December 2003 - Indiana Yard and Garden - Purdue Consumer Horticulture

December 2003

Q. Are there any other varieties of lilies that bloom for more than just one day, besides the Stella D’Oro? Also, why is it necessary to dig up the Canna variety but not others? Is it naturally tropical? I love lilies! Thank you. — Josie Kramer, Clear Lake, Ind.

A. The range of color, shape and size of daylilies is wonderful, but breeders are working hard to create more reblooming daylilies. Most daylilies bloom for a few weeks but, by selecting early, mid- and late season daylilies, the season can be extended to cover much of the summer.

Most reblooming daylilies will bloom for around three weeks, rest a couple of weeks, then send up another scape with forming buds. The rebloom will usually last until frost, depending on the growing conditions. Short, gold ‘Stella D’Oro’ is the most well-known rebloomer, followed by ‘Happy Returns,’ a slightly taller, softer, yellow daylily. ‘Happy Returns’ can easily send up more than 100 buds at the beginning of the season, and its developer has used it to breed a wide range of other rebloomers. Look for ‘Apricot Sparkles’ (peachy apricot), ‘Red Hot Returns’ (red), ‘When My Sweetheart Returns’ (lemon with a rose-pink eye) and more in the Returns series, which will hit the market over the next few years. ‘Rosy Returns’ (pink) will be most readily available.

Do any of them bloom as much as ‘Happy Returns’ or ‘Stella D’Oro’? Early reports are mixed. Experiment if you’d, like but expect the price to be steep for a few years. ‘Happy Returns’ originally sold for more than $25 per plant but can now be found for under $8. The others will reach the market with a similarly high price tag. These plants are patented, so propagation is prohibited.

Other good reliable rebloomers include ‘Penny’s Worth,’ ‘Penny Earned’ and ‘Mini Stella,’ all very small, yellow daylilies reaching only 14 inches in height.

You also asked about Cannas, although you may have meant Calla lilies. Both are tender here and must be lifted from the ground each fall and stored for the winter. For more information on storing tender bulbs, go to or call the Purdue Extension office in your county and request a copy of HO-85W, “Winter Storage of Geranium, Canna, Gladiolus, Caladium and Begonia.”

Q. I hope you can give me some insight to what type of vine or airborne type vine I have. I was looking at my hardy mums and actually thought my husband had dropped old weed-eater string on top of my mums and not thrown it away! But after looking closer, it was an orange-colored vine attaching itself to the mums and choking them out. I went to the stems, thinking I could pull it up and get rid of it, but there were no stems in the ground anywhere. So I sat down and took each one off; what wouldn’t peel off, I broke the mum stem off just to be rid of it. Within days, it was back. I cannot get rid of it, and now it is blooming with tiny white flowers. Please try to find out what it is so I can get rid of it. I am stymied. Thanks for your help. — Sharron Francis, Kingman, Ind.

A. You’ve discovered one of the most interesting and frustrating weeds of the flower garden. Dodder is a parasitic weed that must obtain its moisture and nourishment by attaching to a green, living plant. It belongs to the Morning Glory family, but it bears little resemblance to the garden types, other than its vigor.

Dodder is an annual that reproduces by seed. As the seedlings emerge, they start to twine around any type of support that might be available, especially garden plants. The yellowish-orange, string-like stems form dense masses while sending root-like projections into the host plant.

The plant appears to be leafless but may, in fact, bear tiny bracts. The clusters of tiny white flowers eventually give rise to small pods containing seed, providing opportunity for dodder to invade your garden in future years!

Now, for the really bad news. There is no herbicide that can be applied to garden or landscape plants once dodder is growing on them. Hand pulling and pruning are the only methods of control once the dodder is established. Prior to germination, dodder can be prevented reasonably well with the application of a pre-emergence herbicide called Dacthal or mention Trifluralin, sold as Treflan or Preen. Be sure to read and follow all label directions before using. A pre-emergent is a wise move considering the seed has a very hard seed coat and can remain dormant and viable for many, many years. Only a small percentage of the existing seeds germinate in a given year, meaning that once you have dodder seed in the soil, you’re likely to continue to have a battle for many years.

Q. My mother bought me some iris bulbs last summer. I planted them, and some started growing. Some would grow about 6 inches and then rot and die. Then, it would grow again just to rot and die. This continued for the rest of the growing season. This year, I had one that grew well, to the point where it had a shaft with flower buds on it. This shaft then rotted and died before the flowers had a chance to open. What is happening, and is there anything I can do about it? I have these irises in a bed with others. Do I need to remove them so it doesn’t spread? — Marianne Kromkowski, Rochester, Ind.

A. Iris rhizomes require good drainage and shallow planting to prevent them from rotting. The rhizome should be planted so the top half receives sunlight, and you should take care not to mulch over it. Do not plant them in areas with poor drainage or heavy clay.

Iris borers can also cause the rhizome to rot. The adult iris borer is a moth. In late August and September, the female moth lays her eggs in clusters on the iris leaves, the base of stalks and other nearby plant debris. The eggs overwinter in the plant material and hatch in April or early May as the new iris leaves are expanding.

The small, young, larvae crawl up onto the new iris leaves and make tiny pinpoint holes as they enter. Once the larvae enter the foliage, they act as leafminers, tunneling to the base of the leaves throughout the spring. This leafmining damage appears as water-soaked, brownish spots and streaks on the leaves. By early to mid-July, the larvae reach the soil area and tunnel into the rhizomes.

In the rhizome, the fat-bodied, pink larvae with brown heads grow to be 1.5 to 2 inches in length. Their tunneling in the rhizome is particularly damaging to a smaller-rhizomed iris, such as Japanese or Siberian iris. A tall, bearded iris, with its larger rhizomes, frequently is able to sustain this damage and still survive.

In late July to early August, the iris borer larvae move from the rhizomes into the soil to pupate. Adult brown moths emerge in late August and September to mate, lay eggs and repeat the cycle previously described.

Usually, the main problem with iris borer infestations is the accompanying invasion of bacterial soft rot. Rhizomes infected with bacterial soft rot become slimy, soft and foul smelling. The combination of bacteria and borer can cause rapidly appearing serious injury.

With close, regular inspection of leaves from April through June, iris borer larvae can be easily detected at the lowest point of the mine and squashed while leafminers are within the leaf.

Fall sanitation is very important for iris borer control. Following the first hard frost, remove and destroy old iris leaves, stems, rotted rhizomes and nearby plant debris. This will help to get rid of the overwintering egg stage. Insecticides labeled for iris borer control may also be used in the spring of the year on new foliage.

Q. This summer, I purchased two plastic patio containers with strawberry plants in them. I’ve pinched the blooms off them over the course of the summer, but I’m unsure of what to do with them for the upcoming winter months. We live in southern Indiana, and any information you can give me would be appreciated. Thank you. — Roz Ketchem

A. I’m sorry this answer reaches you late in the season! For future reference, the plants should be planted in the ground and mulched with a 2-inch layer of straw. If straw is not available, weed-free materials such as hay, fresh corn cobs or bark chips may be used. Grass clippings and leaves are not suitable because they tend to mat and form a layer that smothers the strawberry plants. The following spring, at about the time when the first new leaves begin to develop, rake off most of the mulch and put it around the plants. Complete growing information is available at or call the Purdue Extension office in your county and request HO-46W “Growing Strawberries.”

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