The top reasons a rosemary plant will die is over watering causing root rot, too much shade, sooty mold. Rosemary plants can also die if they are underwatered and can die off turning the leaves brown. The signs that a rosemary plant is dying of too much water is the leaves will start to turn black on the ends, whereas if the leaves turn brown it is due to not enough water.
Too much water causes rosemary root rot
Rosemary is a Mediterranean plant that likes free draining soil. They have evolved growing on rocky outcrops in bright sunny positions. Rosemary can easily get too much water in tropical and sub tropical areas.
I am living on the Eastern side of Australia and we are getting far more rain than the Mediterranean. My soil does not dry out as quickly and I have to find the sunniest position for my rosemary in my garden.
If you live in a sub-tropical area like me that gets lots of rain and humidity it is best to plant your rosemary in a pot to allow it to drain freely and dry out between watering.
Root rot in rosemary is caused when the roots are sitting in water or wet soil for too long. The roots can’t get enough oxygen and the plant will starve. As the roots rot away the plant won’t be able to absorb nutrients and will end up dying.
Solution to overwatered Rosemary
Stop watering your rosemary and let the soil dry out. Only water your rosemary if you feel the soil is dry 1-2 inches below the soil.
If your rosemary is planted in the ground, watch it over the next 2-3 weeks and if the problem gets worse and the leaves turn even darker, then it is best to dig out your rosemary and place it in a pot. You may get it out of the ground before it ends up dying.
Plant it in free draining potting mix and add some river sand if you have some to add extra structure..
Too much shade leads to root rot in rosemary
Rosemary grown in shade is more likely to spend longer in damp soil than those planted in full sun. Shade can increase the water that says around the roots of the plant leading to root rot.
How to solve the problem of too much shade for rosemary
Choosing a sunny spot to plant your rosemary in will help to prevent root rot as the soil will dry out quicker. Rosemary plants like a sunny spot that dries out between watering so avoid shade if you can.
Soil is too dense and not free draining
Rosemary plants can die quickly if the soil is too dense, contains too much clay and is not free draining. The main problem with this type of soil is that it stays wet, holds less oxygen and the rosemary will struggle to survive.
Solution to dense soil for rosemary
Before planting rosemary dig organic matter into heavy clay soil. This will help the soil to drain for your rosemary. If you already have your rosemary planted in heavy soil, the only solution may be to dig it out and move it into a pot.
Powdery Mildew on Rosemary
Powdery mildew looks like a white powder on your rosemary leaves. It is caused by heavy rain or moist conditions and is a fungus that forms on the leaves of the rosemary. The rosemary plant can survive with powdery mildew for a while but eventually it can cause rosemary to die.
The leaves will not be able to photosynthesize if they are covered with mildew and the plant can starve.
Solution to powdery mildew on rosemary
The best solution for powdery mildew is to give your rosemary lots of sunlight, lots of airflow and not overwatering. Slow down any water that you are adding and only add water on the soil and not the leaves.
Surround your rosemary with tree mulch to avoid soil and water from splashing onto the rosemary leaves
Underwatering can cause rosemary death
Underwatering will turn rosemary leaves brown and the plant can eventually die. Unlike overwatering where the rosemary leaves will turn black, underwatering will cause your rosemary to dry out and turn twiggy.
Solution to underwatered rosemary
Rosemary can be saved if you catch underwatering quick enough. Give your rosemary a deep water with a hose or watering can. Add extra seaweed solution to the water to support root recovery.
Repeat the process 2-3 times over 2 weeks to see if new leaves will sprout through. Old leaves will not grow back but new leaves will start to come through on the stems. Old leaves can be trimmed down back to healthy leaves.
How to revive a dying rosemary plant
Decide if the rosemary is getting too much water or not enough
Adjust your watering to meet the needs of your rosemary. Let it dry out before watering if you notice that the leaf tips are turning black. This is a sign you are giving too much water. If this is the case limit the water over the next few weeks and if it does not improve move it into a pot with new potting soil.
If your rosemary leaves look brown and dry it is underwatered and needs extra water to survive. Give it regular water to help to revive your rosemary.
Check your potted rosemary to see if it is pot bound
If your rosemary is planted in a pot, you should check to see if the roots have filled the pot. Gently wiggle your rosemary free of the pot and see if the roots have reached the outside. If they have grown too big for the pot, find a new larger container and replant it into new potting soil.
Yellow rosemary leaves mean not enough nitrogen
Rosemary can sometimes suffer from not getting enough nitrogen and this will be indicated by yellowing leaves. This is less common in rosemary but it can occur. Solve it easily with a nitrogen rich liquid fertilizer to give your rosemary a nitrogen boost. Add pelleted chicken manure around the root zone for slow release nitrogen.
Rosemary Plant Dying – FAQ
A rosemary plant can be revived by first identifying if it is overwatered or underwatered. Overwatered rosemary will have black leaf tips so leave it to dry out between watering and move to a sunny position. Underwatered rosemary should be given 2-3 deep watering sessions in 1-2 weeks. Add seaweed solution to help the roots to repair.
Overwatered rosemary will have blacked leaf tips which will spread slowly to the whole leaf and down the stem. The stem and leaves will wilt and the plant will eventually die.
Rosemary plants can be killed by overwatering, underwatering, too much shade, mold and root rot. Heavy soils and shade can starve the roots of oxygen and nutrients and cause the plant to die. Plant rosemary in a sunny, well draining spot and let it dry out between watering to keep it alive.
Rosemary can wilt if it is overwatered, the leaves will blacken and the stems will wilt over. Test the soil and if seems too damp and the leaves are black, let the rosemary dry out or lift it out of the ground and plant it in a new pot. If your rosemary is turning brown and the leaves are wilting, water it every second day for a week to see if new leaves will sprout.
Rosemary should be watered when the soil is dry 1-2 inches below the surface. Test with your finger and only water when the top soil is dry. Rosemary may need watering three times a week in very hot summer weather and may need no extra water at all in winter if you live in a high rainfall area. The key is to test the soil first and add water if it is dry.