As I have in the past, I just started the usual suspects (tomatoes, Brussels sprouts, plus ground cherries) indoors in soil.

I also have a bunch of seed packets that instruct to start them outdoors, often with the note "after the danger of frost." Among them are beans, corn, various greens, melons, and nasturtiums; that's just the edibles: there will also be various decorative plants.

Is there any reason NOT to also start them indoors? Does the answer depend on what sort of plant? I figure one can obviously buy seedlings and those are presumably started indoors.

Yes, there is a reason. Some plants do not take kindly to being transplanted so it's best to wait and sow the seeds directly into the garden. If you plug your zip code into the planting calendar here on NGA you will see which seeds are okay to start early indoors, and which would prefer to be started out in the garden.
Good luck and happy growing!

Ah, thanks. Slight puzzlement: I checked the calendar here, and among those recommended for indoor planting are greens like spinach, mustard, lettuce, and kale, which are some of those whose seed packets (I have mainly Seed Saver's) say to plant directly after frost. Does that mean I can treat arugula like those, starting indoors rather than out (as on the packet)?

I've started all of the plants that you mentioned (beans, corn, etc) inside and then transplanted them out, without problems. Don't start them too early, you want to transplant fairly small plants -- and with as much of the growing medium (I use regular Miracle-Gro potting soil) as possible - to avoid setting them back.

That said, you undoubtedly have a longer growing season than I do (my main reason for starting a lot of things indoors) and it IS a lot less work to direct sow the seeds outdoors. Plus, depending on how much you are growing, things like beans and corn take up quite a bit of room to grow -- so those considerations might affect whether you decide to do so.

Happy gardening!

Scott_R said:...recommended for indoor planting...spinach, mustard, lettuce, and kale...seed packets say to plant directly after frost.
Does that mean I can treat arugula like those, starting indoors rather than out (as on the packet)?

Those mentioned, arugula, spinach, mustard, lettuce, and kale, are cool season plants. You can either plant them early indoors or plant the seed directly in the garden at the correct time. But for the plants listed there would be no benefit. Started early indoors and set out (and once they get over the transplant shock), the plants would be about the same size as if they had been direct seeded. From my experience, plants from the direct-planted seeds were stronger and healthier than those that had been set out after being grown indoors.

Arugula takes about 10 - 14 days to germinate. You could plant arugula seeds indoors today and set them out after your last frost date. Or plant arugula seeds directly in the garden. Either way, in a month you would have arugula plants but the ones direct seeded would most likely be stronger and healthier.

Plants requiring a longer growing season are the ones that deserve valuable indoor real estate; things like tomatoes and peppers. You'll be growing those indoors for up to 8 weeks.

While everyone here is right, greene has the actual answer to your question: practically speaking, for a gardener there isn't an advantage. On the other hand for particular reasons, certain people might like to do it:

-- Some people claim they can't grow from seed, so they actually buy already started corn or leaf lettuce plants, etc. from a nursery.
-- As a one time learning experience. Examining up close how things grow (and factoring in the unnatural temperature regime and considerable lack of light inside) can be eye opening to a thinking mind.
-- It's just fun. (The outcome need not be a practical necessity.)
-- Sometimes cold weather crop seed won't germinate if it is too warm. For instance, leaf lettuce has difficulty germinating above 80°F. This might be a problem if you want to plant in late summer for a fall crop. In such a predicament, starting seed in a cooler location indoors does the trick.
-- etc.

Setting aside any specific reason, the extra money, and especially the enormous amount of extra time needed (comparative to direct planting in the garden) just doesn't make sense to gardeners who never have enough time in the spring to get things done.

Notwithstanding these forums, many of us don't always agree with how advice is officially worded on this site. For the particular crops mentioned here, for instance, there could be an asterisk with a qualifier saying "not usually recommended, but useful in some circumstances" or something similar. But this is small potatoes in the big scheme of things.

I'm trying peas inside, mostly because I want to garden and there's snow on the ground. My thinking is I can get the peas out there early enough that they won't succumb to the heat. I'll plant some direct too. We'll see what I end up with.....other than a jungle in my house for the next couple months.....