them and cross my fingers too.

This may be obvious, but I'll say it anyway:

Pot up the biggest, fastest-growing seedlings first. Those are your best plants - keep them!

When you have as many yogurt cups filled as you have room for, leave the rest in their 72-cells or harden them off outside with whatever cover and warmth you have available. If any survive, plant them and "mess up" the root-bound root-ball (meatball root pruning) as you plant out. The extras may or may not do much.

Alternatively, depending on your neighbors, offer them some of the slower 72-cell seedlings to pot up.

Thanks Rick for the great info !! That makes a lot of sense so I'll keep an eye on the front runners.

If my lettuce is any indication, if you pot up your plants will get bigger and healthier. The one in the paper pot was more than double the size of the ones left in the plug trays. The paper pots are wrapped around a soup can so your yogurt cups should work fine. My husband just takes a drill and drills a drain hole through a big stack at a time.

Hello Arlene, your lettuce looks great. Looks like we are almost neighbors. I also have some lettuce growing but it's not as far along as yours. Thank you for the response to my question.

Ah, sorry David, I should have clarified. Those are last year's seedling. My plug trays for this year only got planted last weekend.

Yep, looks like we are neighbors for sure!l

You may want to save the space and direct-sow your alyssums unless you have reason to start them early indoors. They grow very quickly just tossed on the ground in spring, and they keep going until the bitter end--at least for me.

Thank you Taqiyyah for the response. I have never grown the alyssum before so in my haste I started a tray of 72 of them about one week ago. They have all germinated so I may have wished I had waited as you suggest. It seems that the growing charts that I read said to start them indoors in January for my zone.

It is always nice to hear from someone with experience with a particular plant instead of relying on charts. Thank you !!

In my experience, you will get much better petunia plants if you pot them up early on. I start them in my GH in March and always end up with large blooming plants before I can set them out (typically late May here). I start mine in the little 4 pack pots and then move them into 4 inch pots as soon as they're big enough to handle.

Thank you Woofie for the insight. I can already see that I will need to pot up soon. Luckily I have the space and containers to do this, I was just trying to be lazy. I suppose that if I had wanted to keep from the extra step of potting up I should have waited until closer to spring to start in the 72 cells. That's assuming they could handle going from this size straight into the garden if weather conditions permit ?

Spring for us can begin anytime in March; although we always seem to have one or two freezes after a few weeks of what seems like summertime weather. My zone says to wait until March 30th but the few landscapers that I know say they always wait until April 15th just to be sure.

This picture was taken in early May. I may have started them a bit earlier that year, but you can see what I mean about the size.

Well that must have been nice to come in to on chilly days before they could go out.

Thanks again Woofie. They look great ! Love the greenhouse too.