Despite a sharp increase in costs recently, wood products remain a common landscape and garden material. They can be used for building structures, such as arbors and sheds, or for hardscapes and garden accessories, like raised vegetable garden beds or landscape timbers used for edging. Many homeowners may be confused on the safety of using certain wood products, especially around plants grown for consumption. This article hopes to explain the various options and the known safety concerns.
Raised beds are a common use of treated lumber in the garden. Credit: Molly Jameson/UF IFAS
Gardeners seem to be mostly concerned with the safety of using preserved wood products around food plants. Pressure-treated lumber is usually suggested whenever the material will be exposed to the elements and especially when in contact with the soil. Non-treated lumber, while free of any preservatives, will simply not last as long in the landscape, especially in Florida where we have a long growing season, are wet, and have lots of organisms – termites, fungus, etc. – that love to break down wood. If the wood is in direct contact with the soil, such as in a raised bed garden, you can expect non-treated lumber to last a year, maybe two, compared to three to five years with pressure-treated lumber. Wood products used for structures not in contact with soil can last significantly longer but, even then, non-treated products will need to be protected with sealers or paints to extend their longevity.
To address the safety of pressure-treated wood products, the wood products industry, and the federal government, in 2004, phased out the use of potentially hazardous chemicals used in the process – namely arsenic and chromium. Wood products preserved with these compounds were either chromated copper arsenate (CCA), ammoniacal copper arsenate (ACA), or acid copper chromate (ACC). Since 2004, much of the lumber available at hardware stores is micronized copper azole (CA) or alkaline copper quaternary ammonium (ACQ). The abbreviations for each are usually found on the little label stapled on to the lumber. So, while copper used to prevent fungal damage is still a component of pressure-treated lumber, the arsenic and chromium used to protect the wood from insect damage has been removed. Railroad ties, sometimes still in use and for sale, are much more toxic than even the older pressure-treated products because of the use of creosote and other oil-based compounds to preserve the wood.
Preserved wood products contain the preservation method on the tag stapled to the product. Credit: USDA Forest Products Lab
By removing these potentially hazardous compounds from pressure-treated wood products, gardeners should expect no adverse effects from it’s use. A Human and Ecological Risk Assessment of ACQ treated wood that was done in 2007 found exposure levels well below health benchmarks when directly contacting the wood and even with some ingestion of the material, such as contacting the wood and putting hands directly in mouth.
Even though these hazardous materials have been removed, there are still some precautions you should take when using pressure-treated lumber. These precautions include wearing a mask when cutting the lumber and not burning the lumber. This is to prevent inhalation of the chemically treated sawdust or smoke. It’s also not recommended to compost pressure-treated lumber since the chemicals can affect the microbes in your compost pile.
For those still concerned with the use of pressure-treated wood products around food crops, there are other options. In addition to using non-treated wood products or a plastic liner to separate the pressure-treated lumber from your edible garden plants. There are many other materials that can be used instead. Concrete blocks or other stone materials can be a good option. Logs from cut trees, although will rot like non-treated lumbers, can add a natural type of look to the garden.
Stone, metal, and concrete blocks are good alternatives to lumber. Credit: Mark Tancig/UF IFAS.
For anything growing in the ground, soil is a very important thing. Soil gives plants a place to anchor their roots so they don’t fall over, holds water and nutrients for them to use, and supports a wide variety of living things that contribute to plant growth. Whether you want to grow a lawn, garden, or landscape bed, knowing a little about your soil can make a big difference in the quality of your plants!
There are a lot of terms that relate to soils. Some helpful ones to know include:
A chart of soil textures. Credit: Natural Resource Conservation Service
Soil particle sizes / soil texture. A soil that is composed of large particles is sandy, a soil with tiny particles is clayey, and a soil with mid-sized particles is silty. Multiple sizes of particles can mix together to form a soil, which is why you may see soils referred to with terms like, “sandy loam” or “silty clay loam”. This mixture of particle sizes gives a soil its texture.
