Are concerned that you may be overwatering or underwatering your petunias? I have seen many petunias suffer from water issues, and I know it can be tricky to get it right.
From my experience, I have observed that most of the problems occur because either the petunias have recently been planted or because the penguins are planted in pots or hanging baskets and dry out in the sun (because our petunias need to grow in full sun to flower to their best).
As a general rule, water petunias once a week, with a thorough watering to promote healthy roots. Petunias prefer soil that is evenly moist, yet well draining as damp soil causes root rot. Wait until the top inch of soil feels only slightly moist before watering petunias again with a generous soak.
Because there are a few different ways to plant your petunias, I created a quick reference table for how to water petunias in garden soil, pots, hanging baskets, and in hot weather…
| Conditions: | How Often to Water Petunias: |
|---|---|
| Petunias planting in garden soil. | Typically water once per week with a generous soak. |
| Petunias in pots and containers. | Water thoroughly at least once a week then let the top inch of the soil dry slightly before watering again. |
| Petunias in hanging baskets. | Water generously twice a week and monitor the soil’s level of moisture as hanging baskets can dry out very quickly. Water generously if the top inch of the soil starts to dry out. |
| Petunias in hot weather. | Adjust how often you water petunias during heat waves. Water thoroughly when the top inch of the soil starts to dry out to avoid wilt. |
Keep reading for my tips on how to water petunias to maintain the optimal balance of moisture for flowering and how to establish a watering schedule for petunias according to your climate and conditions…
My Tips for Watering Petunias
The best way to water petunias is to give them a really good soak early in the morning, then wait 7 days before watering again. Petunias are relatively drought resistant and require well-draining, somewhat moist soil and do not tolerate boggy or overwatering.
I like to water petunias first thing in the morning as it charges them with moisture before a hot summer day ahead.
Pro tip: Petunias prefer lower humidity, so watering early in the morning also gives a chance for any water on the leaves or around the petunias to dry off, as watering in the evening (when temperatures are cooler and there is less evaporation) can promotes conditions that cause powdery mildew and other fungal diseases.
I must emphasize the importance of always watering petunias with a really generous soak once a week rather than a light watering every day or so (this is a really common mistake I see).
The reason we water thoroughly is because it encourages the roots to develop and establish in the soil so that the roots can draw up moisture when it is required.
What we want to avoid is watering too lightly only moistens the surface of the soil which encourages the roots to grow shallow near the surface to access the limited available moisture.
Shallow root systems are not able to access the moisture that petunias need in times of drought or nutrients for healthy growth and good flowering.
How Often to Water Petunias (in Pots and Containers)
I find it’s always helpful if we understand how our plants grow in their natural habitat so we can recreate these conditions in our gardens…
Petunias are native to South America where they grow in warm, open areas with low humidity and in well-draining soil.
Due to their South American origins, petunias are actually quite drought-resistant, which is why they are so popular for growing in pots, containers, and hanging baskets.
Petunias in pots with well-draining soil should be watered once per week with a really good soak.
As we discussed, watering thoroughly helps petunia roots establish and access moisture deeper in the soil which so they can tolerate drought. Watering more often than once per week can cause root rot, as petunias cannot tolerate boggy soil.
The secret to growing petunias is to plant them in relatively deep pots.
For smaller plants, petunias are actually fairly deep-rooted, which helps them access moisture deeper in the soil and adapt to cope with drought.
If the pot is too shallow, the petunia roots cannot establish and access the moisture they require, which can cause them to wilt from drought stress.
In times of persistent heat and blazing sunshine, I sometimes have to increase my watering frequency to 2 or 3 times per week.
If you are unsure of whether you should water your petunias, then I have a great tip for you! Feel the top inch of the soil with your finger. If you can detect moisture, then delay watering. If the soil feels just as though it is drying out, this is the perfect time to water it with a generous soak.
I personally find this method more precise the using moisture meters and given petunias sensitivity to overwatering.
Leaves of petunias can wilt due to overwatering as well as underwatering and as a way to conserve moisture in extreme heat, so its always best to feel the soil to establish whether your petunias need watering as wilt could be a sign of root rot due to boggy soil.
(Read my article, how to revive dying petunias).
Petunias also require regular compost for potting soil as it can retain moisture, yet it also has the aerated, porous, well-draining structure that petunia roots need to grow and access moisture and nutrients.
Pro tip: If you live in a hot climate (like me) and you are planting petunias in pots or hanging baskets, then I like to amend the potting soil with some leaf mold as this helps to retain more moisture, which mitigates the risk of drought, on blazing hot summer days. I find it makes a really significant difference.
