Question
QUESTION: I want to lay grass over the top of existing garden. I was wondering how deep the soil needs to be before I lay the grass. Should I lay anything underneath the soil? Thanks,Kate

ANSWER: Let me see if I understand you correctly: You want to roll out Sod over an area that is currently covered with vegetation, perhaps Grass, various species of Weeds, some other plants and unused bare areas.

OR maybe you're thinking about using something called Plugs.

One or the other.  You're not planning to use Seed for this project.  Did I get that right?

Now, Kate, you give no clue as to your location.  If you live in Warm Season Grass country, you do this one way.  If you live in Cool Season Grass country, you do it another way.  Please advise.  Preferably with your zipcode so that I can get your weather, your neighborhood Soil characteristics, your most popular Grass and the Grass used by the most knowledgeable people in your region.

While we're waiting for those details, let's go over general Soil prep for Sod/plug installation.  And other things.

First, you get your Soil tested.  Reason: Pure and simple, You CAN'T grow first rate Grass in third rate Soil.

What kind of Soil grows GREAT Grass?  How do you get that Soil?  And the biggest question of all: Why can't you just fertilize the Grass to give it the boost it needs to be gorgeous?

Lettuce begin.

First, the dirt on Soil.  Grass takes nutrients out of the Soil via its roots.  Assuming you have a perfectly healthy Grass plant, the roots will pull water and minerals out of the Soil and shoot them up into the leaf.  We've known that for a long time.

But that's not all that roots do.  In recent years, scientists have found that roots also secrete chemicals.  These chemicals are very good at turning on special Fungi that trade MORE water and MORE chemicals in return for minerals the Grass doesn't want, but the Fungus does.  So they become trading partners.  And the longer they trade, the bigger and better they both get at this partnership.

Which means Soil has 2 things.

ALL the right minerals for the Grass.

And ALL the right Fungus spores to turn on and team up with the Grass.

Got that?

Now, I know for years and years and years, people have been dreading Fungus in their Lawns.  In fact, to most homeowners, a Fungus is something to fear.  Not to ... embrace.

But those special Fungi are INCREDIBLE.  Let me point out something here.  You know how we talk about 'shock' that a plant goes through when you transplant it?  The REAL story behind transplant 'shock' is NOT that the plant (or Grass) is suffering from extreme stress, but that the plant (or Grass) was abruptly detached from the special Fungi that previously surrounded its roots.

All along, those Fungi were pouring nutrition and moisture into the plant.

But when you transplant a plant, you leave the Fungi back in the Soil.  The root-Fungus relationship is broken.  The plant, or the Grass, needs time to build new relationships with new Fungi.

As for disease-causing Fungi, well, most Fungi don't cause diseases.  And the ones that do are so completely outnumbered, you never notice them, because they don't stand a chance.  Unless you give them one, of course.  And this is why you see people who are devoted to their Lawns dealing with Fungus attacks.  They don't know they're causing them, but they do.  We can talk about that another time.

For now, let's get back to our Soil discussion.  Remember, Soil needs to contain 2 things to grow great Grass:  Nutrients/Moisture and Grass-friendly Fungi.

Soil almost always has the Fungi that makes the Grass happy.  But you have to stay away from Fungicides.  And you can't use chemicals like concentrated Fertilizer or certain weedkillers (don't be surprised -- would you put weedkillers on your cereal on the morning?  If you put it in the Soil, the friendly Fungi don't have a choice with that).  Play your cards right, and they will sit there waiting for a nice Grass root to come along and say hello.  And then life is beautiful.

But what about the nutrients in the Soil?  There are HOW MANY ELEMENTS in the Periodic table?  Which ones does the Grass need?  And which ones are in the Soil?

Researchers say you need 16 minerals to grow healthy grass.  At the top of the list is Nitrogen.  Urea (CO(NH2)2) is made in fertilizer factories by combining Ammonia and Carbon Dioxide.  Urea based fertilizer is cheap and VERY high in Nitrogen.  Most packaged lawn fertilizer is Urea-based -- easy to mix with water, easily absorbed by the Grass.

But there are problems with Urea.

Urea is volatile -- VERY easy to wash away, VERY quick to evaporate.  Only hours after the fertilizer goes down, nothing is left.  The Grass gets an abrupt ZING! and then it's suddenly over.  So you have to reapply the fertilizer.  Over and over.  And because this fertilizer is a chemical Salt, it causes very negative side effects.  Use it too much and all hell breaks loose.  Bad Fungi begin their terrorist campaign.  Other diseases comea long and cause further damage.  This is no way to grow Grass.  But it doesn't stop millions and billions of people from trying every year.

