What We Just Learned About Final Frost (& Happy Memorial Day)!

Growing up in the Finger Lakes of New York, high elevation Zone 5, I have the mantra of "Memorial Day is Final Frost" deeply embedded in my brain. I am constantly questioning my assumptions about myself and the world around me; this year I was inspired to dig a little deeper into this maxim. 

Are historic frost dates still relevant?

potatoes are ideally planted three weeks before final frost

Pouring over decades of temperature records in our county from the National Oceanographic & Atmospheric Association (which is totally free and fascinating, I highly recommend it!) from 1930 to present, here are my observations:

a) Our final frost dates have (surprisingly) remained fairly consistent, often occurring just before Memorial Day.

b) Even on years when final frost is weeks earlier than Memorial Day (like May 1st, 1970, which happens 2-3 times each decade), the night temps generally aren't out of the 40s consistently until around Memorial Day.

Which is all to say:

 If you're planting anything solanaceous (tomato, pepper, eggplant, tomatillo, ground cherry), wait to plant after your historic final frost.  In our case, Memorial Day. This will ensure their quick, even growth and earlier fruiting as a result. (You'll find thousands of gorgeous, organic transplants at Fruition's Farm Store, by the way!)

Anything else, push the envelope: you'll likely be rewarded with earlier and more abundant harvests. 

be sure to harden off seedlings before transplanting, even those that are frost-tolerant like this broccoli

Why?

Think of plants as more complex than simply frost-hardy or frost-sensitive.

As spring turns toward summer, here are some delicious considerations:

Frost-Hardy Plants

thrive even in when snow may fly and nights consistently frost

peas

cilantro

greens: spinach, mache/corn salad

brassicas: arugula, kale, radish, pac choi, kohlrabi

Frost-Tolerant Plants

grow when nights are consistently below 40 F and may occasionally frost, thriving more as temperatures rise

Roots: beet, carrot, parsnip

calendula

fennel

greens: chard, lettuce (especially winter density, romaines)

alliums: onion, shallot, leek, chive, scallion

Everything from the above list

Frost-Sensitive Plants

grow when nights no longer frost, thriving more as temperatures rise

Most Flowers

Most Herbs

dark-seeded beans, especially Provider

Corn

Everything from the above lists (except pea, spinach and mache)

Cold-Sensitive Plants

resist thriving if they experience temps below 50 F

Solanids: Tomato, Eggplant, Pepper, Ground Cherry, Tomatillo

Beans

 Cucurbits: Cucumber, Zucchini, Melon, Winter Squash, 

Everything from the above lists (except pea, spinach and mache)

Elevation & Other Influences on Frost:

Elevation

Higher elevations = shorter seasons

We have several farms at Fruition, each one with unique soil and growing conditions. Our lowest farm is often frost-free two additional weeks, one week in spring and one in fall, compared with our farm 800 feet above it, three miles away.

Historic Data

It's enormously helpful to see empirical, historic trends in your backyard. Enjoy perusing the NOOA website (above).

Aspect

Which cardinal direction does your garden face? Southern exposure offers you a longer, warmer growing season.

Slope

Warm air rises and cold air settles. In large, relatively flat areas, slope doesn't play much of a role in frost dates. If you are in the bottom of a valley, cold air will settle around you. often called a 'frost pocket.' You'll be amazed, when temps are around 30 F, what difference even a few feet in elevation and air flow can make.

we are so excited to plant these gorgeous, hardened off strawflowers this week, after final frost

Happy Memorial Day, Friends!

May your gardens surround you with beauty and abundance this season, constantly inspiring you to ask more questions, to research and experiment, to share and to grow!

Know you are not alone :)

Sow Seeds & Sing Songs,

ps

Though the last 15 years have recorded more changeable and volatile weather than the prior century, I was certainly surprised by my own observations looking at final frost dates, expecting warming patterns to be the new normal. Climate change is changing a lot more than our climate; I'll be sure to share strategies so our gardens, our communities and our world can be more resilient.