Mulches are essential in most gardens and are useful for a variety of reasons. Their primary functions are to regulate temperature, conserve moisture and suppress weeds.
Bonus features include building up the soil and adding appeal to the overall design of your garden.
There are several types of mulches that can be used, each with its own advantages and disadvantages. These include organic, inorganic, and living mulches. Below is a list of 10 mulches that you should consider using in a small homegrown strawberry patch.
- pine needles
- leaf mold / oak leaves
- wood or bark chip
- living mulch
- newspaper or cardboard
- plastic or fabric sheeting
- gravel or stone
Types of mulch
1. Straw mulch
As the name suggests, this is the preferred mulch for strawberries. Straw is the chaff that remains after the grain has been harvested.
Please note that straw is not the same as hay. Hay is harvested, as animal feed, with the seeds intact. If these seeds germinate, they will cause havoc in your strawberry patch.
Rice straw is the best if you can get it because it contains very few seeds. Wheat straw is a close second and is more readily available. You could also try barley and oats straw.
You will need to apply a 1-2 inch layer over your entire patch to protect the crowns and new buds.
- Straw is readily available, in bales and bags. A bale is compact and you will be surprised how much ground it covers. It is the equivalent of 4-5 bags.
- It is also inexpensive as it is a by product of harvesting grains and is not suitable as feed for most animals.
- Straw is light which has two benefits. It is easy to work with, even if you are a lone gardener, and it does not put pressure on the delicate crowns and buds.
- Because it is organic, straw breaks down and becomes part of the soil fabric. It decomposes at the rate of 40-50 percent in a three month period so will remain effective as a mulch long enough to see your plants through winter.
- Straw is light therefore it blows around easily. Lay it down when you are expecting a steady rainfall or a few inches of snow to anchor it.
- It also sticks to everything so you might find, as I did, that your shoes are soon covered and that dogs bring it inside. Raised beds and container planting will alleviate this problem.
- Straw is neutral in terms of its pH levels and will not affect the acid or alkaline levels of your soil. Strawberries prefer a slightly acid soil so you might consider mixing it with a mulch that makes the soil more acidic, e.g. pine needles or peat.
- Straw has a reputation for harbouring pests, including rodents, so keep an eye out for these.
- Buy your straw from a reputable dealer that can guarantee that it is free of seeds and has not been sprayed with pesticides or herbicides. The former is a nuisance but the latter can kill your crop.
2. Pine needles
Pine straw has many of the attributes of wheat straw but has the added benefit of reducing the pH levels of the soil as it breaks down.
- Pine straw is light and easy to work with. It will not smother delicate plants.
- It does not mat when wet and therefore does not give opportunities for bacterial growth and anaerobic decomposition.
- Depending on where you live, it could be free. I live near a managed pine forest which unfortunately does not allow unauthorised access. The few trees on our property do not yield enough for even my small patch.
- You will need 3-4 inches of pine needles to create an effective mulch around your strawberry plants.
- Pine needles decompose slowly, especially in dryer conditions. You may need to spend extra effort removing the mulch when it is no longer needed.
- If you are sourcing your pine straw from the forest floor, monitor it for unwanted insects, fungi and other unwelcome pests. Apply it as a mulch around your strawberry plants, without letting the pine needles touch them.
3. Leaf mulch and grass clippings
Leaves from deciduous trees can be a problem for many gardeners who see them as untidy. They are, in fact, a rich source of nutrients for the following season.
- Leaves are free. Each fall, tons of spent biomass drop off deciduous trees. All you need to do is shred them and store them in a dry place for at least 6 months until they can be used as mulch.
- Leaf mulch is easy to make. Fill black garbage bags with the shredded leaves, tie them closed, punch holes in the sides and leave them outside to mature. The bacteria that break down the leaves will need a small amount of water from time to time to survive. Turn the bags or shake them every few weeks.
- The beneficial bacteria that break down the leaves will remain active in the soil when you apply it as a mulch.
- Leaf mulch is light, and will not damage fragile, dormant or new growth.
- Leaves provide nitrogen for the soil when they break down and decompose.
- The leaves of certain trees lower the pH level of the soil when they break down, which is desirable when growing strawberries. These species include oaks and beech.
