Today is the first day of spring, and the first buds and flowers are starting to appear. Here to explain the diversity and scientific complexity of flowers and how to cultivate flower gardens are Dr. Amy Litt, Director of Plant Genomics and Cullman Curator at the New York Botanical Garden, and Kristin M. Schleiter, Curator of Herbaceous Collections and Outdoor Gardens, at the New York Botanical Garden.

Friday the 13th is a date that makes some people cringe. Where does superstition come from and why are people all over the world prone to superstitious beliefs? We’ll be joined by Dr. Edmund Kern, Associate Professor of History at Lawrence University and by Stuart Vyse, Professor of Psychology at Connecticut College.

Petroleum (and all of its byproducts) have shaped our world into what it is today. Discover where oil comes from, how it’s refined and how much of it is left in ground on this week's Please Explain. Dr. John B. Curtis is Professor in the Department of Geology and Geological Engineering at the Colorado School of Mines. Dr. William Fisher is a Professor in the Department of Geological Sciences and Bureau of Economic Geology at the University of Texas.

It may seem like common knowledge that taking vitamins is good for you, but over the last few years several studies have failed to show that vitamin supplements help prevent chronic disease or prolong life. In fact, things like vitamin C, can actually help cancer cells grow. We’ll be joined by New York Times Health Columnist Tara Parker-Pope and Dr. Gery Deng of Memorial Sloan-Kettering Cancer Center’s Integrative Medical Services.

Feeling Blue? Green with envy? Why not try putting on some rose-colored glasses. On this weeks Please Explain learn how color can have a tremendous effect on your mood. Dr. Andrew J. Elliot studies how we respond to color at the University of Rochester. Dr. David Brainard is professor of psychology and studies human vision and color perception at the University of Pennsylvania.

More than 35 million people are looking for love right now on the internet. The demand has led to an explosion of internet dating sites. Jennifer Gibbs is an Assistant Professor of Communications at Rutgers University. Gian Gonzaga is a research scientist at eHarmony Labs and the UCLA Interdisciplinary Relationship Science Program.

Weigh in: Have you tried internet dating? What was your experience?

From superstition to simple probability, luck has different meanings in different cultures. We’ll find out why whether that lucky charm really can help you win the lottery. Richard Wiseman is a psychology professor at the University of Hertfordshire and author of the book The Luck Factor. Jeffrey Rosenthal is a professor in the Department of Statistics at the University of Toronto. His book is Struck by Lightning: The Curious World of Probabilities.

Nearly a third of all NYC households are infested with cockroaches. We find out all about roaches, and why they’re among the hardiest species on the planet! Urban entomology specialist Eric P. Benson is a professor at Clemson University; Richard Cooper of Cooper Pest Solutions says he has a “passion” for cockroaches and ways to kill them.

Please Explain is all about cold - which many of us may have been feeling lately, with high temperatures rarely going above the 30s lately here in NYC! Dr. John Castellani is Research Physiologist with the US Army Research Institute for Environmental Medicine. Dr. David Phillips is one of Canada’s best-known climatologists.

Please Explain is all about our modern food systems, and how food gets from the farm to the table. Susanne Freidberg is associate professor at Dartmouth College and the author of the book Fresh. Rich Pirog is associate director of the Leopold Center for Sustainable Agriculture.