Features Agronomy
Seeding vs. sodding: Which is the best choice in landscaping, lawn care?

SODDING and seeding both have their place in landscaping, but how does a lawn care professional know which method to recommend to his customer?

Sean Jordan, a technical agronomist with Nutrite, presented the pros and cons of each approach in March to an audience of lawn care professionals in Guelph.

Speaking at a forum sponsored by Nutrite, he said the first question to be answered is whether the intent is to establish or renovate.

“Are we putting in new grass where there had been grass before or are we having to replace grass that for some reason died?”

The professional needs to know why grass reached the point where it failed and was in need of renovation. Jordan said if the professional entered an area and “slapped down some grass”—seed, sod or otherwise—without looking at what’s there, he’s going to make the maintenance work afterward that much more difficult because if he doesn’t take the time to assess the environment and look at the soil and note the species of grass present, he’s in for an uphill climb.

He said the professional should ask himself: Do I want something that’s a pain to maintain and keep green, or do I want something that, because of a good plan, is easy to make green and thick and dense?

The lawn care professional must carefully look at the situation when he visits a property. Jordan said the first thing he likes to do is go to Google Maps and look at the site layout from an overhead point of view. When doing so, he will look for two things: trees and shade from neighbouring buildings, and access to morning sunlight for the turf. He will also look at the property from the vantage point of standing across the street where he will study air flow issues and traffic flow patterns among children.

Finally, he will take a “worm’s eye” view from up close to look at the soil.

At a new development, there may be little topsoil. But Jordan said that’s not to say one can’t grow grass on poor soil. It just takes more work.

“I’ve seen some absolutely beautiful grass grown in a gravel pit,” he said, “but it is taken care of regularly and not everyone can babysit a lawn like that.”

Taking a soil test is a logical first step to note the quality of soil on which to work. Jordan said to look for pH level, organic matter and nutrients.

“In soil tests, we’re looking for things that are either ridiculously deficient or way out of whack in terms of its ratio to everything else.”

Use of a soil probe will help to see if there are layering or thatch issues and to see how compacted the soil might be.

“That one device will tell you a lot, and the more you use it the more you relate what you’re feeling and what you’re seeing to the state of the turf, the better you’re going to get with that tool.”

When shade is an issue, it’s important to note that shade-tolerant grasses are not good with traffic, he said. By the same token, there are traffic-tolerant grasses that can’t handle the shade very well.

The lawn care professional must work with the customer to determine the lawn’s use, asking if there will be ample traffic on it, and to learn from the customer how much he’s willing to pay for the lawn. Jordan said it is amazing how well a lawn will fare if the homeowner is willing to go out and become a part of the program, by doing such things as pulling weeds and mowing regularly.

If shade is an issue, the professional must ask the customer how much he values his trees and if he’s willing to thin them out for the sake of the turf’s well being.

Jordan said homebuilding contractors tend not to understand the need for quality topsoil which they scrape from a site during construction. In addition to lawn care professionals having to work with a lack of quality topsoil, they might also be dealing with a lawn that has failed and should learn whether sod had been there previously. If sod was once there, they need to learn why it failed, especially if sodding again is a consideration.

That determination needs to be made before fertilizer or calcium amendments are considered. Other considerations include the level of compaction and the presence of salt in the soil. Salt will reduce the structure of the soil, taking an open, breathable soil and “turning it into a brick.” Salt can be alleviated through gypsum applications, where it will flush out the sodium and replace it with calcium.

Both sodding and seeding have certain amounts of aftercare required. Seeding will take a little more weed treatment afterward, whether it’s through manual, chemical or other means. Sod will require more aeration during the first couple of years to help break up the interface.

Jordan said the question isn’t so much the cost of putting in the lawn, but rather what it will cost over time with its ongoing care.

One of the advantages of seeding is that there is a greater variety of seed types available when seeding into the existing soil. At sod farms, Kentucky bluegrass is the predominant species grown because of its rhizomes which knit well and enable the sod to be easily rolled. It can be lifted, transported and transplanted with relative ease.

The advantage of seed is the greater number of varieties available, but the disadvantage is it requires more water and weed management, and takes a longer period of time from establishment until use.

When it comes to weeds, sod is generally clean because pesticides can legally be used on the turf while it is growing at the farm.

“There will be lower weed pressure because you’ll have nice, dense turf.”

When seeding, Jordan said, the ground has been tilled and a seed bed has been opened, but it’s also a big, open seed bed for weed seeds to fly into or they may also already exist in the soil.

The biggest advantage of sodding is that it produces an almost instant lawn, it controls erosion and has lower weed pressure. When weeds appear on a newly-sodded lawn, it is usually along the seams. Jordan said it is therefore important to ensure the seams are tight.

