Pot size - small & repot, or start large?

Question

I have a few different houseplants. I'm also currently starting a few different vegetables, from seedlings and from seeds. I've been trying to research the best way to grow all of these in containers, but there's a lot of conflicting information.

The consensus is that pots being too big is a problem - root rot, only repot a few cm larger at a time, etc. I've also had this problem with a lot of my houseplants, and needed to size them down. At the same time, every time I look up information on starting vegetables in containers, the pot sizes they recommend seem to be gigantic. For example, I have some jalapeno seedlings - the recommended pot sizes I've seen are at least 8"-10". Am I supposed to immediately plant in that size? How would a huge pot for the plant work out in this situation, but be advised against otherwise? Are you supposed to only water them shallowly, or something else that mitigates the whole pot being soaked constantly?

I feel like I'm missing something that bridges the gap between all of this advice.

Edit: To clarify, this is not specifically about vegetables/annuals - just an example.

Answer 1

The (now deleted but since restored) answer you were originally given has the right of it, it was a good one, I'm not sure why @b.nota deleted it.

There is a general rule that you pot up only one or two sizes at a time for plants, but there are exceptions, which are fast growing annual plants that are expected to produce fruits during the relatively short period of summer. Your basil is not expected to produce fruit, it is grown for its leaves, and is only a relatively small plant when compared with, say, a tomato plant. When a plant grows rapidly and puts on topgrowth in preparation for fruiting in the same year, the roots also grow quickly and rapidly take up space in the large pot you've used. But if you put, say, a small seedling of a non fruiting perennnial plant such as lavender in a very large pot immediately, the roots don't grow quickly because the plant doesn't get that large and isn't such a fast grower, it's a shrub. That means the potting soil is largely unoccupied, and you would need to keep it wetter in order to ensure the small amount of roots actually receive any water at all. And a large amount of unoccupied, wet potting soil is prone to souring and may become unhealthy for its small occupant, and fungal problems are likely. This also applies to most houseplants, since they are not annual, rapid growing, fruiting plants either.

Therefore, if you want to grow, say, a tomato or a pepper, then, when the seedling has developed into a small plant, they should be potted straight into the large container they will stay in until the growing season is over. But a basil plant, or, say, an indoor Schefflera or Sansevieria should not be put straight into a large container for the reasons explained above.

Answer 2

Growing vegetables or houseplants are two different things. Vegetables are usually annuals, which means they grow only one year (season), which means you'll have to time them right (sow them early Spring, harvest end Summer or Autumn). Houseplant are usually tropical plants or from arid parts of the world, and can be kept for years.

In my opinion there is therefore different advice for vegetables or for houseplant. So here my advice:

For vegetables, I would sow them in small pots first. I mean really small, like seed trays for example. When the seedling is big enough, you can repot the plant into a larger pot (or in your garden). This pot should be big enough for the rest of the season, so if they advice you to put jalapenos in a 8" pot, use that size.

However, for houseplants, you usually want to put them in just a little bit larger pot, because they don't grow that fast as your vegetables. It would not really be a problem to put your houseplants in a way too large pot, but it won't probably be a nice sight (aesthetically). To prevent root rot it is important that the pots have good drainage (holes under the pot).