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When to Plant Osteospermum in Boulder, CO

One of the first steps you take when you are determining 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 osteospermum is to examine the USDA zone info for Boulder.


Planting Calendar for Osteospermum

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

Since osteospermum are one of those plants that can tolerate a little bit of cold weather you can plant them a little earlier in the year than other frost tender plants.

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

The earliest that you can plant osteospermum 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 osteospermum and expect a good harvest is probably September. If you wait any later than that and your osteospermum may not have a chance to really do well. If you are starting your osteospermum 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 is on April 15 in Boulder. In the coldest months of winter you can expect an average low temperature of -15°F.

Just be sure to remember that USDA zone info for Boulder may not be accurate from year to year and the actual date of last frost can change quite a bit 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 osteospermum if you have a surprise late frost.

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.