- Leaf mulch requires effort, time and space to produce. Ideally, leaves need to be shredded and stored until they have decomposed sufficiently to be used as a mulch. You can shred the leaves by running a lawn mower over them a few times, or running them through a wood chipper.
- If you have not bagged the leaves, your leaf piles need to be turned once or twice a month to aerate them, and kept under shelter to prevent them from becoming too wet. Excess moisture crowds out the oxygen necessary for bacterial decomposition. This will result in a much slower and less desirable, anaerobic fungal rotting to take place. You will end up with a stinking pile of sludge rather than usable and beneficial leaf mulch.
- Freshly fallen leaves that have been applied directly as mulch, without being shredded, will mat and cause the same anaerobic problem as the leaf piles. Matting can be prevented by leaving the leaves to dry out on your lawn, shredding them and then applying them as a mulch, in conjunction with equal amounts of straw.
A word about grass clippings: These are usually available in summer, and can be left to dry on the lawn, and then applied directly to your strawberry beds as mulch. Just bear in mind that they are rich in nitrogen and will stimulate the growth of foliage. Otherwise, they can be stored and treated much the same as leaf mulch.
Compost is another form of mulch that you can use to help your strawberry plants to survive the winter. Compost is comprised of organic substances that are actively decomposing. Once they have broken down completely, your compost becomes a type of soil, known as humus.
- You can make your own compost from kitchen scraps, fallen leaves, newspaper, and manure from a nearby farm.
- Alternatively, compost can be obtained from most garden centres or nurseries.
- While compost breaks down, it generates additional heat which will protect your strawberry plants in the cold of winter.
- Ultimately, compost breaks down and becomes nutrient rich soil.
- You can shape the compost into the ridges needed for the mound system used when growing everbearing strawberries.
- Compost breaks down slower in winter, especially when it is spread out.
- Weeds that were present in the compost may have an opportunity to regenerate when the weather warms up.
- Substances in the compost, that have not decomposed completely, e.g. manure, may be too rich in nitrogen and burn you plants.
5. Peat moss
When moss and other organic matter decompose in a bog, they form peat. The decomposition process is exceedingly slow because it happens without oxygen. Peat bogs grow on average by 1 mm per year.
- Peat moss is an acid medium which is desirable when growing strawberries.
- It degrades and decomposes very slowly and does not have to be replaced as often as other mulches.
- Peat holds several times its own weight in water and therefore acts as a reservoir. It releases the water slowly, as the soil needs it.
- It also holds onto nutrients that the soil needs, preventing them from leaching out with each rainfall or watering.
- Peat is not a renewable resource. The rate at which it is harvested for commercial purposes is far faster than the rate at which it is replenished in the bogs.
- You need to mix peat moss with other substances, such as soil or compost. to make the optimum mulch.
6. Wood or bark chips
Wood and bark chips are a by-product of the timber industry. Several types of wood are used to make the chips, so you may find a mixture of these in your purchase. Chips made from bark and hardwood species last longer than those made from softwood.
- Wood and bark chips can be obtained free from your garden. Each time you prune shrubs or trees, save the sticks and branches and feed them through a wood chipper. The resultant pieces will dry out quicker and become mulch after a few months. You may also offer assistance to your neighbours by removing their offcuts.
- Wood chips, like straw, are relatively inexpensive to purchase. They are even more reasonably priced if you buy in bulk, i.e. before they have been bagged.
- The product is readily available from garden centres and nurseries, or directly from saw mills.
- Wood chips have bulk and substance, and therefore do not blow away as easily as lighter mulches.
- The chips take a long time to break down and do not need to be replaced often.
- For a number of reasons, the chips in your mulch will break down at different rates. The wood types and the size of the chips vary. Smaller pieces will break down sooner than larger pieces.
- Wood chip mulch and pathways are thought to create an aesthetically pleasing landscape.
- Some trees reduce competition in their immediate environment by acting as natural herbicides, e.g. eucalyptus trees. Wood chips from these could kill your strawberry plants or stunt their growth.
- Similarly, the wood from some trees naturally repels insects, eg. cedar wood. Be aware that chips made from these types of trees could deter pollinators.
- On the whole, though, wood chip provides an hospitable environment for insects to live and breed. Keep them away from direct contact with your plants, especially in spring when new life springs up all over the garden.
