Common Iowa Grass Types
Kentucky Blue Grass
In Iowa, Kentucky bluegrass is the best-adapted grass for lawn use. It is dark-green in color, has a medium texture, and will form a tightly knit, attractive sod due to its ability to spread by underground stems (rhizomes). Common types should be maintained at 2 to 3 inches, but the improved varieties will tolerate lower mowing heights. Kentucky bluegrass has moderate wear resistance, but recovers quickly from damage. Kentucky bluegrass grows best on heavy, well-drained, fertile soils and will tolerate partial shade. Water requirements are high during the actual growing season, but during hot dry spells, Kentucky bluegrass will escape drought by going dormant and can usually survive 4 to 6 weeks without water. In most cases, it will recover rapidly during the fall when an adequate amount of moisture and cooler temperatures return.
Seed mixtures will often contain at least two improved varieties of Kentucky bluegrass. It is very competitive, favoring healthy plant growth over weed development.Overall, tolerance to diseases and cold winter temperatures is good, however, it is susceptible to necrotic ring spot and leaf spot diseases. Improved varieties of bluegrass are more resistant to these diseases than common grass types.
Fine fescue is the general name given to a group of fescue grass species characterized by having very fine leaf texture. This group of species includes creeping red fescue, chewings fescue, hard fescue, and sheep fescue. Creeping red and chewings fescues are often used in blends for shaded conditions. They are superior to most cool-season grasses in shade adaptation and compatible in mixes with Kentucky bluegrass. Like perennial ryegrass, fine fescues germinate and establish quickly.
These fine-leaf textured fescues form a lawn of high shoot density, are medium to dark green in color,
and some may spread by rhizomes. The fine fescues have good drought tolerance, but may lose their color rapidly during periods of hot, dry weather. They should be mowed regularly to a height of 1.5 to 2.5 inches, and will respond well under a low fertilization program. The fine fescues are known for their ability to tolerate shady areas as well as their low water and fertility needs. They do not handle wet soils or heat well, and are often mixed with Kentucky bluegrass and/or perennial ryegrass in areas that receive both sun and shade. The ability of the fine fescues to handle traffic is poor.
Tall fescue is the most heat, traffic, and drought tolerant of the cool-season grasses, and it also tolerates wet soils. It is well adapted to shady sites and is often used where a low maintenance lawn is desired. Tall fescue will form a deep root system that is tolerant of clay and alkaline soils.
Medium to dark green in color, tall fescue is coarsely textured. It is a bunch-type grass and forms a coarse, clumpy appearance when used alone. The new, improved turf-type varieties are much finer in texture and possess weak rhizomes. Overseeding every few years is recommended for both common and improved types to reduce the clumpy appearance. Because tall fescue possesses a high-growth rate, frequent mowing will be required as compared to Kentucky bluegrass. When tall fescue is maintained at 3 inches, weeds will rarely be a problem. The improved varieties can handle lower mowing heights, but weeds will likely become a problem. Tall fescue has moderate tolerance of cold temperatures and is suitable for most winters in Iowa. There are few insect and thatch related problems unless the lawn is over-watered or fertilized too much. Tall fescue is very susceptible to brown patch disease, and occasional fungicide treatmentsmay be required. Overall, the new turf-type tall fescues offer a great low-maintenance alternative to Kentucky bluegrass, and are recommended for use across central and southern Iowa in non-irrigated situations.
Perennial ryegrass is a bunch-type grass (lacking any stolons or rhizomes) that is used in seed mixtures primarily because of its ability to germinate and establish quickly. It is medium to coarse in texture, and possesses the darkest green color of the cool- season grasses. Perennial ryegrass can tolerate partial shade, grows well on a wide range of soils, and has good tolerance of wet soils. It should be maintained at a mowing height of 1.5 to 2.5 inches mowing height range.
Perennial ryegrass does not tolerate extremes in temperature, especially low temperatures; therefore it is not generally recommended for pure stands in Iowa. However, because of its exceptional durability and rapid establishment, improved varieties are often blended with Kentucky bluegrass to provide a wear- resistant turf on heavily used areas.
Lawns with sun and shade – use a mixture of Kentucky bluegrass (80%), perennial ryegrass (10%), and fine fescue (10%). Kentucky bluegrass will dominate in full sun areas, perennial ryegrass will provide quick cover and will grow in both sun and shade, and the fine fescues will thrive in the shaded portions of the lawn.
The desire for extreme low-maintenance, low input areas – if low maintenance is more important than overall aesthetics, consider using buffalograss or zoysiagrass.
