Horticulture 2011 Newsletter No. 48 November 29, 2011

Video of the Week: Poinsettias, Choosing the Best

UPCOMING EVENTS

Kansas Turfgrass Conference – December 6, 7 and 8, 2011 Kansas Expocentre, Topeka http://www.kansasturfgrassfoundation.com/annual-ktf-conference.html

Great Plains Growers Conference – January 5, 6 and 7, 2012 St. Joseph, MO http://www.greatplainsgrowers.org/

Kansas Arborists Association Shade Tree Conference - January 11–13, 2012 Ramada – Downtown Topeka, KS http://www.kansasarborist.com/shadetree.aspx

RetailWorks - February 17, 2012 Capitol Plaza Hotel, Topeka, KS

FLOWERS

Poinsettia Care

Modern poinsettia varieties stay attractive for a long time if given proper care. Place your poinsettia in a sunny window or the brightest area of the room, but don't let it touch cold windowpanes. The day temperature should be 65 to 75 degrees F. with 60 to 65 degrees at night. Temperatures above 75 degrees will shorten bloom life, and below 60 degrees may cause root rot. Move plants away from windows at night or draw drapes between them to avoid damage from the cold.

Poinsettias are somewhat finicky in regard to soil moisture. Avoid overwatering because poinsettias do not like "wet feet." On the other hand, if the plant is allowed to wilt, it will drop some leaves. So how do you maintain proper moisture? Examine the potting soil daily by sticking your finger about one-half inch deep into the soil. If it is dry to this depth, the plant needs water. When it becomes dry to the touch, water the plant with lukewarm water until some water runs out of the drainage hole, then discard the drainage water. (WU)

FRUIT

Mouse Damage to Fruit Trees/Plants

Be on the lookout for mouse tunnels around your fruit plants. Trunks and roots of apple trees are among the favorite meals for mice. There is probably no damage yet. But if we receive enough snow to cover winter food supplies, mice will begin to feed on the lower area of tree trunks and roots. This feeding may be severe enough to girdle tree trunks and kill the trees.

Mice like to hide in dead grass and weeds around the trees, especially close to the trunks. They will often tunnel near the soil surface and feed on the tree bark. You can check for mice by placing baited mouse traps in PVC or other pipe near your trees. Insert the traps far enough so that pets are unable to reach the trap. Check the stations about once a week and reset traps if necessary. Mouse damage can be severe enough to kill trees that are old enough to bear fruit. Clear dead grass and weeds away from your trees and monitor for mice if you are using mulch around your fruit plants. (WU)

MISCELLANEOUS

High pH Soils and What To Do With Them

Though there are high pH soils in most parts of the state, soils tend to be more alkaline in the central and western regions of Kansas. These high pH soils can cause problems for plants by reducing the availability of certain micronutrients. For example, most Kansas soils have more than adequate amounts of iron. However, a high pH can make iron unavailable resulting in a condition called iron chlorosis. Iron chlorosis reduces the health of plants by reducing photosynthesis. Lowering the pH of such soils will eliminate iron chlorosis. Now would be a good time to have a soil test done to see if your pH is too high. If so, sulfur can be added either now or in the spring to lower the pH. Different textures of soil require different amounts. A sandy soil needs 7 pounds of sulfur per 1,000 square feet to reduce pH one point. A loam soil needs 11 pounds and clay needs 17 pounds to do the same. For example, if you wished to lower pH from 8.5 to 6.5 on a loam soil, you would need 22 pounds of sulfur per 1,000 square feet.

Unfortunately, adding sulfur to lower pH is not as clear-cut a solution as we would like. Here are some other factors to keep in mind.

Free calcium carbonate: Some soils have free calcium carbonate, actual particles of limestone mixed in the soil. These "calcareous" soils normally have a pH of 7.3 to 8.5, with 8.2 to 8.3 being most common. In order for us to lower the pH with sulfur, all free calcium carbonate must be neutralized first. A recent soil test showed 6.7 percent free calcium carbonate. One pound of sulfur is needed to neutralize three pounds of calcium carbonate. Assuming 80 pounds for a cubic foot of soil, you would need about 1.75 pounds of sulfur per square foot just to neutralize the free lime. Additional sulfur would be needed to lower pH. Adding this much sulfur to a soil at one time is not recommended.

Not all high pH soils are calcareous. Perform this simple test to see if your soil contains appreciable amounts of free lime. Apply one drop of vinegar to dry soil. A vigorous fizz usually means the soil contains at least 3 percent calcium carbonate. A mild fizz suggests a calcium carbonate of between 1 and 2 percent and a fizz that can only be heard suggests the soil has a calcium carbonate content less than 1 percent.

How sulfur works: Elemental sulfur does not lower pH directly. It must first be oxidized to the sulfate form with the result being sulfuric acid. The sulfuric acid produces hydrogen, which acidifies the soil and lowers pH. The oxidation takes place primarily through microbial activity.

Oxidation takes time: Microbial oxidation of elemental sulfur takes time and depends on: - number of sulfur oxidizing bacteria present - temperature (75-104 degrees optimum) - moisture content of soil (too wet or too dry will slow down process) - size of sulfur particles (the smaller the better)

A single sulfur application normally takes at least 2 years for most the sulfur to react and form sulfuric acid. This, of course, depends on the above factors.

