What is Topdressing? In this blog I am referring to Topdressing in lawn and landscaping. It is
a process of spreading material over a lawn or garden, to improve soil quality to grow plants and grass. Some say Old Tom Morris while working on Prestwick golf course had spread sand over the grass and noticed an improvement in the turf, this was the beginning of topdressing. Old Tom Morris is also noted commonly with St. Andrews golf course groundskeeping and course improvements. Similar theory to farmers spreading manure over their fields to add nutrients to the soil, topdressing your lawn or garden adds nutrients to the soil (but not using manure, which the high nitrogen in manure can burn the grass and most plants). Adding material to help the soil absorb water better or on the other hand drain water better. The thickness of the material being spread varies on the purpose or goal, (enriching the soil, overseeding or leveling the lawn. The type of material to use will vary, along with the time of year to do topdressing.
What material do you use? Materials that can be used for topdressing can be topsoil, compost, sand or a mixture of these materials. Topsoil or compost will help add nutrients to your soil, in an organic way. If the soil in your yard has low nutrients for growing grass or plants, the soil drains too fast to be absorbed by the grass or plants, topsoil or compost will help hold moisture to be absorbed by the plants and grass. When the topsoil was removed and subsoil is left to try and grow the lawn or garden, topsoil or compost can be spread over what is currently growing to get organic nutrients to the grass and plants, without removing everything and starting with bare soil. Alternatively, topdressing can be a part of a fertilizing program. Using sand for topdressing is known and talked about on golf courses, sports fields or the people who reel mow they’re lawns. But in any lawn or garden you can use sand, for leveling and smoothing a lawn (sand is the best way to level or smooth out an existing lawn) and if you are looking to smooth out or level or yard there are other steps before/after topdressing with sand which is another topic or blog post. The other common use for topdressing with sand is to help improve poor draining clay soils, sand does hold water in some cases and in other cases sand lets water drain through it and firm up the soil, which is why sport fields and golf courses use sand instead of using topsoil compost or clay soil mixes. Soil Mixtures are made at some suppliers not every stone, mulch, soil supplier. Some clients laughed thinking soil mixtures is a made-up term because it’s rare for homeowners to hear, but golf courses, sports fields and in construction and land development use it and know it. Soil mixtures can have variable amount of topsoil, compost and/or sand, maybe be just two materials for drainage needs and erosion control. So, if you want to add nutrients and improve soil drainage, try a soil mixture.
How thick do you spread material when Topdressing? The common rule for thickness is to never completely cover the blades of grass on a lawn, in a garden the more you cover seeds the longer it will take for the spout to poke through the surface. On lawns when you are reel mowing the blades of grass are under one (1”) inch tall, most lawns are taller in the two (2”) – three (3”) inch range and that would be a lot of material to spread. So, for most lawns a quarter of an inch (1/4”) of material is the average, but you can go thicker. If you are looking to fill low spots, holes or level your lawn, you can leave the tips of the grass blades above the topdressing material or even add grass seed to thicken the spot.
The equipment to do Topdressing. For all of the equipment, the drier the material can be the better it will spread. Shovel- You can always just grab a shovel and spread by hand, either by shaking the shovel as if you are spreading chicken feed or a swinging throw motion getting the material to spread. Labor intensive, can pull a muscle or if your aim isn’t great, you get material clumped or thrown into areas you didn’t want. You can follow up using a stiff bristle push broom or rake to spread out clumps. But for a small yard or tight access this is a good choice. Manual walk/push topdresser or peat spreader/metal basket/grated roller. The roller/ basket/ peat spreader are the different names for the same tool, which is grated metal in the shape of a drum with an access door to fill by hand, then push/pull/or tow. These are available from (24”- 44”) twenty-four inches to forty-four inches (the sizes I’ve found), the wider the roller use a tractor or other machine to tow it. These will also screen the material again as you spread. Faster than using a shovel, spread material evenly and careful that it doesn’t roll away from you. The manual topdressers are smaller non-powered examples of the bigger powered topdressers, you push a hopper filled with your material of choice, as you push and roll the wheels, you spread the material in the same way as using a drop spreader for fertilizer. Evenly spreads the material like the bigger topdressers, but at a lower purchase cost. Heavier to push even on flat ground, holds as much as a roller. Self-powered and tow behind professional topdressers, different styles available on the market and for rent. Most of them have a conveyor in the bottom of the hopper switch moves the material towards agitators to loosen the material before it gets to the spreading device. The machines are available as self-propelled, ground contact tow behinds, PTO powered, or hydraulic powered. These machines have different ways to spread the material, a spinning disc like a traditional fertilizer spreader, and the others use a brush, a roller with a groove pattern on it or another set of agitators and all of these spin at a faster rate than the conveyor. The spinning disc style does clog with wet material (I have access to this style of topdresser), it also doesn’t perform well with a sandy mix either, does spread evenly when the material is dry and light. Narrow areas you would have to make or use deflectors, if you want to allow over spray. The machines with the other spreading style work well with most material you would spread, breaks up the material better for more even spreading the pattern that it spreads material is as wide as the machine is with minor overspray. These are expensive units but are very good at what they do.
The process of topdressing. First, thatch and core aerate the lawn. You don’t want to cover up a thatch layer which could hold insects and disease, slow down nutrients getting down into the soil. Core aerate to have hole to fill with the topdressing material for it to work and mix into the surrounding soil. Then use a drag or a broom to get the material off the grass blades. Watering is preferred after, if you don’t have irrigation sprinklers or plan to do this before it rains. This also aids in getting the material off the grass blades and get washed into the soil. Depending on how big the lawn is and the thickness, is a lot of material even at a quarter of an inch (1/4”).
When do you topdress? Spring or fall when the grass isn’t under heat stress and is growing regularly since you will have thatched and aerated before topdressing. Topdressing can also be done as part of overseeding or renovating of your lawn, not just to add nutrients but cover the seeds with the topdressing material, providing good soil to seed contact, less likely to be blown or washed away, keep some birds from picking at the seeds and hold some moisture around the seeds to help germination.
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