Before planting it is a good idea to find your USDA Zone info to estimate your garden schedule. The most important data that the zone info tells us is average last frost and the lowest expected temperature for your area.

The first opportunity to plant delphinium in Norristown should be figured out by looking at the USDA zone info.

Planting Calendar for Delphinium

Frost tolerance for delphinium:	Tolerant of a very small amount of frost.
When to plant:	Up to 3 weeks before last frost.

Delphinium do ok in a tiny bit of cold which tells us that you can plant them a bit earlier in the year than more sensitive plants.

The earliest that you can plant delphinium in Norristown 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 delphinium and expect a good harvest is probably August. If you wait any later than that and your delphinium may not have a chance to grow to maturity. Starting your delphinium indoors is a great way to get them started a little bit earlier.

Last Frost Date

The average date of last frost is April 15 in Norristown. It might get as low as 0°F during the coldest months of winter.

Keep in mind that the actual date of last frost may not be accurate from year to year because it is based on the USDA zone info for Norristown and it is different every year. Half of the time in Norristown it frosts late in the year after April 15 so be sure to be ready to cover your delphinium if you have a surprise late frost.

USDA Zone Info for Norristown

Here is the info for USDA Zone 7a.

Average Date of Last Frost (spring)	April 15
Average Date of First Frost (fall)	October 15
Lowest Expected Low	0°F
Highest Expected Low	5°F

This means that on a really cold year, the coldest it will get is 0°F. On most years you should be prepared to experience lows near 5°F.

Plants to Grow in Norristown

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