- Because insects love wood, the timber industry makes extensive use of pesticides and fungicides to protect their finished products. Ensure that the wood chips you purchase are untreated.
7. Plastic sheeting and landscape fabric
Inorganic mulches have proven successful as mulches by commercial strawberry farmers. A combination of plastic sheeting in the beds, and landscape fabric between the rows proved to be the most effective by farmers studied by Minnesota Fruit Research.
These solutions are also available to the small home grower, at a reasonable cost.
- Plastic sheeting has proven to be most effective at weed control, water retention and keeping fruit clean.
- Landscape fabric suppresses weeds and stands up better to the foot traffic in between the beds.
- Both substances are relatively easy to lay in a small garden and require little maintenance once they are in place.
- The plastic sheeting is laid before the strawberries are planted and acts as a mulch all year round.
- Plastic mulch heats up the soil by between 5 and 7 degrees and is useful for forcing early spring growth.
- Plastic mulch is available in a range of colours, each with different effects on the crop. Clear and black plastics are most effective in heating the soil. Red plastic sheeting has been shown to increase the size and taste of the fruit.
- Both mulches are inorganic and do not contribute to soil quality.
- Their removal and disposal present an environmental problem as neither substances are biodegradable.
8. Newspaper or cardboard
Paper waste can be found in most homes. Instead of recycling or sending yesterday’s newspaper and the evidence of your online purchases to the landfill, consider using them as mulch.
For maximum effectiveness use cardboard, or several sheets of newspaper, as a layer of protection underneath a layer of soil or compost. This process can be repeated several times, as you would when making a lasagne.
- Both newspaper and cardboard are freely available in significant quantities, in many households, or at least in the neighbourhood.
- If the newspaper or cardboard degrades, it is easy to replace.
- Both materials are biodegradable and will add to the organic matter of the soil.
- They are excellent barriers to weed growth.
- Both will absorb water and allow it through to the soil, while at the same time preventing evaporation from the soil. Cardboard has a slower retention and release cycle therefore needs to be covered with soil or compost to be most effective.
- Newspaper can be used in summer as it does not alter the soil temperature.
- Both of these materials degrade fairly quickly and will look untidy in no time at all. They look best when covered with soil or compost.
- Avoid using newspaper with coloured ink as this may be toxic to the soil.
9. Living mulch
Plants that provide ground cover and do not compete with your strawberries for nutrients, sunlight and water, fall under the category of living mulch. Experiments have been conducted with ryegrass, canola, and camelina. Anecdotal data has also been gathered on the use of clover as a living mulch.
Living mulch should not be used in the strawberry beds but may be a consideration for the space between the beds.
- Living mulch is seen as a more environmentally friendly alternative to mulches such as plastic and fabric.
- Rye grass and canola were shown to be effective at controlling weeds between the beds.
- Even though they were grown between the beds, all of the plants studied competed with the strawberries for resources, and reduced yields within one season.
- The living mulch requires maintenance, such as mowing, which generates extra work.
- Although clover and canola contributed nitrogen to the soil, this is not seen as an advantage as nitrogen is not an essential nutrient for strawberry production.
- Rye grass impaired soil health by reducing both nitrogen and organic matter.
10. Gravel, rocks, or stone
And now for something completely different, these mulches are popular with landscapers and designers because of their aesthetic appeal. They can be used to hold down landscaping fabric or plastic sheeting, and to secure sloping land.
- Large areas of these mulches are pleasing to the eye, and can be used to give your garden a finished, designer or modern look.
- They come in a range of colours. White stones will provide a fresh looking backdrop to green foliage and bright red berries.
- Stones and their derivatives are heavy and could be useful in windy areas.
- They can be used, on terraces or sloping ground, to prevent soil loss and water run offs, after heavy rainfalls.
- They can act as a fireproof barrier, protecting your home, buildings and the more woody plants in your garden.
- Stones are heavy and could compact the soil.
- They do not degrade and add value to the soil over time.
- They are difficult to manage and remove when no longer needed.
- The jury is out on their effectiveness in controlling weeds and retaining moisture in the soil.
- Stones are not good at regulating temperatures as they absorb heat during the day and release it into the atmosphere at night.
- The edges could be sharp and painful to work around. They are probably best used away from the plants, in high traffic areas such as the spaces between your beds.