Getting it to bloom

Why won't my Purple Giant Hyssop bloom? (and how to make it flower)

Also called Purple Giant Hyssop, Figwort-Leaved Giant Hyssop (Agastache scrophulariifolia).

More about purple giant hyssop

About Purple Giant Hyssop

Agastache scrophulariifolia · also called Purple Giant Hyssop, Figwort-Leaved Giant Hyssop · flowering

A tall native North American perennial found in woodland edges, thickets, and moist roadsides from the eastern US through the Midwest. Bears dense spikes of purple to rose-purple flowers from midsummer into autumn, providing vital nectar for long-tongued bees and hummingbirds. More tolerant of partial shade and moist soils than western hyssops. Excellent for native and wildlife gardens.

Plant type: flowering

Watch for — Powdery mildew: Common in humid, warm summers, especially in the Southeast. Improve plant spacing to 60 cm or more, avoid overhead watering, and cut plants back to basal foliage after flowering to encourage clean regrowth.

The reasons purple giant hyssop isn't blooming

Almost every non-blooming purple giant hyssop traces back to one of these, roughly in order of how common they are:

Too little sun — most of these need full sun (or very bright light) to flower well; shade gives leaves, not blooms.
Too much nitrogen feed, driving lush foliage at the expense of flowers (very common with general or lawn feeds).
The plant has not been deadheaded, so it stops flowering once it sets seed.
Irregular watering — drought or waterlogging at the budding stage makes buds abort.
It is still too young or was checked by a transplant and is rebuilding before flowering.

Feeding purple giant hyssop a high-nitrogen general feed and growing it in too little sun — you get a big leafy plant and almost no flowers.

The fix — how to get purple giant hyssop to flower

Maximise sun. Give purple giant hyssop the sunniest spot you have — for most bedding and fruiting plants, more direct light directly means more flowers.
Switch the feed. Move off high-nitrogen feeds and use a higher-potassium "bloom" or tomato-type feed as it comes into flower.
Deadhead regularly. Remove spent flowers often to keep it producing more rather than stopping to set seed.
Water consistently. Keep moisture even through budding and flowering — drought-then-flood swings make buds drop.

Light and feeding do most of the heavy lifting here. Dial in the spot with the light guide for purple giant hyssop and get the feeding right with the purple giant hyssop fertilising schedule — the wrong feed (too much nitrogen) is one of the most common silent reasons a healthy plant makes leaves instead of flowers.

Bloom season and what to expect

Purple Giant Hyssop flowers across its growing season (mostly summer) and, kept fed and deadheaded, can bloom for many weeks or right up to frost.

Post-bloom care so it flowers again

Deadhead, keep feeding lightly, and many will rebloom; collect seed from the best plants at the end of the season if you want to grow them again.

For everything else this plant needs day to day, see the full purple giant hyssop care brief and its watering schedule — a stressed, badly watered plant rarely has the energy to flower at all.

Purple Giant Hyssop blooming — frequently asked questions

Why won't my purple giant hyssop flower?

Purple Giant Hyssop blooms on the season's growth given enough sun, warmth and the right feed — there is no cold or photoperiod trick, just good growing conditions and a bloom-leaning feed. The most common reason it is not happening: Too little sun — most of these need full sun (or very bright light) to flower well; shade gives leaves, not blooms.

How do I make purple giant hyssop bloom?

Give purple giant hyssop the sunniest spot you have — for most bedding and fruiting plants, more direct light directly means more flowers. Move off high-nitrogen feeds and use a higher-potassium "bloom" or tomato-type feed as it comes into flower.

When does purple giant hyssop normally bloom?