Extension Summer 08 Garden Packet 3
Published: May. 30, 2008
NOTE TO EDITORS: This is the final installment of University of Illinois Extension's Summer Garden Packet. May 30, 2008
Source: Martha Smith (309) 836-2363 Contact: Bob Sampson (217) 244-0225 Extension Communications Specialist e-mail: rsampson@uiuc.edu
Drought and Perennials
Many home gardeners wonder how drought affects their perennial gardens, said a University of Illinois Extension horticulture educator.
"All plants need water. When natural rainfall does not provide enough, plants suffer," said Martha Smith. "The term 'drought' refers to a period of time when precipitation is well below normal or completely lacking. During this time, the water content of the soil is reduced to such an extent that plant material can no longer extract sufficient water for normal life processes.
"Large plants such as trees have extensive root systems capable of reaching other possible water sources nearby or deep in the ground. Perennials and annuals don't have as extensive a root system and therefore are subjected to the conditions immediately around them."
Some annuals and perennials can tolerate dry conditions for a long time, while others succumb very quickly, she added.
Wilting is often the first visible effect of drought noticed by the home gardener. Perennials and annuals are herbaceous ornamentals. They do not have a woody structure to support them.
"What holds a herbaceous stem up has a lot to do with the water pressure within," she explained. "Water is pulled into roots because of evaporation at the leaf surface. A water column forms because water sticks together. As it evaporates into the atmosphere through the foliage, it is replaced through the roots.
"If foliage evaporation exceeds the roots' ability to pull in water due to drought, this column breaks and wilting results. If additional water is supplied within a reasonable amount of time, most perennials and annuals will respond and continue normal growth. If drought conditions continue, plants wilt beyond their ability to recover."
Plants that have suffered through one drought may not be able to store enough food to help them through another drought year. They may be smaller in overall size or produce fewer flowers. If dry conditions and high temperatures continue over several seasons, these plants may be lost.
What can be done to minimize drought injury to herbaceous ornamentals? Smith suggested seven tips.
First, prepare the soil. Increase the moisture retentiveness of your garden soil before you plant. Dry, sandy soils benefit when compost and aged manure products are incorporated.
"These materials give soil water something to adhere to," Smith explained. "Tight clay soils also benefit from the addition of these materials. During drought, clay soils become very hard and are difficult to re-wet. Water runs off before it can penetrate. Compost and aged manure open up clay soils and allow easier water penetration."
The second tip is mulch--adding a two-to-three inch layer of mulch helps soil retain moisture.
"Third, group plants according to their watering needs," she said. "Most plant reference books have plant lists for various growing conditions. Artemisia species, Coreopsis species, and Sedum species are all tolerant of sunny, dry locations. These should be considered for a potentially dry area.
"Avoid moisture lovers such as Astilbe species, Trollius species, and ferns."
Fourth, consider planting time. Perennials planted in late spring or early summer may not have enough time to establish a sufficient root system needed to survive a drought. Plant perennials in early spring or fall to avoid this problem.
Fifth, remove moisture competitors.
"Weeds and turf are also seeking water to survive," she said. "Get rid of these and you will have more available soil moisture for your ornamental plants."
Cutting back on fertilizing is the sixth tip. These additional nutrients promote growth, which increases water demand. Plants should be kept lean and mean during a drought.
"Finally, supply additional water," said Smith. "Herbaceous ornamentals benefit from one inch of water every seven to 10 days during the growing season. If this is not supplied by rainfall, drag out the hoses."
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May 30, 2008
Source: Martha Smith (309) 836-2363 Contact: Bob Sampson (217) 244-0225 Extension Communications Specialist e-mail: rsampson@uiuc.edu
Watering Flower Gardens
Watering is the most often abused gardening practice, said a University of Illinois Extension horticulture educator.
"It seems like gardeners sometimes fall into the traps of too much or too little. Where is the in between?" said Martha Smith. "Understanding how plants use water can help the home gardener find that happy medium."
Water is delivered to plant parts through roots. This means water must be available in the soil. Actually, water is available in the air spaces between the soil particles. After a rain, gravity pulls water out of the largest air spaces and what remains is available to plant roots.
