Petunias are well-known for their big colorful blossoms, almost as much as they are famous for being an easy to grow plant. But no plant is completely impervious to problems and you might find yourself with wilting petunias some day.
Knowing what the cause is and how to treat it can help you save your plants. It might not be quite what you think.
What Does Wilting Really Mean?
We often use wilted leaves as a sure sign of possible problems with your plants. Do you really know what it going on to make your houseplants droop?
Plants leaves and stems lose their firmness because the pressure inside their cells drops. The pressure that keeps a plant upright is created by the water in its tissue. When the water drops, so does the pressure. This is why a wilting plant can be a sign that you need to give it a drink.
The catch is that having too little water within the plant isn’t necessarily the same thing as having too little water in the soil. In other words, there are some other reasons you may have wilting petunias.
Why Are My Petunias Wilting?
1 – Water and Soil
Obviously, take a look at the water conditions first. As previously mentioned, petunias will wilt when the soil is dry and the plant is lacking water. It’s a simple concept and the first thing that comes to a gardener’s mind.
Just remember that there are a number of other potential causes too.
Unfortunately, having water-logged soil can also lead to wilting. Yes, it may seem a little ironic but it does make sense when you think about how roots work. Heavy or poorly-draining soil will hold on to too much water and actually start to drown your plant.
Without the added air around the roots that good soil allows, the plant has difficulty drawing in water properly. The result is again wilting petunias because there isn’t enough water in the plant tissues.
There is one more soil issue you should check on for indoor petunias. When plants outgrow their pots, the roots are going to be very crowded under the surface.
At this point, the pot isn’t large enough (or holding enough soil) to supply all the water your plant needs. Time to repot.
If you’re curious about why plants need water, take a look at my 7 Plant Watering FAQ’s.
2 – Insect Drain
Your petunias may also be wilting due to a problem with insects. In particular, the tiny little sap-sucking ones like aphids or scale. They might look to be too small to do much damage but a serious infestation can impact the fluid levels in your plants, again leading to noticeable wilting.
Take a close look to see if this is contributing to your petunias. Aphids are small, translucent pale-green insects with no visible wings. They are very easy to miss.
Scale can be even tougher to notice because it looks like hard brown scales, and not even like an insect at all.
Indoor gardeners probably won’t see too much insect activity on their plants though aphids can sometimes get a foothold indoors. The trick is to find them early and prevent the population from exploding.
For outdoor flowers, you can help bring down the numbers of aphids by introducing or encouraging a healthy ladybug population. Ladybugs feed on aphids and a wonderful way of using nature to protect your plants.
Hand picking both scale and aphids can be very quick and effective if there are only a few of them to get rid of. You can also get rid of aphids with a standard insecticidal soap spray, applies once or twice a day until you see some results.
Scale insects are a tougher call because their little shell of armor makes many standard insecticide treatments useless. Swabbing some neem oil (view on amazon) directly on them can be a better approach.
Incidentally, if your petunias are starting to wilt due to aphids, you can run the risk of attracting ants too. Outside it might not be too much of a problem but bringing ants inside the house is not a smart idea.
Aphids exude a sweet liquid called honeydew, and it will certainly draw sugar-loving ants.
3 – Sunlight
Sometimes your petunias can be lacking water due to excessive heat or sunlight, rather than an actual shortage of water. The hotter the temperature, the more water a plant will need to draw in order to compensate for the extra evaporation through the leaves.
So, even if you are watering as often as you should, it’s still not enough because your plants are struggling in the sun.
Yes, petunias do grow best in full sun so you don’t want to start moving your plants around. Just step up your usual watering schedule to keep up with your thirsty plants.
4 – Disease
Sometimes your wilting problems can be a sign of disease. Once you have eliminated all of the problems already mentioned, this is probably your next option.
Petunias are susceptible to Fusarium, which is a fungus rather than a true disease. The fungus invades the roots, and takes in the water before the petunias can. Just like an under-watered plants, this leads to wilting. You may also see yellowing or browning of the leaves as well.
This is usually an issue with outdoor plants, especially if you are growing crops like tomatoes or eggplant nearby. Unless you have potted your petunias with soil from outside, it won’t likely end up in houseplants.
Unfortunately, there isn’t much you can do in terms of treating this. Pull up your petunias and dispose (don’t compost them, or you will spread the spores). Cover the area with black plastic during the sunny days of summer and the heat will kill off the fungus.
Meanwhile, plant new petunias in another part of the garden.
General Petunia Care
Now that we’ve covered all the bases on why petunias wilt, we should have a brief overview on overall petunia care. As we already mentioned, petunias will bloom their best in sunny locations and should be planted in well-draining soil.
Due to their vigorous blooming habits, they do need a lot of nutrients. Add fertilizer (like this one by Jack’s on amazon) to their soil regularly through the summer. Compost is excellent for outdoor plants but you can use any standard indoor houseplant fertilizer if you prefer.
Depending on the variety, you might want to deadhead any spent blossoms to clean up the plant and to encourage more blooms.
Hopefully, next time you notice your lovely petunias are wilting, you’ll have a few tricks up your sleeve to diagnose and fix the problem.
Growing up with a mom who filled her home (inside and out) with all sorts of plants, Lisa got her start in gardening at a young age. Living now on her own with a home and yard full of plants (including an indoor greenhouse), she shares all the gardening tips she’s gained over the years.