Weed block is good stuff. It has a myriad of uses, from keeping weeds down to backing a wall, to stabilizing soil, to, well, a bazillion things -- more than you'd think; we'll get into them. It's a material that will keep weed and grass seeds from germinating while allowing air, moisture, and nutrients to pass through to the soil and nourish the roots around your plantings.
The principle rationale behind landscape fabric is to keep weed and grass seeds from growing where they're not welcome. And how does one go about doing this? The easiest natural way is to block sunlight from getting to the seeds. If you've ever seen a yellowing patch of grass where someone has left a trash bag or tarp on the turf for several days, that's a prime example of sunlight starvation and is a good example of how the process works.
By way of a very over-simplified explanation, deficiency of sunlight is a contributing factor to chlorophyll deficit and the turf loses its green hue. Landscape fabrics facilitate this process for killing unwanted weed and grass seeds.
Let's enumerate the significant uses for the fabric:
As noted, the main uses are in planting beds, under porches and overhead decks, beneath graveled walkways and patios, et al, to starve the weed seeds of sunlight and keep them from growing.
Helps to retain moisture by minimizing evaporation.
Used as filter fabric in the construction of french drains
, where it is wrapped abound the drainage gravel, and in dry creeks
, where it is the underlay to keep weeds from growing in the rock bed.
Behind retaining walls
, to keep the soil pigments from leaching through and staining the front of the walls.
As an underlay
for water features, although I recommend that you use a double or triple thickness for this application. You sure don't want to punch a hole in the pond liner, given that you won't discover this little problem until the feature is completed and filled with water.
As a mulch
base, to keep the material from inter-mixing with, compacting, or sliding on, the soil. HINT:
if you are mulching a sloped area, I recommend that you use a woven fabric, with a higher friction coefficient
, so that the mulch has a better chance of staying put in a heavy rain. Very disheartening to see a truckload of mulch, freshly placed, slide to the bottom of a hill as the result of a thunderstorm; not that anything like that ever
happened to me.
What fabric won't
do: It won't prevent new weed and grass seeds from sprouting in the mulch on top
of your fabric. Noxious seeds come from birds, pets, or through airborne distribution. (See below for the fastest solution for existing weeds, both above and below the fabric.) The advantage here is that the fabric allows the seeds to grow only minimal roots, making it easy to yank those guys out.
Some folks use regular old plastic sheeting, in varying thicknesses, as a mulch base. It has a number of disadvantages -- mulch will easily slide on it, it generally doesn't stand up well to wear and tear, it is very susceptible to long-term sun damage, and it will suffocate the soil.
It does has a singular advantage in its use as "soil solarization," wherein you use the greenhouse effect to heat the soil and kill noxious seeds and plant pathogens. Soil solarization is a long-term process and is used to best effect when your planting plan is slated for the cool weather of the Autumn.
If you don't have the time for soil solarization, there are a number of non-selective herbicides available for weed suppression and they provide a relatively quick response to weeds in your prospective planting area. HINT: ensure that your chosen herbicide is not a "soil sterilizer" as that will prevent desirable seeds and plants from growing for a considerable period of time (like, um, a year.)
But, I digress. When you lay the fabric down, ensure that you leave no gaps between the pieces or in a few weeks the new weeds peeking through the open areas will show you the error of your ways. Be sure to overlap the edges at least a foot; to keep them stuck to the ground you can use rocks, cinder blocks, bricks, old tires, etc.
But why not use the tools designed for just such a purpose -- pins or stakes? They may have the added benefit of keeping the neighborhood homeowners association from showing up at your door wondering just what in the world you are doing with the all the plastic, junk, and rubble in your yard.
After the fabric is placed and properly pinned, it's a simple task to lay out your plantings, give them the "50 foot look" to ascertain whether they are in the proper spot and aesthetically arranged, and then simply cut a big 'X' at the plant site. Fold the flaps back, dig your planting hole, add your fertilizer and any necessary amendments, plop that baby in there, and back fill with your excavated soil.
Put the flaps back around the the base of the plant, leaving sufficient space around the root ball for watering, pin them securely, mulch the area, and call it a day. You can do the other 400 plants tomorrow!
So much for landscape fabric; at a cost of about eight cents a square foot for plastic and 11 cents for a woven product, it's a real good deal and will save you a bunch of cash in chemicals and labor down the road.