Rescuing herbs from root rot starts with one important precaution:
don't assume root rot is the problem just because an herb is yellow, wilted or generally looking miserable.
Those symptoms can have several causes.
Root problems become more plausible when the plant has been sitting in persistently wet potting mix, drainage has been poor and the root system itself shows deterioration.
If that's what you find, the goal is straightforward:
save what's still healthy, remove what's clearly failing and correct the conditions that caused the trouble.
The most important part of rescuing herbs from root rot happens below the soil surface.
Leaves can tell you that a plant is stressed.
They can't reliably tell you why.
If the herb has remained unusually wet and continues to decline, inspecting the roots gives you much better information than staring accusingly at a yellow leaf.
You are looking for a pattern, not one supposedly magical symptom.
Consider:
Wilting is particularly confusing.
A dry plant can wilt.
But a plant with badly stressed or damaged roots can also wilt because those roots are no longer functioning normally.
Adding more water simply because the leaves are drooping can make an already wet-root problem worse.
The same caution applies to yellow leaves from overwatering.
Overly wet conditions can contribute to yellowing, but yellow leaves have other possible causes.
One yellow leaf is not a root-rot diagnosis.
Before reaching for the emergency repotting supplies, look at the whole situation.
Root rot isn't simply the result of a plant receiving “too much water” on one occasion.
The more useful concern is a root environment that remains excessively wet and poorly aerated for too long.
Several things can contribute:
Often it's a combination.
That's why simply promising the basil that you'll “water less” isn't always enough.
You need to work out why the roots stayed wet.
If the growing medium is already saturated, don't add more water out of habit.
Put the watering can down.
This is not the moment to compensate with fertilizer either.
Fertilizer cannot repair roots that are deteriorating in a poor root environment.
If the plant is mildly stressed and the pot simply needs time to dry, correcting the watering routine may be enough.
But if the herb continues declining, the pot stays wet for an unusually long time or you have good reason to suspect serious root damage, inspect below the surface.
Ease the plant carefully from its container.
Support the root ball rather than pulling the herb out by its stems.
Look at the root system and gently remove enough wet growing medium to understand what's happening.
Healthy roots vary somewhat by plant and age, so don't expect every herb to have identical bright-white roots.
What matters more is condition.
Viable roots are generally firm.
Badly deteriorated roots may be darkened, soft, mushy or easily sloughed apart.
An unpleasant decaying smell can also accompany severe deterioration.
Don't panic because one root is darker than another.
Look for obvious deterioration across the root system.
If part of the root system is clearly soft, mushy and deteriorated while other roots remain firm, remove the badly damaged material with clean, sharp scissors or pruners.
Cut back to tissue that appears firm and viable.
Be conservative.
The objective isn't to give the roots an enthusiastic haircut.
Every viable root you keep can help the plant recover.
Remove material that is clearly failing rather than stripping the plant down because a root doesn't look cosmetically perfect.
Clean the cutting tool before use and again afterward, particularly before using it on another plant.
If the old potting medium is saturated, degraded or clearly part of the problem, don't carefully rescue the roots and then put them straight back into the same conditions.
Use a suitable fresh container potting mix that balances moisture retention with drainage and aeration.
This is where your choice of the best potting soil for herbs matters.
Ordinary garden soil isn't a good default substitute for container potting mix indoors.
The new container must also have effective drainage.
The rescue works only if the surviving roots end up in an environment where both moisture and air can reach them.
Don't automatically move the weakened herb into a huge container.
A much larger volume of potting mix can hold considerably more moisture than a reduced root system can use.
Choose a container that reasonably fits the remaining roots and has functioning drainage holes.
The same principle used when choosing pot size for herbs applies here:
bigger isn't automatically better.
Position the herb at approximately its previous growing depth rather than burying the stem deeply.
Settle the fresh potting mix around the roots gently.
A rescued plant has just experienced root damage, root disturbance and repotting.
It does not need three additional treatments because we feel guilty.
Don't automatically fertilize it.
Don't keep adding water in an attempt to encourage recovery.
Don't repeatedly pull it out of the pot to see whether new roots have appeared since breakfast.
Give the plant suitable light and stable growing conditions.
Manage moisture carefully according to the remaining root system and the fresh potting medium.
Then give it time.
Recovery happens on plant time, which is inconveniently slower than human worry.
Sometimes the roots are in terrible condition while healthy stem growth remains above them.
For herbs that propagate readily from stem cuttings, healthy unaffected shoots may provide a backup plan.
Basil and mint are obvious examples.
Take cuttings only from healthy-looking stem material well above any obvious deterioration.
If they root successfully, you can effectively restart the plant without depending on the damaged original root system.
This doesn't make cuttings a guaranteed rescue method for every herb.
Some species root more readily than others.
But when the original roots are badly compromised, preserving healthy growth can be more promising than trying to persuade a collapsing root ball to stage a comeback.
A successful rescue means little if the same conditions return.
Work backward.
Ask:
If your routine was the main issue, revisit watering indoor herbs correctly and make checking the pot the starting point.
If the problem was persistent saturation, fixing soggy potting mix fast can help you understand the wider combination of drainage, potting mix, pot size and growing conditions.
Rescue the plant once.
Rescue it from your watering habits permanently.
Not every plant can be saved.
If almost the entire root system has deteriorated and the stems or crown are also collapsing, there may simply be too little healthy plant left to recover.
Before discarding it, check whether healthy shoots remain that could be propagated.
If not, replacing the plant may be more practical than repeatedly trying new treatments on tissue that is already severely deteriorated.
That's not a failure.
You now know much more about what happened—and the next herb gets the benefit of that knowledge.
1. Stop automatic watering.
Don't add more water to already saturated growing medium.
2. Look at the whole situation.
Consider moisture, drainage, watering history and plant decline.
3. Inspect the roots if necessary.
Remove the plant carefully and look for clearly deteriorated tissue.
4. Keep viable roots.
Don't remove healthy roots merely because you're already holding the scissors.
5. Remove clearly rotten material.
Use clean, sharp tools.
6. Replace unsuitable wet growing medium.
Give the remaining roots a better-aerated environment.
7. Use a suitably sized draining pot.
Don't compensate with an enormous container.
8. Keep aftercare simple.
Suitable light, careful moisture management and patience.
9. Correct the original cause.
Otherwise you're merely scheduling a sequel.
10. Consider healthy cuttings if the original root system is badly damaged.
For herbs that propagate readily, this can provide a useful backup.
Rescuing herbs from root rot isn't really about one dramatic repotting session.
The repotting deals with the damage.
The important part afterward is preventing the same root environment from developing again.
Check before watering.
Use a container that drains.
Use suitable potting mix.
Pay attention when a pot stays wet much longer than expected.
Adjust the routine when light, temperature or growth changes.
And don't assume every unhappy leaf means the roots need another drink.
If healthy roots remain and you've corrected the conditions around them, give the herb time to respond.
Sometimes the best thing you can do after a careful rescue is wonderfully uneventful:
leave the plant alone and let it grow.
For the complete watering and drainage strategy, return to indoor herb watering and drainage.