At the moment, nothing looks better than the ‘Golden Jubilee’ anise hyssop (Agastache rugosa ‘Golden Jubilee’, Zone 6) in my garden. Almost everything else is showing signs of distress from the weather. Heavy rains collapsed the ‘Annabelle’ hydrangeas, which are now blooming on the lawn. Heat pushed my favourite Japanese beetle-resistant rose, Double Knock Out, rapidly through its first big flush of flowers in record time. But ‘Golden Jubilee’ hyssop is standing straight, with no signs of stress or damage, and blooming like every day has been a piece of cake. This is a very reliable plant.
‘Golden Jubilee’ starts out bright chartreuse in spring and gradually turns almost pure yellow as summer goes along, putting out long-lasting blue flowers. I have a clump of ‘Blue Fortune’ (A. ‘Blue Fortune’, Zone 6), with green leaves and lavender-blue flowers, and it’s also standing tall and in full bloom. These plants like heat and sun, and prefer their soil to be slightly dry. Mine grow at the top of a small rise in grade and drainage has been sufficient to prevent them from standing in saturated soil after heavy rains.
If I were planting hyssops in a flat, level garden bed, I’d give them some soil amendments to improve drainage. A good recipe might be two parts coarse sand or grit, one part garden soil, and one part compost or composted manure. Lavender and shorter ornamental grasses such as variegated purple Moor grass (Molinia caerulea ‘Variegata’, Zone 4) would enjoy the same soil mix and be good companion plants.
There are several other fancy hyssop cultivars with brightly coloured flower spikes, such as ‘Pink Panther’ and ‘Apricot Sunrise’, but alas, they’re hardy only to Zone 7. Even though my ‘Golden Jubilee’ and ‘Blue Fortune’ plants are hardy to Zone 6, I don’t risk losing them in my borderline hardy Zone 6a garden. I put them into pots and winter them over in the unheated garage. I learned this the hard way after losing a lovely ‘Blackadder’ hyssop by leaving it out in the garden over winter. It only takes a couple of minutes to get the hyssops into pots and stored away, and that’s a small price to pay for such beautiful and durable plants.