A sodded lawn also has nice, dense turf from the frequent mowing it receives at the sod farm. Sod growers strive for density to ensure it is rollable.

Aeration is imperative during the first couple of years after sodding to break up the interface between the existing soil and the soil which came in with the sod.

To ensure effective sodding, it’s important to understand the species’ availability so that the sod can be matched to the site, Jordan said. If shading is an issue, a fine fescue can be obtained. Often, the sod may be a mix with Kentucky bluegrass so that it will roll, and they will work together aesthetically.

“The big thing to think about when putting sod down is that what you have underneath is going to be reflected on the surface.”

When grading for sod, the surface must be firm, Jordan said, adding if the professional is leaving behind deep footprints, it’s not packed well enough. The surface will still settle afterwards, but it shouldn’t be too hard.

To be most effective, the sod should be laid the same day it is cut, he said, cautioning to avoid laying it on completely dry soil which will “zap” away moisture from the roots, setting it back. When it is especially hot, the lawn care professional must be concerned about both air and soil temperatures. Jordan said bare soil on a hot summer day can reach temperatures in excess of 140 degrees Fahrenheit.

“If you lay sod in hot conditions, get the crew in early and try to do it before the sun heats up the soil.”

Jordan advised to leave the sod stretcher in the truck, noting the sod shouldn’t be stretched that extra few inches because it will lead to weeds. It is important to make sure everything fits and that the sod is watered as soon as it is laid in place.
“The longer sod goes without water after it’s laid, the worse your results are going to be and the longer it takes to really establish.”

Jordan said he will often see sod laid in a front yard, and then smaller “pizza wedges” are placed to fill in gaps between the lawn and sidewalk. A week later, the smaller pieces of sod have turned brown.

Many landscape contractors swear that rolling newly-installed sod achieves better root contact with the soil and helps the sod better follow the contours.

“If you are going to roll, please try to do it before you water.”

Newly-installed sod should be soaked. If a 1,500 or 2,000-pound roller moves atop wet sod, it’s a setback to the turf.
Jordan said to make sure everything is lined up for fertility and to keep up with mowing and adequate moisture. Overwatering will lead to disease.

Aeration of new sod is critical during the first couple of years, and should be done three to five times, he said. Research conducted at the Guelph Turfgrass Institute found sod that wasn’t aerated yet had been growing for two years with regular mowing and fertility. After the second year, he said a corner of the sod could be lifted and pulled back because the roots had not penetrated into the subsoil. The subsoil was hard because there wasn’t a good opening up of the interface between the sod and soil.

“If we don’t do something to open up this interface, the roots can come down and start working their way laterally or they don’t root very deeply into the existing soil.”

Whether it’s pulling cores or using solid tines, aerating new sod three to five times during the first couple of years is important, Jordan said.

If there are good growing conditions for sod laid as a home lawn, no more than a week should go by without mowing, he advised. If it’s allowed to grow too tall, and then it’s mowed, the turf is being stressed. Mowing when the grass is too tall will lead to excessive clippings which, if they’re not raked off, will lead to shading issues, and it’s still stressing the turf.
He said to mow during the first week because the longer one goes, density is being lost and more stress is being placed on the plant. If a longer-than-anticipated wait is required to mow, due to ongoing rain, the mower height should be raised and then the height of cut can be brought back down.

Between two and three inches is the ideal height for a home lawn, Jordan said, adding it’s not just a matter of height, but ensuring there aren’t excessive clippings left on the surface.

If seeding is the chosen means for establishing a lawn, a good tool for finding the right seed for a particular area is the National Turfgrass Evaluation Program (NTEP) or by consulting a local seed vendor.

Whether seeding or sodding, it is important to apply a little phosphorus to ensure adequate levels, and to make sure there is good seed-to-soil contact if seeding, he said.

“What do you call grass seed that is applied out over the surface of a lawn? Bird food. You’ve got to get it into the soil.”
If seed dries out, it’s “toast” and there is no bringing it back, Jordan said. Good seed-to-soil contact to ensure moisture to the seed is vital. Seeding should be carefully timed, aiming for early fall if possible. It can be done in the spring, he said, but there is the issue of summer annual weeds which can leave a plant potentially weak coming into the stressful months of summer.

He suggested seeding in August or September and not delaying beyond the end of September unless a type of ryegrass is planned. The advantage of a fall timing is that the soil is still warm, there is adequate moisture, and there is more time to get the plant established before it undergoes any type of stress.

This also covers the “I forgot to water” loss results.

“Planning is absolutely irreplaceable.”

Jordan said if the lawn care professional takes the time to figure out what is in the soil, what the external factors are, what the real expectations are for maintenance, the budget and use, and it’s all factored into a concise plan, the end result will be a much better, more maintainable turf. Such a plan will also help make the decision of whether to seed or sod easier, he added.