Spring is in the air and I spent the entire day outside in our front yard gardens. 12 large garden bags were filled with leaves, container remnants and grass clippings. While I was working in the beds I was thinking about a question I’m often asked – When Can I Plant Annuals.
“The actual flower is the plant’s highest fulfillment, and are not here exclusively for herbaria, county floras and plant geography: they are here first of all for delight.
This post is relevant to those who live in colder winter climates, and who have to worry about frosts before planting annuals in their gardens or what perennials are hardy for their garden.
But there are TWO things you need to know to determine what/when plants are for your gardens…
1) What is Your Areas Average Last Frost Date (for annuals)
2) What Is Your Areas Plant Hardiness Zone (for hardy perennials)
If you know your numbers already, skip this part. If you don’t,
Click Plant Hardiness Zone, easy just put in your zipcode!
To determine your Average Last Frost Date, using your zip code.
29°F to 32°F—tender plants killed, with little destructive effect on other vegetation.
25°F to 28°F—widely destructive effect on most vegetation, with heavy damage to fruit blossoms and tender and semi-hardy plants.
24°F and colder—damage to most plants
I live just SW of Chicago, my Perennial Plant Hardiness Zones is 5, and my Annuals the Average Last Frost Date is May 20.
These two numbers are your friends….when selecting perennials, your Hardiness Zone number is what you look for on the plants tag, it mean this plant has been tested to be “hardy” in your area.
Annuals are placed in your garden based on your Average Last frost date. Now there’s no genie who can tell us the exact date of our last frost dates.
Now I know in my area, we can have a frost to May 20th. Remember this the AVERAGE last frost date. It’s a crap shoot, I rarely plant before May 1st. I risk it hoping we won’t get a frost, sometimes I win, and sometimes I’ve lose.
Annuals are broken down into two classes:
Cool season Annuals and Warm season annuals.
COOL SEASON ANNUALS
Cool-season annuals, such as pansy (Viola), primrose, and calendula, Snapdragons, grow best in the cool soils and mild temperatures of spring and fall. Most withstand fairly heavy frosts. When the weather turns hot, they set seed and deteriorate. If you live in a cold-winter area (Zones 1-6), plant these annuals in very early spring or late fall (source).
WARM SEASON ANNUALS
Warm-season annuals include marigold, zinnia and impatiens, geranium’s etc. These plants grow and flower best in the warm months of late spring, summer, and early fall; they’re cold tender and may perish in a late frost if planted too early in spring. Set out these plant according to your zones average last frost date.
Now that you know your numbers, you now know the answer to When Can I Plant Annuals!
I hope you enjoy the Master Gardening Series, it is a lot of work to pull together. It would be nice to hear you do!
So leave me a comment with you numbers!