5 Reasons for Petite Butterflies Sweet Pea Shrub Turning Yellow

Sweet pea shrubs are evergreen plants that make lots of pretty blooms the whole year. This is why it’s considered as a wonderful addition to your gardens and patios. But like all other plants, they also get affected by various conditions like diseases and environmental difficulties. 

Your petite butterflies’ sweet peas can turn yellow because of these 5 reasons- Overwatering, Imbalanced sunlight, Nutrient deficiencies, Fungal disease, and last but not the least, Viral disease.

All these reasons need different kinds of treatment and you have to figure out which reason is behind the yellowing of your sweet pea shrubs so that you can help them in the right way.

But you’re probably wondering if this seems like a lot of work. Don’t worry we have done the research and cut the work short for you. In this article, you will find why your petite butterflies are turning yellow and how to treat them easily. 

So, let’s get this show on the road- 

Why Is Petite Butterflies Sweet Pea Shrub Turning Yellow?

1. Overwatering

Your sweet pea shrub can turn yellow mostly because of overwatering. They sure like some moisture in the ground but they don’t grow well when their roots are waterlogged. Again if you water them with too cold water then your petite butterfly sweet pea shrubs can go into some kind of shock.

But the good news is once they get the balanced amount of water your petite butterflies will stop turning yellow and grow lots of new green leaves. 

Control Measure

Water your shrubs once every week depending on your weather condition. Remember to leave the soil a little moist but not too much.  During the winter season cut back watering a little bit and water your sweet pea shrubs with lukewarm water.

In summer, water them early in the morning. This will also help the shrub to bloom. But the quantity of water will greatly depend on your shrub size and the climate of the area.

2. Sunlight

Sweet peas are warm lover plants. This means they need a good amount of sunshine in their life. So, if your petite butterfly sweet pea shrubs are in a shaded area then their leaves can easily turn yellow. 

Control Measure

Make sure to plant your shrubs in a place where they will get at least 6 hours of direct sunlight. It’s best for their blooming if they get the full morning sun.

If they are already in a shaded place you can carefully uproot the sweet peas and pick a sunny area to replant. 

3. Nutrient Deficiency

One of the most common reasons for yellow leaves on sweet pea shrubs is various nutrient deficiencies. You see the deficiency of nitrogen, potassium, and manganese can cause yellowing. Because these nutrients are essential for photosynthesis.

But the thing with these petite butterflies is, they don’t need so much nutrients. If you go overboard with fertilizer then there will be nutrient toxicity. As a result, their roots will burn and the shrub will wilt.

Control Measure

Feed your sweet pea shrubs with a good multi-purpose slow-release liquid fertilizer once every spring (our pick: Miracle-Gro Water Soluble All Purpose Plant Food)

Remember to avoid over-fertilizing. Because if you do that your shrubs will grow dense foliage but there will be very little blooming.

Sometimes nutrient deficiencies occur because of high pH in the soil. Test the soil pH with a pH test kit and amend the soil with acidic fertilizer if the soil is alkaline (Our pick: Atree Soil Soil Tester Kits with Moisture, Light, and PH Test for Garden)

4. Fungal Disease

Powdery mildew and Ramularia leaf spot are some common bacterial diseases that affect sweet peas.

Powdery mildew initially starts by showing white powdery growth on the foliage but as the disease progresses without proper treatment it turns the leaves yellow.

On the other hand, Ramularia leaf spot is a specific fungal disease to sweet peas. It causes large yellow spots on the lower leaves. In case of severe infection, all the leaves of the plant start to drop. 

Control Measure

Get the best fungicide for your petite butterfly sweet pea shrubs and apply them on your plant as soon as you see the symptoms(our pick: Bonide 811 Copper 4E Fungicide). While applying the fungicide make sure you follow the manufacturer’s direction on the package, Otherwise the dosage can get wrong and end up hurting your shrubs. 

Water them on the ground level. Since these plants are bushy try not to wet the leaves. Because wet leaves will encourage fungal growth. If you have a fungus problem in the area then don’t grow sweet peas in the same area year after year.

Both fungal diseases spread very easily in wet and humid conditions. And these fungi are hard to get rid of because they survive on the foliage for a long time. So, never use the infected plants in making compost. Because if the compost is infected by any chance, the fungus will spread to all other plants wherever you apply the compost.

Have a look at the homemade recipes to use as a fungicide-

#Recipe 1:-Cinnamon Fungicide Recipe


  • 3 Tablespoons of Cinnamon
  • 1.5 Liters of water


  • Mix the water and cinnamon and let it sit overnight
  • Then strain the solution with a fine cheesecloth and pour it on the sprayer
  • Spray it on your petite butterflies upto 2 times every week

# Recipe 2:- Baking Soda Spray Recipe



  • 2 tablespoons of baking soda
  • 2 teaspoons of liquid soap
  • 5 liters of water


  • Mix all the ingredients 
  • Spray thoroughly on both sides of your sweet pea shrub leaves upto  twice a week

Note: Sometimes homemade solutions can burn the leaves. So before starting to apply any homemade recipe, put a small amount in a leaf and wait for the sweet pea plant to react. If no reaction happens then spray the solution on the shrubs. 

5. Viral diseases

Spotted wilt and mosaic are the two most common viral diseases of sweet peas that turn the leaves yellow. In viral wilt, the leaves initially become yellow but later turn brown and wilt.  On the other hand, in viral mosaics, the leaves have irregular greenish and yellowish patches.

Both these viral diseases are spread by some small insects like aphids and thrips. So we have to get rid of the insects as soon as we notice. 

Control Measure

Mosaic and spotted wilt are deadly to the petite sweet pea so you have to stop the transmission of the diseases first. This is why you have to control the insects very quickly and prevent them from attacking in the future. 

Get the best insecticide for your sweet peas to kill the aphids and thrips efficiently(our pick: Natria Neem Oil Spray for Plants Pest Organic Disease Control).

Apply by following the label direction in the insecticide package.

Prevent from using too much nitrogenous fertilizer because it increases the foliage. And these insects are highly attracted to the new foliage.

These homemade recipes will go a long way in controlling these harmful insects-

#Recipe 1:- Dormant Oil Recipe


  • 1 teaspoon of liquid dishwashing soap 
  • 100 ml of olive oil


  • Mix the dishwashing soap and oil in the bowl and pour into a bottle
  • Keep this stored for multiple applications
  • Add 2 teaspoons of this solution with 250 mil water and spray on your sweet pea shrubs. 

#Recipe 2:- Basil Tea Recipe


  • 2 Cup of freshly chopped basil
  • 2 teaspoons of liquid dish soap
  • 1 liter  of water


  • Boil the water and add basil leaves to the boiling water
  • Turn the heat off and cover the pot with a lid to make it airtight
  • After a few hours strain, all the basil leaves from the water and use this infused water as an insecticide
  • Add the liquid soap to make it even more effective
  • Spray on your sweet pea shrubs upto 3 times a week


When your sweet pea shrubs are turning yellow it’s usually due to overwatering or improper sunlight. But yellowing because of fungal and viral attacks are mostly fatal to the shrubs. This is why you have to keep an eye out. Otherwise, these evergreen beauties will die and make the landscape look gloomy. 

I have tried to include every relevant information and hope this piece of writing helped you to navigate the problems with your shrubs easily and gave you their simple solutions.

Leave a Comment