I'm going to start hardening them off this weekend

You are zone 4 and ready to harden off? When is your plant out date?

As to fertilizing seedlings, see link below to previous discussions. Some do, most don't but it all depends on how long before you can plant out. My guess is your plant out date is still more than 6 weeks away so I wouldn't feed those plants now, especially since they look like they are still in plug flats. Wait until you transplant them into larger containers.

JMO

Dave

Here is a link that might be useful: fertilizing seedlings discussions

I'm in the Twin Cities. We've been having a warm spring. Looks like our normal date is right around May 15th and I was looking at pushing it and planting out around May 1st. The seedlings have been potted up once, but I'm using the really deep star plugs (21 to a tray I think) and was hoping to avoid potting up again as they are already deeper than any of the pots I have (5" or 4" greenhouse pots I think). I'll check over in the regional forum and see when people are thinking about planting out this year.

I'll avoid to fertilizer for now. My seedling mix already has a bit in it and the plants look like they are doing fine.

"normal" date? You mean average last frost date? Usually tomatoes go out 2 weeks after last frost. You could try May 15 if it's been warm, but you usually would plant out at Memorial Day (that's what I do here, I'm in 5b but a bit of a microclimate).

Your plants do look good for never having been fertilized - when did you start them? What mix did you use?

Your cotelydons are yellowing - it's ok to fertilize now but only if you pot them up. If I were you: I would put them in gallon pots and irrigate with a soluble fertilizer. If you're hardening them off in warm weather, I'd use 1/2 strength and water 2x a week. In mild weather, I'd use full strength and water 1x a week.

And I would not plant them until at least a week after the frost date. A neighbor of mine got ambitious and planted about a month ago - her tomatoes suffered when we dropped to freezing for several hours a couple weeks ago; they have not grown at all since. Pot yours up and harden them off for the next month and you will have stellar results. Your seedlings already look nice and strong.

Thanks for the tips. I started them in Miracle Gro but the store ran out of that so they were potted up in Jiffy. I think I started them March 19th.

So instead of hardening them off for transplant, what about hardening them off and then just leaving them outside fulltime for an extra week or so while keeping an eye on the weather? That way if temps take a dive I can bring them back in for the night. I'll be running out of height of my shelves in a couple weeks. Temps here right now are mostly in the 50's but it looks like we'll be in the 60's and 70's starting this weekend/next week.

Wow, a month ago in 7b?? I planted early... 4 days ago. Still worried about those mid 50's that pop up until May

I'm in zone 4, not 7b. Are mid-50's that much of a problem? I thought tomatoes were pretty hardy as long as it wasn't freezing.

cakefarm said he had a nmeighbor that planted out in 7b a month ago. That included 2 frosts. 50's aren't bad, but it isn't as good as the 70-80 weve been having with night time temps in the high 50's. Basically, if I have days in the 50's, nights in the 40's for a few days, all that great growth will slow down. I'm past my 90% frost date. In zone 4 I would think you have to wait to plant until June 1 right? Unless you have a microclimate that is warmer.

Some great info here and the other thread on cold damage. Depending on where you look, my average last frost date is between May 1st-10th. I'll wait and keep an eye on things. My biggest concern is running out of room for seedlings. It's my first year growing from seed. Things are working on so far, but it's going to be tight!

Jeff - seriously! I had to pretend to be impressed by her industriousness. We have one final cold snap coming in a couple of days and then I think we're in the clear. Fingers crossed, I've already potted up twice (that worm casting tea is no joke!).

Patrick - that's exactly what I do. Mine are sitting outside 24 hrs a day as long as the nighttime temps are above 50. I will have to haul them all back in tomorrow night when we drop into the 40s but an ounce of prevention is worth a pound of cure.

When you are ready to plant (and honestly, I use this stuff anytime I pull a plant out of one place and put it in another - potting up included), I would also like to recommend a product you can find at a reputable nursery: Espoma's Bio-Tone. It has pro-biotics and mycorrhizae fungi which is excellent at preventing later diseases. You can also buy mycorrhizae fungi (I buy it on Amazon) by itself but I've had such good results with the Bio-Tone, I just use that. I just throw a small handful in each planting hole.

Fertilizing seedlings is Kinda like giving Whiskey to a baby

I don't know - my seeds were started March 12, they look so tiny - only 1 or 2 true leaves but the cotyledons were turning yellow and dropping off some, they were about 3" tall so I just repotted this week in deeper pots, used Fafard #2 in some (nonorganic) and a mix of Burpee organic starter (with turkey litter) and ProMix Veggies and Herbs with mycorrhizae in others to try to give a boost, also put them under 6500K CFLs.

Fafard said the "starter nutrients" they put in only last a couple of waterings - since I soaked the mix before potting, I haven't watered yet, but I was wondering if I should use diluted Neptune's Harvest (how diluted? Bottle says 1 oz to a gallon) to water everything the first time (and every time after that) that I do water?

All my tomatoes were in Jiffy strips - I was not impressed with root development - long tap root coming out the bottom (probably 6-8" of root for a 3" plant!), not many feeder roots and those got torn when I peeled away the cardboard (I had bad experience planting the pots in the ground last year restricted roots and I had to replant the peppers I had in them). I had soaked them when starting, but then just misted after that b/c I didn't want to bottom-water seeds or seedlings, didn't want the strips to soak up all the water and disintegrate. The peppers I have in plastic look much better (haven't potted those up yet so don't know how roots are), still only 2 true leaves but they took longer to germinate, and they are nice and green and big-leafed, not so leggy, as the tomatoes, they were also just misted.

They are getting a bit stretchy, so they could use a bit more light. You could start hardening them off and bring them inside at night if you don't mind moving them a couple times a day. Probably should consider potting up. You might have to do this for a few weeks. Avoid the temptation to plant in ground early. If you do, make sure you have a solid frost plan, as long term forecasts are not reliable. Fertilize if you see any slight yellowing with a weak
mixture.

NOT fertilizing seedlings is kinda like not feeding a baby. IMHO. But technically, I don't consider them seedlings once they are ready for a gallon pot.

Just make sure you don't over do it. Let's be real, the nurseries do it. They don't get that dark green by magic. Just use a weak solution somewhere between 1/8 and 1/2 strength. I've killed smaller seedlings than that by eyeballing, and overdoing the amount. Those look well established though. I would also pot them up to about a 4" pot at least.

edweather is very correct.