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Archive for ISU extension advice
Laura Jesse, of Iowa State University Extension’s Plant & Insect Diagnostic Clinic, wrote the following about garden slugs:
There seem to be plenty of slugs in my garden, but I hope not in yours. Slugs leave small, irregular holes all over the leaves of plants. They especially seem to like my hostas but they are not picky feeders. Slugs are difficult to detect because they feed only at night. Slugs look like snails without a shell. They vary in size from less than an inch up to 2 inches in length, grayish colored, and a bit slimy to the touch. In fact as they crawl along they leave a slime trail.
Slugs need moisture to survive and are found under mulch, rocks, logs, and other damp locations. My hostas tend to be eaten because they grow in a garden that is shaded and holds the moisture longer.
Reducing slug damage is not an easy task and nothing will fix holes already there, so your first question should be – how bad is this and can I live with the damage? If you do decide to try to reduce the slug population you should combine several tactics. First, remove mulch and reduce moisture from around the base of afflicted plants as much as possible. Remove slugs you find either by using a trap such as a board on the ground that slugs will gather under or pan traps with beer as a bait. I assume cheap beer works fine and would not waste expensive beer on this. Remove dead slugs daily or it will get pretty disgusting. Finally there are commercially available slug baits available containing a molluscicide, but they are best used in the spring or fall.
I’ve driven right past my plot in the city gardens, not recognizing it from what it was a week, or even days before. The rain and heat make the perfect recipe for weed season in Iowa. They grow fast and my combat methods are slower than the tillers many people use.
Richard Jauron, extension horticulturalist at Iowa State University wrote the following about weed control in Iowa:
Weeds are those annoying plants that gardeners love to hate. In the garden, weeds compete with desirable plants for water, nutrients, sunlight and growing space. They also may harbor insects and diseases. Allowed to run rampant in the garden, weeds can drastically reduce yields of fruits and vegetables. in addition, they hinder the performance of annual and perennial flowers.
The first step in weed control is identification of the weed or weeds. The type of weed helps determine the best method of control. The two main types of weeds are annuals and perennials. Annual weeds germinate from seeds, grow, flower, set seed and die within one year. Perennial weeds live for three or more years. Most perennial weeds die back to the ground in fall, but their crowns or roots produce new shoots in spring. Weeds also can be classified as broadleaf weeds or grasses.
There are three general methods of weed control in the home garden: cultivation (hoeing and tilling) and hand pulling, mulches and herbicides.
Cultivation and hand pulling effectively control most annual weeds. Perennial weeds are often more difficult to control. Repeated cultivation is often necessary to destroy some perennial weeds. When cultivating the garden, avoid deep tillage. The roots of many vegetables, fruits and flowers grow near the soil surface. Deep cultivation will cut off some of these roots. Also, deep cultivation will bring deeply buried weed seeds to the soil surface where they can germinate. Hoe or till around plants or between plant rows, and pull weeds close to plants.
To effectively control weeds, cultivation and hand pulling must be done periodically through the growing season. Small weeds are much easier to control than large weeds. It’s also important to destroy the weeds before they have a chance to go to seed.
Mulches control weeds by preventing the germination of annual and perennial weed seeds. Established weeds should be destroyed prior to the application of the mulch. In addition to weed control, mulches help conserve soil moisture, reduce soil erosion, prevent crusting of the soil surface, keep fruits and vegetables clean and may reduce disease problems.
Grass clippings, shredded leaves and weed-free straw are excellent mulches for vegetable gardens and annual flower beds. Apply several inches of these materials in early June after the soil has warmed sufficiently. Plant growth may be slowed if these materials are applied when soil temperatures are still cool in early spring. Grass clippings, shredded leaves and similar materials break down relatively quickly and can be tilled into the soil in fall.
Wood chips and shredded bark are excellent mulches for perennial beds and areas around trees and shrubs. Apply two to four inches of material around landscape plantings. These materials decay slowly and should last a few years. However, it’s often necessary to apply additional material annually to retain the desired depth.
Herbicides can be used to supplement cultivation, hand pulling and mulches. However, several limitations prevent the extensive use of herbicides in the garden. Only a small number of herbicides are available to home gardeners. Additionally, most home gardens contain a wide variety of fruits, vegetables and flowers. No one herbicide can be safely used around all garden and landscape plants. If not applied properly, herbicides may cause unintended damage to fruits, vegetables and ornamentals. Herbicides are pesticides. When using any pesticide, carefully read and follow label directions.
