<< Back to Articles Home Page Maintenance Articles Full List of Articles, Copyright © 2019 Ozbreed Pty Ltd | Web Design Smart Web Solutions, Exotic and native plants for home gardens and landscapes, Functional Westringias, Callistemons, Grevilleas and more, Non-invasive, beautiful exotics incl. They are light and fluffy, so spreading them around is a piece of cake, and they don’t compact much as they decompose, so you don’t have to worry about them becoming too thick or forming a rain-impervious mat. It's a very unusual thing to happen but if people are dealing with big bags of mulch, there is a potential danger," said Waghorn. Increased soil nutrition. (Soil conditioner is a ground pine bark product smaller than mini-nuggets that can also be used as mulch.) On a positive note, properly manufactured hardwood mulch releases alkaline benefits to soil as it decomposes, raising the PH level a bit. Decomposing bacteria need an amble supply of nitrogen to break down the mulch. It is bad to have low airflow and constant moist conditions in the top 50mm to 100mm around the crown of plants. Red Cedar Bark Mulch is almost double the price of our Red Wood Mulch because it is shipped from Canada, and we all know that is not cheap (especially with today’s fuel prices!). I recently visited Florida in the USA, and asked a meeting of 40 Landscape Architects (for which I was guest speaker), if they had problems using cheap land cleared tub ground mulch that was not correctly processed. What needs to happen is either we go back to the way the ground cover mulch used to be made from land clearing operations, which was to remove all leaf material and sticks etc, and chip the trunk parts of the tree, making sure to reject any diseased trees. Redwood chip: A medium (20-25mm) Red/Brown colour enhanced wood chip. Repeated applications can contribute to waterlogged soil/root zone by slowing soil water loss via evaporation. This process may cause nutrient deficiencies, especially if the mulch is mixed down into the soil and is of a fine texture. Composted sawdust, composted pine bark, spent coffee grounds, composted organics. Mulch … I have never seen onsite tube ground mulch turned and composted correctly. Soil conditioners are used essentially to add organic matter to sandy soils and to improve water holding in the soil. How does over-mulching kill trees and shrubs? It stays in place because the straw lodges in the soil, building upon itself to create a stable layer of protection. The main recommendation from the Agricultural department was; ‘Mulches with better air-filled porosity would be better alternatives as they suppress some diseases.’. Following is information about the different forms of mulch, why some can be a problem, and how to prevent that. Whether ground cover mulch or soil conditioner mulch, special expertise is required to produce a relatively problem free mulch. However, on poorly drained soils, mulch depths should not exceed 2 inches, especially for shallow rooted plants. Ground Cover Mulch – Should always be coarse grade with no fines. Mulch can lower soil pH slightly. This is a good thing. Even of higher importance, is to stamp out the practice of using incorrectly composted and poorly graded ‘Cheap, Free or Raw’ mulch, which is produced by tub grinding garden and land clearing waste (Not to be confused with composted recycled organics). Ground cover mulch with fines create ideal conditions for disease to live and prosper around the crown of the plant, often causing, or enhancing root rot diseases in many plant varieties. It is a premium quality soil conditioner mulch and will provide nutrient rich organic material to hard, dry soil which will help create an ideal environment for earthworm and microbial activity. Manufactured mulches such as coarse grade hardwood chip, or bark nuggets or other chunky mulches with no fines are ideal ground cover mulches, as are newly available recycled mulches meeting the appropriate standards, and containing less than 5% fines. Used correctly mulch has many benefits, but used incorrectly mulch can become deadly to plants, and can cause maintenance nightmares. Disadvantages: Large chunks can float away from the mulched surface. This so called cheap or free mulch causes major problems; in fact it would be better to use no mulch at all, than use this ‘Pollution Mulch’. (May/June). When organic mulch is placed too close to your house, it can provide pests with hidden opportunities to make their way into your home. Whether it is hard wood chip or any type of mulch, placing it on top of jut mat can lead to prolonged damp conditions, greatly increasing the incidence of disease, particularly root rot. Bark can be bought in different sizes, ranging from a fine grind to 2-inch nuggets. This often