Since you don't have underlayment, nor do you want to install it or use chemicals, you're going to have to pull weeds as Greg Barnes suggested. You can also use boiling water to kill weeds and their ungerminated seeds--it's non-toxic and effective, but a bit unwieldy.

Do you like moss? Acidulate your soil with vinegar, which will kill most vascular plants but will encourage moss growth.

Finally, you could try covering your path with black sheet plastic for several weeks. This will kill whatever is trying to grow under it by denying it sunlight and (if you're lucky) cooking it with the sun's heat.

However, with all of these methods, you're going to have to stay on top of pulling up weeds as they sprout as none of them will prevent seeds that drift in from germinating.

This probably being done by a skunk, racoon, or possum. There is a good chance it won't happen again. Flip the sod back down, water the heck out of it, and see what happens. If it is flipped over again you have two basic choices; physical control or biological/chemical control.

Physical control would be a cyclone fence or something. Very effective against skunks but racoons are a lot tougher. Possums are good climbers but seem put-off by fences.

A dog is probably the best possible/easy thing. If you don't have one you may be able to borrow one. My dog is famous for his anti-vermin qualities but he is getting old.

Bilogical/chemical control includes getting one of the various commerially available repelents and spreading it around. Or, a big, huge bag of hot pepper spice. Spread it around.

A friend on Vashon uses motion sensitive cells to turn on lights, a radio, and fans with metalic/mylar strips that freak out the dear and racoons that raid his garden and chicken shed.

Another thing worth trying is putting sprinklers on a timer so the things turn on for a few moments every couple of minutes all night. Warn the neighbors.

BTW- whatever critter it is is probably trying to root up some worms.

Yes, you can use Praying mantis for pest control.  However, be sure you have pests for them to munch.  If they don't have a food source, they will go after each other!  (I guess they don't play well together!)

I think the following information and sources will address your questions:

From Clark County Extension: . . .There are over 1800 species, mostly tropical. Three are native in North America: the Chinese mantis, Tenodera sinensis, the Carolina mantis, Stagmomantis carolina and the European mantis, Mantis religiosa.. . .  The mantis, also known as mantid is most closely related to grasshoppers and cockroaches. The common name comes from the manner in which they hold up the forepart of their body, with the front legs folded as if in prayer. They range from 2 to 6 inches in length and are varying shades of brown and green.The praying mantis is strictly a meat eater who enjoys moths, beetles, horseflies, leaf hoppers, aphids, and other mantises, even animals larger than themselves, such as frogs, lizards, and young snakes. They almost always start eating their prey while still alive and go for the neck to ensure struggling stops quickly. There is but one generation per year. In the fall, females lay eggs in a large mass about one inch long (30–300 eggs), in a frothy gummy substance that glues them to tree twigs, plant stems and other objects. A few weeks after laying eggs, the mantis dies. The eggs overwinter and tiny nymphs emerge from the egg mass in the spring or early summer. Nymphs look similar to adults, only smaller and have no wings. They quickly grow eating each other until only a few remain and become one of our larger insects. Praying mantis eggs cases are now available for purchase through catalogs, on-line, and at your local nurseries. You can raise your own prehistoric-looking bugs for cultural insect pest control. http://clark.wsu.edu/volunteer/mg/gm_tips/PrayingMantis.html

Retired King County Extension Agent, Mary Robson wrote a great article for The Seattle Times several years ago about beneficial insects and suggested contacting local nurseries--City People’s (Madison Valley), Molbak’s (Woodinville), Sky Nursery (Shoreline) or Swanson’s Nursery (NW Seattle)--or purchase on-line. Mantis’s are usually available in spring. http://seattletimes.nwsource.com/html/homegarden/2003798223_marygarden28.html

Ohio State University has a fact sheet about Praying mantis and includes a source for purchasing: http://ohioline.osu.edu/hyg-fact/2000/2154.html.

I second the Terro stations. They really are the BEST and cheap (the unfortunate part is that it will cause a bit of a swarm to start so... you've got to tolerate more before you get less).

The pro I spoke to said that the 2 big goals are
(1) to make a barrier around the house so that new ants aren't coming in: Bifenthrin or other such poison on the foundation works well. I used something I found at Home Depot. The trick here is to make sure you don't have vegetation that goes from the ground, past the foundation, right onto the house as that will allow the ants to avoid the poison barrier you just spent money to create.

and

(2) to kill the queen of any ants within your walls (boric acid is IDEAL for this).