Weeds are a persistent problem for home gardeners. However, weeds can be effectively controlled by cultivation, hand pulling, mulches and (on occasion) herbicides. Persistence is the key. Gardeners need to be as persistent with their weed control efforts as weeds are in coming back again, and again and again.
You’ve planted your seeds indoors, waited for them to sprout and one day find a container of tiny, droopy plants.
What went wrong?
Damping-off could be responsible for the collapse and death of your seedlings.
The gardening experts at Iowa State University Extension note that damping-off is caused by several different fungi. Environmental conditions usually associated with damping-off are poorly drained potting soil and overwatering.
Damping-off can be prevented by using clean containers, a sterile, well-drained potting mix and by following good cultural practices. Previously used containers should be washed in soapy water, then disinfected by dipping in a solution containing one part chlorine bleach and nine parts water. Flower and vegetable seeds need an evenly moist potting mix for good germination. After germination, allow the potting soil to dry somewhat between waterings.
I’m getting a later than usual start on my seedlings, having just planted my first round today. The earliest I’ve planted seeds indoors was in late January – I had flowers blooming by the end of March. Some plants, of course, need more time to grow than others. The ISU gardening experts also offer this reminder on the starting times for seeds: The crop time (number of weeks from sowing to planting outdoors) for several popular flowers and vegetables are as follows: 10 to 12 weeks – geranium; eight to 10 weeks – petunia and impatiens; six to eight weeks – marigold, pepper, and eggplant; five to seven weeks – tomato, cabbage, broccoli and cauliflower; three to four weeks – cucumber, watermelon, muskmelon and squash. Always check the seed packet if unsure of the correct sowing date.
Richard Jauron, extension horticulturist at Iowa State University, offers the following on spring pruning of berries and other small fruits:
Small fruits that are commonly grown in home gardens include raspberries, grapes, gooseberries, currants and blueberries. For maximum production, small fruit crops need to be pruned in late winter/early spring (March/early April). Proper pruning procedures for raspberries, grapes, gooseberries, currants and blueberries are outlined below.
The pruning procedures for raspberries are based on the growth and fruiting characteristics of the plants.
Summer-Bearing Red Raspberries
Remove all weak, diseased and damaged canes at ground level in March or early April. Leave the most vigorous canes, those approximately 1/4 inch in diameter when measured 30 inches from the ground. After thinning, remaining canes should be spaced about 6 inches apart.
Also, prune out the tips of the canes that have died due to winter injury. Cut back to live tissue. If the canes sustained little winter dieback, remove the top 1/4 of the canes. Cane-tip removal or “heading-back” prevents the canes from becoming top heavy and bending over under the weight of the crop.
Red raspberries sucker profusely from their roots. Plants should be maintained in a one- to two-foot-wide hedgerow using a rototiller or spade. Remove or destroy those shoots that emerge outside the one- to two-foot-wide hedgerow.
Fall-Bearing Red Raspberries (Two Crop System)
Follow the same pruning procedures as described for the summer-bearing red raspberries. This pruning option provides both a summer and fall crop.
Fall-Bearing Red Raspberries (One Crop System)
Prune all canes back to ground level in March or early April. While the plants won’t produce a summer crop, the late summer/early fall crop should mature one to two weeks earlier. Also, total crop yield is typically larger using the one-crop system versus the two-crop system.
Maintain the plants in a one- to two-foot-wide hedgerow.
Black and Purple Raspberries
Remove the small, weak canes, leaving only four or five of the largest, most vigorous canes per clump or plant. Cut back the lateral (side) branches to 12 inches in length for black raspberries and 18 inches for purple raspberries.
Grapevines produce fruit clusters on the previous season’s growth. Before pruning, a grapevine may have 200 to 300 buds capable of producing fruit. If the vine is not pruned, the number of grape clusters would be excessive and the grapevine would be unable to ripen the large crop or produce adequate vegetative growth.
To maximize crop yields, grapevines are trained to a specific system. The most common training system used by home gardeners is the four-cane Kniffin system. The four-cane Kniffin system is popular because of its simplicity. In the four-cane Kniffin system, the canes of the grapevine grow on two wires, one located three feet above the ground and the second six feet high.
