One of the best tools that you have as gardeners to help us estimate your gardening schedule is the 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 maltese cross in Boulder can be figured out by checking out the USDA zone info.

Planting Calendar for Maltese Cross

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

Maltese Cross do well in some cold which means that you can plant them a little bit earlier in the year than more sensitive plants.

The earliest that you can plant maltese cross 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 maltese cross and expect a good harvest is probably September. Any later than that and your maltese cross may not have a chance to fully mature. If you are starting your maltese cross indoors then you might be able to get away with starting them a couple of weeks earlier.

Last Frost Date

On average the last frost when the weather gets warmer is on April 15 in Boulder. In the coldest months of winter you should expect an average low temperature of -15°F.

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 is different every year. Since half of the time in Boulder it frosts late in the year after April 15 be ready to cover your maltese cross if you have 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.