Sandy soils have large air spaces that hold water very poorly. Clay soils have small air spaces that hold water very tightly. Understanding what type of soil you have will determine how often you water. Sandy soils require more watering than clay soils.
"Soil water is used in two ways," she explained. "It is evaporated from the soil surface or it is pulled through the plant into the leaves where it is used for basic life functions such as cooling the plant though transpiration and food production through photosynthesis.
"As water is pulled from the soil by the roots, the smaller air spaces in the soil hold on tighter to the remaining water. The available water is limited and plants have a harder time absorbing it."
Water is supplied to the soil in two ways--Mother Nature or through a garden hose. When not supplied naturally, we have to decide when and how much to apply. How do we determine this?
"There is no set recipe for watering," said Smith. "Look at the plants and take into consideration your soil type and recent weather conditions.
"Look at the plant. A wilting plant indicates a watering problem. But don't always assume it means the plant is dry. Wilting occurs when the turgor pressure within a plant breaks. This can be from lack of water as well as too much water. Always check the soil around the plant. Don't just scratch the surface--poke down four to six inches around the base of the plant."
Weather conditions should also be considered. If it has been hot and windy, sandy soils will need watering more often. Clay soils may be able to hold off for one or two more days before supplemental water is needed.
"Research has shown that one inch of water applied to an average soil will percolate down six inches where the roots are," she noted. "A general rule of thumb is that one inch of water supplied every seven to 10 days during the growing season is adequate for flower gardens.
"Every situation is different and your sandy soil may need water every five days. How do you know when you have supplied one inch of water? Set out measuring devices such as an empty tuna can marked at one inch and turn on an overhead sprinkler. Or if you are hand watering, the experts say five gallons per square yard is about one inch of water."
Smith recommended some other watering tips.
"Water early in the morning through early afternoon," she said. "Late afternoon temperatures increase evaporation so less water will be available for your plants. Avoid watering in the evening. You have a greater chance of disease problems if you allow foliage to be wet at night.
"Water slowly so the soil can absorb it. Avoid a torrential downpour--in nature when this happens most of the water is lost to run-off. Water does not move sideways in soil. You must apply water directly over the area needing it."
-30- May 30, 2008
Source: Sharon Yiesla (847) 223-8627 Contact: Bob Sampson (217) 244-0225 Extension Communications Specialist e-mail: rsampson@uiuc.edu
Composting
Grass clippings, leaves, twigs and other yard waste can be transformed into compost which can enrich the garden, said a University of Illinois Extension horticulture educator.
"Compost looks very much like rich soil and has a pleasant smell," said Sharon Yiesla. "It is helpful to know some basic facts about composting, how it works, and how we can use compost.
"There are certain things that are necessary for composting to occur: sources of both carbon and nitrogen; microorganisms to break the material down; the proper surface area; moisture and air; and a proper volume of material."
Everything organic will break down if given enough time. The key to composting is speeding up that process.
"When composting, we are always looking to produce optimum conditions for fast breakdown of organic matter," she explained. "One way to do that is to have the proper balance of materials in our compost pile.
"The composting process is carried out by microorganisms that live in the soil and on organic matter. These microorganisms need both nitrogen and carbon. By missing different types of yard wastes, we can achieve the optimum balance of these two elements, thus speeding the composting process."
Many carbon sources are readily available in the yard. Materials like wood chips, dried leaves, corn stalks, straw, sawdust, and twigs are good carbon sources. To make these materials easy to remember, think of them as the "browns," since MOST of them are brown in color.
There are also many nitrogen sources in the yard. Grass clippings are probably the most abundant source due to the sheer volume of clippings produced during the average growing season. Other sources include fruit and vegetable wastes, fresh weeds, waste from the flower garden, manure, and coffee grounds.
"To make it easy to remember these nitrogen sources, think of them as the 'greens' since MOST are green in color. But don't forget coffee grounds and manure, which although brown are still good nitrogen sources," Yiesla said.
