Q: This summer, some of my impatiens plants are producing long, stringy tendrils. I have never seen this before. They arise from a node where a leaf is attached to a stem. What are they? I’ve included a photo. — Betty Patterson, Fargo.
A: Your impatiens plant is infected with dodder, which is a parasitic vinelike plant that has no leaves, only stems and tendrils. Dodder is an annual growing from seed and is a parasite that inserts itself into the stems of the host plant to which it attaches, giving the impression that the vines are emerging from the plant itself. Its thin, threadlike stems grow rapidly, entwining and covering their host plants.
Dodder is found throughout the U.S. and Canada. From the Missouri Botanical Garden:
“Dodder seeds germinate in soil and can live on their own for about 10 days until they are about a foot tall. If they have not found a suitable host by then, the seedlings die. Seedlings that find a suitable host twine around the plant and insert modified roots into the tender stem, tapping the host plant’s vascular system for water and nutrients and relying upon their host plant for survival. Small, white, bell-shaped flowers form in late summer and early fall and can produce copious amounts of seed, which can survive in the soil for more than 20 years. Dodder is an annual and is killed by frost.”
As soon as the thin vining stems of dodder are observed, they should be gathered and removed before seed is set, which usually involves removing and disposing of the host plant also. Extraction of dodder from the host plant is usually impossible.
Q: A favorite annual in my flower garden is the dahlia with so many varieties to choose from each year. Because dahlias have a thick, hollow and brittle main stem, I find that mine need to be staked to protect the plants from our region’s wind. I’ve found a method that works, and I thought your readers might find the method useful. Thanks for your articles. — Karen Rosenvold.
A: Karen continues, “I’ve found the plastic sleeves in which my daily newspaper is delivered are a perfect solution when tying dahlia stems to a stake. The sleeve can be looped around the stem and tied loosely enough in one or more spots, giving the heavy stem a bit of flex and still giving room to grow. Just an idea for enjoying these lovely plants a bit longer.”
Thanks for the tip, Karen. The plastic sleeves in which many of our papers are delivered is a bonus for subscribing to a daily newspaper.
Q: I sprayed malathion around my plants and shrubs to kill mosquitoes and also on the petunias. I noticed this morning that the petunias are all discolored and when I read the malathion label, it said it shouldn’t be used on petunias. Will they continue to die or will the new leaves be OK? Thanks! — Niclole Welsch.
A: Malathion is a rather oily-type insecticide that causes burning on some plants. Your petunias should grow out of the damage.
To assist the petunias back to health, I would give them a midsummer cutback, removing the damage. Petunias this time of year often appreciate a heavy pruning, which gives them a new burst of energy for the remainder of summer. This removes seedpods and spent blossoms and encourages petunias to produce new growth and new flowers.
So, although it seems a shame to cut back the petunias, it would accomplish removing the damaged material, plus encourage a new flush of growth and blossoms. Fertilizing with water-soluble fertilizer at the same time would provide extra nutrition for new growth and increased blooming.
If you have a gardening or lawn care question, email Don Kinzler, NDSU Extension-Cass County, at firstname.lastname@example.org or call 701-241-5707. Questions with broad appeal may be published, so please include your name, city and state for appropriate advice.