It varies with some varieties but as a GENERAL guideline, no. Most seeds require a period of dormancy before they will germinate and in most cases they will either dry during that period or will mold and rot. Obviously there are some exceptions. Further some seeds require a period of cold stratification (cold storage) before they will germinate.

But the one thing that is required for germination is that the seed must be mature, the embryo must have been pollinated, developed and matured to germinate.

In most flowers for example (like hibiscus), that means dried on the vine. In some fruits a fresh seed, if mature will germinate IF it doesn't rot first. Coffee beans are usually picked green so are immature seeds.

You can read more about this in the FAQs over on the Saving Seed forum here as the FAQs there list the seed harvest time for many things for best germination odds.

Dave

Seeds are often divided up into orthodox and recalcitrant categories. Many vegetable and annual flower seeds, for instance, are orthodox. This means that the seeds can be dried out pretty well and stored, usually for quite some time. Many perennial and woody plant seeds are recalcitrant. That means they should not be allowed to dry out. Recalcitrant seeds will often die fairly quickly if allowed to dry out very much. An often ignored category is the many seeds that are somewhere in between. Intermediate seeds show characteristics of both orthodox and recalcitrant properties. These seeds may, for instance, remain viable when dried but enter into a deeply dormant state, requiring various methods to "wake them up". A deeply dormant seed might, for instance, require a period of warm-moist stratification followed by a period of cold-moist stratification. In some cases, starting out with fresh (never dried out) seeds and putting them into cold-moist stratification can allow one to skip the warm-moist stratification period.

There are many seed germination guides, and I would recommend using them to determine what treatment is appropriate for any particular type of seed. A few include:

Ontario Rock Garden & Hardy Plant Society Seed Germination Guide

Tom Clothier's Germination Database

Gardener's Supply Seed Germination Database

Backyard Gardener Seed Germination Database

KL Stuart's Seed Germination Database

Trade Winds Fruit Seed Germination Tips

Thyme Will Tell Seed Germination Database

thank you for the comments, i was actually asking specifically about hibiscus and coffee which i recently gathered from a fruit farm, both of these seem to be ripened but are fresh.

For the specific examples you gave to your more general questions, I would recommend a quick Google search after properly IDing the species. The reason I say that is that a lot of information can be obtained without us having to re-write it all here. The coffee part of your inquiry can be answered by simply Googling 'coffee see germination'. I tried that just to be sure, and lots of great info popped up on the first page of results.

The hibiscus might be a little different. There are many different species of hibiscus ranging from tropical plants to quite hardy trees. After you figure out what you have, try Googling the species name plus the word germination, or look it up on one of the reference sites I linked above. The reference sites may give you a quicker answer IF the plant in question is included. Google may be more likely to give you an answer if the plant is not one commonly grown from seed (so not in the quick references).