She added that it is not difficult to get the right mixture of carbon and nitrogen. Simply mixing approximately equal volumes of the "greens" and the "browns" gives a good balance of carbon and nitrogen.
"However, there are three items that should never be put into the compost pile," she cautioned. "First, pet wastes--feces--should be excluded as pet waste can contain parasites and disease organisms that can be harmful to humans. Cats can carry a disease organism that can be harmful to pregnant women and young children.
"Second, do not compost meat, bones, fats, and dairy products. These items attract animals. Finally, do not compost treated lumber. Scraps of treated lumber should be handled according to instructions provided by the seller of that lumber."
As noted earlier, microorganisms are involved in the composting process. The most important decay organisms involved are bacteria and fungi.
"Luckily, these organisms are naturally present in the soil and on organic matter, so we don't need to worry about adding them to the pile," she said. "Although bacteria are the primary decomposers, fungi also play a role. It is not unusual to see mushrooms--fungi--in a compost pile. This is not bad. In fact, it indicates the compost process is working.
"Also, be prepared to find a wide range of other 'critters' in the compost pile, including mites, worms, beetles, ants, and earwigs. This is normal and no cause for concern."
The microorganisms that decompose yard waste work on the surface of that yard waste. If the surface area can be increased, the composting process is speeded up.
"Chopping or shredding yard waste into smaller pieces will increase the surface area," she said. "There are many ways to increase surface area, including cutting up branches with pruners or a saw and shredding leaves in a leaf shredder or with a lawn mower. Although chopping or shredding is not essential to the composting process, it will make it happen more quickly."
Both air and water are needed by the decomposing microorganisms. The compost pile should be as moist as a wrung-out sponge. If the pile is too wet, air will be forced out of the pile. Decomposition will continue but it will be anaerobic decomposition--the yard waste becomes slimy and produces unpleasant odors.
"Usually rainfall can keep the pile moist enough, but during the heat of summer, water may need to be added," she said. "Be careful not to overdo it. If excessive rainfall is predicted, you may want to cover the pile with a tarp to prevent the pile from becoming too wet. If the pile does become too wet, you can help dry it out by turning the pile to add air to it or by adding dry yard wastes to help soak up some of the moisture."
The size of the compost pile can be important. If the pile is too small, it will not heat up and compost properly. If the pile is too big, it may be difficult to turn or work with and may become neglected.
"The minimum size for the pile should be three feet wide by three feet high by three feet long--any smaller and it won't heat up," Yiesla explained. "The maximum size for a backyard compost pile should be five feet wide by five feet tall so that it can be handled easily by most adults. The pile can be as long as you want. Keep in mind that a smaller adult may want a pile that is less than five feet tall. Make the pile appropriate to the person who will be tending it."
On a cold day, steam can be seen rising from compost piles. A well-made compost pile will produce heat. That means everything is working. The hotter the pile, the faster it will decompose. Temperatures within the compost pile can reach between 90 and 140 degrees F. Despite the heat generated in the pile, there is no danger of fire. The heat is produced by the activity of bacteria in the pile.
"As the heat increases, it eventually gets to a level which kills off many of the bacteria," she said. "Once this happens, the pile cools off. The remaining bacteria continue the decomposition process and the heating begins again." Finished compost looks like a rich, organic soil. The times it takes to get to this stage depends on how aggressively the pile is worked. If the pile is simply put together and turned over to nature, it may take a year or more to reach this stage. If the pile is worked to make optimum conditions, the compost may result in as little as four to six weeks.
"Although composting is very easy, there are some misconceptions that keep people from starting a compost pile," she noted. "Composting can appear to require a lot of physical labor. Turning the pile is not essential to the composting process--it simply makes composting occur at a faster rate.
"You can choose not to turn the pile but you must accept the fact that it will take much longer to get the finished product."
Local gardening centers and gardening catalogs carry many tools and gadgets for composting. But you can actually compost with very few tools. The few basics are a pitchfork or other turning tool, a garden hose to wet the pile, and something to chop up yard waste.
