Tag Archives: Yellow Giant Hyssop

Yellow Giant Hyssop Agastache nepetoides

Yellow Giant Hyssop is a strange looking plant. I noticed it as a tall candelabra scaffold of branches tipped with bottle brushes. This second year of looking at it is bringing out the skeletal beauty of the plants.

Agastache nepetoides Kuntze

July to September                                       N                                 Family: Lamiaceae

Yellow Giant Hyssop flower

Flower: Each branch is tipped with a flower spike. The individual flowers have green cup, 5 pointed lobed calyxes. They are in dense whorls on the spike. A few flowers open each day seemingly at random. The flower is tubular, less than half an inch long with rounded lobes at the end. Two lobes are on top. two lobes are on the sides. A single wider lobe forms a lower lip. The flower is listed as yellow but is usually creamy white, turning yellowish as it ages. there are four stamens and a pistil split at the end.

Yellow Giant Hyssop flower spike

Leaf: Leaves are opposite with long, up to two inches, grooved petioles. The leaves are twice as long, up to 6 inches, as wide with coarsely toothed edges. The leaf top is green with indented main veins. The under side is light green and covered with short hairs.

Yellow Giant Hyssop leaf

Stem: One main stem can reach 7 feet tall. A few branches go off oppositely from about half way up the stem. All the branch stems arch out then straight up. The stems are square, have four sharp angles, are light green, feel scratchy and are stiff.

Yellow Giant Hyssop under leaf

Root: The perennial root is fibrous with rhizomes.

Yellow Giant Hyssop stem

Fruit: Four seeds develop in the base of each calyx. they turn deep brown when ripe.

Yellow Giant Hyssop seeds

Habitat: This plant likes light shade and good soil with adequate moisture. It grows in open woods, along streams and roads.

 

Yellow Giant Hyssop

Yellow Giant Hyssop plant

Yellow Giant Hyssop might seem hard to miss because it is so tall. It is easy to overlook because the plants are so open. The flower spikes are long but only a few flowers, all short, open at a time so the spikes can appear to be thick branch tips. The color of Yellow Giant Hyssop is a medium green that blends into a background often much more colorful with brown-eyed Susans or boneset or white snakeroot.

Once noticed, Yellow Giant Hyssop catches the eye every time it is in the vicinity. As there are rhizomes, established plants can be part of small colonies.

The stems feel hard and stiff. They are brittle. The branches snap off the main stem, if pulled down a short ways. The main stem can be snapped off by the wind and the remaining part will send up a new main stem and branches.

I see these plants most commonly along the roadside. They can grow in open areas as overgrown pastures but are more common under trees along ditches.