One of the first steps you take when you are making a decision about your gardening schedule is find your USDA Zone info. The zone info helps tell us things like average date of last frost and lowest expected temperature for your area.

The first opportunity to plant spinach in Boulder should be figured out by checking out the USDA zone info.

Planting Calendar for Spinach

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

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

The earliest that you can plant spinach in Boulder 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 spinach and expect a good harvest is probably September. Any later than that and your spinach may not have a chance to fully mature. You can get started a few weeks earlier by starting your spinach indoors.

Last Frost Date

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

Always keep in mind that the actual date of last frost may not be accurate from year to year because it is based on the USDA zone info for Boulder and it changes from year to year. Half of the time in Boulder it frosts late in the year after April 15 so make sure that you are ready to protect your spinach in the event of one of those late frosts.

USDA Zone Info for Boulder

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 Boulder

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