The Terro stations are boric acid mixed with sweet stuff. The ants find the sweet stuff and then carry it back to the nest where they feed it to their queen and their homebound compatriots. Then they all die. Yay!

Boric acid by itself can be a deterrent when applied in large quantities (they won't cross it if they can help it). In smaller quanitites they walk right across it, it gets stuck to their bodies and they take it back to the nest with them where they die and take others with them. Yay!

I've found that the ants in my house eventually grew tired of the Terro stations. It seems like the near decimation of their nest triggered some kind of flavor craving change. I was still seeing scouts and other random ants, but they just weren't interested in the Terro. So I poked around the internet until I found a place that sells the gel baits that the pros use (I used optiguard but there are several others). I put some gel bait out and that perked their interest in poison again. I haven't seen a single ant since.

Other things I did:
Unscrewed all the power outlet covers and "puffed" boric acid into the space between the walls. I even pulled out the canned lighting things and puffed boric acid into the ceiling space. Basically I put boric acid any place where neither I nor my animals would encounter it --> into the walls, under carpet, and behind the fridge.
I put cinnamon under all my cupboard liners (they don't seem to want to cross cinnamon, and it's not toxic to me or my cats).
I started pouring all my used coffee grounds into the flower beds around the house (don't know if this really works but it certainly didn't hurt).

Other miscellaneous info:

In some types of ants (odiferous, sugar ants), squashed ants release a chemical that tells other ants to send more troops. So squishing can actually attract more. Sweeping, wiping, vacuuming (into a boric acid filled vacuum) or running down sink is what I did. And yes... I occasionally squished.

Some ants tastes change in the autumn to favor fats, and proteins over sweets. There is bait for that too (advantage among MANY others). ;)

It took me about a month to get rid of my SEVERE ant problem. I can now leave cat food out without problems now... so I call it a success.

Diatomaceous earth is supposedly really great. I found it messy and to use it well seems like it requires more attention than I have available. It is however a great alternative for folks who are averse to poison. You can eat diatomaceous earth as a digestive supplement if you're so inclined. I am not. I say: Yay poison! That said, boric acid, though I personally wouldn't want to eat, it is supposedly non-toxic. I suspect Bifentherin is manufactored in hell... which is where I want to send my ants.

You didn't mention what type of flowering plant you have in your apartment?  So, here's my recent houseplant aphid experience; I hope this info is helpful--at least it's another approach to consider.

I recently purchased a Meyer Lemon tree and immediately spotted APHIDS! I want lemons, not insects!! The tree, which had been in a nursery greenhouse, was brought into my house, and, most likely, with the change in environment, the aphids appeared. Once I noticed, the aphids, happily feasting on several leaves and flower buds, I took the tree into the shower and sprayed off the pests--(Note:  you must spray the top and bottoms of leaves). After trying this for a week, I decided to take more action. I visited the nursery where I purchased the tree, explained the problem, and was told to "spray the tree with water" to knock off the aphids. Since I had been doing this for a week, I talked it over with the nursery manager who agreed I should try an insecticide safe for use on a fruit tree. I purchased "Green Light NEEM II." This insecticide is registered for use on fruits, nuts, vegetables, herbs, spices, roses, houseplants, flowers, and shrubs. The label recommends spraying every 7-14 days. I plan to take a more conservative approach. I sprayed the tree outside, carefully spraying the entire plant--top and bottom of all leaves, buds, and flowers, and allowed it to dry before bringing it back inside.  Since spraying 2 1/2 weeks ago and I have seen no pests and will avoid spraying again unless absolutely necessary. I also repotted the tree with new potting soil and a slightly larger pot.

As a way to prevent further problems, I am practicing good plant hygiene by picking up fallen leaves and flowers, misting the tree to encourage good humidity, and watering the appropriate amount each week.  For now, I have the tree isolated from all other houseplants to avoid a mass infestation.  

Would I bring in beneficial nematodes or other predators for houseplants?  No.  If you decide to spray, make sure you select a product that is recommended for the pest you are trying to control (aphids) and make sure the label says the product is registered for use on your plant.  Well, I hope this helps!  

