|JoAnn Bennett, Nelda Koestler and Cindy Toepfer|
Kingman Area Master Gardeners
Question: What is that orange, stringy-looking material that is covering plants in the desert?
Answer: While driving to Lake Havasu, my husband and I noticed a plant that looked like orange spaghetti along I-40. I grew up in the Midwest and had never seen this before. I asked friends what it was and they said dodders or witch's hair.
A dodder is a true parasite. The host plant does not receive any benefit from the dodder and the dodder must have the host plant to survive. It appears leafless but may bear tiny bracts. It lacks chlorophyll to produce any significant amount of its own food. It attaches itself to a host plant with small appendages which allow it to extract carbohydrates, water and nutrients. It is usually an orange or golden color, but it can also be tinged with red or purple.
Dodder flowers are numerous and are white, pink or yellowish. They are approximately 2 to 4 mm (5/32 of an inch) long. The flowers normally appear from early June to the end of the growing season. The flowers produce small fruits 1/8-inch in diameter and contain one to four seeds. The dodder seeds drop to the ground and germinate for the next growing season. The seeds may remain dormant for 20 years or more. They require moisture and sunlight for germination and do not need to be associated with a host plant to germinate.
Dodder seedlings sprout in the ground like other plants but they must attach to a suitable host within a few days or they will die. The seedlings send out vining tendrils in search of a suitable host plant. When they find one, the dodder tendrils wrap around it and insert haustoria (modified roots) into the host plant.
Once the above-ground connection is made, the original connection to the soil where the seed germinated is no longer needed and this portion of the plant shrivels away. From this point forward the dodder is completely dependent on the host plant. As they grow older, the dodder vines will continue to form more attachments to their host plants. Dodder is an annual plant and dies each winter in our temperate climate.
Dodder hosts can widely vary and dodder will attack roadside shrubs as well as vegetable and ornamental plants.
Some dodder resistant plants are all grasses including grains such as corn, cool-season vegetables such as lettuce, broccoli or cauliflower. Also, many monocots such as lilies, irises, palms, or orchids and soybeans.
Some dodder susceptible plants are beets, carrots, chrysanthemums, dahlia, trumpet-vine, petunias, garlic, and nightshade family plants such as potatoes, eggplant or tomatoes.
The easiest way to control dodder is to manually remove when possible. This is not an easy task if the host is a woody plant. Try to remove the dodder before it goes to seed in the summer. Small areas can be cleared by hand but larger areas may require mowing or pruning.
If you have a dodder infestation, try to plant the area with non-host plants. Some other references cite the use of a pre-emergent herbicide to prevent dodder germination.
Q: Why do my shrubs and plants look dead or foliage is only on some branches?
A. Our past winter was cold and temperature lows may have been in the single digits for a few mornings, depending on where you live in the Kingman area. Many plants that are sold locally have a hardiness only down to 20 or 30 degrees Fahrenheit. Even ones hardy down to 10 degrees F may have suffered some frost damage.
Frost damage turns the branch or end of the branch a lighter color, usually tan. Take the branch in your fingers and gently bend it to the side just a little. If it snaps off, it is dead. If it seems pliable, it is alive. Another method for checking is to scrape the side of the branch with a knife or your fingernail just below the surface. Do not take off too much or the branch may not recover if it is alive. If you see any green, the branch is alive.
Also, I've seen some one-year-old plants like Texas sage or desert willow look like an entire side has died. But do not prune these branches off unless you know they are gone - they will be a different color than the rest of the branches, brittle and will snap off. Some growth may be slow to emerge and it is best to give them time, especially the low-water plants that thrive in our heat. In many cases, the leaves will eventually grow back.
When purchasing plants, read the tag and check the hardiness. If it is above 10 degrees F, it is best to plant in a warmer microclimate of your yard. By warmer microclimate, I mean an area that is warmer than the rest of your yard, such as next to your house or between your house and a wall or an area that doesn't get the cold, north winds.
Trees that may have some die-back or will not survive cold winters are eucalyptus, shoestring acacia and other acacias, palo verdes, mesquites, olives, bottle tree, palms and pomegranates. Cold sensitive vines are bougainvillea, Carolina jasmine, grape ivy, orchid vine and cape honeysuckle. Cold sensitive shrubs are oleanders, hummingbird bush, desert and cape honeysuckles, cassias, orange bells and red bird of paradise.
If you have some of the above varieties that were unaffected by the cold winter, it could be your area did not get too cold or you have them in a warmer microclimate. Not all will be affected. If you completely lost the plant, it probably wasn't hardy to single digit temperatures.