Why aren't my seedlings growing much?

I've started lots of flats of seeds, and have found that so many of them just don't seem to be growing, getting new sets of leaves, getting stockier, etc. Some of the flats I just sowed recently have really taken off. Do annuals tend to grow a lot faster than perennials? My amaranthus still look like threads, the nigelia and nemesia are barely getting their first true leaves (they sprouted back in mid-March). I used sanitary seed starting mix (and on some used peat pellets, though I didn't get as good of germination in those), bottom water with a little hydrogen peroxide in it, removed the lids when they had all sprouted, and have them about 2" under fluorescent lights in my kitchen, roughly 68-70 degree F.

Am I doing something wrong?? At this rate, they will never be strong enough to plant outside! Meanwhile, the alyssum and zinnias that are a good two-three weeks younger are looking fantastic, and the basil and dill are really taking off.

Angie

I wouldn't be surprised that the annuals are taking off faster, after all they know they have to get their whole life in during a much shorter time period so they're in a hurry to grow up and flower and set seed. As long as you're watering them properly and giving them enough light and fertilizing them a bit and they look healthy otherwise I don't know that you need to worry, they'll take off eventually. The other possibility is they may need to be thinned a bit, I've found when I have a whole bunch of seedlings crammed up together they don't grow very fast, but if I thin them out a bit then they grow better.

If anything is a bit cramped, it is the annuals, and they look happy as clams. I didn't get near the germination on the perennials, and at that point I was doing cells and peat pellets. I've since started just filling rectangular flats with the seed starting mix, and sowing in rows or just sprinkling, depending on the size of the seed.

What kind of fertilizer do you use on seedlings? I thought you weren't supposed to fertilize till they were bigger. . .? I imagine it would have to be pretty diluted to not burn the roots?

I start fertilizing not too long after they get their true leaves. You just dilute the fertilizer to 1/4 or 1/2 strength rather than applying it full strength. I use whatever fertilizer I have around, lately it's been Ironite but I know I've used Miracle Gro in previous years too.

I didn't realize some stuff doesn't have flowers till the second year. I read that about hollyhocks and I was checking them every five minutes to see if they had a bloom. (after I put them outside.)
I've had the same problem with candytuft, those weak little stems. They are growing good , just those stems are driving me nuts. Are they supposed to be like that? I waited till they had several true leaves to put them out.

Ecrane, don't you just hate pulling out those little babies .? I hate it, but I sia for 2 hours thinning and then took the ones I'd taken out and worked to get those little things in a pot too. Actually worked on some, but they were petunias. Not like they are rare!!!

It really doesn't bother me, I know that the ones that are left will grow better and honestly if all 1000 of them grew up into plants I wouldn't have enough room in my garden! But I don't have to thin stuff too often, usually only with things that have self-sown themselves in the garden. Most of the things I start indoors from seed are tropical trees/shrubs which come in packets of 5-10 seeds, so they each get an individual spot in a cell pack from the start.