If using the four-cane Kniffin system, select four canes on the upper wire, two going in each direction. Also, select four canes on the lower wire. To aid identification, some gardeners tie brightly colored ribbons or strips of cloth on those canes they wish to retain. All remaining one-year-old canes should be completely removed.
Going back to the upper wire, select two of the remaining four canes (one going in each direction). Prune these canes back to one or two buds. These short one or two bud canes are referred to as renewal spurs. The renewal spurs provide the shoots or canes that will produce next year’s crop. Prune the remaining two canes on the upper wire back to eight to 13 buds. The number of buds left on the fruiting canes is determined by plant vigor. If the grapevine is vigorous, leave 13 buds per cane. Leave only eight buds per cane if the grapevine possesses poor vigor.
Prune the four canes on the lower wire the same as those on the upper wire. When pruning is complete, no more than 60 buds should remain on the grapevine. When counting the number of buds on the grapevine, include both the buds on the fruiting canes and those on the renewal spurs.
Gooseberries and Currants
Gooseberries and currants produce the majority of their fruit on 2- and 3-year-old shoots. Shoots that are 4 years old and older produce very little fruit. After the first growing season, remove all but six to eight vigorous, healthy shoots. The following year, leave four or five 1-year-old shoots and three or four 2-year-old canes. After the third growing season, keep three or four shoots each of 1-, 2-, and 3-year-old growth. A properly pruned, established plant should consist of nine to 12 shoots. Pruning of mature plants consists of pruning out all 4-year-old shoots and thinning out some of the new growth.
Blueberry plants are shrubs like currants and gooseberries. Blueberry yields and fruit quality decline when blueberry shoots (stems) reach 5 years of age. In late winter/early spring, prune out any dead or diseased stems. Also, prune out stems that are 5 years old and older. Allow one to two new shoots to develop each year.
The pruning of small fruits really isn’t difficult. It requires a basic understanding of plant growth and pruning techniques, proper pruning equipment and (sometimes) a little bit of courage.
The following is by James Romer, Extension Horticulturist at Iowa State University:
This time of the year gives many gardeners an empty feeling. It is hard to keep warm and dry when temperatures dip below zero and it snows every other day. It is reminiscent of those classic song lyrics — “All the leaves are brown and the sky is gray … California dreamin’ ….” Anyway, this is a great time of the year to do some planning and pruning.
The late dormant period (February to early April) is an excellent time to prune deciduous trees. The absence of foliage at this time of year gives the home gardener a clear view of the tree and allows him/her to select and remove appropriate branches.
Proper pruning improves the appearance, maintains the health and prolongs the life of trees. Improper pruning destroys their natural beauty, weakens them and may lead to their premature death.
It is essential to make proper cuts when pruning trees. Do not make flush cuts. Flush cuts are cuts made as close as possible to the trunk or main branch. Flush cuts produce large wounds, destroy the tree’s natural mechanisms that promote healing and slow the “healing” process.
When pruning trees, make the final cut just beyond the branch collar and branch bark ridge. The branch collar is the swollen area at the base of the branch. The branch bark ridge is the dark, rough bark ridge that separates the branch from the main branch or trunk. Pruning just beyond the branch collar and branch bark ridge retains the tree’s natural defense mechanisms and promotes the healing process. When a branch is pruned properly, a slightly raised area remains on the trunk or main branch. However, do not leave stubs.
Do not apply wound dressings to pruning cuts. The application of wound dressings or paints doesn’t stop decay and may actually inhibit or delay the healing of wounds.
There is one exception with not applying paint to oak trees. Oak wilt is a fungal disease that is lethal to many oaks. Oak wilt infections occur most commonly in spring and early summer and are spread from infected trees to healthy trees by sap-feeding beetles. To reduce the risk of the spread of oak wilt, don’t prune oaks from April 1 to July 1. If oak trees must be pruned between April 1 and July 1, for example, to correct storm damage, immediately apply a latex paint to all cut surfaces to avoid attracting sap-feeding beetles to the wounds.
Use the three-cut procedure when cutting large branches to prevent extensive bark damage. Make the first cut about one to two feet from the main branch or trunk. Cut upward and go about halfway through the branch. Make the second cut a few inches beyond the first. Cut downward completely through the branch. Make the final cut just beyond the branch collar.
