DRY WEATHER STRESSES TREES AND LAWNS, FRUITS AND VEGETABLES (Not to mention field crops)

 July 26, 2012

While what happens in lawns and gardens during hot, dry weather isn’t perhaps as critical to the economy of most of us as is what happens in the fields around us, it is still shocking and worrisome to see leaves falling off your trees 2 or 3 months ahead of schedule. The current situation is widespread across the region and people’s livelihoods are at stake. If you have a lawn care business, that has suffered, as have the golf courses. Orchards, corn and soybean growers and more are adversely affected as well. I am merely concerned for my trees and hostas, which survival is not important to my business. Losing them, however, would affect me economically as I would have to replace them at major cost. Irrigating is in itself an
economic factor. If the drought worsens, communities could see reductions in water availability. I have 2 well-established trees that have browned and are losing leaves and my river birch, planted 5 years ago, has yellow falling leaves. Probably your trees and mine will survive, unless they were in poor health to begin with or have only been planted within the past three to five years. Trees planted more recently than that need to be watered deeply every week to 10 days, in a normal year. The newly planted trees don’t have the root system to cope in abnormally dry years and need to be watered to survive. Once you start watering you cannot stop until 1-inch rains become common. Only you can decide whether to lend a hand or let Mother Nature determine the outcome.

Some trees, like the river birch, cope by shedding their leaves to conserve moisture while others may just appear to be dying. Indeed, they may be dying if your tree is unhealthy even though it appeared to be fine. The added stress of drought will speed up the decline of these trees according to Jesse Randall, Iowa State University Extension and Outreach forester. It is always difficult to lose a tree, especially if it is a good shade tree, so precautions can help eliminate or reduce losses. Watering in early morning or late evening is best, giving the tree a good soaking.

I attended the drought webinar at the extension office last week, which attempted to answer the questions of whether or not to intervene. In a nutshell, it is best to protect your investment in trees if they are under the age of 7 years. For mature trees, forget it. How much water, you say, and how often? Normally, a watering one to three times a week for the first few months when they are first planted is sufficient. The area under the canopy should be slow watered daily on the surface in extreme conditions, such as we are experiencing,
with 2-4 gallons per inch of trunk caliper. This can be scaled back according to time of year and weather. The hotter and windier it is the quicker the plant loses water. Trees with insufficient water will experience increased insect and disease problems and even root death. Mulching helps conserve moisture as well as enhancing your landscape and keeping the weeds at a minimum. Mulch around your trees also keeps lawnmowers and other potentially damaging equipment away from the trunk.

In general, whether you are watering your lawn, vegetable garden, flower beds or trees, a schedule that allows 1-1½ inches of water per week to each area is best carried out in the early morning hours from 6-9 a.m. This allows for most of the water to soak in deeply with the least amount of evaporation. Midday watering is less efficient, especially when using a sprinkler, due to increased evaporation and stronger winds that can carry the water away from where you want it, causing uneven watering and waste. Watering in the evening can increase disease problems. When watering the lawn, if you choose to do so, a single application of 1-1½ inches of water allows the roots to penetrate more deeply into the soil than does frequent shallow watering. Shallow rooted turfgrass is more susceptible to pests and is also less drought tolerant. If you are
sprinkling, place 2 or 3 containers or rain gauges within the spray pattern to judge the amount of water you are applying. According to Dave Minner, a webinar presenter on turfgrass, there is no one good answer as to whether or not to water. Most lawns are just dormant from the drought, but could be dying in some cases. Dry, brown grass with roots in thatch may die, as well as roots in sand. For dormant lawns during drought, Minner recommends watering with 1” of water every 3 weeks and if you are mowing, cut grass no shorter than 3-1/2” in height. One other thing to consider is planting more drought-resistant types of grass, such as turf type tall fescue, especially if your lawn dies and you need to replant.

Minner’s bottom line, “Pray for rain, but prepare for drought.” Ajay Nair spoke on fruits and vegetables, saying first “There are major vegetable issues. First there was the April frost, Japanese beetles in some areas and now the excessive heat and drought.”