HOWEVER...

If you have GREAT SOIL, WHO CARES????

You don't need fertilizer!

And this is one reason for you to get your Soil tested.  It will calculate the amount of, say, Sulfur -- which the Grass needs to make Chlorophyll.  It tells you what you have, what you don't have, and what you need to do to make it just right.

There's an excellent essay on all this at the website of The Orchid House.  It's called 'What is plant nutrition?' and you can read it here:

retirees.uwaterloo.ca/~jerry/orchids/nutri.html

I will tell you where to get your Soil tested when you provide your Zipcode.  Most local Extension services will run a test for a modest fee.

So now we assume our Soil is wonderful.  What about those Weeds and the unwanted Grass and plants?  How can we get rid of them?

Here's how:

Step 1: Mow/Hack/Pullout all vegetation above ground.  If you mow Weeds regularly before this plan of attack, they will not be at a stage where they can set Seed.

Step 2: Rototill.  This will yank out all Weeds by the roots.  Rake up stones and separate them from the dead Weeds.  You'll need a tough, steel rake and some illegal aliens to accomplish this.  Throw in a nice corner of the yard, somewhere that has no view, and build a pile of these dead things.  This is your first compost pile.  With 5 1/2 acres of Weeds and Grass, you can make 5 1/2 of these mounds, but a big one is better because it will cook faster.  Water the pile and wait for it to turn into gold.  Back to the Lawn.

Step 3:  Mix in some Pelletized Lime AND a generous amount (since money is no object) of Organic Compost and/or Humus and/or Manure from your neighbor's horse farm.  Bone Meal is expensive but terrific stuff for your future grass if you don't think the cost prohibitive.  Superphosphate does not have the lifespan of Bonemeal; it's cheaper but you'll have to reapply; it risks burning roots if not applied carefully, and it does not work as well - like eating a single healthy meal a week (Superphosphate), instead of 3 meals a day plus snacks (Bone Meal).

Step 4:  More illegal aliens now should use a large rake to even out the Soil surface.  It should be nice and smooth.  WATER the bare dirt.

Step 5:  Cover your 5 dirt with 5 1/2 acres of clear polyethylene sheets from Home Depot anchored with large rocks or cinder blocks.

I see that look on your face.  It is the look of disbelief.

Let's just take on faith that I know what I'm doing since this is way too long already and I am afraid the pc will crash before I finish my novel.

Under the clear plastic sheets from Home Depot, heat builds and builds, until it's 150 degrees in there.  The Soil heats up too.  Nothing survives.  Earthworms and Beetles wiggle away.  Anything that can, leaves.  2 months later, all Weeds and other vegetation are history.

So now we are at Step 6.  Remove the plastic.  Mix in whatever things your Extension Office thinks are missing from your Soil -- and include LOTS of Organic Matter.

Definition of Organic Matter: Compost, Humus, Aged Manure -- anything that conditions the Soil to boost its nutrition content and make it a happy place for Grass to live.

If you are not ready to put Grass down in any shape or form, at this point you put down a place-holder that will also build up your Soil even better!  Clover, Alfalfa, Crown Vetch.  My vote goes to Alfalfa, but a lot of people love Buckwheat.  It sprouts with incredible speed, and grows happily in worthless Soil.

I think that about does it.  Send you zipcode and we can address some of your other concerns.

THE LONG ISLAND GARDENER




---------- FOLLOW-UP ----------

QUESTION: Thanks for the great answer the problem is that somehow my message was confused. I am not laying on existing garden but on tile. That is, the area is currently tiled and I would like to put soil directly on top of the tile and then lay sod. Would this work? My area is on the north shore of Sydney Australia (warm with average rainfall and no frost) Thanks, Kate

Answer
Pity, because Tile will interfere -- badly -- with drainage.  And drainage is critical.

No drainage, no air.

No air, no Oxygen.

No Oxygen leads to anaerobic bacteria (leading to a number of bacterial diseases), suffocates Oxygen-deprived roots, kills your Grass.  You either have to remove the tile or install some kind of highly efficient drainage system.

Sorry, but that's the facts.  No drainage means no Oxygen.  You can't live in an Oxygen starved environment.  Neither can Grass.  Any other options here?

L.I.G.