Math for the Home Gardener

Math for the Home Gardener

Math isn’t always fun! Here is Euclid explaining math in Raphael’s The School of Athens. Credit: Creative Commons.

There are a lot of things gardeners need to know to cultivate a beautiful landscape. Between plant zones, scientific names, soil chemistry, and pest identification, being a gardener takes curiosity and willingness to learn new things. Unfortunately, one topic that needs to be well understood, especially when it comes to applying pesticides and fertilizers, is a subject that many cringe when they hear it – mathematics!

Some of the most common mathematical concepts to have a good grasp on for gardening include area, converting decimals to percentages and vice versa, estimating volume and converting units, and determining how much fertilizer to be applied based on your fertilizer grade.

Here’s a couple tips to help you gardeners out with math.

Area

Most often, we need to know the square footage of our gardens. Rectangles are straightforward, you multiply length (in feet) by width (in feet) to get feet squared. Since most yards are not rectangles, we sometimes need to use other shapes to best calculate the area, such as circles and/or triangles. The area (A) of a circle is , where “π” is 3.14 and “r” is the radius (half of the diameter or the distance from the center to the edge). Remember that the little raised 2 means you multiply the radius by itself twice, not by two.

Most of the time, square feet is the best area unit to use. But just in case you need to know, one acre equals 43,560 square feet. So, if you find your lawn is 10,000 square feet, that means you have 0.23 of an acre (10,000/43,560).

Get your calculator’s out! Credit: iStockphoto.

Percent Conversions

This one may be better understood by most, but this becomes important later when we determine fertilizer needed or doing volume conversions. Basically, any percent can be divided by 100 to convert it to a decimal that can be used easily in other calculations. For example, 15% is the same as 0.15 (15/100). The easy way to remember is that 100% is the same as one, and 50% is the same as 0.5.

Volume Estimation and Conversions

Determining volume is required when figuring out how much mulch is needed for a garden bed or soil required for a raised bed. Converting one unit to another is especially important when determining how much pesticide product is needed to prepare a mixture.

For mulch and soil, the cubic feet (cf) or cubic yards (cy) are needed to figure out how many bags or truckloads will be needed. Most bulk products are sold by the cubic yard. Since we are dealing with volume, we need three measurements, the length, width, and depth. If we want to add three inches of mulch to a 500 square foot garden, we multiply the 500 by 0.25 feet (3”/12” equals 0.25 inches) to get 125 cubic feet. That is about 62 bags of mulch from the hardware store, which are often sold in 2 cubic foot bags. If we divide 125 cubic feet by 27 (three feet in a yard so 3’ x 3’ x 3’ = 27) we now have the answer in cubic yards and find that we need about 4.5 cubic yards of mulch. One cubic yard is roughly a half of a full-size pickup truck bed.

When it comes to converting liquid volume units to help with pesticide mixtures, fortunately we have the internet to help. However, it is a good idea to at least be familiar with converting ounces to gallons and vice versa. Since 128 ounces equals 1 gallon, to go from gallons to ounces you multiply by 128. For example, 0.5 gallons equals 64 ounces (0.5 x 128). To go from ounces to gallons, we just divide by 128. For example, 192 ounces equals 1.5 gallons (192/128).

Applying the proper amount of fertilizer keeps your landscape healthier and protects local waterbodies. Credit: UF/IFAS.

Calculating Fertilizer Needed

Okay, bear with me, as we are about to do some hard math and piece together several of the above concepts. First of all, most fertilizer rates are provided by extension resources and given in terms of pounds of a particular nutrient for a set area, usually 1,000 square feet. For example, when using slow-release fertilizer a homeowner should apply no more than one pound of nitrogen for every 1,000 square feet of lawn. To figure out how much actual fertilizer to apply to meet the recommendation, we will need 1) the recommended rate, 2) the size of the lawn, and 3) the fertilizer grade on the product (the three numbers that represent the percent N, P, and K). Our rate is one pound nitrogen per 1,000 square feet. The size of our lawn is 50 feet by 30 feet, so 1,500 square feet. We are going to use a 16-0-8 fertilizer. Now, here is the hard part! To figure out how much of our 16% nitrogen fertilizer will provide one pound of nitrogen, we need to convert 16% to a decimal (16/100 = 0.16) and then divide the amount of fertilizer we need by that number – 1 pound/0.16 – to find that 6.25 pounds of our fertilizer product are required for each 1,000 square feet. Since we have 1,500 square feet, we need to multiply our answer by 1.5, which gives us a total of 9.4 pounds.

