Large crabgrass (Digitaria sanguinal)

Crabgrass is the bane of many people seeking a ‘nice’ lawn. It is a weedy grass which will out-compete desirable grass species and take over in a short time. Crabgrass has a wider blade, is lighter in color and grows faster than the lawn making it obviously stand out as a weed. Its seed germinates earlier and at lower ground temperatures than other desirable turfgrasses giving it a jump in growing time.

The best defense against all weeds of lawns is to maintain a healthy stand of turfgrass by having soil pH and nutrients at the correct levels. Healthy soil supports healthy grass. Lawns mowed at a height of three inches or taller has less crabgrass and other weeds as the soil it shaded, excluding light from reaching the seeds which initiates germination. Crabgrass is an annual growing new plants from seed each year. None of last year’s crabgrass lived through the winter.

Low cut grass invaded by crabgrass.

 

 

Chemical control against crabgrass is applying a pre-emergent herbicide. They attack the newly produced tissue from the germinating seed up to young plants with a couple of leaves. Pre-emergent herbicides have no effect on seeds in the soil that do not break dormancy and start to grow, only the seeds which start to grow. Timing of application is before the crabgrass seeds start to germinate when to the soil temperatures are 50 to 55 degrees Fahrenheit. This is the same time the forsythia is just past its full bloom stage and starting to but out some green leaves.  The germination period ends when the lilacs begin to bloom. Just remember to apply after forsythia and before lilac flowers. Forsythia and lilac make a great plant indicator for applying the pre-emergent herbicide against crabgrass.

Forsythia bush

Forsythia bush.

lilac .psu.edu-lilac

Lilac, photo (psu.edu/lilac)

There are several different pre-emergent herbicide active ingredients with varying rates of how long they last in the soil. Products containing pendimethalin will last about four months out in the environment. Other active ingredients, dithiopyr, benefin+trifluralin, prodiamine, will last a shorter period of time. Read the labels for the residual rate for each formulation’s time it will last. Most pre-emergent herbicides will stop all seeds from continuing to grow after germinating. This means you will not be able to plant desirable grass seed after applying it. Products containing Siduron are the only pre-emergent herbicide that will allow cool season grass seeds to grow while eliminating crabgrass.

-Carol Quish

 

The ideal “monoculture” lawn, sparkling with dew. Photo: J. McInnis

Lawns are an American obsession, and the most common form of garden activity in the U.S. Even yards with no trees, shrubs or flowers almost without exception have some form of lawn. And they are big business:

+ As of 2004, the annual value of the U.S. turf grass industry was $35 billion.

+ Total acres of turf in the U.S. is estimated to be 46.5 million acres.

+ Over 25 million acres of lawn are tended in the US equals a land mass greater than that of Pennsylvania, Delaware and Rhode Island combined.

+ As a seed crop in the U.S., turfgrass ranks # 2.

+ Nationally, homeowners spend $6.4 billion per year on lawn care.

(Source: The Lawn Institute)

As is evident from the numbers above, the turf grass industry has done a superb job of capitalizing on homeowners’ quest for that perfect expanse of lawn.  It has also been instrumental in shifting fashion to a high-maintenance, intensively managed landscape.

Dutch White Clover Photo: J. McInnis

This wasn’t always so. Before WWII, Dutch White Clover (Trifolium repens) was a staple component of lawn seed mixes. As a member of the legume family, clover possesses that clan’s unique ability to fix atmospheric nitrogen to the benefit of the surrounding turf. At the urging of the companies who produced chemical fertilizers and other lawn-care products, tastes began to trend toward the more uniform look of a grass-only monoculture that we see today.

DWC is now generally regarded as a weed, and most literature available discusses its eradication. Maintenance of a monoculture lawn, with heavy applications of nitrogen and broadleaf-weed herbicides, is incompatible with the cultivation of clover. The lawn-obsessed may be disappointed that with a clover-mix lawn there is less to do!

Clover In Lawns

Clover performs best in a pH range that is compatible with the cultivation of turf grasses (6.2-6.8), but withstands New England’s acidic soil conditions very well. Tolerant of diseases and insect pests, it withstands foot traffic and mowing. The relatively weak stolons of clover combine with the roots of turf grass in a symbiotic relationship that stabilizes soil and prevent erosion in poorer soils. Clover will grow in shade and may dominate where lawn grasses struggle. Once established, it is fairly drought resistant. It’s tough.