"Compost has many uses," she said. "It makes a wonderful soil amendment. It enriches the soil, adding nutrients. It also helps improve the structure of soil, opening up tight, clay soils and making them drain better and easier to till.
"Compost can be used as mulch, which helps reduce weed growth, conserves moisture, and prevents wide fluctuations in soil temperatures. Compost lends a natural look to the garden, and as the compost breaks down it will enrich the soil over time."
Yiesla noted that compost can be added to potting soil to make it richer.
-30- May 30, 2008
Source: Jennifer Fishburn (217) 782-4617 Contact: Bob Sampson Extension Communications Specialist Phone (217) 244-0225; rsampson@uiuc.edu
Cucumbers
It's not too late to plant a vegetable garden, said a University of Illinois Extension horticulture educator.
"Most vegetables are easy to grow in a sunny location in your backyard or a container garden on a patio," said Jennifer Fishburn. "The number one reason for growing your own vegetables is taste. If it isn't convenient to have a vegetable garden, be sure to purchase fresh vegetables from a local farmers market."
A popular, great-tasting homegrown vegetable is cucumbers, she noted.
"This warm-season vegetable produces an abundance of fruit when given proper care," she said. "The first crop can be planted after the danger of frost has passed and a fall crop can be planted in mid- to late-summer.
"What does it take to have a great crop of cucumbers? Lots of water."
Cucumber plants have shallow roots and require ample soil moisture at all stages of growth, she explained. Adequate moisture is most critical when fruit begins to set and mature.
Warm soil is also needed by cucumbers for germination and proper plant growth. Fertile soils will produce the best yields. Incorporate compost or well-rotted manure before planting. Side-dress with nitrogen fertilizer when the plants begin to vine.
"A cucumber is of best quality when it is uniformly green, firm, and crisp," she said. "Harvest cucumbers before the seeds fully develop. The best size depends on use and variety. Pick slicing varieties when they are six to eight inches in length. For pickling cucumbers, pick when they are three to four inches in length.
"Be diligent and inspect plants at least every morning for fruits. Be sure to remove all mature cucumbers from a plant as over-mature cucumbers left on the vine will halt the growth of new cucumbers. Refrigerate fruits after harvesting."
In some years, cucumbers have a bitter taste, she noted. What causes this bitterness?
"Most cucumber plants contain bitter compounds called cucerbitacins B and C, which can be present in the foliage and sometimes spread to the fruit," she said. "Bitterness tends to be a result of stress, such as lack of moisture, high temperatures, wide temperature swings, or poor plant nutrition."
Be sure to water plants during dry periods. A layer of organic mulch will also help conserve soil moisture.
"Some bitterness can be removed by cutting off the stem-end and removing the skin," she added. "Cucumber cultivars differ in their tendency to be bitter, so be sure to select bitter-free cultivars."
More information about growing and harvesting cucumbers can be found at http://www.urbanext.uiuc.edu/veggies on U of I Extension's Watch Your Garden Grow website.
Cucumbers add a crisp snap to salads and sandwiches. Cucumbers are mostly water and have little nutritional value. They do have a small amount of beta carotene, which is found in the green peel.
"If at all possible, leave the peeling on cucumbers since this is where most of the nutritional value is found," said Fishburn.
Dilled cucumbers, a tasty, healthy snack, can be made following these directions:
--2 medium-sized cucumbers --1/2 cup sour cream or yogurt, reduced fat --1/4 cup chopped fresh dill --salt or freshly ground pepper --optional sliced onions
Thinly slice the cucumbers. Combine yogurt and dill with sliced cucumbers. Season to taste with salt and pepper. Serve chilled. Store for up to four days in the refrigerator. Nutrition facts: 40 calories, 2.5 grams fat, 10 mg. sodium, 4 g carbohydrates.
"The only practical way to preserve cucumbers is pickling," she said. "The National Center for Home Food Preservation is your source for current, research-based recommendations for home food preservation.
"Pickling information can be found at http://www.uga.edu/nchfp/, the University of Georgia National Center for Home Food Preservation website."