Some trees, such as maple, birch and elm, bleed heavily when pruned in late winter or early spring. However, the heavy bleeding doesn’t harm the trees. (The trees won’t bleed to death.) Eventually the flow of sap will slow and stop. Heavy bleeding of susceptible trees can be avoided by pruning in late June or early July.
The pruning of deciduous trees by the home gardener should be limited to small trees and the removal of smaller branches that can be reached from the ground in medium to large trees. Branches high up in large trees and those near utility lines should be left to professional arborists. Professional arborists should have the proper training and equipment to safely perform the job.
If that’s not enough to do, another enjoyable winter activity is to leaf through garden catalogs. Many contain colorful plant photographs. Some carry specific merchandise, such as seeds, perennials, roses or fruits. Others carry a wide variety of products.
Also, visit a bookstore or public library and browse through some of their gardening books. Excellent reference books for home gardeners include “Manual of Woody Landscape Plants” by Michael Dirr; “Continuous Bloom” by Pam Duthie; “Herbaceous Perennial Plants” by Allan Armitage, and many others.
Remember also that your Iowa State University Extension county office has numerous publications on gardening in Iowa. Most of these publications also are available from the ISU Extension Online Store at www.extension.iastate.edu/store.
So get busy planning, pruning and dreaming about plants for this spring.
The following Q&A is from Iowa State University Extension’s garden experts:
I recently purchased a Norfolk Island pine. How do I care for it?
The Norfolk Island pine is a popular houseplant. During the holiday season, many individuals turn their plants into living Christmas trees by decorating them with miniature lights, ribbons and ornaments. The Norfolk Island pine thrives indoors when given good, consistent care. Place the Norfolk Island pine in a brightly lit location near an east, west or south window. Rotate the plant weekly to prevent the plant from growing toward the light and becoming lopsided.
Thoroughly water the Norfolk Island pine when the soil surface becomes dry to the touch. Discard the excess water, which drains out the bottom of the pot. From spring to early fall, fertilize the plant with a dilute fertilizer solution every 2 to 4 weeks. A temperature of 55 to 70 degrees F is suitable for the Norfolk Island pine. Winter is often a difficult time because of low relative humidity levels in most homes. Raise the humidity level around the Norfolk Island pine with a humidifier or place the plant on a pebble tray. Low relative humidity levels, insufficient light, or infrequent watering may induce browning of branch tips and lead to the loss of the lower branches.
Which trees and shrubs provide food for birds during the winter months?
When attempting to attract birds to the landscape, trees and shrubs that provide food during the winter months are extremely important as natural foods are most limited at this time of year. Trees that provide food for birds in winter include hackberry (Celtis occidentalis), hawthorn (Crataegus species), eastern red cedar (Juniperus virginiana) and crabapple (Malus species). Shrubs that provide food for birds include red chokeberry (Aronia arbutifolia), northern bayberry (Myrica pensylvanica), sumac (Rhus species), roses (native species and Rosa rugosa), snowberry (Symphoricarpos species), nannyberry (Viburnum lentago) and American cranberrybush viburnum (Viburnum trilobum).
Can I dispose of my wood ashes in the garden?
Wood ashes contain small amounts of several plant nutrients. The nutrient content of wood ashes depends on the type of wood burned, the thoroughness of its burning, and other factors. Generally, wood ashes contain 5 to 7 percent potash, 1 percent phosphate, and small amounts of other elements. However, the largest component of wood ashes is calcium carbonate. Calcium carbonate is a liming material. Liming materials raise the soil pH.
The soil pH is important because it affects the availability of essential nutrients. The pH scale runs from 0 to 14. Any pH below 7.0 is acidic and any pH above 7.0 is alkaline. A pH of 7.0 is neutral. Most vegetables and perennials grow best in slightly acidic soils with a pH between 6.0 and 7.0. Plants may not perform as well in soils with a pH above 7.0 because of the reduced availability of some essential nutrients.
Avoid applying wood ashes to garden areas with a pH above 7.0. Applying wood ashes to alkaline soils may raise the soil pH and reduce the availability of some plant nutrients. An application of 10 to 20 pounds of wood ashes per 1,000 square feet should be safe if the soil pH is below 7.0. If the soil pH in your garden is unknown, conduct a soil test to determine the pH of your soil before applying wood ashes to flower or vegetable gardens.