Watering St. John's Wort

St. John’s Wort is a shrub that thrives in poor soils and becomes more drought tolerant as it matures. The fibrous root system can be trained to go deep into the ground where it will be more protected from heat, cold, and dryness of the weather. Watering with drip irrigation or a soaker hose system also helps to target water to the root zone reducing evaporation and wet foliage issues. 


How To Tell If St. John’s Wort Needs to be Watered

St. John’s Wort needs minimal supplemental watering after it has fully established, but it does require consistently moist soil after first planting. Lack of watering is indicated by drooping foliage and flowers that either fail to open or fall off the plant before opening. The berries may also stay smaller than usual without sufficient watering.  


How Often To Water St. John’s Wort

Newly planted shrubs require around 1 inch of water a week. If there is not enough rainfall, supplement with 2 or 3 watering sessions during the week. Watering for longer periods less often during the week forces the roots to grow deep in the ground. Watering more often for short periods of time encourages very shallow root systems that are not able to survive periods of drought and heat.

St. John’s Wort will need less supplemental watering as it matures. If you garden in a zone that experiences rainfall during the summer months, no extra irrigation may be necessary. In zones where summers are dry, watering an inch every week to 10 days will be sufficient. The most critical times to pay attention to watering will be just as the flower buds form and later in the summer as the berries begin to form.

Container-grown St. John’s Wort will need regular attention to watering. Let the pot dry out a bit between sessions so that the roots do not stay wet all of the time. When the top 2-3 inches of soil are dry, it is time to water. Soak the container long enough that excess water runs out of the drainage holes. Depending on the size of the pot, watering may need to be done on a daily basis during very hot or dry weather.

Best Time To Water St. John’s Wort

Watering is always best done early in the day, while the soil is still cool and possibly even slightly damp from the night. Evaporation will be at a minimum and the plant will be transpiring less through its leaves. Watering during the winter is not normally needed for St. John’s Wort. The shrub is in a dormant state through the winter until the weather warms in the spring.

How to Water St. John’s Wort

Step 1 - Is the shrub newly planted?

Watering needs to be done 2-3 times a week for a total of 1 inch of water per week. Long, infrequent watering encourages deeper root growth.

Step 2 - Does the shrub have drooping leaves, unopened and dying flower buds, or small fruit?

Watering the mature St. John’s Wort is only needed if there has not been sufficient rain in growing areas that are hot and dry during the summer.

Step 3 - Is this a container-grown plant?

St. John’s Wort growing in a container needs watering on a consistent basis. Daily watering may be necessary during the hottest part of the summer. Let the pot dry out in between watering. 

St. John’s Wort Watering Tips

  • Hypericum is a drought tolerant shrub after it has established and matured
  • Using drip irrigation or soaker hoses efficiently gets the water to the plant's root zone with little evaporation
  • Container-grown pots may need more frequent watering
  • Watering is most critical during flower bud formation and berry setting
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Author Robbin Small - Published 8-15-2022