Kalanchoe black rot right at the start of autumn - keep watering like this and it will surely die

Why is kalanchoe prone to black rot?

Causes of black rot

At the turn of summer and autumn, the weather is muggy and the heat hasn't fully gone. During this period, kalanchoe has just come out of dormancy, its roots are relatively weak, and a little too much water plus sun exposure causes root suffocation, leading quickly to black rot.

Symptoms of black rot

Kalanchoe black rot starts with blackening in the middle of the stem, then spreads rapidly to the roots and leaves, causing root and stem rot, drooping branches, and leaves that become soft and wrinkled; in severe cases they fall off at the slightest touch.

Some people mistake the black spots and water-soaked rot on kalanchoe leaves for black rot, and believe black rot can be cured, which is unscientific. This is usually not black rot but black spot disease.

In fact, even without medication, black spot disease can be stopped from spreading by stopping watering and making its growing environment dry.

What to do after kalanchoe gets black rot?

1. Isolate immediately

Black rot is highly contagious. Once discovered, isolate the diseased plant at once and clean up the rotting stems and leaves.

2. Prune and disinfect

In the early stage of the disease, the roots are usually not damaged. At this point you only need to cut off the affected stems and leaves and apply carbendazim or chlorothalonil powder to the wounds to prevent further infection.

If the black rot is very severe and the roots are completely rotten, you must change the pot and soil. After taking the diseased plant out of the pot, cut off the healthy upper part, soak it in a carbendazim solution, and re-cutt it after disinfection. The original soil must be thrown away, and the original pot must be thoroughly disinfected.

3. Prevention beats treatment

The key to disease lies in prevention. During sensitive seasons, it is best to spray a fungicide on the leaves after every watering (spraying carbendazim or chlorothalonil is fine), and also spray after rain.

At the turn of summer and autumn, not only are adult kalanchoes prone to black rot, newly cut kalanchoes are also prone to black rot. Below I'll teach everyone how to avoid black rot in cuttings!

How to avoid black rot when cutting kalanchoe?

The reason for black rot in cuttings is very simple: too much water! So the key to preventing black rot is how to water correctly!

1. Switch from watering to misting

The roots of cuttings are relatively weak and their water-absorbing ability is insufficient, so flooding the soil easily leads to lack of oxygen and root rot. You can switch from watering to misting, using a sprayer to moisten just the top 2cm of the soil surface.

2. Control the water amount

For a flower pot 10 cm in diameter, mist about 15ml each time; for a pot larger than 20 cm in diameter, mist 30ml each time, once every 5~7 days.

3. Better dry than wet

The watering principle for kalanchoe: better dry than wet. A plant short of water will at most produce one or two withered leaves and will never die, but too much water brings not only black rot but other diseases as well.

Notes

1. The potting soil must be breathable

No matter what flower you grow, breathable potting soil is the most important thing. Muggy potting soil not only creates conditions for bacteria to multiply but also lowers the roots' resistance. For kalanchoe, a mix of garden soil and coal cinder, or peat, coal cinder and perlite, is fine.

2. Soak the roots before repotting

After autumn begins, whether repotting or transplanting, first rinse the roots clean with water, then soak them in a carbendazim solution to reduce the chance of disease.