Giant hyssop (Agastache 'Purple Haze')
Agastache 'Purple Haze' (Giant hyssop) is an upright, low-maintenance perennial offering smoky bluish-purple summer blooms for borders and attracting pollinators.
Complete Plant Information
Overview
Agastache ‘Purple Haze’, commonly known as Giant hyssop, is a standout herbaceous perennial celebrated for its extended bloom period and striking columnar appearance. This cultivar provides a soft, “bluish-purple haze” aesthetic to summer and early fall gardens, drawing in essential pollinators like bees and hummingbirds. The aromatic foliage, scented with anise or licorice, adds another sensory layer to garden beds where this variety thrives.
As a hybrid Giant hyssop, ‘Purple Haze’ often exhibits superior garden performance and hardiness compared to some species forms. It forms an upright, clump-forming silhouette, reaching about 2 to 2.5 feet in height with a manageable spread of 1 to 1.5 feet, making it an excellent choice for defined borders. Gardeners value its low maintenance requirements once established, provided its critical need for excellent drainage is met.
Its densely packed, smoky bluish-purple flower spikes contribute substantial vertical interest from mid-summer well into autumn. The combination of drought tolerance (once rooted) and deer resistance makes Agastache ‘Purple Haze’ a reliable workhorse for sunny, low-input perennial landscapes.
Fast Facts
- Plant Family: Lamiaceae
- Plant Type: Herbaceous perennial
- Hardiness Zones: USDA Zones 6-9
- Size at Maturity:
- Height: 2-2.5 ft
- Spread: 1-1.5 ft
- Bloom Time: July to September
- Bloom Description: Smoky bluish-purple
- Sun Exposure: Full sun
- Water Needs: Medium
- Maintenance Level: Low
How to Grow
For optimal health, Agastache ‘Purple Haze’ requires planting in the spring after all danger of frost has passed, allowing it time to establish roots before winter. The single most critical factor for successfully growing this Giant hyssop is soil drainage; it must be sited in very well-drained soils, even if they are only average in fertility. While it prefers sharp drainage, it tolerates medium moisture and heat once mature.
Water newly planted specimens regularly to establish a robust root system. Established plants handle medium water needs, but they absolutely cannot tolerate heavy, slow-draining clay soils, as this almost guarantees crown or root rot, resulting in winter failure. Fertilizing is generally unnecessary; over-fertilizing can lead to weak, floppy stems, which diminishes the upright appeal of this variety.
Maintenance for Agastache ‘Purple Haze’ is generally low. Deadheading faded flower spikes can encourage a second round of blooming through September. In late winter or early spring, cut back the old, dead foliage near the crown. If winter survival is a concern in the colder end of its range (Zone 6), consider placing plants in protected spots, like against a warm south-facing wall, and leaving the stems uncut over winter for insulation.
Landscape Uses
The upright habit and extended bloom time make Agastache ‘Purple Haze’ an outstanding choice for sunny, mixed borders where vertical accents are needed. Its strong, architectural spikes contrast beautifully with softer, mounding perennials. Because it is aromatic and highly attractive to pollinators, it fits perfectly into cottage gardens designed to maximize wildlife interaction.
Consider planting this Giant hyssop near patios, seating areas, or along frequently used walkways. This placement allows gardeners to fully appreciate the anise-scented fragrance both from the foliage and the masses of tiny, dusky flowers. While listed for annual use in some regions, its perennial nature in Zones 6-9 means it provides reliable structure year after year.
This long-blooming perennial is also effective when used as an informal hedge or planted in drifts for mass color impact. It combines well with silvery foliage plants or perennials that bloom earlier in the season, ensuring continuous garden interest.
Standout Features
Flower Qualities
- Showy
Noteworthy Characteristics
Agastache, commonly called giant hyssop, is a genus containing about 30 species of upright herbaceous perennials, most of which are native to North America. Hybrid flowers typically feature dense terminal spikes of tiny 2-lipped tubular flowers that bloom mid-summer to fall atop stiff square stems clad with fragrant, gray-green to medium green leaves. The specific cultivar ‘Purple Haze’ creates an impressive smoky bluish-purple haze in the garden and grows to about 32 inches tall. Its flowers are inherently attractive to vital garden visitors like bees, hummingbirds, and butterflies.
Tolerances
- Deer
Potential Problems
The primary concern when growing Agastache ‘Purple Haze’ revolves around soil moisture management. Crown rot or root rot is highly likely to develop if the soil retains too much water, especially during winter dormancy periods. This is why maximizing soil drainage during planting and siting is crucial.
While generally robust, keep an eye out for common fungal issues that affect related plants. Powdery mildew, rust, and leaf spots can occasionally appear, usually in very humid conditions or when air circulation is poor. Ensure plenty of space between plants to promote good air movement, which helps reduce disease pressure. No serious insect pests commonly bother this variety of Giant hyssop.
Frequently Asked Questions
What hardiness zones is Giant hyssop suitable for?
Agastache ‘Purple Haze’ is typically hardy in USDA Zones 6 through 9, allowing for reliable perennial growth across much of the temperate US.
How large does Agastache ‘Purple Haze’ grow?
This upright perennial generally reaches a mature height between 2 and 2.5 feet tall, spreading modestly to about 1 to 1.5 feet wide.
When does Giant hyssop bloom?
Agastache ‘Purple Haze’ offers a continuous bloom display starting around July and continuing beautifully through September, showcasing its smoky bluish-purple flowers.
What sun exposure does Agastache ‘Purple Haze’ need?
This plant thrives best when situated in a location receiving full sun throughout the day.
Conclusion
For gardeners seeking long-lasting vertical structure, reliable drought tolerance, and excellent pollinator attraction late in the season, Agastache ‘Purple Haze’ is an essential perennial. This superb Giant hyssop cultivar delivers striking bluish-purple tones with minimal fuss, provided drainage is excellent. Before planting, confirm your site receives full sun and has sharp drainage, ensuring your commitment to this beautiful plant pays off season after season.
Companion Planting
Companion planting near Agastache ‘Purple Haze’ should focus on species that also thrive in full sun and demand excellent drainage. Pairing it with plants that possess lighter foliage helps contrast the darker flower colors of the Giant hyssop. Consider incorporating ornamental grasses, which share similar sun/drainage needs and provide textural contrast.
Plants like Sedum varieties (especially upright types), Coneflowers (Echinacea), or Coreopsis offer reliable summer bloom times that overlap perfectly with the flowering schedule of ‘Purple Haze’. Avoid moisture-loving woodland edge plants, as placing them near the Giant hyssop will inevitably lead to conflicting soil management needs and potential rot issues for the Agastache.
Design Ideas
Using Agastache ‘Purple Haze’ as a spacer plant between larger drifts of perennials allows its slender, upright form to interrupt the mass without overwhelming it. It functions beautifully when massed in groups of three or five within a sunny perennial border, creating a repetitive vertical rhythm across the landscape.
When designing spaces near seating areas, incorporate herbs like culinary sage or thyme nearby; while these plants have different structures, their aromatic qualities complement the anise scent of the Giant hyssop foliage. In modern or drought-tolerant gardens, interplanting Agastache ‘Purple Haze’ with Yucca or ornamental grasses like Panicum creates a dynamic, water-wise tapestry.