-30- May 30, 2008
Source: Maurice Ogutu (708) 352-0109 Contact: Bob Sampson Extension Communications Specialist Phone (217) 244-0225; rsampson@uiuc.edu
Blossom-End Rot Disease
Blossom-end rot is a summer disease very common in tomatoes and fruit vegetables such as peppers, eggplant, and sometimes melons and summer squash, said a University of Illinois Extension horticulture educator.
"It is a non-pathogenic disease, a physiological disorder," said Maurice Ogutu. "It is a symptom of calcium deficiency in the fruit. Calcium deficiency may be caused by low soil calcium, low calcium in maturing fruit, or fluctuating soil moisture. It is usually severe following extremes in soil moisture conditions--either too dry or too wet."
Calcium, he explained, is required in large amounts by fruits for normal cell growth. When a rapidly growing fruit is calcium-deficient, normal cell growth is interrupted and the tissues start breaking down. This leaves a characteristic dry, sunken lesion at the blossom end of the fruit.
"Blossom-end rot is induced when calcium demand exceeds supply," he said. "This may come as a result of low calcium levels or competition for calcium uptake with other mineral nutrients in the soil.
"The other factors that can predispose plants to blossom-end rot are very little moisture in the soil caused by drought stress, excessive soil moisture fluctuations which reduce uptake and movement of calcium into the plant, or rapid vegetative growth due to excessive nitrogen fertilization."
In tomatoes, the first visible symptom of this disorder is a small, darkened or water-soaked area around the blossom end of the fruit. The spot darkens, enlarges, and becomes sunken as the fruits mature. Larger lesions may show concentric rings. The affected tissue is leathery and firm unless invaded by secondary decay organisms.
"Blossom-end rot usually causes the fruit to ripen prematurely and it then becomes inedible," Ogutu said. "Sometimes the affected areas become infected with secondary pathogens which appear black on the affected areas. The affected area can be small or may cover most of the fruit.
"Blossom-end rot appears as tan in color in peppers and should not be confused with sunburn that appears whitish in color mainly away from the blossom end. It appears mainly on the first cluster of fruits in tomatoes and peppers."
The disease can be controlled by selecting sites with deep, well-drained soils where plants will develop well-formed root systems for optimal uptake of calcium and other mineral nutrients.
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"Test your soil after every three years and lime it if needed," he said. "Avoid use of ammoniacal nitrogen fertilizers such as ammonium nitrate as the ammonium inhibits calcium uptake. Do not overfertilize the plants at planting.
"Provide adequate moisture throughout the growing season and mulch the plants. Avoid severe pruning of the plants, and when controlling weeds, do not dig deep closer to the base of the plant. Foliar sprays can be used as a short-term measure but their absorption by the fruit is very poor. Calcium chloride can be used as a foliar spray only in tomatoes and should be sprayed when it is not too hot to avoid burning the leaves."
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May 30, 2008
Source: David Robson (217) 782-6515 Contact: Bob Sampson (217) 244-0225 Extension Communications Specialist e-mail: rsampson@uiuc.edu
Anthracnose of Shade Trees
Spring weather promotes growth of trees, flowers, and lawns, but also spurs many diseases that attack the plants, said a University of Illinois Extension horticulture educator.
"None of these diseases is probably more noticeable and frustrating than shade tree anthracnose," said David Robson. "Anthracnose affects most of the major shade trees. However, while symptoms appear similar, different fungal organisms affect different plants."
Anthracnose thrives and develops when spring temperatures are on the cool side and moisture is adequate. The spring of 2008 has been ideal for this problem. The good news is that while disease symptoms increase as temperatures become warmer, when temperatures move into the 80s consistently the infections become less and less.
"The disease causes spots or lesions on leaves, flowers, twigs, and branches," said Robson. "Lesion colors range from tan to brown to olive green to black. Leaves curl, die, and fall off. Many trees appear defoliated or sparsely leafed out. Symptoms are noticeable during the latter part of May and into June.
"Trees usually affected include ash, birch, catalpa, dogwood, elm, hickory, linden, maple, oak, poplar (including cottonwood and aspen), tulip tree, and walnut."