Soil acidity / pH. The pH of a soil refers to its level of acidity. The pH scale ranges from 0 to 14. Low numbers mean the soil is acidic, while higher numbers mean it is basic, or alkaline. 7 is neutral, and many plants grow best in a slightly acidic soil (around 6.5). Some plants, like blueberries and azaleas, prefer a more strongly acidic soil (4.3-5.5). If the soil pH is too far from the plant’s preferred level, it may not be able to take up the nutrients it needs even if they are present in the soil. To raise the pH or make the soil less acidic, we can add garden lime; to lower the pH or make it more acidic, we can add sulfur (though this is not as long-term a solution).
Organic matter. All the living things out there die at some point, and when they do, other living things break them down as food. Fungi, bacteria, tiny insects, and more are all out there working to make sure you aren’t wading through piles of dead things. Instead, all that decomposed and partially decomposed plant (and animal) matter become part of the soil. Organic matter is part of a healthy soil, and helps it hold onto water and nutrients that plants can use.
Compost. When you make a pile of dead plant matter and help it decompose on purpose, you’ve made compost. By controlling the material you put into a compost pile as well as the amount of water and oxygen it gets, you can speed up the decomposition process and end up with organic matter to use in your garden.
Mulch. Mulch is any substance that sits on top of the soil. Wood chips, bark nuggets, pine straw, or even synthetic mulches like sheets of plastic are used to help keep weeds from growing and retain soil moisture.
Sandy soils can grow gardens, though they may need a little more attention!
To gather information about the soil, it can be a good idea to do a soil test. Your local Extension office can help you figure out how to do this. Once you do, you’ll receive information on your soil pH, what plant nutrients are in the soil, and recommendations on how much lime and fertilizer you’ll need to add for the year. Test your soil before you add any major amendments such as lime or fertilizer. This will help you add the right amounts at the right time – too much fertilizer, for example, can harm plants or run off into surrounding water bodies, causing environmental damage.
You can find more information on soil testing here, or visit your local Extension office. Soil tests can take up to two weeks to return a result, so plan ahead!
At one time or another, we have all added rocks or broken pieces of clay pots to the bottom of a container to improve drainage. This practice can actually have the opposite effect, causing the potting soil to stay too moist. Since many container-grown plants like good drainage, we end up with plant issues. Learn the method for potting up a plant that allows your soil to have good drainage with UF IFAS Extension Escambia County.
Houseplants can soften up the interior of your home and help clean the air. They can also supplement your holiday decorations and help create stunning focal points. To help determine what plants do best under certain conditions and to give pointers on plant care, this month’s Gardening in the Panhandle LIVE! was all about houseplants.
A spider plant on a coffee table. Photo Credit: University of Florida/IFAS
Environmental Conditions for Houseplants
Unless you live in a glass house, you’ll probably want to choose houseplants that do well in low light conditions. A guide for what light level different houseplants prefer can be found on the Gardening Solutions Light for Houseplants page. This page also provides useful tips on supplemental lighting.
Some houseplants are better at cleaning the air than others. A list of houseplants that do a good job improving indoor air quality can be found on the Gardening Solutions Houseplants That Clean the Air page.
The best way to determine if your houseplants need water is your own green thumb or whatever finger you choose to stick in the potting mix, but for some interesting information on outdoor soil moisture meters check out this informative publication on soil moisture sensors.
Houseplants need a good quality, well-drained potting mix to thrive. Tips on selecting a potting mix can be found on the Gardening Solutions Container Media page.
Houseplant Pests
One of the best ways to rid houseplants of insect pests is to set the plants outside for a few days and let the pests move on. For some information on pest control products in and around the home check out the publication Natural Products for Managing Landscape and Garden Pests in Florida.
Fungus gnats are mainly a nuisance, but some species can feed on living plant tissue. Darkwinged fungus gnats are known to feed on ferns, orchids, and geraniums.
Houseplant Propagation
One way to increase your houseplant population and save a few dollars is to propagate your own plants. The University of Florida/IFAS created the Plant Propagation Glossary to help with any propagation questions you may have.
