Is it Bed Yet? An epilogue to bed prep by smothering.

We have a large yard, new to us. As professional gardeners we have little time for our own gardens. So to make big new beds we trade waiting time for labor hours. The bed behind the blue line was smothered two years ago and extended last year by smothering. The bed on the left is just being readied to smother.

We have a large yard, new to us. As professional gardeners we have little time for our own gardens. So to make big new beds we trade waiting time for labor hours. The bed behind the blue line was smothered two years ago and extended last year by smothering. The bed on the left is just being readied to smother.

One way to prepare a new garden or renovate an old one that has become filled with run-amuck perennials or weeds is to smother the area. (We gave you the blow-by-blow of this process in What's Coming Up 95. It's a pdf. Download it to read pages 6-7.) Where there is no hard pan that requires loosening, when we can afford the waiting time and if we do not want to physically remove the sod, smothering is the way to go.

It is time for us to check on beds we smothered last year to see if they are clear of weeds and ready to plant.

It is also time to add some footnotes to that What's Coming Up 95 article. Clarifications based on questions and variations. So, first, the back story on this bed we are checking:

Smothering process

We smothered lawn last June. We separated the smother area from the adjacent lawn by digging out sod along the edge. That trench slows or stops roots from without from growing into the smothered area and vice versa.

The sod we dug out to make that trench - we laid it upside down within the smother area.

Next we laid newspaper over the smother area, like so: Open a newspaper section wide, add or remove pages as needed so it is 4-5 full sheets in thickness. Lay it on the ground. Open another section and lay it down so it overlaps by half with the first section. Continue, laying out a row of paper then doubling back to make the next row, always overlapping neighboring papers by half.

See the trench made by lifting out sod along the edge of the smother area? That sod is upside down now, right of the trench.

See the trench made by lifting out sod along the edge of the smother area? That sod is upside down now, right of the trench.

In this smothering operation we knew the plants in the bed would not die so quickly as plain lawn grass. This bed area had in it the tall field grass called Johnsongrass. You can see it in the upper right corner. It's a tough customer.

In this smothering operation we knew the plants in the bed would not die so quickly as plain lawn grass. This bed area had in it the tall field grass called Johnsongrass. You can see it in the upper right corner. It's a tough customer.

What happens under the paper

It's important to overlap. What the paper does, besides block light from reaching the plants we are smothering, is that it forms a physical barrier to plants trying to push up. The paper layer forces the plant to lay down and grow horizontally, using up stored energy as it grows in the dark, seeking the warmth that means "sun above." If the papers do not overlap, plants find that warmth where two papers meet, turn up and emerge.

In smothering last year's new beds we did run out of paper at one point. Then we used yard waste bags. We cut them to lay flat, one bag covering a 4' x 4' area, and overlapped them 12" on all edges with neighboring papers or bags.

In smothering last year's new beds we did run out of paper at one point. Then we used yard waste bags. We cut them to lay flat, one bag covering a 4' x 4' area, and overlapped them 12" on all edges with neighboring papers or bags.

Keep the smothering layer in place

While laying paper we kept a bucket of mulch at hand, placing a double handful of mulch on each paper to keep it in place. Wind always tries to undo papering.

Some people wet the paper to make it stay down. We are often working in cold weather and always crawling about on the paper layer. Wet paper, not for us.

On top of the paper we dump mulch 3 to 4 inches deep. That holds the paper down and blocks more light. In the previous photos the papered bed is waiting for its deep blanket of mulch. In this case the mulch was fresh chips from the tree removal crew that took down a nearby maple.

What ever happened to earth-tone tarps?!

What ever happened to earth-tone tarps?!

No mulch or paper?

A heavy tarp that does not let light through can work. Weight it with stones. Beg the neighbors' tolerance. Caution: Many plastic tarps do let light through and plants can live under them. To test it, hold up the tarp. Have someone shine a flashlight on the opposite side. If you see the light, that's not a good smother tarp.

If we use a tarp, we accept looking at that tarp for a year, rather than cover it with mulch. Moving all that mulch aside when it's time to remove the tarp is more work than we care to do. And don’t even talk to us about putting down fabric as a smother, and leaving it there. You have not been listening at all if you don't know that we feel landscape fabric is one of the worst things anyone can do to a landscape.