Math is hard and there are usually many methods to get the same solution. When using pesticides and fertilizers in the home landscape, it’s important to make sure we’re using the right amount of materials to minimize the chance of harming ourself, our plants, and the local environment. If you need help, or would like someone to check your work, contact your local extension office.

Going bats for insect control

Going bats for insect control

The Case for Bats

Biological control is a pillar of integrated pest management.  It may seem a bit daunting the principle is simple.  All things in nature have predators including insects.  Biological control is simply building a conducive environment for the predators of undesired pests.  One animal not often thought of in this capacity is bats.  Insectivores by nature, these underutilized creatures have a big impact to your open spaces.  Their steady diet of moths (Lepidoptera), beetles (Coleoptera) and flies (Diptera, which includes mosquitoes) reduce insect pressure to your gardens and landscaping.

I know what you are thinking.  How effective can they possibly be?  Pregnant females consume up to two thirds of their body weight through the summer months while rearing pups.  Bats are small but keep in mind that these are not solitary animals.  In south Texas, a single large colony consumes enough insects to save cotton farmers an estimated $741,000 per year in insecticides.  That is just to illustrate the point as you won’t be able to attract huge colony.  There is no reason to believe a smaller colony will not provide similar services in your gardens.

Habitat

Now that your interest is piqued, how can you attract bats to your property?  Installing a bat house is the easiest way.  They are typically a two foot by one foot structure holding single or multiple chambers in which bats roost.  It provides shelter from predation and weather while providing a place to rear pups.  Though commercially available they may be built at home with minimal cost.  Place the bat house in a location with morning sun at least 12 feet off the ground.  Ensure there is enough airflow around the house to keep them cool, but that the structure is watertight.  Mount houses on poles next to buildings and you’ll have better success attracting residents.  With everything in place, it is time to discover who will most likely be your new neighbor.

bathouse on pole

photo: Joshua Criss

 

The Bats of North Florida

Florida is home to 13 species of bats statewide.  Of these, 11 may be found in the Panhandle but only 3 are common enough to be routinely seen.  The Brazilian free-tailed bat (Tadarida brasiliensis) is the most common.  Medium sized with brown fur, they have a long tail, wrinkled cheeks, and roost in man-made structures.

Brazillian free tail bat

Photo: IFAS

Second most common are Evening bats (Nycticeius humeralis).  These dark brown to yellow bats have short ears with a broad hairless muzzle.  They are tolerant of other bat species often roosting in tandem with them.

Evening bat

Photo: IFAS

Finally, the panhandle is home to Southeastern Myotis (Myotis austroriparius).  Easily the smallest of these bats, they are dull gray to brown with a lighter belly and long hairs between their toes.  This species is the bat most likely to eat mosquitoes.

Southeastern Myotis

Photo: Jeff Gore, FWC

Finally, the panhandle is home to Southeastern Myotis (Myotis austroriparius).  Easily the smallest of these bats, they are dull gray to brown with a lighter belly and long hairs between their toes.  This species is the bat most likely to eat mosquitoes.

A Word of Caution

No article on wildlife would be complete without a word of caution.  Bats are wild animals and should be treated as such.  Never touch a bat on the ground as it most likely is not healthy.  Bats do not generally cause issues but have been known to be disease vectors.  Call a professional to collect the animal and never bring it into your home.

Bats can be a wonderful tool in controlling pests on your property.  Creating habitat can help reduce pesticide need and cost to the homeowner.  For more information on bats, see this Ask IFAS document, or contact your local extension agent for additional information on this and any topic regarding your gardens and more.