The heat and lack of rain affects crop establishment, plant growth and development. Temperatures over 95 degrees significantly reduce pollen count and viability. Poor pollination equals poor quality crops. At those temperatures, or with water stress, vegetables such as beans, tomatoes, peppers, and peas will drop their flowers. One product on the market is a cooling spray called Surround, which reduces canopy temperatures, though it may need to be re-applied every 7-14 days.

Taking a soil sample at the beginning of the growing season to determine if extra calcium fertilizer needs to be applied is a good idea. A lack of calcium, not enough water to move the calcium even if present, too much nitrogen, inadequate moisture or high soluble salt concentrations in the soil near the roots can result in blossom end rot. These issues can be determined with a soil sample, and steps taken for prevention.
Managing fruits in drought is a bit more complicated and watering needs depend on several factors including soil texture, soil depth, rooting depth of the crop, crop development and factors affecting the need for water (heat, light, humidity and wind) Soil moisture content should be at 50-80% for optimum growth. Below 50% plants show stress.

For example, strawberries have a rooting depth of 1 inch and should be watered to a depth of 6 inches; raspberries, blackberries, gooseberries and aronia berries have a root depth of 2 inches and need water at 12-15 inches. Tree fruits and grapes have 3-foot roots and need water at 24-30 inches. There is not “one size fits all” answer to the irrigation issue for fruits, and is a lengthy subject deserving its own column.

For fruits and vegetables as well as flowerbeds, a soaker hose or drip irrigation system is more efficient and causes fewer disease problems than sprinklers. Also, keeping weeds at bay is as important as water management, as the weeds compete for both water and nutrients. Yes, hot and dry conditions are troubling on many fronts, but for those of us who like to grow things it is especially difficult when the gardens start to go downhill. However, gardeners are optimistic, as are farmers, and surely next year will be better.

To get an answer to a specific question there are specialists available at hortline@iastate.edu or you may call 515-294-3108. The Yard and Garden FAQs website at http://expert.hort.iastate.edu/ is a good place for answers to tree and other yard and garden questions.

Julie Johnston, Master Gardener intern

Dear Iris

Repelling garden pests naturally 

Jul 26, 2012

Did you know that the metabolic rate of rodents (squirrels, voles, muskrats, beavers, chipmunks, woodchucks, gophers, mice, rats, and shrews) is so high that they must eat almost constantly to sustain themselves? They are the most numerous of Iowa’s wild mammals and share ranks with birds, moles, rabbits, raccoons, and deer as unwanted garden visitors. Repellants, scare tactics, traps, and barriers are all natural ways of repelling your varied garden invaders.

Repellants: Everyone has heard of blood meal or human hair sprinkled around the garden, but have you heard of bars of strong smelling soap such as Irish Spring spread helter skelter on the ground or in little net bags or formerly discarded plastic berry containers from the store? Carnivorous human male 1st urine of the day or predator urine or any other strong offense odor on a rag here and there on the garden fence or distributed around the garden perimeter is a strong deterrent as long as it is reapplied every two weeks and after every rain. Cayenne pepper liberally sprinkled on wet leaves will deter even the most determined garden pests. The very tall and pretty but lethal castor bean plants and seeds deter birds, moles and deer. Always wear gloves when handling any root, leaf, flower or seed from this deadly plant!

 Scare tactics: Reflective items such as aluminum foil or discarded cds/dvds randomly startle intruders. Fake owls or toy snakes here and there in the garden that are periodically moved around tend to keep birds and small animals at bay. A scarecrow will also keep those smaller animals away and sometimes the larger ones as well. Noise makers such as chimes, dogs, radios on timers or empty plastic bottles over garden stakes also chase away intruders.

Traps: Trap crops are plants sacrificed so the intruder will stay away from the crop you really want to harvest, such as planting some lettuce near invader burrows. With a bit of luck, rabbits and woodchucks will eat “their” lettuce instead of yours. Conventional traps whether kind or harmful are also options.