Danger, I believe Earwigs are feeding on your sweet basil. Earwigs are reddish-brown insects about 3/4" or less in length. Both males and females have pincers at the rear end. Earwigs are largely beneficial, feeding on many pests such as aphids (including apple aphids), mites, and nematodes, as well as on algae, fungi, and decaying plant material. However, earwigs can also damage plants. They sometimes feed on flowers (such as Dahlias), shoot tips, or leaves. Damaged shoot tips may fail to develop properly, sometimes stunting growth. Damaged leaves exhibit small to large holes.

So, what to do?  Here's an old, tried and true, remedy to get rid of these pests. Place wet/moistened newspapers around the base of the plant—burlap bags or flat boards also work in the garden—to monitor and trap the earwigs. Earwigs prefer narrow, enclosed hiding spaces. In the morning the earwigs will likely be in the newspaper and can be destroyed when the material covering them is removed. Be vigilant. You'll want to do this every evening and removed the newspapers each morning. There are some insecticides registered for use, but I’d try this old method first. Good luck!  I hope this helps.

P.S.  Dahlia lovers often place cut flowers on newspapers before bringing them into the house to get rid of earwigs.  -MG Andrea

Ivy and horsetail are tough plants to eradicate, as I imagine you already know.

There is some useful information on the web about ivy, including these tips from the Washington Native Plant Society's Ivy OUT and King County Noxious Weed Control. Local garden writer Ann Lovejoy said in the Seattle Post-Intelligencer:

"To safely and steadily get rid of ivy, begin by cutting all vines... If you miss a few stubborn scraps here and there, don't worry about it. Just be sure that none of the vines remain uncut or are left dangling. Now remove all ivy at ground level by pulling strands and prying roots with a small hand-mattock or hori-hori (Japanese farmers' knife). Even if you miss a few roots (as you will), they won't all sprout back. Finally, mulch with a combination of woodchips and compost if you plan to replant soon. If you just want to keep the ground clear for a while, use coarse wood chips for mulch. To keep the mulched area clear, check it two or three times a year. You can quickly remove any new shoots that appear, along with as much root as possible."

The same basic techniques will work for horsetail. The Garden Answers Knowledgebase at millerlibrary.org has the following suggestions:

Here is an article from Oregon State University Extension Service

Here is what Ciscoe Morris said about this plant in the Seattle P-I (April 29, 2006):

"Hands down, horsetail (Equisetum arvense) is the worst weed you can get in your garden. If you've got it, just be glad you weren't gardening in prehistoric times. Back then, horsetail grew to 90 feet tall and you were in danger of being stepped on by a brontosaurus while weeding.

The worst thing about horsetail is the speed with which it returns to make your life miserable after you weed it. No matter how great a weeding job you do, it will be back, practically to full size, within a week!

Do what we did at Seattle University. Plant a mix of shrubs, ground covers and fast-growing perennials that are thick and tall enough to hide the horsetail. Shrubs that hide horsetail include Cistus (rockrose) Lonicera pileata (privet honeysuckle) Lonicera nitida (Box honeysuckle) and rosemary. My favorite perennial to hide horsetail is the prolific hardy Geranium oxonianum 'Claridge Druce.' It will seed all over your garden, but new seedlings are easy to remove in spring. These drought-tolerant plants look great in their own right and because they are so thick and tall, no one will see the hoards of horsetail growing within."

Washington Toxics Coalition recommends controlling it by persistently hand-pulling or hoeing the above-ground growth as soon as it appears. This will weaken the plant over time. It does die back over winter, when you could cover the affected area with black plastic (for a duration of 2 years), but even this may not be entirely successful.

An article by Irene Mills in the Fall 2008 issue of the Northwest Perennial Alliance's Perennial Post says that pulling, digging, and covering with black plastic are a waste of time. The author recommends keeping an eye out in April for emerging spore-bearing stalks, and cutting these off and disposing of them in the garbage. She suggests improving the soil texture (improve drainage, add organic matter, increase soil fertility, and in some cases increase soil pH). She recommends this guide called "Controlling Horsetail" from Swanson's Nursery, originally published in Gardens West by Carol Hall.

Alternatively or in combination with other methods,you might try sheet mulching. Here is a description of that process, written by one of my colleagues here at the Miller Library:

"The general idea is you spread out a layer of cardboard or newspaper (about 4-6 sheets) and then cover that with a layer of organic mulch (compost, straw, alfalfa hay--available at feed stores, wood chips, coffee grounds, etc.). Then wait 6-8 months. This is not an exact science because there are many variables, such as thickness of newspaper, type of mulch and what type of plant you're trying to kill. Perennial weeds and especially coarse grass will push through the cardboard once it starts to break down so it is critical that if and when this happens you pull the mulch back and put down more newspaper/cardboard, and then replace the mulch."