goes unnoticed until the following spring when the "tree doesn’t look good." Mulch keeps weeds at bay and protects your plants’ roots. (Photo for this mulch supplied by Centenary Landscaping Supplies in Queensland. If you’re heating with wood, odds are you already have a ready source of bark available, now all you need to do is convert it to usable mulch. Once established, the disease organisms ultimately invade the inner bark, starving the plant, and finally kill the plant. There is an effect of mulch type on surface temperature. This is true when you use mulch with NO FINES, as weed seeds find it very hard to germinate. Pull mulch back from plant stems and trunks—a rule of thumb is 3 to 5 inches away from young plants, and 8 to 12 inches away from mature tree trunks. Please do not confuse professionally recycled tub ground mulch with, with this non composted land cleared tub ground mulch. The Humus can also be dug into heavy clay soils with the addition of Gypsum and possibly a medium sand. The trees are ground into chips or shredded. The Problems with Dyed Mulch. In fact poorly composted mulch with a high degree of fines, typical of most non composted tub ground land cleared raw mulch actually causes nitrogen to draw down, locking up nutrients needed for plant growth. This article has listed many reasons why mulches with fines should not be used for covering the ground. The chip is generally 30mm in size. Since bark mulches have little nitrogen available, the bacteria utilize the soil nitrogen. Once this mulch is ‘ready’, it is usually spread by the landscaper on site, and then planted with plants; often resulting in major plant loses due to disease. This scenerio is similiar to composting, where temperatures within inner mulch layers may reach 120° to 140° F. This high heat may directly kill the inner bark/phloem of young plants, or may prevent the natural hardening off period that plants must go through in the fall in preparation for the winter. Many believe mulch spread on top of the ground will provide nutrients into the soil. In Queensland and other areas, where humidity is extra high, even 5% fines can have bad effects, so zero fines are always safer. After a couple of years of plants dying, weed invasion etc, everyone stopped using it. Other benefits of Humus & Soil Conditioner. If they really cared about the environment, they would instigate correct mulch production and composting techniques, as is conducted by professionals in the recycled organics industry. Mulch depth should standardly not exceed 3 inches. Cypress garden mulch is an organic mulch made from pond cypress trees (Taxodium distichum var. This unique process saves you money, as well as providing a mulch … Australian Native Landscapes. To produce soil conditioners from mulch and other waste products, a thorough composting procedure must be adhered to, with solid quality control inspections. Rutgers Cooperative Extension, a unit of the Rutgers New Jersey Agricultural Experiment Station, is an equal opportunity program provider and employer. Sometimes, plants cannot tolerate micronutrient toxicity, becoming stressed and killed by secondary disease organisms and insects. After the soil becomes acidified, some nutrients are not available to the plant, and others, such as iron, manganese, and zinc, become readily available at high, toxic levels. Rutgers, The State University of New Jersey These wrongly used mulches provide none of the benefits that people expect from ground cover mulch. So unless land developers are willing to undertake professional standards, the reality is that soil conditioners should be made by specialists off site. Visually look for the presence of a root flare; if not visible, at least some may be partially buried and must be exposed. Chunky ground cover mulch with NO FINES (No more than 5% of fines), lets the water freely flow through to the ground below, but still helps keep the soil below cool, reducing the amount of water evaporation from the soil into the air. While mulch may make a landscape look crisp and tidy, it’s more than an accessory. Mulches from broadleaf trees and shrubs. It takes a bit longer to break down as well and it doesn't contain any nitrogen or nutrients. If such wet conditions continue long enough, the phloem tissue may die, starving the roots since they then receive none of the essential photosynthates produced by the leaves. Pine Bark Mulch Problems. Both Mulch Makers and Australian Native Landscapes have told me they are looking into ways to do this, and are currently producing sample products, with the hope of having these products available by the time this article is read. Zero percent fines are better for the plants, however until standards improve and for the purposes of this article, 5% fines or