Oil production in the United States peaked in 1970; North Sea oil peaked in 1999; since then both have been in decline.  While industry opinion has long held that the global peak of regular oil would occur in 2010, the Association for the Study of Peak Oil and Gas considers it already to have happened—in 2003.   New Scientist magazine recently placed the year of peak production in 2004.   The measurement by which these projections are made is essentially the ratio between reserves and rates of extraction.  As China, India and Brazil move toward first world status, thereby driving demand ever higher, that rate of extraction will increase.  As to reserves, geologists say there are no more big fields to be found: Ghawar, the Saudi’s massive super field, is dying and there will never be another like it.  Matthew Simmons, a Houston energy analyst and banker at Simmons & Co. International, which includes Halliburton and World Bank among its clients, and who served on Dick Cheney’s secretive energy task force, claims that Saudi Arabian oil production is already in decline.  The world’s known reserves are being drawn down at four times the rate of new discoveries.   In the know, the big oil companies are spending less and less on exploration.
Eventually, maybe as soon as fifteen years, maybe as long as forty, we will be out of oil.  Those expecting Science or Technology to come up with a convenient substitute source of energy shouldn’t hold their breath.  Certainly, there are other means of generating electricity.  Chances are good that we will be able to keep the lights on and the internet up without oil, maybe even without coal.  But some of the other benefits petroleum bestows, such as cheap (some might say profligate) transportation, will be harder to replace.  There is nothing as energy dense as petroleum, particularly in terms of the energy required to effect its release.  We will replace petroleum, but not at anywhere near the same low costs.  
The loss of cheap transportation will likely benefit those flower growers whose marketplace is nearby.   It will definitely pinch those brokers relying on crops grown hemispheres away.  But we have more to thank petroleum for than just our lights and our rides.  Petroleum distillates have fashioned our everyday merchandise.  A partial list of petroleum products includes ink, dishwashing liquids, paint brushes and rollers, telephones, toys, unbreakable dishes, insecticides, herbicides, fungicides, antiseptics, insulation, fishing rods and lures, deodorant, linoleum, tents, refrigerator linings, floor wax, shoes, electrical tape, plastic wood, glue, trash bags, soap dishes, skis, hand lotion, clothesline, dyes, soft contact lenses, shampoo, panty hose, cameras, food preservatives,  combs, transparent tape, anesthetics, upholstery, dice, disposable diapers, house paint, awnings, ammonia, safety glasses, hair curlers, vitamin capsules, movie film, rubbing alcohol, credit cards, to name just a few.
Many of these, you say, you can live without.  But some you cannot, or at least people you may love cannot.  Fortunately, most of these products could be made from plants.  There is an enormous world of chemistry with its roots in the soil.  Of course, someone will have to cultivate those plants.  Maybe you could.
The plants that produce the most chemicals tend to be those that evolved in harsh or competitive environments.  They did so to discourage herbivores by being bitter or even toxic.  They might have been seeking purchase on mean soils and so became allelopathic to  ward off competition.   Perhaps the forest got rainy and they wanted to abstain from rotting.  Or maybe they just wanted to beguile an unlikely pollinator.  The overwhelming majority of these plants evolved in tropical or subtropical climates where there was no opportunity to take a break, because there was no frost to crash insect populations or send megaherbivores into hibernation.   Nevertheless, many can be cultivated in temperate latitudes (and as we increase coal generation of electricity and those latitudes become heretofore temperate, there should be even more).  
We are seed eaters.  Wheat, soy, corn, rice, and several others compose the dietary staples of most of the world’s population.  These are generally grown in gigantic monocultures, making them susceptible to massive infestations by herbivorous insects and mutating microbes, as well as competition from weeds.  Given this paradigm,  pesticides are necessary to maintaining a steady global food supply.  The planet will not transition to sustainable agriculture overnight.  Without pesticides, there will likely be a period of massive starvation.   
Here are some pesticidal plants you might be able to cultivate:

Acorus calamus, sweet flag, Araceae, hardy perennial, Mediterranean, semi-aquatic, insecticidal, oviposition-inhibiting, S.E. United States.  It inhabits perpetually wet areas like the edges of streams and around ponds and lakes, in ditches and seeps.  Leaves used as insecticide in Appalachia, India, Ceylon, China.  Vapors from roots as repellent.

Aleurites fordii
, tung tree, Euphobiaceae, tree, subtropical to temperate, western China, broad-spectrum insecticidal.
Azadirachta indica, neem, Meliaceae, repellent, insecticidal, antibacterial, antifungal, antifeedant, oviposition and growth inhibiting, and crop and grain protectant (Prakash; Rao, 1997: pp. 35-103) India.  A wonder tree.
Chenopodium ambrosioides, epazote, Mexican tea, Chenopodiaceae, annual, repellent, tropical Americas.  Anthelmintic.  Fruit contains substances toxic to corn weevil, Sitophilus zeamais, (Tavares, 2003).  The plant is used as a fumigant against mosquitoes and is also added to fertilizers to inhibit insect larvae.  Bown. D. Encyclopaedia of Herbs and their Uses.  Propagates easily from seed, likes moderately fertile soils, full sun, tolerates pH range from 5.3 to 8.2.

Derris spp
., poison vine, Fabaceae, perennial vine, Contact insecticide (Prakash; Rao, 1997: pp. 154-163) India to Indonesia.  Primary source of rotenone.

Euphorbia tirucalli, pencil tree, Euphorbiaceae, shrub/small tree, insecticidal, repellent (Prakash; Rao, 1997: p. 180); Tropical East and South Africa. One common name is petroleum plant.  Back in 1976, Nobel chemist Melvin Calvin was quoted as saying that E. tirucalli might be capable of producing 10 to 50 barrels of oil per acre per year (Maugh, 1976). “The latex is used as insecticide, as a mosquito repellent and as a fish poison.” –webpage, College of Science and Mathematics, James Madison University.   “Take a mature branch of the plant and pound it finely.  This paste is dipped into a 10-litre container filled with water and allowed to extract for some time.  The solution is filtered and ready to be sprayed for control of aphids, termites and leaf blight.  For control of cutworms 10 drops of oozing sap from a cut branch were collected, added to 1 litre of water and ready to use.” –Natural Crop Protection in the Tropics by Gabriele Stoll.  Tanzania (Zanzibar): “In 1992 they began work on E. tirucalli. Leaves and seeds are soaked in water and sprayed on the crop. Extract from this plant seems more effective than the neem products and does also control rice beetles (Latin name not given). Extracts from tobacco have shown some, but limited, effect. Leaves from E. tirucalli are spread around houses to protect against army ants.”

Gliricidia sepium, madre de cacao, Fabaceae, tree, insecticidal, repellent, and rodenticidal, Central America.  Acid soils with low to medium fertility; could find no science, only folklore. Pods quite commonly used as rodenticide, may be the ultimate agroforestry plant.

Pachyrhizus erosus, jicama, yam bean, Fabaceae, insecticidal, antifeedant. Mexico and Central America. Seeds and pods contain rotenone.

Physostigma venenosum, calabar bean, ordeal plant, Fabaceae, perennial vine, insecticidal, Africa.  Carbamates are based on compounds from these beans.

Quassia amara,  bitter ash, Simaroubaceae, tree, insecticidal. Suriname.  Several early clinical studies performed on amargo verified its traditional use as a natural insecticide.  Researchers in India have discovered larvicidal activity against several types of insects, including mosquitoes.  Many remarkable medicinal values.

A comprehensive list is available at www.ascfg.org