White clover is classified into three growing types: low, intermediate and large.  ‘Wild White’ or ‘Dutch White’ are best for lawns, with their ability to tolerate foot traffic and mowing. (The taller varieties are used in agriculture as cover crops, living mulch and forage.)

Benefits of Clover

For those who prefer the easier care of a clover-turfgrass mix lawn, there are benefits in addition to nitrogen fixing. Clover is an excellent forage for pollinators, providing both pollen and nectar to bees. Fruit growers report increased production in crops grown in proximity to or with a groundcover of clover. (In agriculture, the taller types of clover are used.)

Aesthetics

Environmental and cultural advantages aside, the decision to include white clover in a lawn is a matter of individual taste. The bands of creamy-white blossoms, buzzing with the activity of bees, that appear in spring are a welcome sight to some gardeners, who may even go one step further and introduce bugleweed (Ajuga reptans), adding a dash of blue to the mix. For those who wish for a lawn maintenance regime that consists of nothing more than mowing, white clover is definitely the way to go.

J. McInnis

Weeds are making a fast and bold appearance in lawns and gardens this week. I am seeing strong growth of ground ivy, (Glechoma hederacea). Ground Ivy is a perennial weed commonly found in turf. It  spreads by creeping rhizomes, rooting at  the nodes to produce new plants. The purple flowers produce seeds, another way for the plant to spread. Hand pulling is one way to eradicate this creeping vine, but not very effective as the vines break where the nodes are rooting in new spots. It tends to creep through the grass lower than the blades of the lawn mower, thereby not controlled by regular mowings. I find it mostly on the fringes of the lawn, reaching into the flower and vegetable gardens. The best way to kill it is to use a broad leaf weed killer containing 2,4-D or triclopyr. This plant will need more than one application to completely rid the lawn of plants present. New plants will be created from germinating seeds throughout the season. Watch for new invasions and treat accordingly. A pre-emergent herbicide can be used to stop the germination of seeds.

Figure 1: Juniper branch with a mature Cedar-Apple Rust gall displaying gelatinous tendrils. (provided by Dr. George Hudler, Cornell University)C

Figure 4: Juniper with Cedar-Apple Rust displaying a developing gall---the winter survival structure. (provided by Dr. George Hudler, Cornell University)

Cedar Apple Rust fruiting structures are appearing on the branches of cedar and juniper trees this week. They look like an orange sticky sea creature shocking people not familiar with this fungal disease. Cedar-apple rust is caused by the fungus Gymnosporangium juniperi-virginianae. The orange horned structure grows out of the overwintering hard brown gall after a few days of rain and cool weather. Spores are produced from the structure beginning and mid-summer, becoming air-borne and dispersed by the wind. These spores will land on the alternate host in the Malus or apple family to continue its life cycle. Once an apple or crabapple is infected with the new spores, the fungus develops on the leaves, creating spots and eventually turn the leaves yellow. Early defoliation of the malus tree usually follows.The cedar tree retains the deformed tissue some find unsightly.

Control measures used are planting resistant cultivars of trees, sanitation and fungicide sprays.

Resistant cultivars of apple include Delicious, Empire, Jonamac, McIntosh, and Paulared. Resistant crapapples are Ellwangerina, Henry Kohankie, Ormiston Roy, and Red Baron. Resistant junipers are Juniperus chinensis var. sargentii, J. communis cv. Aureospica, and J. virginiana cv. Tripartita.

Sanitation measures reduce the incidence of infection. Cut off all orange and brown growths on the cedar trees. Do not put these in the compost or them might continue to release spores even after being cut.  Bag them for disposal in the the trash. This one action will reduce the amount of spores released in the air. Remove either host trees for up to one mile, although this usually not possible! Fungicide options are available for the apple and crabapple trees, used as a preventative measure before the spores land on the leaves. Fungicide used on the cedar and juniper are not very effective. Rake and remove to the trash any fallen leaves of the apple species. The fungus can overwinter on the leaves to keep the disease cycle going into the next spring.

Fungicide labeled for use on apple and crabapple in Connecticut are chlorothalonil, mancozeb, triadimefon, propiconazole, and myclobutanil. Sulfur can be used as an organic fungicide option. Thorough coverage of all leaves are needed for protection. Follow all label directions, more than one application may be necessary for season long control.

cedar-apple rust on apple leaf

-Carol