less will be classed as No Fines. Most fungal and bacterial diseases require moisture to spread and reproduce. Humid summer areas such as Sydney and Brisbane should never entertain such practices, and should always strive to have good airflow around the crown or collar of a plant. It is long lasting, excellent at stopping weed seed from germinating, allows water to easily flow through to the soil below, and best of all, it has excellent air-filled porosity, which helps suppress diseases in plants. Symptoms may take several years to appear, depending on the plant and the soil type. This mulch with fines had many major instances of Phytophthora occurring, which lead to many plants dying, particularly, but not limited to any areas near paths where water ran off the path and caused water logged conditions. Think about starting a fire with two sticks, it is the fine pieces of wood that ignite easily, not the big pieces of stick. The entire health of the plant is thus affected. This is hard to do on site. Quite simply the bigger and heavier the particle, the less likely it is to move. Incorporate into the soil. This will help everyone. To achieve a usable product from this process, this raw tub ground mulch would have to be graded and treated. Pine Needles Can Work as Mulch Pine needles, also known as pine straw, make fine mulch for some flower beds. Recently, one roadside project had its poor grade mulch catch fire, killing many of the newly planted plants. This is causing the deaths of many plants around Australia, as well as removing the benefits usually gained from using ground cover mulch. nutans) and bald cypress trees (Taxodium distichum). The most common causes are: Suffocation of the tree roots is the most common cause of tree and shrub death from overmulching. Myth two: All mulch inhibits weed growth. It also shields the soil, keeping it moist and preventing it from washing away. Pine Bark Mulch. Mulch also helps to keep soil moist and moderate its temperature. Recently, there has been a move to clearing land, pushing the trees and shrubs into piles, and then using large tub grinders to mulch everything into a ‘bits and pieces’ mulch. Unfortunately, there is a recent trend to use soil conditioning mulch as ground cover mulch. (It is on top of this conditioned soil that the specialist ground cover coarse grade mulch with no fines can be used.) Hardwood Chip: Mulch favored by the NSW Roads and traffic authority. Mulch reduces weeds by blocking light from the soil below, preventing seeds from sprouting. Remove all soil or mulch up to the junction of the roots and trunk collar (taking care not to damage the tender bark) to expose the root collar. These disadvantages make dyed mulch far superior to natural options. Fire can be one more result of using this tub ground non composted mulch with fines. (Photo for this mulch supplied by Centenary Landscaping Supplies in Queensland. Generally, contractors with little professional mulch making experience are producing this mulch. Australian Native Landscapes, Sydney. Wet soils may not need any mulch. Ground cover mulch should be chunks of wood or bark. This type of mulch used correctly can also make a landscape project look great. Chunky Pine Bark: This attractive tan bark consists of 50mm curly chunks of clean bark. Job Opportunities | Webmaster. Wood Chip (Cypress pine): A wood chip created from the waste wood when the cypress pine tree is milled for its attractive timber. This type of mulch also is well known to spread weed, cause nitrogen draw down, and repel water, causing drought stress in plants. In particular, pine bark mulch is quite acidic (pH of 3.5 to 4.5), and can cause the soil to become acid with constant use year after year. Piles of mulch next to the trunk may also provide cover for chewing rodents such as mice and meadow voles. Symptoms appear as yellowing of foliage, often with prominent green veins. Centenary Landscaping Supplies in Queensland. The Gypsum will help break the clay down over time while the humus will add organic matter. In general, soil conditioners should preferably be applied to a depth of 50mm, and then incorporated to a depth of 200mm using implements such as a rotary hoe, or power harrow. Obviously poorly composted soil conditioner could have the opposite effect, consequently only buy professionally made product. Many believe that by spreading mulch over the top of the ground, weed invasion is reduced. Pine straw looks better. A mountain of mulch, piled high against the tree trunk, does not kill a tree immediately—it results in a slow death. Soil conditioner is where fine grade mulches should be used, not in ground cover mulch. The crazy aspect is that the people organizing this mulch, claim they do it for the environment, recycling rather