Perennial success with a flower that's usually an annual for the patio

"Fielding Questions" columnist Don Kinzler also hears from readers about a houseplant quarantine and the best watermelon.

A reader had a good summer of blooms with this hardy perennial hibiscus.
Contributed / Special to The Forum

Q: I wanted to share my experience with a hardy perennial hibiscus. The photo is my Summerific Evening Rose Hibiscus and it had 11 beautiful flower blooms open at one time this past summer! — Lori K.

A: Thanks, Lori, for your great photo, and the chance to discuss winter-hardy perennial hibiscus types, which aren’t as familiar as the non-hardy patio hibiscus pots marketed heavily every spring at garden centers.

Lori continues: “Perennial hibiscus was just spectacular in the flower garden. I planted it the previous summer so this was its second year. It made it through the winter just fine, although it didn’t show signs of growth until June 1. It is definitely late to show up in the spring but then the plant really takes off. I love the perennial hibiscus because it blooms at a time when the daylilies and so many of the other perennials are done for the summer and the garden needs a blast of color. I planted ‘Candy Crush’ in another garden this year.”

These perennial hibiscus types are also called rose mallow, and Summerific Evening Rose is a cultivar marketed by the Proven Winners brand of plants. They’re considered winter hardy in zone 4, and will winter quite well in our northern zone 3 areas if given a 12- to 18-inch layer of mulch applied in mid-November and planted in a protected microclimate.

Perennial hibiscus can be found at many locally owned garden centers in a variety of colors ranging from blue, pink, white, red, purple and burgundy. As Lori mentioned, they are slow to emerge in the spring, but patience is well-rewarded with tremendous blooms.


Q: When I bought a few new houseplants last year, I think they spread insects to my older plants. Now I’ve read you should keep new houseplants isolated for a while to be sure no insects are on them, but the article didn’t say for how long. Any idea how long to keep new plants in quarantine? — Gladys L.

A: First, it’s always a good idea to buy new houseplants from local garden centers or floral shops, because they’re more likely to have the knowledge and expertise to keep their houseplants insect-free. National chain stores often lack personnel trained in insect detection and management.

Regardless of the source, it’s wise to keep new plants isolated and carefully observed to be sure they’re free of insects. Recommendations vary from one to four weeks. One week seems on the light side, and four weeks might be longer than needed. I’d opt for at least two weeks.

During the quarantine, be sure to give the houseplants the light and care they need. If they’re given less-than-optimal light, they can quickly languish. Before relocating any plants in close proximity to your other plants, it’s also wise to first rinse the plants in the sink or shower, targeting both upper and lower leaf surfaces.

Q: I’m ordering seeds for this year’s garden, and I know you’ve mentioned several watermelons that you’ve found have done well in our climate. Can you remind me what they are? — Carl S.

A: Watermelons are among my favorite items to grow in the garden. One variety that is outstanding in flavor, sweetness and quality is Sweet Dakota Rose, which ripens well in our growing season. It was developed by Prairie Road Organic Seeds, Fullerton, N.D. and can be ordered from their web catalog. Some locally owned garden centers also stock Prairie Road seed racks.

For a second watermelon, Blacktail Mountain has performed well and can be found in several seed catalogs.

If you have a gardening or lawn care question, email Don Kinzler, NDSU Extension-Cass County, at Questions with broad appeal may be published, so please include your name, city and state for appropriate advice.

Don Kinzler, a lifelong gardener, is the horticulturist with North Dakota State University Extension for Cass County. Readers can reach him at
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