There's great pleasure, for me, in planning a garden; always has been. I like to work with graph paper to give myself a spatial representation of what the garden will look like. But I also work better with a progressive list of planting dates, so I can keep track of what I need to plant when. I've already begun sprouting some seeds. Among these are crops that need the longest season to mature (onion, leeks, and celery root), as well as fast growing plants that tolerate cold temperatures very well (lettuce and kale). In my ambition to produce as much of our own food as possible, I will sow seeds and transplant seedlings from February through August this year, saving the garlic bulbs to plant last of all in mid-October. If this year is anything like last year, we'll harvest apples in November, and continue harvesting leeks throughout the winter. But I also hope to have more root crops and more cold-tolerant greens under cold frames and row covers for fall and winter harvest.
"Farming looks mighty easy when your plow is a pencil and you're a thousand miles from the corn field." - Dwight Eisenhower
The timing aspect of sowing and planting comes down to local conditions as well as individual knowledge of the gardener. I could tell you when I plant, transplant, and direct sow my seeds in zone 6, but it wouldn't be very helpful for those of you in other hardiness zones. Fortunately, there are plenty of useful guidelines out there. Indeed, Ali at Henbogle recently linked to Kathy's Personalized Seed Planting Calendar which you can customize with the dates of the first and last frost dates in your area. Once I plugged in the relevant dates for my own area, I found it to be an excellent starting point for my scheduling. But the schedule includes some plants I won't be growing and omits others that I plan to include. Also, my own experience will guide me to diverge slightly from the suggestions of the automated schedule.
For instance, while the conventional wisdom is to plant tomato seedlings two weeks after the last frost, I prefer to plant even later than that. In my experience, exposure to temperatures lower than 50 F will prevent even the smallest, greenest fruit on the plant from ever developing into a tomato with good flavor. So I transplant when I can be reasonably certain that the nighttime temperature will not fall below 50 degrees. In my area, that means the tomatoes don't go in the ground until June 1st. It's worked well for me. I don't get the earliest tomatoes, but my first tomatoes are worthy of the name.
Also, I'll plant my pumpkins and winter squash on the late side, because I want to harvest them when outdoor temperatures are as low as possible. Warm temperatures shorten the shelf life of pumpkins, and a mid-May planting will mean a September harvest. I'd rather see them finish off in early October, so I'll wait for June to plant them. That will let me store them well into the late winter months.
Another excellent timing reference that I rely on is Eliot Coleman's Four-Season Harvest, which contains an index of planting guidelines for late season crops, based on the first frost date in the fall. The indices alone are worth the price of the book, in my opinion. Also, don't forget that if you live in the US, you have a great resource for local gardening knowledge in the Master Gardeners. You can reach these volunteers through your state's local Agricultural Extension Office. There should be one in every county in the US. These trained and experienced gardeners will have some of the most specific recommendations for your location.
While various authorities can give you general guidelines for planting dates, it's important to remember that these sources will be giving you averages. But different varieties of a given crop also vary in the number of days they need to reach maturity. Tomatoes may take as few as 55 or as many as 80 days to produce fruits from the time they are transplanted. That's a big range; more than three weeks. Lettuces range from 50 to 70 in days to maturity. Check the seed packets of the specific varieties you've ordered to find this information, in order to plan accordingly.
If you're an experienced gardener, you may well want to decide your planting dates for yourself. Here's a nice online tool I use to help me count backwards from two different dates: the average date of the first fall frost, and the date when we'll see less than 10 hours of daylight at my latitude. It will also help you count forward from a given date, based on the days to maturity for your seeds.
It's hard to compare your location to another one for several reasons. Hardiness zones reflect the average low winter temperature in an area. But within a given zone, there's a wide range in the first and last frost dates. Your last frost date might easily match that of a distant location in a warmer or cooler hardiness zone. And latitude determines day length, which also has no direct correlation to either frost dates or hardiness zones. To see evidence of this, just follow any east-west running line across that hardiness map to see how many different zones exist at a given latitude. There's a lot to learn about how the weather behaves in any given area - and we haven't even mentioned precipitation!
I know that when you're inexperienced with gardening the details can be sufficiently overwhelming to induce paralysis. Don't let that discourage you. Plants want to live and grow. They will do most of the work if you give them a decent chance. Try a wide range of plants, and something is bound to do well for you. Just don't get overeager and plant seeds so early that the seedlings get rootbound in their containers. Few plants can rebound and produce well if their roots are constrained early in their growth. Keep some notes on how things do in your garden each year, including planting dates, harvest dates, and a few weather notes, so that next year you can make better decisions. Most of all, just try it! Gardening is definitely something you learn by doing.
Green blessings for your garden this year!
Late Frost and Tender Seedlings