than burning it. Mulch with fine grade material has very poor airflow, and will remain wet for long periods, causing many problems, including crown rot. Off the Leaf newsletter #303. Well composted fine grade mulch at least has any disease composted out of it with heat from the constant turning and composting. Eg: Make 20 to 40mm, or make the pieces chunkier. When it rains, water drips off the tips of the outermost … (Ph: 02 9450 1444). The humus will help retain valuable moisture in the landscape. This mulch is then usually left in piles, to supposedly ‘compost’, which it will not do unless it is turned regularly. In particular, pine bark mulch is quite acidic (pH of 3.5 to 4.5), and can cause the soil to become acid with constant use year after year. Look for symptoms of leaf yellowing on new growth. Layering this over the top does not create soil laying problems. Australian Native Landscapes, Sydney. I recommend buying the Red Wood Mulch to most people simply because it is much more affordable $26 … It is a very hardy and long lasting ground cover that breaks down very slowly during the life of the landscape. It will help get rid of the land cleared waste, it will improve the soil, and it will allow the mass planted areas to live. Fine, black composted. So why is it that all too often, soil conditioner mulch is used as a ground cover mulch, or worse still, poorly produced non composted tub ground land cleared mulch (Raw Mulch) with fines. For decades plants such as Lomandra, Agapanthus, Dieties, Liriope etc have been used with great success, but the recent use of these poor, land clearing tub ground mulches is threatening the success of these very tough plants. It’s only down side is that it is virgin material coming from forestry. The large size deco bark is a fair mulch to use for shrubs and ground covers. It is airflow that makes good ground cover mulch. It would be better to simply tub grind it repeatably until it is fine enough, than composted well and professionally, and used as soil conditioner. This can really help improve the health of plants, and reduce the incidence of disease. Some mulches heat the soil as a function of solar radiation absorption more than bare soils. This is a problem because plant roots need oxygen to survive. The constant disease pressures from using the wrong mulch, is causing even tough plants like these to fail. How to use woody mulches around the garden. C. Carlson. For these native plants, products such as Greenlife® `Mulch & Compost™’ available from Australian Native Landscapes are recommended. The disease spreading implications of not banning this practice are immense, and I am surprised the various state quarantine, agricultural and land and water conservation departments have not stepped in to stop the practice. Only ground cover mulch with no fines will do this, as mulches with fine grade material generally become water repellant. This results in a minimum of 25% by volume being organic matter. Copyright © 2020 Rutgers, The State University of New Jersey. I believe future improvements could make it even better. With water occupying most soil porespace, air content is mimimal and diffusion of oxygen is essentially blocked. If this crown is covered by mulch with fines, it is often kept moist, particularly in wet humid times of the year. with Rutgers websites to: firstname.lastname@example.org or complete the Report Accessibility Barrier or Provide Feedback Form. They laughed, and all told me they would not use such trash. Even if the plants are planted in such a manner, the first heavy rain sees the mulch pushed up against the plant anyway. Recently, an observation was made that showed mulch with too many fines can cause disease problems. School of Environmental and Biological Sciences, New Jersey Agricultural Experiment Station, Office of Continuing Professional Education, Tree, Shrub, and Flower Growing Publications, Report Accessibility Barrier or Provide Feedback Form, Rutgers, The State University of New Jersey, Executive Dean of Agriculture and Natural Resources, Deborah Smith-Fiola, Agriculture and Natural Resources Agent, Ocean County. A thin layer of mulch can certainly help to insulate plants and regulate soil temperature to prevent fluctuations. Again, whether on site or in a mulch manufacturing business, this needs to be done by specialists. Pine bark is long lasting, and when it does break down it enriches the soil with organic material. Wood chunks are preferable to bark. Well composted fine grade mulch reduces the disease problem, but only slightly. Bark mulch is a great way to keep weeds down in the garden while adding soil fertility. 