Petunias are one of the most popular flowering plants in gardens. These fast-growing bloomers come in any color imaginable and do well in any climate.
You may want to plant petunias because they give your garden a lovely floral scent. That said, you may feel confused about how much water they need.
That’s because there are hundreds of petunia varieties, and each type has different watering needs. What’s more, soil type, climate, and planting location all influence how much you should water these annuals.
Don’t worry if this sounds overwhelming. I’ll discuss everything you need to know about watering petunias in this quick guide!
Petunias are native to South America and do best in warm, sunny climates. They have funnel-shaped flowers that can come in single or double-bloom varieties.
These flowers are technically perennials, but many grow them as annuals. They bloom from early summer until early winter.
It’s important to know that petunias can’t stay dry for long. You must water them regularly, but you should also avoid turning the soil soggy.
According to the LA Times, it’s game over once a petunia wilts from over or under-watering.
Luckily, with proper care and well-draining soil, you can get healthy petunias blooming all summer long!
Wilting and yellowing leaves are signs that you’re under-watering your petunias. However, you should avoid letting the petunias reach this stage as they might not recover.
Following a strict watering schedule helps, but this method isn’t foolproof. Changes in weather and seasons can affect how wet the soil is.
Instead, the best way to tell if petunias need watering is through the ground moisture.
You should regularly check the top two inches of the potting mix. If it’s dry, it’s time to water the petunias.
To add to this, you may want to invest in soil moisture sensors to determine if it’s time for watering.
You can have different watering methods depending on where and when you plant your petunias. Here’s what you need to know.
Some varieties of petunias grow well in containers, while others do better in garden beds. Each has specific needs, and you should consider this when watering based on planting location.
Common varieties that grow well in garden beds are the multiflora and ground-cover petunias.
Multiflora petunias, like the Carpet variety, are compact and smaller than other varieties. They’re resistant to wet and rainy conditions so you don’t have to worry about overwatering.
Meanwhile, ground-cover petunias have excellent heat and drought tolerance. Yet, if you give them plenty of water and fertilizer, they’ll spread rapidly throughout your garden.
Ground-cover petunias need more frequent watering than multiflora petunias. In general, it’s ideal to do a once-a-week deep watering.
According to the University of Minnesota, you should soak the soil six to eight inches deep every week.
Avoid watering less than this amount when you have petunias in garden beds. Doing so can result in shallow root growth.
The most common petunia variety for hanging baskets and window boxes is the Grandiflora. This is due to its beautiful cascading habit.
Grandiflora petunias struggle in hot climates, and you have to water them daily depending on their size and container volume.
You may want to bring the hanging basket indoors if you have rainy weather.
Grandifloras can’t handle a constant flow of water. Even humid environments can cause droopiness in these plants!
Similar to petunias in hanging baskets, those in containers, like the milliflora variety, need daily watering.
Milliflora petunias are miniature plants perfect for containers. This is so you can view them up close.
To determine if you need to water the pot, my tip is to feel the soil for moistness. If the top one to two inches are dry, it’s time to water your potted petunia.
It’s worth noting that Millifloras have a high tolerance for wet conditions. You can water it more often than Grandifloras in hanging baskets.
Young petunias require less water than mature ones. Here’s how to wear your petunias based on the growth stage.
Petunia seeds need moist soil.
To water them, pack the pot with soil until it’s one inch from the top. Next, partially submerge the bottom in water and wait for the surface to get wet.
After this, allow the soil to drain for 15 to 20 minutes before sowing the seeds.
Cover the pot with cling wrap to maintain the moisture levels. Remove this covering once the petunias germinate in seven to ten days.
From here, you should let the potting mix dry between waterings to make the stems stocky. Only transfer the seedlings into bigger containers once they produce three leaves.
It takes 10 to 12 weeks for petunia seedlings to become established. In the meantime, since the young plants grow in bunches, they might absorb more moisture than mature plants.
Make sure to constantly check the soil moisture and give your growing petunias adequate water in their early stages.
Petunia seedlings don’t have deep roots yet, and it’s a must to water them lightly and frequently. You may need to water daily even—but check for soil moisture before doing so.
If the surface is dry, sprinkle or mist it with water immediately.
You should use a good draining potting mix, as too much water can wash soil away too. As a result, the young seedlings won’t develop a proper root structure.
The weather and seasons have an impact on your watering schedule. Here are some petunia watering tips based on the weather.
In hot climates that rarely receive rain, you may water petunias up to two times daily. This is because petunias grow in full sun, and the heat can dry soil out.
Mulching can help you retain soil moisture in this case.
If you live in an area with constant rain, you should hold back on watering your petunias.
You may want to move petunia pots to a covered area to prevent overwatering. If your flowers are bedded, you can cover them with plastic sheets as well.
For those in warmer climates, you can continue watering petunias during winter. Take note that you should lessen the amount of water since these flowers can go dormant.
Instead of watering bedded petunias deeply, you should only sprinkle water on the top few inches of the soil once it’s dry.
For potted petunias, cut the stems back, bring the plants indoors, and water only when dry.
Yes, it’s possible to overwater petunia plants if you’re keeping them in containers.
Pots and hanging baskets may not have enough drainage holes. This means water can get trapped in the pot and drown the petunia’s roots.
Overwatered petunias have yellowing or browning leaves that may start to fall off. Root rot will develop, and it’ll make the plant susceptible to infections as well.
To revive an overwatered petunia, stop watering for a few days to let the soil dry. Pruning the dying leaves will help the plant recover.
If you notice root rot, you should change the wet soil.
To do this, gently take the petunia out of the pot and brush all the soil away. Remove damaged parts and transfer them to a new pot with fresh soil.
If you have potted petunias in areas that don’t receive much rainfall, you may need to water them once a day.
For petunias in garden beds, however, deep water them once a week.
The amount of water petunias need depends on weather and plant maturity. As a general rule, petunias need a constant moist environment to thrive.
So, the soil should be moist most of the time, but it shouldn’t get soggy.
For bedded petunias, six inches of water once a week is ideal. Meanwhile, for potted petunias, one to two inches of water per day is necessary.
The best time to water petunias is early in the morning. That’s because it’ll give the flowers enough moisture to withstand the afternoon heat.
Moreover, watering in the morning can prevent oversoaking. The excess moisture evaporates throughout the day, saving you the hassle.
Petunias need a well-draining type of potting mix. Loose soil can let water run through to avoid overwatering your plants.
To achieve this, you could use a garden fork to loosen the top ten inches of soil. It helps mix sand or gravel into clay soil and improve drainage.
Petunias are one of the fastest-growing flowering plants. However, because of some factors, you may need to water them accordingly.
Variety, weather, and planting location all affect how much water you should use on petunias. These annuals have varying watering needs based on their growth stage as well.
Be careful not to overwater or underwater petunias! Once they wilt, it’s difficult for them to recover.
Don’t worry. If you follow this petunias watering guide, you’ll get healthy blooms all summer.
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.