Yes, ingestion of poppy seed bagels or poppyseed cake can indeed cause a false positive on a urine test for opiates. Ingestion of poppy seeds can result in a positive drug test as long as two days after ingestion. According to the myth-busting website snopes, "as little as a single bagel covered with poppy seeds could produce a false positive test for these drugs".
They are many and all of them beautiful. Deciding which type to grow is up to you, and your environment for growing be it indoors or out, hot and dry or wet and cool.
The poppy belongs to a family of plants called "Papaveracea". There are about 200 species that belong to this family of plants. The most famous, naturally, is the species "papaver somniferum" which produces Opium, from which Morphine and Codeine are extracted for use as an analgesic narcotic in the treatment of mild to severe pain.
Papaver Somniferum, aka the Opium Poppy, is a hardy annual that can grow almost anywhere in North America, Europe, Asia, and Australia. There are many different species of papaveraceae, but none is as prized as the somniferum, for both its beauty and its seeds, which are used in baking and in the production of cooking oil. It is striking in appearance, with stunningly colourful blooms, and stark mournful pods. Its pods are often dried and used in flower arrangements. Papaver Somniferum has also been used medicinally for centuries; as a painkiller, muscle relaxant, diarrhoea remedy, and intoxicant.
California Poppies are not Papaver, and therefore do not contain any of the familiar alkaloids that are present in strains such as the Somniferum.
According to American folk medicine herbals-they were used by the native americans-the sap for toothache-tea for colic in babies-used for mild pain as a tea or soaked in hot water then used as a compress.
Used by pioneers to treat insomnia, nervous disorders, pain, muscle spasm. Also a diuretic because of its affect on cramping pain, water retention and anxiety. It was used by women for menstrual distress.
It has been suggested that it can be smoked as a legal sort of high, but it is unlikely that you will get any noticable effect.
The short answer is No. Poppy seeds themselves are inert, and contain no alkaloids.
The long answer on the other hand, is well... kind of. It is possible for sap to "leak" on to the seeds from inside the seed pod, coating them with miniscule amounts of alkaloids. This is documented in the many cases of positive drug tests resulting from the consumption of poppy seed food products.
Some people have tried soaking large quantities of poppy seeds (several hundered grams) in water, lemon juice etc, and then drinking the liquid the seeds were soaked in. Mild effects have been reported as a result. Often as not though, those who have tried this method have reported back no effects at all. While it has been argued that It could be just a placebo effect, this is likely not the case. It is not recommended that anyone try this looking for a cheap "legal high" -- there has been at least one recorded incidence of a young man dying after consuming poppy seed tea. So beware.
In the end, most people tend to think that even if minor effects can be obtained, given the massive quantities of poppyseed required it is not worth the hassle, waste, and potential exposure to other unknown substances in the seeds.
As with any substance used medicinally or recreationally, poppy tea may trigger or exacerbate a number of unwanted effects in a user. These possible side-effects range in severity from mild to deadly serious. Relatively small dosages may induce dizziness, nausea and sedation. Many people experience itching. Constipation and urinary retention is not uncommon. Overdoses may result in respiratory depression and cardiac arrest. Alcohol should be avoided because it can greatly enhance the chances of experiencing these more serious adverse events.
All ethnobotanicals, including poppy tea, should be treated with great respect.
Chances are, you won't. The only guaranteed way to avoid addiction is not to start in the first place. But if you can't or won't do that, then at least try to limit yourself to only using once or twice a week. These alkaloids will build up in your system and stay there for 24 to 48 hours, so using every other day is going to get you into trouble real fast. If you have been using for awhile, try to taper off gradually to reduce the amount of alkaloids in your bloodstream, this will also lessen the withdrawal symptoms somewhat. It takes a strong willed person to be able to resist the temptations of Mother Opium, but if you don't, she will teach you a harsh lesson, one that you won't soon forget. She will have a pound of your flesh, and many more of your sanity. Can you say "Weekend Warrior"?