Fall color in the perennial garden

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(Host) Commentator Charlie Nardozzi says that a couple of new additions to his garden are guaranteed to keep the flower show going until frost.

(Nardozzi) While many perennial gardens have enjoyed the cool, rainy weather we’ve endured this summer, come fall most perennial gardens turn into a two-flower show. Asters and sedums certainly are the all-stars of the late summer garden, but there are some other choices that will give your fall garden a color boost.

The first perennial on my list is a gaudy plant, but I love it. The perennial hibiscus looks like the tropical hibiscus often grown as a houseplant, but this one is hardy in Vermont. It dies back to the ground each winter, regrowing rapidly from its roots in spring. Some varieties reach heights of 5 to 6 feet by August.

The flowers remind me of Southern belle’s hoop dress. They’re 12-inches in diameter, showy, pie-shaped, come in colors from white to red, and flower continually until frost. I’m particularly fond of the flower buds with their interesting spiral shape as they unfurl. ‘Kopper King’ is a favorite variety because it only grows 3 to 4 feet tall and has copper colored leaves.

Many gardeners know the cardinal flower, Lobelia cardinalis, but fewer are familiar with its lesser-known cousin, the Great Blue Lobelia or Lobelia syphilitica. This dark green leaved perennial grows 3 feet tall. In August it sends up flower spikes ringed with vivid blue blossoms. The Great Blue Lobelia tolerates part shade and wet conditions, but watch out. It spreads like a demon and often needs to be weeded out each spring.

The common name of Physostegia virginiana, or the obedient plant, has more to do with its flowers than its growth habits. Obedient plants grow well in wet soils, sending up pink or white wands of trumpet-shaped flowers in late summer. When the flower spikes are nudged left or right or twisted into spirals, they often stay in the direction they’re pointed until you rearrange them. Hence, the common name.

However, this 3 to 4 foot tall perennial can be very disobedient when it comes to growth. It spreads by underground roots so it can become invasive. For a most obedient, obedient plant, try the white-flowered variety ‘Miss Manners’, which grows in a compact clump form.

Another great fall perennial is actually a small shrub. The Rose of Sharon, or Hibiscus syriacus, is a tropical-looking plant that displays its 2- to 4-inch-wide trumpet-shaped flowers in late summer and fall. The single or double flowers come in colors such as white, red, purple, and sky blue. Although it can grow to 12 feet tall in a protected location, I’ve mostly seen them in the 4 to 5 foot height range in Vermont.

Rose of Sharon can be planted as a focal point in a lawn or in the back of a perennial border. They are marginally hardy in our climate. However, if they suffer winter damage, they will probably still flower since the blooms emerge from new growth each spring.

This is Charlie Nardozzi in Shelburne.

(Host) Charlie Nardozzi is an all-around gardening expert with a special fondness for tomatoes and roses.

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