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When to Plant Nasturtium in Boulder, CO

One of the first steps you take when you are estimating your gardening schedule is find your 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.

A way of estimating when it's the best time to plant nasturtium is to use the USDA zone info for Boulder.


Planting Calendar for Nasturtium

Frost tolerance for nasturtium: Not tolerant of frost.
When to plant: After all chance of frost has passed.

Nasturtium do not do well in cold weather which tells us that it is important to wait until it warms up after the last frost when the weather gets warmer before you can plant them.

JanFebMarAprMayJunJulAugSepOctNovDec
Legend 
A good time to plant nasturtium
Possibly ok, but a risky time to plant nasturtium
Probably not a good time to plant nasturtium

The earliest that you can plant nasturtium in Boulder is April. However, you really should wait until May if you don't want to take any chances.

The last month that you can plant nasturtium and expect a good harvest is probably August. You probably don't want to wait any later than that or else your nasturtium may not have a chance to fully mature. If you are starting your nasturtium indoors then you might be able to get away with starting them a little bit earlier.

Last Frost Date

On average the last frost has passed is on April 15 in Boulder. You can expect an average low temperature of -15°F in the coldest months of winter.

Keep in mind that the actual date of last frost is an average because it is based on the USDA zone info for Boulder and it will vary from year to year. Since half of the time in Boulder you get surprised by a frost after April 15 be ready to cover your nasturtium 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.