One of the best tools that you have as gardeners to help us estimate your gardening schedule is the 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.

You will be able to figure out when it's a good idea to plant alternanthera by using the USDA zone info for San Juan.

Planting Calendar for Alternanthera

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

You really shouldn't plant alternanthera until after the last frost because they require warm weather.

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

Last Frost Date

The average date of last frost is February 15 in San Juan. You should expect an average low temperature of 25°F in the coldest months of winter.

Remember that USDA zone info for San Juan is just an average and the actual date of last frost is different every year. Since half of the time in San Juan you get a frost after February 15 be ready to protect your alternanthera if you have one of those late frosts.

USDA Zone Info for San Juan

Here is the info for USDA Zone 9b.

Average Date of Last Frost (spring)	February 15
Average Date of First Frost (fall)	December 15
Lowest Expected Low	25°F
Highest Expected Low	30°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 30°F.

Plants to Grow in San Juan

You may be interested in your other planting guides for San Juan.