One of the best tools that you have as gardeners to help us determine 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.

By looking at the USDA zone info for Hillsboro you should be able to figure out when it's a good idea to plant sunflowers.

Planting Calendar for Sunflowers

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

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

The earliest that you can plant sunflowers in Hillsboro 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 sunflowers and expect a good harvest is probably August. If you wait any later than that and your sunflowers may not have a chance to really do well. If you are starting your sunflowers indoors then you might be able to get away with starting them a couple of weeks earlier.

Last Frost Date

On average all chance of frost has passed is on March 15 in Hillsboro. It might get as low as 10°F during the coldest months of winter.

Remember that the actual date of last frost is just an average because it is based on the USDA zone info for Hillsboro and it is different every year. Half of the time in Hillsboro it frosts late in the year after March 15 so always be ready to protect your sunflowers if you have one of those late frosts.

USDA Zone Info for Hillsboro

Here is the info for USDA Zone 8a.

Average Date of Last Frost (spring)	March 15
Average Date of First Frost (fall)	November 15
Lowest Expected Low	10°F
Highest Expected Low	15°F

This means that on a really cold year, the coldest it will get is 10°F. On most years you should be prepared to experience lows near 15°F.

Plants to Grow in Hillsboro

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