MARCH
2002

 

 

 

By
Beverly Shaw
 
Advanced
Master Gardener
Purdue University

 

 

 

 

 

3-7-02

Question and Answer

Q. I read your article on fire blight. We have a bad case of fire blight on one of our pear trees. You spoke of doing a pruning of the diseased parts, and we were wondering when would be the best time to do the pruning--spring or fall? -- Linda Am Rhein, Scipio, Ind.

A. Fire blight-infected limbs and branches should be pruned during late winter when there is much less chance of spreading fire-blight bacteria on cutting tools. However, it is often necessary to make immediate cuts to prevent the disease from going into the main framework of the tree. This is especially critical on young trees with diseased branches attached to the main trunk. Use great caution when pruning infected limbs during spring or summer. Cut 8 to 12 inches below the diseased tissue and, most importantly, sterilize cutting tools between each cut. A 70-per cent denatured-alcohol solution, made by mixing three volumes of denatured alcohol with one volume of water, is recommended for sterilizing cutting tools. A 10-percent solution of liquid laundry bleach (sodium hypochlorite) can also be used, but this preparation is corrosive to most pruning tools. If it is used, the tools should be thoroughly rinsed and oiled after cutting.

Fire blight usually first appears during bloom. The blossom clusters wilt and turn dark brown or black. This is followed by twig blight infection of the current season's growth. The most obvious symptom of twig blight is a scorched appearance of affected stems in which the leaves wilt, turn brown and cling to the stem. It is this stage that gives the disease the name "Fire Blight."

Often, the tips of blighted twigs have a crooked appearance resembling a fishhook. Fire blight may continue to spread downward from the blighted twigs into main scaffolding limbs and trunk. The outer bark of infected branches becomes shriveled, while the inner bark appears water-soaked and reddish-brown. There is usually a distinct separation of the infected (cankered) and healthy tissue. The cankered areas are often slightly sunken and have a darker appearance than that of adjacent healthy bark tissue.

 

Q. I have two Concord grapevines that were planted about 70 years ago. They produced well until last year, when all I had were long heavy vines and no grapes. I trimmed them in December 2000, instead of February or March 2001. Did this early cutting cause the vines not to produce? All other factors have remained the same. -- Larry Kreigh, Ossian, Ind.

A. Cold injury may have damaged the dormant buds. Pruning can be done any time during the dormant season; however, it is best to delay pruning until late winter or early spring because pruned vines are more susceptible to cold injury than unpruned vines. In addition, delayed pruning allows for adjustments in bud number in the event of winter injury. It is important to assess bud survival before final pruning, especially on cold, tender cultivars. Pruning is the most important cultural practice in the management of grapevines. It is done to select fruiting wood, maintain vine shape and form, and regulate the number of buds retained per vine. Grapevines require annual pruning to remain productive and manageable.

There are fairly complicated guidelines for pruning grapes to balance the fruit productivity and vegetative growth. I highly recommend downloading a copy of Purdue Extension Publication HO-45, "Growing Grapes," which is available at www.hort.purdue.edu/ext/garden_pubs.html.

 

Q. I just received a shipment of garlic bulbs, and they don't look really healthy like the ones I see in the grocery store. What should I look for when I buy them? -- Richard Hunt, West Lafayette, Ind.

A. Garlic sets should be firm and clean. Avoid those that feel soft when you give them a gentle squeeze. Garlic, Allium sativum, does best in the Midwest as a fall-planted crop. Garlic for planting should be purchased from a reliable garden center or mail-order catalog. Storage temperature of the dormant garlic affects the bulbing of the future plants. Temperatures above 77 F may inhibit bulb formation, so using garlic from the grocery is ill-advised for planting purposes. Garlic that has been stored at about 40 F for several months is ideal for starting a new planting.

Garlic can adapt to a wide range of soil types, but it must have a well-drained soil. Garlic can be planted in either fall or early spring. Bulb formation is optimum as days are getting longer in late spring. Generally, most gardeners find it easier to get the garlic planted in fall, since early spring soils are usually too wet for planting.

 

Q. I am trying to help my daughter cover a bank in her yard, approximately 50 feet wide by 20 feet, very steep and in full sun. It is now covered with bushes that resemble burning bush, but they have grown up wild. I heard a radio talk show about killing with Round Up in April, then cover soil with mulch and plant one plant of purple ? for every square foot. I was driving and couldn't write it down. Can you tell me what this is, or do you have any other suggestions of what else we might use? I was wondering about what they use along state highways that looks somewhat like alfalfa. -- Harv (via e-mail)

A. The plant in question is probably purple wintercreeper, also known as Euonymus ‘Coloratus.’ It is a groundcover that will cover the area and help hold the hill in place. Its leaves are glossy green in summer, but they take on a purple or burgundy tint in the winter, thus, its name.

You might also consider daylilies for a more colorful hillside in the summer. The drawback is a lack of foliage in the winter. This increases the chance of erosion and provides no winter interest. Either choice will still require some weeding. Tree seedlings, poison ivy and wild raspberries always try to take root.

For a wilder look, consider a prairie planting. Don’t fall for the meadow-in-a-can that is too readily available! It relies largely on annual flowers that won’t help you control the bank in the long run. And most of those mixes are intended for the entire country. We all know our weather isn’t the same as Oregon or Arizona! Instead, contact a reputable source for a seed or plug mix created for the Midwest. You can find information on many sources at www.hort.purdue.edu/ext/sources_IN_wildflowers.html.

I believe the plant that you're seeing along the highways is crown vetch. It has pretty pink flowers but spreads aggressively and can be a nightmare to control. As it increases, taking over more territory with each growing season, it chokes out native vegetation. Additionally, it is difficult to kill if you want to change what is planted there. Avoid crown vetch!

It may be simplest to leave the existing burning bush and supplement the planting with a groundcover like purple wintercreeper. Removing the existing bushes will increase the likelihood of erosion.

 

Contact: B. Rosie Lerner
Editor: Olivia Maddox,