While I have not seen your seedlings, my guess is that they are doing fine. Do not compare them with the nursery grown plants that have growth regulating chemicals as well as controlled temperature and light to produce plants that will sell. Al

No, these are definitely puny and stunted. When I used to start seeds at my old garden the seedlings were way bigger.

My seeds I start in a community pot and at two true leaf stage transplant into salvaged sixpacs. Up until they are ready to transplant into four inch pots they are bottom watered as needed. In the winter they are exposed to a high light source this time of year no artificial light is needed. If you feel yours are sub par while on artificial light I would suggest you are not using a strong enough light. I use 400 watt HID light source and regulate distance to plants with the help of a light meter. Al

do you use fertilizer? If not, you should.

They grow fine once I get them in the ground.

Have you tried planting seeds directly in the ground? I used to mess with pots and such, finally just started putting the seeds right into the soil where they are to grow. Much, much, easier! Get row covers or some other protection if you need it.

2 things will keep seedlings small - pot size and no fertilizer.

If you pot up seedlings to 4 inch pots they will grow larger, then on to gallon pots. This way you can get large transplants while waiting for warm weather.

Potting soil has very little food in it. When you pot up add some compost to the mix. Use a liquid fertilizer at 1/4 strength when you water.

Thanks for your responses everyone.

I doubt pot size is it, as I started my tomatoes in 3" pots, and used the larger 6 packs for greens and such.

I have sometimes fertilized, albeit, unscientifically, with very diluted alfalfa tea.

I am going to really lighten up my soil mix and see if that helps, as I am about to start my fall veggies.

Hoovb, good idea.

Your soil mix I doubt is a problem. For what you are growing, any potting mix would be fine. I only use seed starting mix for slow to germinate ornamental plants. With the warmth of the summer soil, germination in the ground should not be a problem if you can manage the soil moisture and the pests already in the garden soil and hungry for lunch. I would bait for slugs a few days before planting and protect from birds. Al

OP wrote "very diluted alfalfa tea"

That's not considered fertilizer. Starvation is probably the reason for the stunting.

Pictures could help us help you.

Hi, I grew some seedlings which were filled with potting mix in the small black tube containers. The ones which I kept in boxes with poor drainage did not grow very high (only a few centimetres after six months). The two seedlings which I took out of the boxes had plants which grew about a foot high after six months (they were tea tree seedlings). Perhaps your drainage is a problem. Seedlings need about a foot square of well-draining soil to grow in from what I have read.