15-40mm Forest Blend (Currently the best recycled product): This is a product available from Australian Native Landscapes in Sydney (Ph: 02 9450 1444), but if you live elsewhere, I am sure other mulch makers could create something that fits the specification. Greenlife mulch and compost: 100% recycled green waste. If the thick layer of mulch persists for too long, then the plant can die due to lack of oxygen for the roots. Another alternative is to have the tub ground mulch graded. Mulches with lots of fine grade material that are used for ground cover actually act as a potting mix, or seed raising mix. It can be pieces that are 15mm, 20mm or 30mm, depended upon what the client wants, but should never have any material less than 15mm. Mulch can be a very effective way of controlling weeds, but organic forms of mulch also can be ideal places for pests to live and breed. (Fines are the smaller particles, often with soil like texture). Finer textured mulch, such as double shredded mulch, may need only a 1- or 2-inch layer. Over-mulching is a waste of mulch (and money!). (Phone: 07 3373 4900). Soil scientists will all tell you that layering soil types is bad. The soil conditioner mulch would need to be tub ground again, or regarded, and well composted, ensuring any pathogens were killed, as the lack of airflow in this type of mulch would create an ideal environment for pathogens. This type of mulch is usually too poor to fit into either category of ground cover or soil conditioner mulch, and really should not be used at all. The interlocking nature of the mulch gives it more stability when compared to other products of its type. The fine grade material in the mulch still however greatly reduces the air flow around the crown off many plants or the collar of trees and shrubs, so it is much better to use coarse grade ground cover mulch with no fines. Coarser textured mulches can be placed a bit deeper due to better oxygen diffusion into the soil. The wet mulch layers piled up next to the trunk may begin to heat up when the bark begins to decompose. Very fine particles of pine bark mulch can rob nitrogen from the soil. A simplistic description of the processes involved is as follows; fines and pieces too small to be used in ground cover mulch would be screened into one pile (called the soil conditioner mulch), whilst chunky pieces at least 20 mm or larger would go into another pile (called the ground cover mulch). Pine bark is used widely as a bed preparation material but should not be. An uncomposted 100% recycled wood waist, with a particle size of 15mm to 40mm, with no fines, and good air filled porosity. One of the greatest aspects of using these products is too increase the presence of beneficial fungi and bacteria, which in turn help displace bad micro-organisms. Using Cypress Garden Mulch. Don't Miss the Drip Line. However with new work cover laws, large wood chippers are often thought to be dangerous, so in practice this is hard to do on site. The root flare stem and trunk tissue is quite different from root tissue—it cannot survive a continually moist environment, and must be able to breathe through lenticels. Two types of mulch were used in a planting, one was course grade hardwood chip with no fines, which did not show any major outbreaks of Phytophthora, and the other was composted tub ground mulch which, unfortunately, contained considerable amounts of fine grade material. Often this scenerio is accompanied by bark beetles and borers, that are also attracted to stressed plants, expedite the decline, and also allow entrance of other fungal pathogens into the plant. Coarse grade mulch with no fines has good airflow, and as such does not act as a soil. This is considered a temporary condition. Unfortunately, by the time the symptoms are noticed, it is generally too late to correct the problem. Mulch with large amounts of fines behaves like soil, so layering a soil like substance on the top of soil is soil layering, and by definition, bad. In reality, on site processed land cleared mulch needs to be used as soil conditioner, as I doubt it could ever be graded correctly to form ground cover mulch with no fines, and no diseases. Fire is another reason to only use coarse grade mulch without fines. It is generally a chip with sizes of 15mm plus. If you have a problem with excess mulch, dig through the landscape to see how deep the mulch really is. Currently there is nothing the same, but professional mulch companies are now offering good recycled products, with less than 5% fines, which hopefully can be 0% soon. Increased surface temperature due to pine bark mulch has been shown to cause nearby leaves to lose more water. I rang Hedges Direct, who said that bark chippings can cause problems, as the wood may have been treated with various chemicals, which get absorbed by the plants. Pine bark Mulch Advantages: This type of bark mulch is slow to