NOVEMBER
2010

 

 

 

By
B. Rosie Lerner
 
Purdue
Extension
Consumer Horticulturist

 

 

 

 

 

11-04-10

Question and Answer


Q. We enjoy your articles and were wondering about Jack-in-the-pulpit seeds. Do they have to be stratified? Would you do an article about the different seeds and which ones need stratification and or softening and abrading?

A. Seeds of many plants in our climate have an immature embryo that requires a period of moist-chilling (stratification) before they are able to germinate. Although the length of the chilling period varies with the plant species, most seeds are adequately stratified for three to four months at 35-40 degrees F. In nature, seeds are stratified by laying in cold, moist soil over winter. Gardeners can stratify seeds in a more controlled manner by placing the seeds in moist packing material, such as peat moss, vermiculite or sand, and storing in the refrigerator (not the freezer). Seeds of some species may also have a hard, impermeable seed coat that needs to be softened, or abraded, by soaking, filing or otherwise abrading the outside surface. Such seeds are said to require scarification.

Although some references indicate that Jack-in-the-pulpit seeds require no pre-treatment, most references recommend two months of moist chilling followed by immediate planting. Remove the pulp from the seeds using gloves and eye protection, as the juice from the berries can be a skin irritant.

Q. I have some black-eyed Susans. How do they reseed themselves? I have been looking on the net and can't find anything about that. I know that wherever you plant them they take over everything.

A. Rudbeckia, aka black-eyed Susan, are bountiful self-seeders. Depending on the perspective of the individual gardener, this may or may not be a good thing! The seeds mature as the flowers fade and either fall to the ground or are distributed by the many birds that enjoy the snack. If you prefer to reduce the amount of self-seeding, remove the spent flowers--referred to as deadheading--just as soon as the petals fade. The plants will look better, and preventing seed production will also encourage additional blooms.

Q. I have a peony bush that has beautiful deep-pink blooms. For the last two seasons, about the time the flowers bloom, the leaves get very dark brown. Some leaves are completely brown and others are mostly brown. What happened? Do I have to get rid of these plants and start over, or is there some way to treat them?

A. Peonies in Indiana are quite likely to develop a fungal disease called leaf blotch, also known as red spot and measles. Discolored blotches (lesions) occur on leaves or stems, and may start as tiny red spots ("measles") but eventually progress to larger brown or purple blotches. It is not unusual for the peony plant to be completely defoliated by the end of summer from this disease, but surprisingly, the plant seems to be able to tolerate the infection. The fungus survives the winter in infected plant debris and produces spores in the spring, which are then splashed onto young foliage and stems through rainfall or overhead watering. Remove dead plant residue in late fall or early spring before new growth emerges to reduce the severity of this disease next season. When possible, use drip irrigation to minimize fungal infection. The Purdue Plant and Pest Diagnostic Lab has additional information on peony leaf blotch at http://www.ppdl.purdue.edu/PPDL/weeklypics/8-20-07.html.

Q. The green leaves on my tomatoes turn yellow with black spots. My acorn squash leaves are green and seem to be growing good and then get white on the leaves and the plants die. What is wrong with my garden? Is there something wrong with the soil?

A. The black spots on your tomato leaves are likely unrelated to the white leaves forming on the acorn squash. Tomato leaves turning yellow with black spots could be one of several diseases, with early blight and/or Septoria leaf spot being prime suspects, particularly given the wet weather experienced early in the growing season this year. Septoria leaf spot usually appears initially as small black spots on the lower leaves after the first fruits set. Despite its name, early blight usually appears a bit later in the season after the fruits set; it also appears on the lower leaves first. The spots are dark brown to black and distinguished from Septoria by their larger size and concentric "bulls-eye" rings that develop in the spot. The area around each spot turns yellow, and soon the entire leaf turns yellow and drops. Early blight fungus also infects stems and may produce stem cankers. Both of these diseases are likely to be problematic during wet weather and periods of frequent overhead watering, and it is certainly possible to have both diseases on the same plant.

More information on identifying and controlling these tomato diseases is available at http://www.ppdl.purdue.edu/ppdl/weeklypics/7-12-10.html.

White spots on acorn squash leaves are likely caused by a fungal disease called powdery mildew. Unlike many of the other fungal diseases, powdery mildew is favored by extended dry spells, so it was particularly problematic late this summer. More information and photos can be found at http://www.ppdl.purdue.edu/ppdl/weeklypics/8-9-10.html.

Fall clean up of the garden and rotating susceptible crops to substantially different areas of the garden will reduce the risk of infection next year. Look for disease-resistant cultivars when purchasing seed or plants for next year's garden.

 

Writer: B. Rosie Lerner
Editor: Olivia Maddox,