 

Controlling Cogongrass

Controlling Cogongrass

Over the last decade or so, the Panhandle has been overrun, and I don’t just mean by the summer beach traffic.  Rather, by an aggressive, exotic perennial grass that quickly displaces all native species, is not useful as a forage to wildlife or livestock, can spread by roots or seeds, and has no natural enemies.  If you own property in the Panhandle or spend any amount of time on its roads, chances are you have become acquainted with this worst of invasive species, Cogongrass (Imperata cylindrica).

A native of Southeast Asia, cogongrass was introduced into the US in 1912 around Mobile, AL as a hitchhiker in orange crate packing.  Then the 1920s, 30s, and 40s, it was intentionally introduced from the Philippines into other Gulf Coast states, including Florida, as a potential pasture forage for livestock.  Since then, cogongrass has become one of the most economically and ecologically important invasive species in the US and worldwide, infesting nearly 500 million acres and is now found on every continent.

Cogongrass in Calhoun County, FL. Photo courtesy of Daniel Leonard.

Cogongrass is easily identified in late spring, when the grass throws easily spotted fluffy, white-colored seedheads above the mats of grass beneath.  Additionally, patches of cogongrass are almost always noticeably circular in nature, radiating out indefinitely from the initial infestation.  A closer inspection of the grass will reveal light green leaves up to 4’ in length, with an off-center, silvery colored midrib (the primary leaf vein that runs from the base of the leaf to the tip) and serrated leaf edges.   Underground, cogongrass exhibits a dense underground root system that can reach as deep as 4’.  This feature is the primary reason cogongrass outcompetes other plants, withstands any drought, fire, or soil condition thrown at it, aids in its resistance to herbicide activity, and generally makes it very difficult to manage.

The first step in managing cogongrass is prevention.  If your property or the property you manage doesn’t have cogongrass, do everything you can to keep it that way.  While the species can spread distances through seed dispersal, it is much more frequently moved around by fragmented rhizomes hitching a ride on equipment.  If you or a contractor you’ve hired are working in or around an area with cogongrass present, avoid disturbing it with equipment and be diligent in monitoring the site for outbreaks following the job’s completion.

If you find cogongrass on your property, effectively eradicating it requires patience, persistence, and several years’ worth of herbicide applications.  Currently, of the hundreds of herbicides available for purchase, only two chemistries have been proven to be very effective in destroying cogongrass, impazapyr (Arsenal, Stalker, etc.) and glyphosate (Roundup, Cornerstone, etc.).

  • Imazapyr is an extremely effective non-selective, residual herbicide that controls a wide variety of weed species, including cogongrass. Just one or two applications of imazapyr can provide 18-24 months of effective cogongrass control, with follow up treatments required as needed after that.   However, Imazapyr has a major downside that limits its use in many settings.  Because it is a non-selective herbicide with significant soil residual activity, it cannot be used around the root zones of desirable plants.  Oaks, other hardwood trees, and most landscape plants are especially sensitive to imazapyr.  This herbicide is best limited to use in fields, waste/fallow areas, natural areas, and monoculture pine plantations – it is not appropriate in most residential and commercial landscapes.
  • The other option, glyphosate is a non-selective herbicide with no soil residual activity. It is often a better option where severe injury or death of desirable hardwood trees and ornamental plants cannot be tolerated.  However, due to its lack of residual soil activity, glyphosate applications on cogongrass patches will need to be repeated on an annual or biannual basis for up to five years for eradication of the infestation.

*Regardless of which herbicide you choose, controlling cogongrass is a multi-year affair requiring diligence and patience. 

For more information on cogongrass and for specific herbicide recommendations and application rates/timing for your site, please contact your local UF/IFAS County Extension Office.

 

Timing is Everything when Controlling Lawn Weeds

Timing is Everything when Controlling Lawn Weeds

Hot, summer months are not the time to be using most lawn herbicides.

One issue is the heat of summer. Most lawn herbicide labels include statements such as the following.

“Do not apply when temperature exceeds 90°F.” “Do not broadcast apply this product when air temperatures are above 90°F (85°F for St. Augustinegrass) unless temporary turf injury can be tolerated.”

Every year we’ll see lawns that are injured or killed because of lawn herbicides being applied when temperatures are too hot.

