Sunpatiens wilting and rotting – treatment and recovery

Stunted growth and spots on leaves reveal rotting fungus under sunpatiens.

Does your Sunpatiens look wilted? Does it seem like it’s rotting away?The most probable culprit is a fungal infection due to waterlogged soil.

Read on to learn more about what causes this rot, how to treat it and what can heal your rotting flower.

What is this rot on my Sunpatiens ®?

Plants of the Impatiens family love water but they’re quite vulnerable to a host of water-related diseases. Although new hybrids such as the Sunpatiens ® series are specifically bred to resist them, extreme conditions can nonetheless weaken them to the point of triggering disease.

Downy mildew is a fungal disease that has been wiping out vast swaths of Impatiens plants for the past decade, and Sunpatiens ® is resistant to the disease. However, other fungus that lead to root rot are still potent and can threaten the plant’s survival.

The two main types of fungus that Sunpatiens is vulnerable to are the Pythium and Rhizoctonia strands .

Favorable conditions that trigger both of these root rots are:

  • Overwatering
  • Heavy, clay soil
  • Poor drainage
  • High planting density
  • Combination of summer heat and moisture

Note that if all seems lost, don’t despair! All you need is a single healthy-looking stem to start a new cutting!

Different types of Sunpatiens ® root rot

Both types of root rot, Pythium and Rhizoctonia, result from fungus contaminating the plant. The fungus is usually already present in the soil in the form of spores or in a dormant state. When moisture and heat conditions become favorable, the fungus starts looking for host plants. Wounds in the roots are entry points and from there the fungus spreads throughout the entire plant. Both of these cause root rot in many other plants, such as this diseased vinca.

Symptoms of a Pythium infection on Sunpatiens

Black strands start appearing along the stem and leaves. They’re especially visible when a diseased stem is cut: black spots can be seen in contaminated channels that convey sap and nutrients up and down the sunpatiens.

The plant starts rotting, usually from the ground upwards.

Symptoms of a Rhizoctonia infection on Sunpatiens

The rotting starts at the crown or top of the Sunpatiens plant and then progresses downwards. The name for this is crown rot.

Sunpatiens leaves turn pale green and then yellow, always harboring a lot of moisture. They droop over as the structural integrity of the stem collapses.

Diseased cells accumulate in the plant which disintegrates into a slimy mush.

How to treat a wilted, rotting Sunpatiens ®

For infected Sunpatiens growing in pots

Usually Sunpatiens grown in pots won’t get infected, but if ever you recognize the root rot symptoms described above:

  • avoid overwatering and let the soil dry down to a depth of an inch before watering again
  • increase drainage in the soil (mix sand and organic matter in)
  • add a drainage layer at the bottom of the pot: clay pebbles or gravel
  • check that the drainage hole isn’t obstructed
  • spray either a garlic decoction or fermented horsetail tea which are excellent organic fungus antidotes

Always use fresh, new soil mix when planting your sunpatiens ® in pots. Be sure to disinfect your pots and tools with white vinegar beforehand, letting the vinegar dry off before planting.

For Sunpatiens rotting in a growing bed

If the ground where the Sunpatiens is growing is lower than surrounding areas and the soil is heavy, your Sunpatiens are at risk of contracting some form of root rot.

  • Stop watering completely until the soil has dried up down to an inch under the mulch.

To know when you  can start watering again, simply sweep aside the mulch and press your finger to the ground: if it’s rather dusty and feels dry, start watering again. However, if tiny clumps of dirt adhere to your finger, best wait a few more days. Don’t worry about the plants not getting enough water at this point: they’ll start sending roots down to the deeper levels of the ground.

  • if it’s raining a lot and you can’t control the watering, remove the mulch for a couple weeks

This will help the soil dry out faster between rain showers.

  • increase drainage: pierce holes to a depth of about 8 to 10 inches across the growing bed

The more the merrier, ideally every 2 inches or so. This will help excess water seep to the ground and increase air circulation around the roots. A sturdy pencil can do the trick if you’re ready to sacrifice it, but it’s easier with a foot-long iron or steel stem of some sort (like the small stakes used to anchor a tent down when camping), best if the tip is sharpened somewhat. Note: it’s similar to what is done for lawn care maintenance with those shoes studded with nails. Prevent the spread of fungus by dipping all gardening tools in methylated spirits or any other strong, 40+ proof alcohol between jabs.

  • Cut out the part of the plant that has rotted away.

If you want maximum protection, uproot that plant entirely since the fungus has possibly spread everywhere. This should protect the other plants. Loosen the soil up and pull the diseased plant out delicately to ensure most the roots are removed, instead of slicing through with a spade which would open wounds in the roots of healthy plants. Wounds on the roots are how the fungus gets in the plant.

  • Resume watering only when you notice a slight wilt in otherwise healthy plants.

They’ll bounce back within the hour, not to worry. Actually, the wilting is a symptom of light water stress. This stress diverts energy to the root system to expand and strengthen it. Having the habit of only watering when you notice that slight wilt is the best thing you can do for your sunpatiens!

To be thorough, check with the nursery you purchased the plants from: perhaps they or other customers are experiencing the same issue, which means the whole batch might be infected.

How do I know my soil is too wet for Sunpatiens ?

It’s often easy to discern. Having the impression of a drenched, completely waterlogged soil is the start of it.

Clay soil can’t drain and tends to retain water, forming a thick paste.

Mulch that contains wood chips is often a great indicator. Indeed, if wood chips have turned black, it’s a marker of high fungal anaerobic activity. This isn’t necessarily evil, but it shows that conditions are perfect for both beneficial and detrimental fungus.

In extreme cases, rootlets of the sunpatiens flower start appearing above the soil, weaving themselves in and out of the surface or mulch, trying to get a bit of air. Such soil types are really heavy and full of water, and roots need to breathe as much as leaves do.

Preventing root rot and crown rot on Sunpatiens flowers

Fungal infections remain in the soil for years. If you’re not able to improve the soil drastically, try setting up a raised garden bed. Indeed, a raised garden is a great way to reduce risk of root rot for all plants.

Another option is to find other plants to grow that will love wet, moist soil.

It is however quite easy to make clay soil lighter and of course remember to spray organic fungicides every fortnight for two months to control contamination.

If you live in a mild climate (no frost or freezing), you can plant the Sunpatiens back for the following year, but if the weather gets cold spare yourself the effort and either sow green manure which will further enhance the clay soil or go for nice beautiful winter plants.

Read also:

Credits for images shared to Nature & Garden (all edits by Gaspard Lorthiois):
Sick and rotting sunpatiens by Joyce Gerber,
Nature & Garden contributor