Best single source (book/web/app) for when & how to plant seeds?

I'm looking for a recommendation from an experienced gardener on the best single source - book or web or even app, I don't care - for when and how to plant seeds. Ideally each plant would have an identical, chart-like, well-laid-out page that would make it easy to determine for each Zone (or only Zone 6) based on both temperatures and estimated frost dates.

Or, even better, I could just enter my list of seeds and location, and it would compute all this for me and present me with optimal answers for my specific location, integrated and updated with weather forecasts.

All of these items for Indoor, Outdoor/Fall, Outdoor/Spring

1. The degree to which Indoor+Transplant vs. Outdoor/Fall vs. Outdoor/Spring is preferable
2. Seed stratification start time range and methods - optimal & limits
3. Seed sowing time - optimal & limits - how bad is it if it gets below a certain temp / frost?
4. (for Indoor) Transplant time - optimal & limits

My problem is that a lot of the packets and sites are both mutually- and self-contradictory and don't do a good job of specifying what exactly they mean.

For example, one seed packets suggests sowing "2-4 weeks before average last frost or late fall, cooler soil temps are preferred (55F). Stratification is recommended." Leading to questions the ideal source I am searching for would make clear such as:

1. What does 55F mean - some statistical function of high and/or low temperatures over some time span, average soil temperature at some unspecified depth (does any weather site actually provide this info?), something else?
2. Does "55F is preferred" mean the plant will do a lot better when you plant the seed at this temp, or if you plant it earlier will it just wait until it's more around 55F?
3. Why the hell would it suggest planting the seed 2-4 weeks before last frost, when temps are in the range of say 24F-40F, right before stating this is really non-optimal.
4. What are the cases when you need to do stratification? I'm guessing you wouldn't need to if planted 2-4 weeks before average last frost but would if freezing temps are no longer happening, but it doesn't state this.
5. What is the recommended stratification method?

Thanks!

 

UPDATE: So far the best sites I've found are below. I really hope there is a book or app I'm missing, because they are all kind of basic and none answer all my questions, although major kudos to their owners:
* Rob's Plants seed germination: http://www.robsplants.com/seed/germination.php
* Tim Clothier: http://tomclothier.hort.net/index.html
* The Seed Site UK: http://theseedsite.co.uk/db1.html
* Dave's Garden "When to sow advice" user spreadsheet: https://docs.google.com/spreadsheets/d/1vR96TfP0MxG5vzCtu4hTwG-X08RB3C6DQR8Qx6rkbgE/edit?usp=sharing

 

I agree with toni. I have found over the years that there is no one right answer to this question. The sources you have found can serve as a guide but in the end it is your own experience with your garden, your climate, your soils, your sun levels that should dictate the right answer.

The nature of your question also suggests that you are trying to push the limits by getting things in the garden as soon as possible. One thing I have learned over the years is that, when in doubt, waiting a week is almost always better than not. Every year I do a few experiments in which I will plant things a weeks or so apart for two or three plantings and then take notes as to how they did. I find that planting date makes a lot less difference that you might think.

If you are talking about vegetable seeds then it is understandable that you want to get stuff in the garden so you can start getting your own fresh produce. We all go though this. One solution is to experiment with overwintering crops. Parsnips, kale, some collards greens (try Flash - occasionally hardy for me in zone 4), some types of carrots and a host of other crops will overwinter for you in zone 6 with some care. That way you won't put so much pressure on yourself to get your garden to produce.

Just my 2 cents.

 

Stratification is often given as 33-35f for x hours. It is as meaningless as any of the other information unless you have a specific seed in mind. So many cultivated plants are not from your area and as visitors from far off lands, the needs can vary. The soil temps are the same way. There will not be too many unified things about gardening. The reason is your soil is different from the person writing the blog. It is really important to know YOUR solar exposure, temps, soil type yada yada and with that knowledge you can FILTER all the advice out there. This chart might help on the temps. Plants run on hormones, those chemistries being driven by energy, heat, solar, the energy stored in leaf sugars etc, but even then what that plant evolved to do is related to whatever himilayan mountside or amazonian valley where it developed.

 

I like Margaret Roach 's tool for when to start seeds (either indoors or direct sow).

I also like Mother Jones' Garden Planner tool. You can do a garden plot layout, "planting " various crops. It will tell you how to space them, when to direct sow, when to start seeds indoors, etc. Also gives info on pests, companion planting etc.

It will keep previous years plans for you & alert you if you are intending to plant tomatoes in the same are as you did two years ago.

You can print out your garden plan & take it to your (in my case) community garden plot so you know where to plant things, how far apart, etc

 

There are a series of charts that depict averages of various climate measures available here. About 3/4 of the way down there is one that depicts the growing season for the location you have chosen. Note that this chart is based on air temperature not soil temperature but can be helpful when figuring out when to plant shoulder season crops.

 

Since roots are so important, I am sorta stuck on soil temps. Black plastic "mulch" can help you roll early, and then when it gets too hot you can roll white or aluminum if you need to to drop the temps. Pay attention the the recycle aspect, the poly versions are a bit useless in that way, but color thick paper or aluminum do not suffer the same landfill future.