decompose and generally lasts a year or more. So, mulch with fines used as ground cover mulch actually wastes water, whilst good airflow chunky ground cover mulch saves water. The weeds’ seeds blow in, receive water, and then germinate. So unless you know what you are doing, producing recycled mulch can even be dangerous. What's a drip line? Sure, many will say just plant the crown of the plant above the mulch, or push the mulch back from the tree, but this is simply unpractical. Phloem death may also occur when pop-up sprinkler heads continually saturate the mulch placed against the plant’s trunk. Open mulches with lots of airflow allow weed seeds that blow in to either fall to the bottom of the mulch, thus smothering their growth. Perhaps random tests for pathogens could be conducted. Mulching trees and shrubs is a recommended cultural maintenance method with many benefits, yet it can literally kill plants if mulch is applied improperly. This of course is rarely if ever done. The wood in pine bark mulch and other mulches doesn't provide much nutrition for termites, and without external food sources, the insects cannot sustain a colony. Contractors planting thousands of plants find this hard. So far I have been told this is difficult, but achievable, and it would have to be done by professionals. Myth three: All mulch releases nutrients into the soil. Hedge/shrub prunings and stems from younger trees or tree suckers can be shredded and applied directly as a fresh mulch on unplanted or planted areas. Cyprus Pine Mulch and Pine Bark Chips Cyprus pine mulch also has a repellent affect on termites. Before spreading pine bark mulch in your garden, however, you should consider common problems to ensure that the mulch is helpful rather than detrimental. The challenge is for recycled mulch companies, to come up with something that looks and works similar to hardwood chip. Soil conditioners are highly recommended as a way to develop better soils from poor soils. This also occurs when trees are planted too deep (the root flare is buried). Ground cover mulch is used to keep moisture in the ground, inhibit weeds until the plants cover the ground, and even to slowly release nutrients into the soil below. The fine and medium sized products are the worst choices. If the trunk is girdled (>50% chewed around the trunk), there is little that can be done to save the plant outside of bridge grafting. Mulch at this stage should be graded into separate mulch products and then treated correctly. New Jersey Agricultural Experiment Station Research shows that an amazing number of plants have rapidly improved in color and vigor within months of root collar excavations. Unless poor mulching practices are stamped out, humid climate states such as Queensland and NSW, will find themselves with a very small range of plants that can survive, if any. Wood, including bark from larger, mature trees can be chipped and applied as a fresh mulch on both unplanted areas and around plants on well-established beds. This is especially common in the spring and the fall, which are critical periods for root growth, and during other wet periods. Rutgers is an equal access/equal opportunity institution. Inner bark (phloem) death comes from the piles of mulch placed directly against the stems/trunks of trees and shrubs. Benefits of Pine Bark Mulch. Myth one: All mulches save water by keeping the ground moist. Even well composted mulch, with fines catches fire more easily than the chunky mulch without fines, although even chunky mulch can catch fire. Phytophthora is devastating to many plant types, especially in NSW and Queensland. Another recent dubious practice is to put mulch on top of jute mat. There have been many instances on the side of the road or even in the back of trucks where piles of composting mulch left for a week or more, particularly when palm plants are included, and these piles are not turned, that the mulch has got hot and caught fire. Not only are many projects using the wrong type of mulch, but too many are using a new and very dangerous form of mulch; non composted tub ground mulch (Raw Mulch) which is often disease ridden, and is produced by land cleared site wood and leaf material, that is not even composted correctly. Or after much rain they can still germinate in the top of the mulch, but the open air regions of the mulch make it very hard for the roots to reach the soil below, generally causing the weed to die soon after germination. We will bring you this research in the next issue of Landscape Manager. By placing mulch with fines at 75mm to 100mm thick over the ground will only inhibit weed seed germination for those weed seeds already in the soil, but will not stop weed seeds that blow in.
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