Mowing, Plant Growth Regulators, and Shade

What is mowing?

Periodic removal of a portion
of turfgrass shoot growth

Why do we mow?

Maintain top growth within a specific limit

– Control undesired vegetation

– Sustain an ornamental or recreational turf

– Produce a true putting surface

– Develop a sod crop

What are the main downsides with mowing?

Causes a temporary cessation of root

growth

• Reduces carbohydrate production and

storage

• Creates ports of entry for disease-

causing organisms

• Temporarily increases water loss from

cut leaf ends

• Reduces water absorption by the roots

What are the 3 mowing types?

– Reel mower

– Rotary mower

– Flail mower

Where to use reel mowers?

Widely used on golf

courses, athletic fields,

and sod farms

• Typically used for low

heights of cut (< 0.5

inches

What are the two main issues with reel mowers?

They are extremely expensive and they cannot cut long grass/stems well.

How does a reel mower cut?

It cuts with a shearing action.

What does dull blades result in?

A tearing motion that leads to brown tips.

What is a rotary mower and where used?

Used on utility turf and

home lawns

• Typically used to cut

turf at heights > 0.5

inches

• Cuts by impact as the

horizontally mounted

blades rotate around a

vertical shaft

Why use a rotary?

It is more versatile than a reel and can actually cut through heavier brush.

What are the two impact mowers?

Rotary and flail commonality.  

Where are flail mowers used?

Mainly in infrequent mowing locations like roadsides.

What do all turfgrasses have specific to their mowing?

Each turfgrass has its

mowing tolerance

range

• Below this range the

turf will thin during

stress periods or be

overtaken by weeds

What happens at <0.25 inches of mow height?

Stimulated aerial growth

– Increased shoot density

– Smaller shoot size

– Decreased root and rhizome growth

– Decreased synthesis and storage of

carbohydrates

– Increased plant succulence

– Less tolerant of environmental stresses

– More prone to disease

– More dependent on cultural management

How should you mow warm/cool season grasses during their respective dormant seasons?

Raising mowing height on cool-season

grasses during summer months can

compensate for heat and drought

stress

• Raising mowing height on warm-

season grasses in late fall can

compensate for cold stress and

reduced photosynthetic activity

What are the two rules to allways follow to avoid stressing turf?

Never remove more than 1/3 of the vertical

shoot growth per mowing

– Avoid mowing during the heat of the day

when the lawn is under the greatest

amount of drought and heat stress

What do you need to avoid cutting into putting greens? How do you avoid it?

Mowing in one direction over and over

can create “grain”

• Grain is the horizontal orientation of

shoots

• Mowing in alternate directions will

reduce grain and improve putting

quality

What is commonly said about clippings thats not true?

That it causes thatch.

How much N gets reurned per year by using clippings?

can contribute 2 lbs

N/1000 ft2/year in addition to other

nutrients

What do/are PGRs do?

Chemicals applied to the turf to

promote or inhibit some facet of growth

What are the benefits of PGRs?

Reduce clipping

production

– Increase turf density

– Reduce seedhead formation

– Enhance turf color

What are the 3 PGR types?

Type I PGRs

– Cell Division Inhibitors

• Type II PGRs

– Gibberellin Inhibitors

• Other Growth Inhibiting PGRs

How do type 1 PGR inhibitors work?

Suppress plant growth by inhibiting

cell division and differentiation in

meristematic

Type 1 PGR examples?

Embark (mefluidide)

• Limit (amidochlor)

• Royal Slo-Gro (maleic hydrazide)

What are type 1 PGR inhibitors mainly used for?

used to reduce Poa annua

seedheads

How quick are type 1 PGRs?

Take 5-7 days to work but quickly leave.

How do type 2 PGRs work?

Suppress vertical shoot growth by

inhibiting biosynthesis of gibberellin

– Gibberellin is needed for cell elongation

Examples of type 2 PGRs?

– Primo (trinexapac-ethyl)

– Trimmit or TGR (paclobutrazol)

– Cutless (flurprimidol)

What is the most popular growth regulator?

Primo (trinexapac-ethyl)

What are the beneifts of primo?

growth reduction

– improved turf quality, density, chlorophyll

content, and stress tolerance

When do you avoid PGRs?

In the dormant months of the grass.

How do we get annual bluegrass (poa annua) out with PGRs?

Trinexapac ethyl and paclobutrazol along with overseeding.

How does proxy work?

Promotes ethylene production from
leaves, which inhibits cell elongation, but
promotes leaf senescence

What can also be used as a PGR?

Wattered down herbicide like glyphosate.

what is the main worry with herbicides as PGRs?

Causing resistance in weeds

What causes leaves to elongate and not as thick?

Shade

How are PGRs used in shade?

They can reduce growth resulting in thicker grasses despite shade

When should you grind reel blades or bedknives?

when nicks appear or

when cutting edges become

rounded or worn

Which PGR is used in the shade to increase tolerance?

Trinexapac-ethyl