However, he added, no tree gets hit as much as the sycamore, which has lived with the disease since records have been kept.
"Just looking at sycamore should give the gardener a clue as to the amount of damage to expect on other plants," he said.
In most cases, the disease starts out as small, irregular-shaped spots on the leaf, usually at the leaf margins or tips. Spots enlarge and leaves may curl. The oldest leaves appear infected first, but newer leaves can show symptoms if the weather is ideal.
"The color of the lesions varies," he said. "Dogwood exhibits a dark purple color. Elms show a gray to black color while lindens are light brown with some yellow."
Ash, maple, and sycamores are most often the hardest hit. Ash trees start with tan to brown lesions on the leaflets, usually at the margins or along the veins. Leaves curl, become distorted, and fall.
"Maple infections vary," Robson said. "Japanese maple shoots may turn black and shrivel. Purple or brown streaks develop along the veins of Norway maples, including the 'Crimson King' varieties. Greenish brown to reddish brown spots form between the veins of sugar maples. Spots merge as they get larger and leaves curl."
Sycamore anthracnose appears the most serious, though the trees recover easier than any others. Leaves develop brown lesions along the veins. Entire leaves then turn brown, curl, and fall. Sycamore anthracnose also attacks twigs and young shoots, girdling them, and causing them to die back and drop.
"Trees seldom die as a result of anthracnose," he said. "Most have the ability to produce new sets of leaves. Since environmental conditions are different in June and July, anthracnose fungal spores seldom infect new leaves and twigs.
"However, producing new leaves does limit the tree's growth and reduces the food reserves. Repeated infections over the years can reduce the plant's vigor and make it more susceptible to other disease and insect problems."
Control, Robson noted, is difficult. Protective fungicide sprays are usually too late and too costly to provide any acceptable control except on small trees.
"Sanitation is crucial for good control," he said. "Rake up fallen leaves and branches. Leaves may be composted to kill the disease spores if the compost pile reaches 140 degrees or more."
Trees should be fertilized in the late fall to maintain the plant's vigor. Watering may be necessary throughout the summer to reduce the tree's stress.
"Water thoroughly and deeply as opposed to small amounts daily," he said. "Make sure the tree is mulched with two to four inches of wood chips."
-30- May 30, 2008
Source: Ron Wolford (773) 233-0476 Contact: Bob Sampson (217) 244-0225 Extension Communications Specialist e-mail: rsampson@uiuc.edu
Tips for Roses, Trees, and Houseplants
A few tips can make life easier for the summer gardener who deals with roses, trees, and what to do with houseplants while on vacation, said a University of Illinois Extension horticulture educator.
"For roses, avoid fertilizing after mid-August," said Ron Wolford. "Fertilizing roses after mid-August can promote new growth that will not have time to harden off before the cold temperatures set in. After roses have gone dormant, you can fertilize and the fertilizer will be available to the plant in the spring.
"Watch out for black spot on roses. Circular black spots appear on the leaves starting from the bottom of the plant and moving upward. Splashing from rain or watering will spread the disease. Spray weekly with a fungicide after reading and following all label directions. The fungus causing blackspot overwinters on fallen leaves, so raking and removing the leaves in the fall will provide some control."
Watch for leaf drop and leaf scorch on trees in hot, dry weather, he said. Maple and ash trees are especially prone to dropping leaves when under stress from heat and drought.
"Leaf scorching occurs when the leaf tissue turns brown and dies," he said. "Scorching occurs on the leaf edges. Water is being lost from the tree faster than the tree can replace it. Watering trees during dry periods can reduce leaf drop and scorch."
Going on vacation and wondering how to water your houseplants?
"Set up a temporary houseplant self-watering system in your bathtub," said Wolford.
"All that is needed is an old dish-drying rack, white cotton shoelaces, and a bathroom that gets some natural light. Set the dish rack upside down in the tub and place the plants without saucers on the rack. Poke three to four inches of shoelace into the soil through the drainage hole. Run a few inches of water into the tub. The shoelace will act as a wick and keep your houseplants from drying out."
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