Summer is usually a rainy and windy time of the year. Many lawn herbicide labels include statements such as the following.

“Allow 12 hours after application before watering lawn for maximum effectives on listed weeds.” “Apply only when wind is no more than 10 mph.” “Applying this product in calm weather when rain is not predicted for the next 24 hours will help to ensure that wind or rain does not blow or wash pesticide off the treatment area.”

It is critical to read and follow the label directions and precautions for any pesticide you use. Pesticide labels, including herbicides, include the following statements.

“To the extent consistent with applicable law, the buyer assumes all risks of use, storage, or handling of this product not in accordance with label directions.” “It is a violation of Federal law to use this product in a manner inconsistent with its labeling.”

Crabgrass plant growing in centipedegrass lawn

Crabgrass growing in centipedegrass lawn. Photo credit: UF/IFAS Extension

By the time summer arrives, many of the lawn weeds are mature, which means they are well established with extensive root systems. These mature, well established weeds are much more difficult to control. They are more susceptible to herbicides when they are small, young, and not well established. Also, these mature weeds have been allowed to produce countless numbers of seeds as they move into summer. Most weeds are prolific seed producers. For example, a single crabgrass plant (a common summer lawn weed) can produce 150,000 seeds.

Applying a preemergence lawn herbicide in February to help prevent summer annual weeds such as crabgrass or applying a postemergence lawn herbicide during spring while the weather is mild and before the weeds are out of control simply makes more sense than waiting until summer.

The best options now with lawn weed control involve continuing to follow good mowing practices, maybe hand removal of some weeds, and just simply waiting it out until next February and spring to worry with the use of lawn herbicides.

In the meantime, you may want to read the following UF/IFAS Extension publication on lawn weed control.

https://edis.ifas.ufl.edu/pdf/EP/EP14100.pdf

Larry Williams, UF/IFAS

Centipedegrass Weed Control:  You Only Need 3 Herbicides!

Centipedegrass Weed Control: You Only Need 3 Herbicides!

Nearly everyone likes turfgrass lawns.  They’re pretty and green.  They filter water, chemicals, and nutrients before they enter our groundwater systems.  They provide a recreation spot for people and pets.  But lawns also come with maintenance tasks, one of which is weed control.  Fortunately, keeping our common Centipedegrass lawns relatively weed free is as simple as smart management and utilizing herbicides effectively.  Though the number of herbicides available for purchase can be overwhelming, you only need three to keep weeds at bay – a selective grass herbicide, a strong broadleaf herbicide, and a sedge herbicide!

Dollarweed in flower

Dollarweed, one of the toughest broadleaf weeds for homeowners to control. Picture courtesy of  Julie McConnell, UF/IFAS.

First up on the essential herbicide list is the selective grass herbicide Sethoxydim.  While most folks’ weed focus is centered on broadleaf weeds, grassy weeds like Crabgrass, Bahiagrass, Goosegrass, and others can be just as problematic and make for a very unsightly lawn.  Enter Sethoxydim.  Cheap and easy to find, Sethoxydim is offered as the active ingredient in many branded products like Fertilome Over the Top Grass Killer, Hi-Yield Grass Killer, and many more.  These products control weedy grass species without seriously harming Centipedegrass or broadleaf ornamental trees and shrubs (Centipedegrass may temporarily be yellowed after sethoxydim application but will recover).  Not only will it kill out the unwanted grass growing in your Centipede, but it will also remove these weeds from your flower beds!

Second, having a strong broadleaf herbicide on hand is necessary.  I say “strong” because many of the homeowner grade products available at garden centers simply don’t have the “juice” to control tough broadleaf weeds like Dollarweed, Doveweed, Virginia Buttonweed, and others.  For this job, I prefer to use a commercial grade 3-way product like Celsius WG by Bayer.  Celsius WG is a 3-way combination herbicide with a healthy dose of Dicamba as its primary ingredient.  Though Dicamba is a notoriously volatile chemical known to cause damage to unintended plants through drift in hot weather, combining it with the two other products in Celsius WG makes it safe to use in lawns, even in the heat of summer.  While strong broadleaf herbicides like Celsius WG are expensive on the front end, don’t let that deter you.  These products wind up being very cost effective in the long run due to minute mixing rates (one bottle goes a very long way in most residential lawns) and effectiveness – you simply will not need to waste time and money spraying lawn weeds over and over to obtain control like is necessary with lesser products – one or two applications will solve the toughest broadleaf weed problems.

