Agastache 'Black Adder' (Giant Hyssop) - Image 2

Categories: Agastache, Perennials

Agastache ‘Black Adder’ (Giant Hyssop)

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Plant information

Colour: Blue, Purple
Height: 90cm-100cm
Spread: 80cm-90cm
Soil: Can tolerate moderately poor soils, but avoid heavy clay that holds water
Position: Full Sun, Part Shade
Flowering Period: Summer to Autumn
Hardiness: Frost Hardy to -8°C (H4)

Plant Description

Agastache ‘Black Adder’ is a compact variety ideally placed at the front of borders or in containers. It features impressive large blue/purple flower spikes accompanied by lush green foliage. This plant brings continuous blooming joy throughout the summer months. ‘Black Adder’ displays resilience, thriving in poor soils and demonstrating tolerance for dry periods once it has established itself. With its captivating appearance and adaptability, this agastache variety is a fantastic choice for enhancing gardens or potted displays.

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🌿 How to Care for Agastache ‘Black Adder’ (Giant Hyssop)

How much sun do Agastache ‘Black Adder’ (Giant Hyssop) need?

Agastache ‘Black Adder’ (Giant Hyssop) thrives in full sun—around six hours a day. While it can tolerate light shade, you’ll get the best flowering in bright, open spots.

What type of soil is best for Agastache ‘Black Adder’ (Giant Hyssop)?

Agastache ‘Black Adder’ (Giant Hyssop) prefers well-drained soil, ideally sandy or chalky. Rich or heavy soils can cause the plant to flop and reduce flower production.

How often should I water Agastache ‘Black Adder’ (Giant Hyssop)?

Water well during the first growing season to help it establish. Once settled, Agastache ‘Black Adder’ (Giant Hyssop) is drought-tolerant and rarely needs extra water unless it’s extremely dry.

Do i need to feed Agastache ‘Black Adder’ (Giant Hyssop)?

Agastache ‘Black Adder’ (Giant Hyssop) doesn’t require much at all. In fact, too much fertiliser—especially nitrogen—can lead to more leaves and fewer flowers. A light feed in spring is plenty, if needed.

Should I deadhead or cut back Agastache ‘Black Adder’ (Giant Hyssop)?

Yes—regularly remove faded flowers from Agastache ‘Black Adder’ (Giant Hyssop) to encourage more blooms and stop self-seeding. You can cut the plant back in autumn or early spring to tidy it up and boost new growth.

When should I divide or propagate Agastache ‘Black Adder’ (Giant Hyssop)?

Divide Agastache ‘Black Adder’ (Giant Hyssop) into clumps every 3 to 5 years in spring or autumn to keep them healthy and vigorous. You can also take soft cuttings in spring.

Are Agastache ‘Black Adder’ (Giant Hyssop) drought-hardy?

Yes, Agastache ‘Black Adder’ (Giant Hyssop)is drought handy. Once it’s established, it copes brilliantly in dry conditions, making it perfect for sunny borders and gravel gardens.

What pests or diseases affect Agastache ‘Black Adder’ (Giant Hyssop)?

Agastache ‘Black Adder’ (Giant Hyssop) is generally low-maintenance, but it can occasionally suffer from aphids or powdery mildew—especially in humid or overcrowded spots. Good airflow and spacing usually prevent problems.

Agastache ‘Black Adder’ (Giant Hyssop)

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🌿 How to Care for Agastache ‘Black Adder’ (Giant Hyssop)

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