Well, obviously, it depends on what you're growing and where you're growing it. I believe, if memory serves me, you're in the Toronto area, so your climate is essentially the same as mine here in the Detroit area, give or take a few days either way. I'd suggest the following timetables:

Leeks, onions -- by the end of January, but grow them cool. Can plant outside by mid-April, after a few weeks of hardening off.

Peppers, Eggplants, Globe Artichoke -- by late February, outside in May. Be sure to use lots of light.

Early Tomatoes, for large transplants -- late February to early-mid March, outside in May.

Main crop tomatoes -- late March is a about right, outside in May

Vine crops -- cucumbers, melons, squash, similar crops - early April, about 4 to 5 weeks ahead of transplant time.

Peas -- actually, these can be done as transplants, but there really isn't much of an advantage to doing so. If you do transplants, just do them about 2 to 3 weeks before planting out, and start them warm to get them to germinate, but move them as soon as they're up to a cool greenhouse or coldframe. You can direct sow as soon as the ground thaws (although I'd use treated seed, and wait a few weeks later for the sugar snap types), and really anytime for about the next 4 or 5 weeks.

Greens -- lettuce, etc -- about 4 weeks before transplanting.

Brassicas, cabbage, etc. -- about 6 weeks before transplanting. Don't get too much in a rush to get broccoli or cauliflower going, though, as these will just "button" or make tiny, premature heads, if they go out when it's too cold.

Root crops -- with the possible exception of beets or the round, Parisian type of carrots, which can be done in cell packs, all of these need to be direct sown. Times vary by crop, from radishes as soon as the ground thaws, to about 2 weeks before last frost for carrots and beets.

Hope this helps a bit.

Thanks a lot for the info! Much appreciated. Do you think most of those plants would actually be harmed by starting them out earlier and then transplanting them?

BTW, yes I do live in the Toronto area, zone 5, so pretty similar to Detroit.

Canuckistani wrote: " Do you think most of those plants would actually be harmed by starting them out earlier and then transplanting them? "

Um, well, it depends on the conditions you have to grow them in. A lot of people try to grow transplants indoors in insufficient light and too warm of temps, which can be a recipe for disappointment. If you have adequate light and proper temps (varies widely by crop, of course, from near-freezing for peas to 80 fahrenheit for eggplant), many of them could be started reasonably early. After many, many years of doing this, I'd say that the suggested start dates I gave you above are about optimal, assuming your plant-out date for hardy crops is mid-late April, and for tender crops mid-late May.

If you REALLY are anxious to start something right away, you could go ahead and do onions and leeks anytime, really. You could also start a sweet potato as a houseplant, in order to have nice cuttings ready to take in April. Otherwise, it's pretty much WAY too early for everything else. Perhaps you could do some indoor gardening under lights -- salad greens and herbs are easy this way.

Denninmi, nice list that works for my area also if I push plant out date back a week or so. Your timeline is now in my clippings!

canuckistani, I've started seeds alot earlier with hopes of having bigger plants. Usually I ended up with plants that didn't fit my growing space. It was hard to provide adequate light. They needed larger pots, thus more space and most didn't really give me much of a jump on the harvest. I'm hoping to try more season extenders outside this year such as a coldframe and row covers. Also may try some plastic sheeting to warm the soil before planting out. That may help with an earlier harvest as much as larger transplants.

canuckistani,
Give the Grow Guide a try.
Just plug in your first and last frost dates and it will do the rest of the figuring for you. If you change the "Select a planning date" option to some time in, say . . . March, April, etc. it will tell you what to start on that date.
:)

Great advice. Thanks again folks.

For me in Kansas, Zone 5, I start slow growing (habaneros) peppers around Valentines day. I also start my hoop house tomatoes a week later. I plant out my hoop house tomatoes around April 1. I start the rest of my seedlings around the early March (Usually during my spring break for school).

I start my hoop house cucs, 2-3 weeks prior to planting, usually about end of march or early April. Seedless watermelons around April 1st.

I usually plant out peppers and tomatoes by the end of April. I almost froze them this year. 2 days too early.

Good Luck!

You could start some of your peppers now if they are of the Chinense species because they are very slow growers. Annuums can be started mid to late Feb. or even later. My chinense's will be started the 1st of Jan (give or take a few days). It really depends on what sort of setup you have. You do not want them to outgrow thier home before it is time to go outside.

Dale

Would like to grow tomatos, cucumbers, squash, melons, roots crops, peas

Cucumber, squash, melons, and most root crops are best direct seeded rather than used as transplants. Same goes for peas. This is not to say that some of them can't be started as transplants, just that most studies show they do quite a bit better if direct seeded. So that just leaves tomatoes on your list. ;) They should be started approx. 6-8 weeks before your transplant out date.

Starting transplants months earlier, unless one has quite the ideal set-up such as a greenhouse would provide, only results in spindly, leggy transplants that are stressed. They don't tolerate the required hardening-off period and don't transplant well and are often more susceptible to disease and pest problems because of the stress they have endured.

Dave

Denninmi, excellent information. I am in your area and you're dead on with the start dates. The only thing I start earlier than you is lettuce. I like 6+ weeks to put out bigger transplants, especially in the Fall.

Chris

What do you guys mean by 'hardening off' transplants? Leaving them outside for a few days before actually transplanting?

Thanks again

What do you guys mean by 'hardening off' transplants? Leaving them outside for a few days before actually transplanting

That is close to it. The first time outside needs to be only about 3 hours though that could be longer on a cloudy day. Then increase the time daily for 5 or 6 days. Tomatoes will be alright at 45°F and melons above about 54°F. I don't have the Centigrade temps.

On your original list only tomatoes and melons [for northerners] benefit from transplants. Of course peppers and some other things are started earlier.

Here in central Indiana I start tomatoes about the 30th of March and they are plenty big by early May. Melons I start about the 22nd of April and some more about May 1st. These are plenty big by the 10th to 23rd of May.

I'm planning on growing under 400w Metal Halide lights indoors with reflectors. I want to experiment a bit with growing larger transplants- at least for the tomatoes, melons, peppers, beans, cukes and some roots crops. I'm thinking of trying transplanting some 3-4 month old tomatos, peppers and melon plants in April with wall-o-waters and row covers protecting them- really would love to get an earlier harvest for them. Any suggestions on how I should grow them for late transplanting aside from hardening them off before transplanting? Are there any other growing suggestions for late transplanted crops?

Thanks again folks

Are there any other growing suggestions for late transplanted crops?

Yeah, Don't do it. LOL. Partly kidding here as it is your garden.

Transplanting root crops? You may do better by direct seeding root crops. After all, the productive part of the plant is the carrot, beet, parsnip, etc. and transplanted roots usually don't develop well.
Be sure to put your melons, tomatoes, etc. into bigger pots so they don't become root bound. Again, transplanting a large rooted plant is usually less successful than transplanting one that has less root mass and can adjust to the different condition more easily.
Good luck with your experiment, and let us all know how it works out!