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.
Here is 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 generous twice a week and monitor the soils 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 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…
How to Water 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.
Watering petunias first thing in the morning charges them with moisture before a hot Summers day ahead.
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.
Always water petunias with a really generous soak once a week rather then a light watering every day or so.
Watering thoroughly encourages the roots to develop and establish in the soil, so that the roots can draw up moisture when it is required.
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 roots 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)
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. Watering thoroughly helps petunia roots establish and access moisture deeper in the soil which so they can tolerate drought. Watering more often then once per week can cause root rot as petunias cannot tolerate boggy soil.
This advice is on the basis that petunias are planted in a good sized pot and importantly that the pot is not too shallow.
For smaller plants, petunias are actually fairly deep rooted which helps them access moisture deeper in the soil as an adaption to cope with drought.
If the pot is too shallow the petunias 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, you may have to increase watering frequency to 2 or 3 times per week.
If you are unsure of whether you should water your petunias, 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 with a generous soak.
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 compost for potting soil as it is able to retain moisture, yet also has the aerated, porous, well draining structure that petunia roots need to grow and access moisture and nutrients.
Planting petunias in compost along with watering once per week helps to maintain the optimal balance of moisture for your petunias.
Water petunias 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 petunias roots.
Ideally place your 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 air flow both of which favor petunias, however this means petunias can require watering as often as once every 2 or 3 days in 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 you basket is fairly shallow or crowded with other plants then you should water the petunias more often.
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 increase demand for water.
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 per 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 with a good soak to promote healthy root growth.
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 air flow, as it can sap moisture from the leaves and if there is hotter, dryer weather.
As recommend, 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 then 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 your petunias should display lots of flowers, if they are in full sun.
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 this promotes the conditions for root rot and fungal diseases.
- Water petunias in pots at least once per week with a good soak, 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 required to keep the soil moist but not boggy. Soil dries out in hanging baskets much quicker which increase petunias demand for water. Typically water once every 2 or 3 days to ensure that petunias have enough moisture.
- Water petunias in garden soil once a week with a through 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