Lawns with minimal shade – use 100% Kentucky bluegrass or tall fescue for lawns receiving full sun. Choose a seed mixture that contains two or more improved cultivars of Kentucky bluegrass. Often, because Kentucky bluegrass may be slow to establish from seed, 20% to 50% perennial ryegrass may be included in the mixture to increase establishment speed. Kentucky bluegrass should not be seeded in the spring. The weather in spring 2014 was great
for bluegrass seeding, however this is a rarity and it is not advisable to seed Kentucky bluegrass in the spring.
Difficult shade areas where other grasses have failed – use 100% fine fescue. If fine fescue struggles or fails to grow, substitute shrubs, ground covers, or mulch.
Heat and drought areas – use a mixture of tall fescue (90%–95%) and Kentucky bluegrass (5%– 10%). Tall fescue can tolerate poor growing conditions while the Kentucky bluegrass will help provide a uniform establishment.
Info On Weed Control
Fertilizer-herbicide combinations allow a homeowner to combine two operations into one application. A disadvantage of the combination is that the proper time for weed control often does not coincide with the optimum time to fertilize. Combinations with pre-emergence herbicides are generally effective in controlling annual grass weeds as long as applications are made at the appropriate time. Postemergence herbicide combinations require wet leaf surfaces so that granules will stick to leaves.
Control of Annual and Perennial Grasses
A key to the successful control of annual grasses (such as crabgrass) in established lawns is the correct timing
of preemergence herbicide application. Preemergence herbicides must be applied before the grassy weed seeds germinate. Preemergence herbicides should normally be applied in early to mid-April in southern Iowa, mid-April to first of May in central Iowa, and late April to early May in the northern part of the state. Weather often varies considerably from year to year in Iowa. Accordingly, home gardeners should make minor adjustments in the timing of the preemergence herbicide application. If the weather in March and April is consistently warmer than normal, apply the preemergence herbicide early in the normal time period. Apply the herbicide late in the recommended time period if Iowa is experiencing a cold, early spring. If still uncertain as to when to apply the preemergence herbicide, Mother Nature provides some helpful clues. Preemergence herbicides should be applied when the forsythia blossoms start dropping or when redbud trees begin to bloom. Crabgrass seed germination typically begins after these events.
Postemergence control of crabgrass can be obtained with an application of dithiopyr, quinclorac, or fenoxaprop to small and actively growing crabgrass. A second application 7 to 10 days after the first treatment with quinclorac or fenoxaprop may be required for complete control. A single application of dithiopyr prior to the fifth leaf stage (first tiller) will provide early postemergence control. The turfgrass may experience temporary discoloration from the use of some products.
Control of Perennial Grasses
Few options are available for the selective control of perennial grasses, such as nimblewill, quackgrass, and common tall fescue, in lawns. Oftentimes, the most effective herbicide option is the nonselective herbicide Roundup. Nonselective herbicides kill virtually all plants (both desirable and weedy) to which the material is applied. Spot treat the weedy perennial grasses. A single glyphosate application should effectively kill common tall fescue. However, quackgrass is extremely difficult to control. Several repeat application of glyphosate (applied over a period
of three to four months) will likely be necessary to kill quackgrass. Nimblewill can effectively be controlled with use of the postemergence herbicide mesotrione
Control ofYellow Nutsedge
Yellow nutsedge is a warm-season perennial weed with a growth habit similar to grasses except that it has a triangular stem. The grass-like leaves are light green to yellowish in color and shiny in appearance. The leaves come off the stems in sets of threes. Yellow nutsedge reproduces by
seed and small underground tubers called nutlets. Flowers are yellowish or yellowish brown and are borne on small spikelets. Yellow nutsedge grows most rapidly during the hot summer months and is often found in wet or poorly drained soils.
Yellow nutsedge is difficult to kill. Postemergence herbicides are most effective when plants are small and actively growing. Products with active ingredients of sufentrazone, bentazon, and halosulfuron provide the best control.
Control of Broadleaf Weeds
Annual broadleaf weeds, such as prostrate knotweed, can be controlled with an application of preemergence herbicide in the spring. A second application at a reduced rate may be necessary for season-long control.
Perennial broadleaf weeds can be controlled with an application of a broadleaf herbicide in the fall (late September to early November in Iowa). In the fall, perennial broadleaf weeds are transporting carbohydrates from their foliage to their roots in preparation for winter. Broadleaf herbicides applied in fall will be absorbed by the broadleaf weed’s foliage and transported to the roots along with the carbohydrates, resulting in the destruction of broadleaf weeds. The most effective broadleaf herbicide products contain a mixture of two or three herbicides as no single compound will control all broadleaf weeds.
A single application of a broadleaf herbicide effectively kills many broadleaf weeds. Difficult-to-control weeds, such as violets, ground ivy (“creeping Charlie”), and dandelions, will likely require two or more applications of a broadleaf herbicide to achieve satisfactory control.