Barriers: Barriers include netting, natural barriers and fences. Draping a net over fruit trees/bushes/plants or over hoops secured over rows in the garden work well to protect from birds, and less adventurous animals. Shrubs or an old fashioned moat will deter many walking pests. Fences seem to work best for most people for most types of garden invaders. If the bottom edge of the fence (at least 10”) is buried underground and the rest (3’ for small animals and 8’ for deer) is above ground, the number of pests in your garden will be substantially reduced. To increase the chances of keeping out all deer, place another fence no more than 3 inches inside of the outer fence because they will not have enough room to land from the first jump and make the second one.

Every tactic you undertake involves time and perhaps also money, so it is important to first identify who your garden invaders are and then “chose your weapons.” Remember that your unwanted visitors are shrewd. If you periodically change your tactics using any combination of the suggestions here or in part I printed May 31 in The Fairfield Ledger, your efforts will be rewarded and your plants will be the healthiest and happiest you’ve ever grown.

Aideen Vega-Van Auken is a Master Gardener.

Dear Iris - Tomatoes

 Recognizing tomato problems

Jul 19, 2012

Tomatoes are the most popular vegetable crop in Iowa. Many diseases and disorders can affect tomatoes during the growing season. Some of these include Septoria leaf spot, early blight, and Anthracnose.
Septoria leaf spot, caused by the fungus Septoria lycopersici, is the most common foliar disease of tomatoes in Iowa. It first appears as small, water-soaked spots that soon become circular spots about 1/8 inch in diameter. The lesions gradually develop grayish white centers with dark edges. The light-colored centers of these spots are the most distinctive symptom of Septoria leaf spot. Spores are spread to new leaves by splashing rain. Heavily infected leaves turn yellow, wither and eventually fall off. Lower leaves are infected first. Defoliation can be severe after periods of prolonged warm wet weather. Infection can occur at any stage of plant development but appears most frequently after plants have begun to set fruit. The fungus survives the winter in tomato debris.

To control Septoria leaf spot, a combination of cultural practices is often needed:
• Plant disease-free transplants far enough apart that the plants will not be crowded after they are full grown. This will allow air to circulate and the foliage to dry rapidly.
• Water at the base of the plants, and in the morning rather than the evening, to minimize the amount of time that the leaves are wet.
• Remove as much plant debris as possible in the fall and promptly plow under or bury the remaining residue.
• Avoid working with plants when leaves are wet.
• Rotate crops so that tomatoes are not grown in the same area of the garden every year.
Early blight, caused by the fungus Alternaria solani, is common in Iowa tomato plantings. Premature loss of lower leaves is the most obvious symptom of the disease. Brown to black spots, 1/4 to 1/2 inch in diameter with dark edges, appear on lower leaves. Spots frequently merge, forming irregular blotches. Dark, concentric rings often appear in leaf spots, resulting in the “target” appearance. Warm, wet weather favors rapid spread of early blight.

Cultural and chemical controls for early blight are the same as for Septoria leaf spot.
Anthracnose, caused by the fungus Colletotrichum coccodes, is probably the most common fruit-attacking disease of tomato in Iowa. Symptoms first become visible on ripe or ripening fruit as small, circular, indented spots in the skin. As these spots expand, they develop dark centers or concentric rings of dark specks, which are the spore-producing bodies of the fungus. In moist weather, these bodies exude large numbers of spores, giving diseased areas a cream to salmon-pink color. By this stage, decay has penetrated deeply into the tomato flesh. Anthracnose appears most commonly on overripe fruit.
The fungus survives the winter on diseased vines, in the soil and in the seeds. Weeks before the fruit ripens, anthracnose can become established on the leaf spots caused by other fungi or by insect-feeding injuries. Spores are spread by rain splash. Warm wet weather causes the disease to spread and the symptoms to develop.