So, what do you do about calcareous soils? See the accompanying article. (WU) Iron Chlorosis and Calcareous Soils

Iron chlorosis due to high pH soils is a significant problem in Kansas. Though Kansas soils normally contain adequate amounts of iron, a high pH makes that iron unavailable to the plant. Iron plays a major role in the production of chlorophyll. Thus, a lack of iron reduces the amount of chlorophyll and results in yellowing of leaves. Iron chlorosis weakens, and in severe cases, may kill a susceptible plant.

A popular recommendation for high pH soils is adding sulfur to lower pH. This works well for many soils, but not those that are calcareous. Calcareous soils are those that contain actual particles of calcium carbonate (limestone). Calcareous soils can be difficult to practically impossible to acidify because the sulfur must neutralize all the free limestone before the pH is affected long term. In many cases you would need well over a pound of sulfur per square foot just to neutralize the free lime.

So what do you do? That depends on the situation. With vegetable gardens and annual flowerbeds, work products into the soil during the time of year when there are no plants present. Oregon State University suggests mixing 5 pounds of sulfur per 100 square feet into the soil before planting. The idea is to form little pockets of acidity that result in enough iron availability for the plants during the year of application. Note that this must be done each year. Another possibility is to use iron chelates. Iron chelates hold the iron in such a way that the plant can get to it. However, not all iron chelates will work in high pH soils. For soils with a pH over 7.2, use a chelate that contains FeEDDHA (iron ethylenediamine-di- (ohydroxyphenylacetate)). This can be found in the products Sequestar 6% Iron Chelate WDG, Sequestrene 138 and Millers FerriPlus. If these products cannot be located locally, Sequestar 6% is available form rosecare.com or www.montereylawngarden.com. Chelates can either be mixed into the soil at planting or sprayed on the foliage early in the season. Reapply as needed. (WU)

Soil Tests and Plant Growth

Though soil tests are useful for identifying nutrient deficiencies as well as soil pH, they do not tell the whole story. We often receive soils from gardeners who are having a difficult time growing crops even though the soil test shows that nothing is deficient.

Here are some factors that can affect plant growth that are not due to nutrient deficiencies or pH. Not enough sun: Plants need a certain minimum amount of sun before they will grow well. As a general rule, flowering (and fruiting) plants need at least 6 to 8 hours of full sun per day. There are, of course, exceptions such as impatiens that bloom well in shade. Move sun-loving plants out from the shade or use plants that are better adapted to shady conditions.

Poor soil physical characteristics: Roots need oxygen as much as they need water. A tight clay soil can restrict soil oxygen levels as well as make root penetration of the soil difficult. Increasing the organic matter content of clay soils can help break them up. Add a 2-inch layer of organic matter and till it in.

Walnut trees: Walnuts give off a natural herbicide that interferes with the growth of some plants such as tomatoes. Vegetable gardens should be at least 50 feet away from walnut trees if possible. For a listing of plants that are susceptible to walnut, go to: http://www.omafra.gov.on.ca/english/crops/facts/info_walnut_toxicity.htm

Tree roots: Trees not only compete with other plants for sun but also for water and nutrients. Extra water and nutrients may be needed.

Shallow soils: When new homes are built, the topsoil is often stripped off before the soils are brought to grade. Though the topsoil should be replaced, it sometimes is not or is not replaced to the same depth as it was originally. You are left with subsoil that usually does not allow plants to grow well due to a lack of soil structure. Adding topsoil to a depth of 8 to12 inches would be best but this often is not practical. In such cases, try to rebuild structure by adding organic matter and working it into the soil.

Added soil: Sometimes soil is added to smooth out an area or topsoil is added but only a shallow layer is used. Roots will not go from one soil type to another. Always blend in added soil to existing soil so there is a gradient from one to the other. For example, let’s say you want to add 6 inches of topsoil. Add 3 inches and till in to a depth of 6 inches and then add the remaining 3 inches of topsoil. You now have a gradient that goes from the topsoil to the existing soil.

Improper watering: Roots develop where conditions are best for growth. Shallow, frequent watering leads to roots developing primarily near the surface of the soil where the soil is moist. Such shallow root systems are easily damaged by heat and any interruption in the watering schedule. It is better to water less frequently and to a greater depth to encourage a deeper root system that is less sensitive to heat and water stress.

Watering during the evening can also be detrimental to plants if the irrigation wets the foliage. Many diseases are encouraged by free water on the leaves. Watering late in the day often will keep the foliage wet until dew forms. Dew will keep the foliage wet until it evaporates the next morning. It is better to water early in the morning so leaves do not stay wet as long. If you must water late in the day, use drip irrigation if practical (such as in a vegetable garden).

Gas Leaks: Make sure that a natural gas line does not run under the affected area. Leaks from that line can kill existing vegetation. If this is the cause, everything in that area will be killed. (WU) Contributors: Ward Upham, Extension Associate

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Kansas State University Agricultural Experiment Station and Cooperative Extension Service