Fertilizing St. John's Wort

Hardy perennials and shrubs generally need far less fertilizing than tender perennials and annuals to perform at their best. St. John’s Wort will benefit from an annual feeding early in the spring to support blooming and fruiting of the berries if it is planted in average or moderately fertile soil. Gardens that have poor soil may benefit from an extra application after blooming if fewer berries are formed than usual. 


How to Fertilize St. John’s Wort

St. John’s Wort grows well in just about every soil type and pH level. Fertilizing in the early spring with a balanced, slow-release fertilizer will support all parts of the shrub while not encouraging too much foliage growth. Lightly scratch a granular feed into the soil around the root zone of the shrub, which will slowly dissolve into the soil every time the plant is watered.

The slow-release formulas deliver nutrients in smaller doses over a longer period. Be careful to brush any fertilizer off the foliage to prevent leaf burn. Always water in granular fertilizers at the end of the application. 


Best Time To Fertilize St. John’s Wort

A fertilizer application early in the spring as the shrub comes out of dormancy is the best time to fertilize this shrub. The plant's roots will be growing and eagerly seeking out moisture and nutrition. More than one application during the growing season is rarely needed if you use a slow-release granular feed. Feeding shrubs late in the summer or fall is not recommended. The plants are preparing for dormancy and do not need as much nutrition going into the fall and winter. 

Best Fertilizer For St. John’s Wort

Slow-release, granular fertilizers work best for shrubs planted in the ground. Look for one that has a balanced ratio of Nitrogen, Phosphorus, and Potassium (NPK). Fertilizers with a 10-10-10 NPK ratio will benefit general overall growth, particularly if the blooming and fruiting have been consistent.

If the blooming and berry development start to decline, look for an NPK ratio of 1-3-2 in a fertilizer. The middle and end number  (Phosphorus and Potassium) specifically support flowering and root formation. Brands such as Fox Farms and Espoma have blends specifically designed for flowering shrubs such as roses. 

St. John’s Wort Fertilizing Tips

  • One application of a slow-release, balanced fertilizer early in the spring will support season-long growth
  • Use a fertilizer made for blooming shrubs if the flowering or fruiting declines as the plant mature
  • Late-season fertilizing will disrupt the plant's preparation for dormancy.


-Always wear protective gloves and a face mask when handling chemical fertilizers.

-Closely follow all directions and storage guidelines that are on the fertilizer label.

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Author Robbin Small - Published 8-15-2022