Before planting it is a good idea to find your USDA Zone info to figure out your garden schedule. The zone info helps tell us things like average date of last frost and lowest expected temperature for your area.

It's possible to figure out when it's a good idea to plant osteospermum by reviewing the USDA zone info for Watertown.

Planting Calendar for Osteospermum

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

Osteospermum do ok in a little bit of cold which means that you can plant them just a bit earlier in the year than more sensitive plants.

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

The last month that you can plant osteospermum and expect a good harvest is probably August. If you wait any later than that and your osteospermum may not have a chance to grow to maturity. If you are starting your osteospermum 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 May 15 in Watertown. You should expect an average low temperature of -25°F in the coldest months of winter.

Remember that the actual date of last frost is an average because it is based on the USDA zone info for Watertown and it changes from year to year. Half of the time in Watertown you get a frost after May 15 so just be sure to be ready to cover your osteospermum if you have a surprise late frost.

USDA Zone Info for Watertown

Here is the info for USDA Zone 4b.

Average Date of Last Frost (spring)	May 15
Average Date of First Frost (fall)	September 15
Lowest Expected Low	-25°F
Highest Expected Low	-20°F

This means that on a really cold year, the coldest it will get is -25°F. On most years you should be prepared to experience lows near -20°F.

Plants to Grow in Watertown

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