Finally, any good lawn weed control program will include a quality sedge control herbicide.  Sedges (often called “nutgrass”) look like grasses but are a completely different category of plants and as such, require specialized herbicide chemistries to achieve control.  Sedge weeds prefer wetter areas of lawns, though they can occur in pretty much any lawn site and are very unsightly.  For this weed category, there are several options available to homeowners.  The one that consistently provides the best control in lawns is Halosulfuron-methyl, the active ingredient in the aptly named product Sedgehammer.  Conveniently coming in individually pre-mixed packets for small lawns or a larger bottle when more acreage is to be treated, Sedgehammer couldn’t be easier to mix and use. While Sedgehammer and similar products are extremely effective in controlling various sedge weeds, they tend to work very slowly, and patience is required.  Weeds immediately stop growing following a Sedgehammer application, but it can take up to three weeks to notice the sedges dying.

While having and using the above three herbicides can control almost any weed homeowners may encounter in their lawns, it is important to remember that herbicides are not substitutes for proper lawn management.  When good cultural practices in lawns are followed, such as mowing at the correct height, only watering when necessary, following UF/IFAS fertilizer recommendations, etc., chemical weed control may not even be necessary in many cases!  Also, once the decision to purchase and use chemical herbicides has been made, it is critical that one always read the label before using any herbicide product.  This ensures safe and effective use of the product; the label is literally the law!

For assistance in choosing the correct herbicide for your lawn and other lawn care concerns, contact your local UF/IFAS Extension Office!  Happy Gardening!

 

Landscape  Q & A

Landscape Q & A

On August 12, 2021, our panel answered questions on a wide variety of landscape topics. Maybe you are asking the same questions, so read on!

Ideas on choosing plants

What are some perennials that can be planted this late in the summer but will still bloom through the cooler months into fall?

Duranta erecta ‘Sapphire Showers’ or ‘Gold Mound’, firespike, Senna bicapsularis, shrimp plant, lion’s ear

Where can native plants be obtained?

Dune sunflower, Helianthus debilis. Photo credit: Mary Salinas UF/IFAS Extension.

Gardening Solutions: Florida Native Plants  – see link to FANN: https://gardeningsolutions.ifas.ufl.edu/plants/ornamentals/native-plants.html

What are some evergreen groundcover options for our area?

Mondo grass, Japanese plum yew, shore juniper, ajuga, ferns such as autumn fern.

What are some ideas for partial morning sun butterfly attracting tall flowers to plant now?

Milkweed, salt and pepper plant, swamp sunflower, dune sunflower, ironweed, porterweed, and salt bush.

I’m interested in moving away from a monoculture lawn. What are some suggestions for alternatives?

Perennial peanut, powderpuff mimosa, and frogfruit.

We are new to Florida and have questions about everything in our landscape.

Florida-Friendly-Landscaping TM Program and FFL Web Apps: https://ffl.ifas.ufl.edu/

https://ffl.ifas.ufl.edu/resources/apps/

UF IFAS Gardening Solutions: https://gardeningsolutions.ifas.ufl.edu/

What are some of the top trends in landscaping today?

Houseplants, edible gardens, native plants, food forests, attracting wildlife, container gardening, and zoysiagrass lawns

Edibles

Artwork broccoli is a variety that produces small heads. Photo credit: Mary Salinas UF/IFAS Extension.

What vegetables are suitable for fall/winter gardening?

Cool Season Vegetables: https://gardeningsolutions.ifas.ufl.edu/plants/edibles/vegetables/cool-season-vegetables.html

North Florida Gardening Calendar: https://edis.ifas.ufl.edu/publication/EP451%20%20%20

Florida Vegetable Gardening Guide: https://edis.ifas.ufl.edu/publication/vh021

How can I add herbs to my landscape?

