How closely should herbs be spaced?

Question

Newbie herb planter here who is very confused by all of the different information online about how best to start planting herbs.

I have started with the following basic herbs:

Basil Oregano Coriander

I have three ~15cm planters or so on a windowsill that gets good sun. I started out by just lashing a handful of seeds into the pots. While the herbs started out strong, they now seem to have stalled. Is this because they have been sown too densely? I don't intend on re-planting outside (live in an apartment with no garden), so how many seeds should I be placing in each planter? I've read online that basil seeds should be sown ~10 inches apart, but surely this would mean I'm only looking at planting one seed per pot, or else I'd need huge pots completely unsuitable for a windowsill.

Fundamental questions I know, but I can't find consistent info. Thanks in advance.

Answer 1

Technically you're right - not more than two, maybe three, plants in each 15 cm pot, or they won't have room to develop properly. Oregano spreads sideways and not up - planted outdoors in a garden bed, it makes a good ground cover, spreading up to 2 feet easily in a sunny spot; it will cover the entire top of your pot over a fairly short time, so only one plant in there, though if you use it frequently, you could leave two to grow on on the strength you'll be cropping it a lot.

Now that the pots have so many plants growing in them, if they're still small, hopefully you can remove excess plants to leave just two or three in each pot without disrupting the roots of the ones you want to keep. It might have been better to just sow half a dozen seeds in each pot, because then it's easier to pull out weaker seedlings as they start to grow. If you can't remove plants without destroying them all, you might need to start again; hopefully you have some seeds left.

UPDATED ANSWER:

In response to your comment, you're right, supermarket potted herbs have more than one plant growing in the pot. This is done for speed, to get them ready for market quicker, and they only last a limited time if left uncut before they start to keel over.

If you're going to sow straight into your large pots, put half a dozen, spaced out, in each one, and allow 3 basil, 3 Coriander and two maximum Oregano to grow on, removing the rest. Unless, that is, you want to keep all six, cut them mercilessly as they get to a useable size, then re-sow from seed again in a couple of months, it's really down to how many leaves you need and how often you'll be using them.

The disparity between planting distances when grown outside is because, in that situation, the plants are given sufficient space to develop and grow properly, at both root and branch level, which means perennial ones (oregano for instance) can be used for cropping, but will survive year on year, and the annual ones (you'd sow more of those outdoors too if you use a lot) will carry on right through the growing season, without the need for frequent re-sowing.

Answer 2

This is an excellent project for you to be doing and learning from. Can't just throw seed in the ground and expect to EAT anything anytime soon to save your life.

You need to use potting soil whenever you plant anything in pots. Planting seeds you need TINY pots...inch to 2 inches in diameter and as deep...maximum. You need to keep moist, not wet. They need far more light than a south window will allow you to do.

For now, until you want to get serious by purchasing grow lights, just plant ONE seed in a tiny pot of soil...an inch wide by 2 inches deep? Use JUST potting soil. No fertilizer as yet. Consistent warmth. Move the baby plants away from the windows at night.

15 cm is about...8"? Too large. It is tough to thin seeds like that without destroying the plants you want to keep. There are seed starter trays with tiny partitioned 1" X 2" sections that work well. 70+ seeds can be started in one 'tray'. Go to a Pot Growing Store.

They will be able to enlighten you enough to be able to start any seeds and direct you towards proper lighting, ventilation, soils, pots and great fertilizer. This is how you learn to grow your own food. Spices, herbs, ornamentals. Some nurseries might be able to have staff that know what they are talking about. The Pot stores are a bit more motivated towards success.