Tom is correct, Horsetail does not like to be controlled!  I’ve also read prehistoric Horsetail grew to enormous heights. I guess the Horsetail we see all over the PNW could be worse. 

 A neighbor tried spraying vinegar but had little success in eradicating this annoying weed.  

Some facts: Horsetail grows as a perennial (comes back every year) with a creeping root system (rhizomes). Horsetails are found primarily in moist to wet areas, although once established, horsetails can thrive in drier conditions. In Oregon, Horsetail is considered a noxious weed. The worse thing about Horsetail is that once you think you've completely cleared it away, it appears again almost overnight.

 Washington State University’s Hortsense recommends an Integrated Pest Management (IPM) approach (http://pep.wsu.edu/hortsense/. 

First try Mechanical controls such as:
1. Inorganic mulches, such as plastic, commercial "weed barrier" fabrics and other materials such as roofing paper, is an effective weed management option. Cover inorganic mulches with a thin layer of soil or organic mulch.
2. Maintaining a healthy planting or turf area to provide competition will prevent weed establishment.
3. Reduce weed infestation by handpulling weeds.

If you must use pesticides,  WSU Horstsense lists one possible control--dichlobenil (Casaron trade name). Hortsense states, “Apply (pesticide) in winter or early spring when soil is cool and moisture is available. Bark mulch may be spread over treated area to reduce volatilization. There is a product available to professional applicators which can be applied to turfgrass in severe cases.”

I caution the use of any chemical, especially when it comes to such a determined weed as Horsetail.   You will often see it growing near roadsides and or next to streams.  I don't want to apply any pesticide that could get into our storm drains and streams.

In my garden, I maintain some control hand-pulling or mowing and I continue to try to improve the drainage and plants with desirable shrubs to shade out the undesirable Horsetail. I wish I could be more encouraging!  (P.S.  Years ago I spoke to a homeowner who had moved here and wanted to know where he could buy that pretty plant he saw all over.  Turns out it was Horsetail.)

Here's the sorry truth: you can't get rid of ivy. Ivy is the source of all the evil in the world; the roots go down to the center of the earth, where they lie in wait for opportunities to put out new shoots.

There's a few things you can do for mitigation, though. First off, strip it off of everything and haul it away. Be aware that ivy is one of those magic plants that can reroot itself from any fragment, so if you leave a bit lying around -- a leaf, a stem -- it will turn into a whole new ivy plant. See what I mean about evil?

You'll hear people say "oh, just cut it and the part above will die". Not really. And even if it does, it's still weighing down your building and trees and whatnot, and blocking their light. You want to get it all out of there.

Next, start going back to the roots. Ivy is spectacularly good at winding its roots around things, including other plants and trees, parts of your house, rocks, and whatever you've got. Follow ALL of those strands back, and dig down, and kill as much as you possibly can. Kill, kill, kill. Note that some of these roots will be as large as your arm or leg. KILL THEM.

If you can afford to have your yard look like a dump for several years, you can really do a lot of damage to ivy by putting down black plastic and several layers of cardboard to completely block out all the light. Ivy needs light to survive. But you have to leave it there for FIVE YEARS, and be vigilant about the new growth that will magically appear at the edges.

If you can't do that, you're going to have to face the fact that it WILL be back. At least once a year, go back and zap any and all new vines you see a-creeping, and follow them back to their source, where you will inevitably find new, larger root systems that you missed before.

Killing ivy is not a destination but a journey, in other words. Two hundred years from now when you and I are long gone, and possibly even human civilization, the spot where your house was will be marked by a towering mound of ivy. I guarantee it.

I think that is caused by spittlebugs, also known as froghoppers. They excrete a foamy substance to hide themselves from predators. They feed on plant sap, but are relatively harmless.

http://gardening.about.com/od/insectpestid/a/Spittlebugs.htm

Sounds like you've found some Lycogala! Common name is wolf's milk slime mold or toothpaste slime.

Does this look like the blobs in your garden?
http://en.wikipedia.org/wiki/Lycogala_epidendrum

(Might not be that particular species -- any local mycologists want to comment?)