Cardboard can work as a smother layer. It takes much longer to break down than paper so you may find yourself cutting through cardboard at planting time.

We used cardboard on daylilies at one of our Detroit Zoo beds. We dug out many daylilies first, but knowing there were still viable roots in the bed, we laid down cardboard and mulch. The daylilies found openings - or maybe they created openings, the darned creatures. So we took to digging those as they popped through. 15 months later we were able to replant the area.

Mulch over cardboard over the wild groundcover variety of daylily.

Mulch over cardboard over the wild groundcover variety of daylily.

We could have smothered the daylily area and then applied herbicide to survivors as they appeared. We prefer not to handle herbicides so we find other ways.

Even after a year under cover the "ditch lilies" continued to pop up. We broke the tops off for a few months - done religiously this can starve the roots. However, we tired of that game while the daylilies were still coming. We dug out the survivors.

Even after a year under cover the "ditch lilies" continued to pop up. We broke the tops off for a few months - done religiously this can starve the roots. However, we tired of that game while the daylilies were still coming. We dug out the survivors.

When there is a rock edge on a bed, we smother the rocks as well as the bed. We will have to dig the rocks out later but if we don't cover them the weeds under the smother will just squib out between the rocks.

This rock-edged bed also had a woody weed in it - ivy. We cut it off at the ground and carted away the debris before smothering. A smothering layer must be pretty tight to the ground to succeed. Woody vines and stumps create pockets where plants survive and lift the cover.

This rock-edged bed also had a woody weed in it - ivy. We cut it off at the ground and carted away the debris before smothering. A smothering layer must be pretty tight to the ground to succeed. Woody vines and stumps create pockets where plants survive and lift the cover.

How long must we wait?

Smothered by May, we figure we can plant the following fall. Smothered by September, we set our sights on the next May for planting.

If you just can't wait, well, that happens. We have often planted the main features ahead of schedule, this way: Smother as long as the gardener can stand. Agree on just a few things that will go in earlier than is best. Rake the mulch away in a circle at least three times as wide as the root ball you will plant, cut out the paper layer. Dig through the soil there and remove still-live roots.

How to know a live root? Can you tell usable carrots from way-past-use-date carrots in your crisper drawer? Firm and normally colored is usable. Limp and discolored is compost. Same for roots. Firm and white, watch out!

We raked away the mulch, then cut the paper layer - it's on top of the black plastic.

We raked away the mulch, then cut the paper layer - it's on top of the black plastic.

All the lawn grass has died and decomposed yet there are still living quack grass roots.

All the lawn grass has died and decomposed yet there are still living quack grass roots.

Some situations call for longer smothering. The most tenacious weeds and running perennials may lie dormant a year or more and then emerge.

We smothered a bed filled with Japanese anemone (Anemone x hybrida) last August that may not be ready until 14 months have passed. We did dig the bed first to remove all we could of those devilish roots but we know some remain.

If we dig and then smother bindweed, the bindweed may have so much energy stored in remaining roots that the vines can grow in the dark all year and even reach the edge of a big smothered area.

Spring tough guys such as lily of the valley and bulbous weeds such as wild onion, grape hyacinth (Muscari armeniacum) and star of Bethlehem (Ornithogalum umbellatum) can lie under smother all of summer and fall without effect. They will only begin to use up energy and start wasting away the next spring. They may or may not be dead 18 months later.

Notice the plywood covering part of this bed. The lily of the valley that filled this area put up that much of a fight, that we dropped  a board over the most tenacious plants.

Notice the plywood covering part of this bed. The lily of the valley that filled this area put up that much of a fight, that we dropped a board over the most tenacious plants.

Is the wait over?

We smothered this particular lawn ten months ago. Good bluegrass or fescue should be dead. However, quack grass and Johnsongrass live there, too, so we will take no chances. To learn if we can plant, we raked away the mulch in an area, cut through the paper and soil and checked for live roots. If there are none we are good to plant. Check it out in the video on our Youtube channel, Get Ahead in Early Spring, part 7.

(Spoiler alert: Woo hoo! We can begin to plant!)