Planting petunias in compost, along with watering once per week, helps to maintain the optimal balance of moisture for your petunias.
Water petunias are in pots and containers with a generous soak so that excess water trickles from the base of the pot. This ensures that the water has infiltrated the soil so that it is evenly moist and reaches the petunia roots.
Pro tip: What I like to do is place my petunia pots and containers on pot feet to elevate them off the ground to help ensure water can escape freely from the bottom of the pot as petunias require moist soil but do not tolerate damp soil as this causes root rot.
How Often to Water Petunias in Hanging Baskets
Water petunias in hanging baskets at least once a week with a generous soak. Hanging baskets have exceptional drainage and increased airflow both of which favor petunias, however, this means petunias can require watering as often as once every 2 or 3 days during a heat wave to avoid wilting.
Exactly how often to water your petunias in hanging baskets largely depends on the size of the hanging basket, how much moisture the potting medium retains, the weather, and airflow.
As there are so many variables that can affect how often to water petunias in hanging baskets it is always best to feel the soil to an inch depth.
Petunias thrive when they are watered thoroughly and in full sun, then the soil is left to dry somewhat to the point it should only feel slightly moist before watering the basket again.
This replicates the typical cycle of watering that they experience in their native South America and maintains the balance of moisture that allows the petunias roots to draw up the moisture they need without being in soil that is too damp and causes root rot.
If your basket is fairly shallow or crowded with other plants, then you should water the petunias more often.
To be honest, I use an automated watering system for my hanging basket petunias, which is set to water once per week, but I top it up halfway through the week if it has been particularly hot, but I always feel the soil beforehand.
Shallow baskets have less capacity for soil and, therefore, less moisture, which can cause the petunias to wilt quickly in high temperatures.
If the hanging basket is relatively crowded then the roots of the plants are competing for moisture which increases water demand.
Important tip: If you keep feeling the soil to detect when the soil typically starts to feel somewhat dry then you can determine the correct watering schedule for your hanging basket according to your climate to ensure the optimal balance of moisture to keep petunias healthy and displaying flowers.
How Often to Water Petunias in Garden Soil
Typically, watering petunias once a week in garden soil ensures a good balance of moisture to support flowering yet avoid root rot. Adjust how often you water petunias if the soil dries out quickly, and always water them with a good soak to promote healthy root growth.
However, this depends on how recently your petunias are planted. Petunia is, of course, perennial (which means they come back every year), so if your petunia is established, then they may not need much watering at all.
But generally if this is the first year of planting I recommend watering your petunias once per week with a really good soak to get them estblished.
Exactly how often you should water petunias in garden soil also depends on factors such as drainage, climate, and airflow conditions.
I recommend amending garden soil with lots of compost in the planting area prior to planting petunias in your garden.
Compost retains the moisture necessary for petunias to thrive and allows for good drainage to prevent root rot.
You may need to increase how often you water petunias if there is lots of airflow, as it can sap moisture from the leaves and if there is hotter, dryer weather.
As we previously discussed, the best way to establish the optimal water schedule for your petunias is to monitor the soil to see when the top inch of the soil starts to feel dry, at which point, water your petunias thoroughly.
Generally, petunias in garden soil require watering less often than potted or hanging basket petunias and should benefit more from rainfall.
However, diligent monitoring of the soil moisture allows you to establish the optimal watering schedule for your climate and conditions.
This cycle of watering supports healthy growth, and if your petunias are in full sun, they should display many flowers.
Key Takeaways:
- Water petunias as often as required so that the soil is moist but not boggy. Petunias prefer evenly moist yet well-draining soil. Typically, watering once every 7 days provides the optimal balance of moisture for petunias. If the soil is too damp, it promotes the conditions for root rot and fungal diseases.
- Water petunias are in pots at least once per week, and they should be soaked well so that excess water trickles from the base of the pot. Water petunias again if the top inch of the soil starts to dry out, with a thorough watering to promote healthy root growth.
- Water petunias in hanging baskets as often as necessary to keep the soil moist but not boggy. Soil dries out in hanging baskets much quicker, increasing the petunia’s water demand. Typically, water once every 2 or 3 days to ensure the petunias have enough moisture.
- Water petunias in garden soil once a week with thorough watering to help establish the roots. Petunias are relatively resistant to drought but do not tolerate boggy soils, so wait until the top inch of the soil is somewhat dry before watering the petunias again with a generous soak