Control measures for anthracnose are the same as for Septoria leaf spot. In addition, harvest at frequent intervals and pick all ripe fruit at each harvest.
Other problems are not caused by infectious microorganisms but rather by environmental stresses on the plant. Some of the physiological problems are blossom end rot and fruit cracking.

Why are my tomatoes cracking?
Fruit cracking is a common problem on tomatoes. Cracks usually appear at the top or stem end of the fruit. Cracks radiate out from the stem or circle the fruit in concentric rings. Fruit cracking is associated with wide fluctuations in soil moisture levels. A heavy rain or deep watering after a long, dry period results in rapid water uptake by the plant. The sudden uptake of water results in cracking of ripening fruit. Generally, fruit cracking is most common on the large, beefsteak-type tomatoes. Fruit that has reached the ripening stage during dry weather may show considerable cracking if the dry period is followed by heavy rains and high temperatures. Mulching and avoiding heavy applications of nitrogen fertilizer should help reduce fruit cracking.

Why do my tomatoes have a spot of rot?
Blossom end rot is a very common problem of green and ripe tomatoes. It first appears as a sunken, brownish black spot 1/2 to 1 inch in diameter on the blossom end of the fruit. Although blossom end rot itself causes only local injury, secondary organisms frequently invade the lesion and cause complete rotting of the fruit. It often occurs in rapidly developing fruit during hot, dry weather. To avoid blossom rot, water consistently and mulch around the plants to conserve soil moisture. Remove the affected fruit so that later-maturing fruit will develop normally.

Sharie Leazer is a Master Gardener Intern.

Dear Iris

Cultivating Friends, Making Memories

By Kathy Tollenaere, Master Gardener | Jul 12, 2012

PHOTO SUBMITTED - 

Gloriosa Lily - Gloriosa supurba

If you were to ask me to name a few favorite plants in my gardens, I would say without reservation that many of the “Number-One-Top-Favorites” are those received from special people in my life. Gardening lends itself to the creation of memories: memories of “plant forays” to nurseries, trips to interesting and/or notable places, and most especially, cultivating relationships with friends and relatives.

For example, my parents have shared many plants (what about that large-flowered, pale yellow daylily my dad and I purchased in Mason City many years ago? Upon returning home, we divided the plant so we could share it!) Not only did I receive daylilies, phlox, Virginia Bluebells and several other herbaceous perennials over the years, but also raspberries, asparagus, strawberries and rhubarb.

My Aunt MEA also has shared many plants over the years including: two varieties of phlox, several hostas, lily bulbs, a fern leaf peony, two varieties of Ginger, Blood Root and Geum triflorum (commonly called Purple Smoke).

Following a quick walk around the yard last night, I found I’ve received daylilies from Joan, Clustered Bellflower from Marty, Ostrich fern from Chris, Bleeding Heart and Glory Lily Gloriosa supurba from Kris, Hosta from Neil, Gooseneck Loosestrife from the church, and Heuchera from Connie. I hope I haven’t left anyone out!

A few very special items have been received from fellow Garden Bloggers. Because I’ve maintained a garden blog for over five years, I’ve “met,” through our posts and communications, gardeners not only from many states, but also several countries. We share information, inspiration, seeds and plants (we trade!). I’ve received seeds for Tennessee Coneflowers from Gail (Tennessee resident), Ligularia seeds from Jim (Ohio), Queen-of-the-Prairie from Kathleen (Colorado), Monarda plants from IVG of Des Moines, and several unusual plants from Iowa Boy of Iowa City.

“Landmark memories” might include nurturing the love of gardening in a child, the year of hardscape and landscape improvements, memories may involve such things as weather conditions or a battle with “critters.” What about garden parties, birthdays, graduation and wedding celebrations?
Whatever your interests or activities, take a walk around your yard. Perhaps you’ll find you’ve already created some pleasant, long-lasting memories. Gather some friends, share some plants, and make a few more special memories.

Happy gardening!

Kathy Tollenaere is a Master Gardener.