If you are planting outdoors, find out when your frost-free date is and plant then.

I get personalized planting reminders bi-weekly by email from the Old Farmers Alamanac, which is super handy. Here is the calendar for Toronto:

https://www.almanac.com/gardening/planting-calendar/ON/Toronto

All Ontario calendars:

https://www.almanac.com/gardening/planting-calendar/ON

I can't find the link where you can enter your email address though :(

I've often seen recommendation not to transplant cucumber and dill but to direct seed in their final location. Dill has a taproot that doesn't much like being transplanted, but happily it's easy enough to grow it in a container. Cucumbers have a fleshy delicate root that doesn't like being transplanted so it's usually seeded in place outdoors. It can be grown in a large container, though.

I did an experiment once with cucumber seeds. I started some in my greenhouse 5 weeks early and they were small plants when planted in the garden. In an adjacent spot I planted seeds at the same time I planted the seedlings. In 3 weeks you couldn't tell difference and they both set fruit about the same time. Since that time I've always direct sowed my cucumbers

HU, you need to know more than your zone. You need specific information on your exact area, as sacharum suggests. US zones only give information on average winter minimum temps. They tell us nothing about summer conditions. You'll see that theoretically I'm in USDA z8/9 because I have relatively mild winters. But I couldn't sow cucumbers outdoors until late June at the earliest and I'd probably get no fruit. Cucumbers, tomatoes, zucchini and other squash are routinely transplanted over here. It works fine and for me it's the only way to reliably get a crop.

Parsley and dill can be sown direct since they do not need the high germination temps of the crops mentioned above and they have tap roots.

"But I couldn't sow cucumbers outdoors until late June at the earliest"

I am just curious why? What area do you live in?

It says on my name, SW U.K. The soil isn't warm enough for them to germinate until almost midsummer. You can sow under a cloche a little earlier but it's hit or miss. Most people grow cucumbers in a greenhouse. Outdoor growing is a lottery.

Do you have South West England in mind? It is quite a big area. Always thought it has a very mild climate.

And yes HU-397624596. You are in Canadian zone 7a.

Yes, SW U.K. which is SW England. The climate is mild in so far as winters are not very cold. But summers are not very hot either. It's a temperate maritime climate. July is our warmest month with an average temp of 62f. Jan is our coldest with an average of 39f.

If your in British Columbia sign up for these FREE Nodding Onion Seeds: https://bcwf.thankyou4caring.org/2019-seed-package