Choosing pot size for herbs would be wonderfully easy if the rule were simply:
bigger pot = happier herb.
Unfortunately, plants have once again declined to make gardening that convenient.
A container needs to provide enough room for the roots and suit the way the herb grows, but moving a small plant straight into a huge volume of potting mix can create its own moisture-management problems.
The better question isn't:
“What's the biggest pot I can fit on this windowsill?”
It's:
“What size pot makes sense for this herb right now?”
Choosing pot size for herbs means balancing several things:
Too small can become restrictive.
Far too large can make watering harder to judge.
Somewhere between root prison and parsley penthouse is the container you're looking for.
Don't choose a container solely according to the name printed on the plant label.
Two basil plants can be very different sizes.
A newly purchased starter plant and a mature basil that has been growing vigorously for months do not necessarily need identical containers just because they're both basil.
Look at:
Start with the plant in front of you rather than the theoretical basil it may become someday.
Roots need access to water, air and growing space.
As an herb grows, its root system develops too.
Eventually, the existing container may no longer provide enough comfortable room.
But giving a small root system an enormous amount of extra potting mix isn't automatically helpful.
Imagine moving out of a studio apartment because you need another cupboard and accidentally buying an airport terminal.
More room has technically been achieved.
Proportion may have been lost somewhere along the way.
A container that has become too small can eventually make the herb harder to manage.
Possible clues include:
None of these signs needs to be interpreted in isolation.
A root poking through one drainage hole isn't automatically an emergency evacuation order.
Look at the overall plant and root system.
Oversized containers create a different challenge.
A small plant may occupy only a fraction of a large volume of potting medium.
After watering, all that extra mix can remain moist while the relatively small root system uses water much more slowly.
That's particularly relevant indoors, where evaporation and plant water use can already be lower than outdoors.
The result can be a pot that stays wet far longer than you expected.
If that's already happening, Fixing Soggy Potting Mix Fast will help you troubleshoot the entire setup.
Pot size isn't only about diameter.
Depth matters too.
Different herbs develop different root systems and growth habits, so a broad shallow container and a deeper pot aren't automatically interchangeable.
This is another reason rigid rules such as “all herbs need a 20-centimeter pot” aren't particularly useful.
Think in three dimensions.
Your herb certainly does.
A compact chive plant, vigorous basil and spreading mint don't behave exactly the same way.
Some herbs stay relatively compact.
Others become bushier, taller or spread aggressively when conditions suit them.
Container choice should allow for that growth habit without requiring you to predict the plant's exact dimensions six months from now.
Mint deserves particular attention because giving it its own container is also a convenient way to keep its enthusiastic spreading habit under control.
If you're growing mint indoors, see Mint Indoors Container Rules for the herb-specific setup.
The container itself influences watering.
A small pot has less growing medium and may dry relatively quickly.
A larger pot holds a larger volume of medium and may stay moist longer.
Pot material, light, temperature, plant size and the potting mix also influence what happens.
That's why watering by calendar alone can become unreliable.
If a pot that once behaved predictably suddenly needs water much more frequently, the roots and container size deserve a look.
If it stays wet dramatically longer after moving into a much larger pot, that deserves attention too.
The pot is giving you information.
A perfectly sized pot with nowhere for excess water to escape is still a poor setup.
Choose containers with effective drainage or use a draining inner pot inside a decorative outer container.
Pot size and drainage solve different problems.
One doesn't compensate for ignoring the other.
If you've found a bargain decorative container with questionable drainage, see Drainage Hacks for Cheap Pots.
Don't repot simply because a calendar says you've owned the herb for six months.
Let the plant provide evidence.
A larger container becomes worth considering when several clues suggest the root system is becoming genuinely crowded or the existing pot is making normal care increasingly difficult.
That might include:
Our next guide, repotting rootbound herb plants, will deal with exactly what to do when you decide the answer is yes.
When a plant needs more room, move to a reasonably larger container rather than automatically choosing the largest pot available.
The goal is to give the roots useful new growing space without surrounding them with an unnecessarily huge reservoir of wet potting medium.
There isn't one universal step-up measurement that applies perfectly to every herb, root system and container shape.
Use the existing root mass as your reference.
Give it additional room.
Don't give it a postcode.
A large shared planter can look fantastic.
It can also turn three simple herb pots into a small negotiation committee.
Herbs sharing a container should have reasonably compatible:
Also consider what happens when one plant becomes much larger than its neighbors.
Separate pots give you more control over watering, placement and repotting.
For beginners—and particularly in small apartments—individual containers are often wonderfully uncomplicated.
When you're deciding whether an indoor herb needs a different container, work through this:
Successful choosing pot size for herbs is mostly about resisting extremes.
Don't keep a growing herb squeezed indefinitely into a badly cramped container.
But don't move a tiny starter plant into a bucket simply because bigger sounds generous.
Look at the plant.
Look at the roots.
Watch how the pot behaves when watered.
Consider the herb's growth habit.
Then choose a container that makes sense for what you're actually growing.
If the roots have genuinely filled the current pot, continue with Repotting Rootbound Herb Plants once that page is available.
If your oversized container is already staying persistently wet, see Fixing Soggy Potting Mix Fast.
For drainage problems, see Drainage Hacks for Cheap Pots.
And for the complete root-zone picture, return to Pots, Soil, and Feeding.
Your herb doesn't need the biggest home you can afford.
It needs one that fits.