Herbs in the Florida Garden: https://gardeningsolutions.ifas.ufl.edu/plants/edibles/vegetables/herbs.html

My figs are green and hard. When do they ripen?

Why Won’t My Figs Ripen: https://www.lsuagcenter.com/profiles/rbogren/articles/page1597952870939

What is best soil for raised bed vegetable gardens?

Gardening in Raised Beds: https://edis.ifas.ufl.edu/publication/EP472

And there are always questions about weeds

How can I eradicate cogongrass?

Chamber bitter is a troublesome warm season weed in our region. Photo credit: Brantlee Spakes Richter, University of Florida, Bugwood.org

Cogongrass: https://edis.ifas.ufl.edu/publication/WG202

Is it okay to use cardboard for weed control?

The Cardboard Controversy: https://gardenprofessors.com/the-cardboard-controversy/

What is the best way to control weeds in grass and landscape beds?

Weed Management Guide for Florida Lawns: https://edis.ifas.ufl.edu/publication/EP141

Improving Weed Control in Landscape Planting Beds: https://edis.ifas.ufl.edu/pdf/EP/EP52300.pdf

Landscape practices

Can ground water be brackish and stunt plants?

Reclaimed Water Use in the Landscape: https://edis.ifas.ufl.edu/publication/ss545

How can I prevent erosion from rainwater runoff? 

Stormwater Runoff Control – NRCS: https://www.nrcs.usda.gov/wps/portal/nrcs/detail/national/water/?cid=nrcs144p2_027171

Rain Gardens: https://gardeningsolutions.ifas.ufl.edu/design/types-of-gardens/rain-gardens.html

And https://gardeningsolutions.ifas.ufl.edu/pdf/articles/rain-garden-manual-hillsborough.pdf

What is the best time of the year to propagate flowering trees in zone 8B?

Landscape Plant Propagation Information Page – UF/IFAS Env. Hort: https://hort.ifas.ufl.edu/database/lppi/

Which type of mulch works best on slopes greater than 3 percent?

Landscape Mulches: How Quickly do they Settle?: https://edis.ifas.ufl.edu/publication/FR052

When should bulbs be fertilized?

Bulbs and More – UI Extension: https://web.extension.illinois.edu/bulbs/planting.cfm

Should I cut the spent blooms of agapanthus?

Agapanthus, extending the bloom time: https://gardeningsolutions.ifas.ufl.edu/plants/ornamentals/agapanthus.html

http://blogs.ifas.ufl.edu/wakullaco/2020/10/07/extending-bloom-time/

Plant questions

Monarch caterpillar munching on our native sandhill milkweed, Asclepias humistrata. Photo credit: Mary Salinas, UF IFAS Extension.

I planted native milkweed and have many monarch caterpillars. Should I protect them or leave them in nature?

It’s best to leave them in place. Featured Creatures: Monarch Butterfly: https://edis.ifas.ufl.edu/pdf/IN/IN780/IN780-Dxyup8sjiv.pdf

How does Vinca (periwinkle) do in direct sun? Will it make it through one of our panhandle summers? Can I plant in late August?

Periwinkles  and  No more fail with Cora series: https://gardeningsolutions.ifas.ufl.edu/plants/ornamentals/periwinkles.html#:~:text=Plant%20your%20periwinkles%20where%20they,rot%20if%20irrigated%20too%20frequently.

Insect and disease pests

What to do if you get termites in your raised bed?

The Facts About Termites and Mulch: https://edis.ifas.ufl.edu/publication/IN651

How to combat fungus?

Guidelines for ID and Management of Plant Disease Problems: https://edis.ifas.ufl.edu/publication/mg442

Are there preventative measures to prevent diseases when the humidity is very high and it is hot?

Fungi in Your Landscape by Maxine Hunter: http://blogs.ifas.ufl.edu/marionco/2020/01/16/fungi-in-your-landscape/

 

If you missed an episode, check out our playlist on YouTube https://www.youtube.com/watch?v=bp0HfdEkIQw&list=PLhgoAzWbtRXImdFE8Jdt0jsAOd-XldNCd