Agastache Isn't Blooming

Agastache requires little maintenance during the growing season to support healthy growth and continued blooming. When these plants are not blooming well, a variety of reasons. Lack of full sun exposure, soil that is too acidic, and over-fertilization are three common situations that are easy to correct when growing these herbaceous perennials. Using certain pruning techniques can also influence how well and how long Agastache blooms through the summer months. 


Common Reasons Why Agastache Isn’t Blooming

Agastache plants prefer to live in a Mediterranean-type climate. This includes lean soil, which will keep the plant from growing excess foliage. Full sun exposure is also a must for Agastache to produce the most and largest flower spikes. Provide at least 6 hours of full sun exposure, and move plants if they are in too much shade. Excellent drainage, especially during the winter months, is key to preventing root rot diseases and frozen roots. Soil with pH levels below 6.0 can prevent the plant from taking up important micronutrients. Test your soil and make sure that the pH is between 6.0 and 8.0 if flowering is poor or even non-existent. 

Pruning Agastache To Help It Bloom

Encouraging flowers in herbaceous perennials requires two types of annual pruning techniques: pinching and deadheading. Pinching involves snipping the top 1-2 inches of each stem just above a set of leaves; it should be done early in the spring as new growth emerges. Pinching promotes bushy stems that have more flowers. 

Deadheading is used to extend the blooming season and to control self-seeding plants. After the flowers die back and before they set seed, cut the stems down to a set of leaves. This will allow any flower buds further down the stem to develop and continue the blooming season. 

Fertilizing Agastache To Help It Bloom

Agastache is an herbaceous perennial that requires minimal fertilizing when planted in slightly acidic to alkaline soil. One feeding in early spring, as new growth comes up, is generally more than sufficient to support healthy growth and large flower spikes. Choose an organic fertilizer with a balanced NPK ratio in a granular, slow-release form. Fertilizers high in nitrogen (N) encourage too much foliage growth at the expense of flower development. Mulching with organic compost early in the spring or in the fall before the plants go dormant will also add low levels of nutrients to the soil while suppressing weeds and aiding in moisture retention. 

Get Agastache To Produce More Blooms

Long-blooming perennials like Agastache typically retain flowers throughout the season with little attention. The tall flower stems seem to grow taller as they bloom from the base to the top of the spike. Pinching and deadheading will encourage the plant to produce more flower buds, which will continue to develop late into the summer. 

Why Agastache Isn’t Blooming

  • Planted in too shady of a location
  • Soil pH is outside 6.0 - 8.0 range
  • Over-fertilized or fed too much nitrogen
  • Spent blooms are going to seed
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Author Robbin Small - Published 7-16-2023