One of the best tools that you have as gardeners to help us figure out your gardening schedule is the USDA zone info. The most important data that the zone info tells us is average last frost and the lowest expected temperature for your area.

The USDA zone info for Ontario can be looked at to figure out when to plant romanesco.

Planting Calendar for Romanesco

Frost tolerance for romanesco:	Tolerant of some frost.
When to plant:	Up to 5 weeks before last frost.

You can plant romanesco a bit earlier in the year because they are moderately cold tolerant.

The earliest that you can plant romanesco in Ontario is February. However, you really should wait until March if you don't want to take any chances.

The last month that you can plant romanesco and expect a good harvest is probably September. If you wait any later than that and your romanesco may not have a chance to fully mature. If you are starting your romanesco indoors then you might be able to get away with starting them a little bit earlier.

Last Frost Date

The average date of last frost is April 15 in Ontario. In the coldest months of winter you can expect an average low temperature of -15°F.

Since the USDA zone info for Ontario is just an average the actual date of last frost can change quite a bit from year to year. Half of the time in Ontario it frosts late in the year after April 15 so make sure that you are prepared to protect your romanesco in the event of a surprise late frost.

USDA Zone Info for Ontario

Here is the info for USDA Zone 5b.

Average Date of Last Frost (spring)	April 15
Average Date of First Frost (fall)	October 15
Lowest Expected Low	-15°F
Highest Expected Low	-10°F

This means that on a really cold year, the coldest it will get is -15°F. On most years you should be prepared to experience lows near -10°F.

Plants to Grow in Ontario

You may be interested in your other planting guides for Ontario.