Air layering is a propagation technique that not only allows the prospective plant to thrive from the nutrients of the mother plant, but it also saves space.
A moth orchid (Phalaenopsis spp.) outdoors. Photo Credit: University of Florida/IFAS
Specific Species Info
Orchids in the genus Phalaenopsis are easier to care for than other genera of orchids. The American Orchid Society provides some great tips on caring for orchids indoors. Some people choose to water their orchids with ice cubes. The Ohio State University has a publication that provides some more insight on watering Phalaenopsis orchids with ice cubes.
A lot of cacti do well indoors. A popular cactus during the holiday season is Christmas cactus. Christmas cactus have interesting foliage, but their blooms are what people want to see. Some tips on getting your Christmas cactus to bloom on time and general care information can be found in this Christmas Cactus Preparation fact sheet.
Have you ever wanted to grow fruit trees indoors or do you want some tips on bringing containerized fruit trees indoors for the winter? The Growing Fruit Crops in Containers publication provides some good tips on growing fruit trees indoors.
Unless you have a house with a lot of windows or a sunroom, plumeria don’t make the best houseplants. They need at least six hours of sunlight per day and need to be at least three years old to bloom. If you are interested in propagating plumeria, then check out this publication on propagating plumeria from cuttings.
Potting soil, potting mix, garden soil, topsoil. The bags are all sitting side-by-side on the shelf at the garden center. Your challenge is to figure out which one you need for your project. What’s the difference? To begin with, none of them are dirt. The Soil Science Society of America defines dirt as “displaced soil”, the dead nuisance material left on your hands after working with soil. Soil is a blend of sand, silt, clay and organic matter. It is alive with nutrient and water holding components. But, all soil is not equal.
Soil contains decayed organic remains. It may be composted leaf tissue and/or microorganisms. The terms potting soil and potting mix are often used interchangeably, but there is a significant difference. Potting soil contains compost or the flora responsible for the breakdown process. Potting mix is soil-less. It is a blend of sphagnum moss, coir, bark, perlite and/or vermiculite. While these are natural occurring materials, they are in their original state. No decomposition has occurred. In the absence of compost, the resulting potting mix is sterile and free of fungus spores and insect eggs. Potting mixes are excellent choices for container growing, especially for house plants. The sphagnum moss, coir and bark hold and release water and nutrients, while the vermiculite or perlite keep the mix loose and well-drained. Some blended products add microbes, which then requires the word soil be added to the packaging. These are still suitable for potted plants.
But, if the potting soil is made from mostly compost, the potential of having poor drainage and fungus gnat problems increases substantially. The only containers these type of potting soils should be used in are raised gardens. Depending on the compost source, these soils can sour, grow mushrooms or become extremely hard.
Garden soil is a blend of soil and soilless ingredients. It can be used in very large containers (24” or greater) or added to native soils to enrich planting areas.
Then there is topsoil. It varies widely in composition and quality. Use it to fill holes in the yard, build berms or mix it will compost to increase water retention in dry garden areas.
So, when standing in the store comparing prices, don’t let price dictate your purchase. To keep your containerized plants doing well, do some bag reading. Choose the product that has aged forest products, sphagnum moss and perlite. Use the soils made from bio-solids and composted materials to improve the sand in the yard. When you’re done, go wash the dirt off your hands.
potting mix are often used interchangeably, but there is a significant difference. Potting soil contains compost or the flora responsible for the breakdown process. Potting mix is soil-less. It is a blend of sphagnum moss, coir, bark, perlite and/or vermiculite. While these are natural occurring materials, they are in their original state. No decomposition has occurred. In the absence of compost, the resulting potting mix is sterile and free of fungus spores and insect eggs. Potting mixes are excellent choices for container growing, especially for house plants. The sphagnum moss, coir and bark hold and release water and nutrients, while the vermiculite or perlite keep the mix loose and well-drained. Some blended products add microbes, which then requires the word soil be added to the packaging. These are still suitable for potted plants.
