Extreme Garden Weather

Posted by on Aug 6, 2015 in Grow Better Greens Podcast | Comments Off on Extreme Garden Weather

In Episode 10 we’re talking temperature extreme garden weather! How hot is too hot in the garden and how cold is too cold? For most of us, year round gardening is a fantasy, due to winter snowfall or oppressive summer heat. We’ll share what we know about extending your growing season in either direction, along with some basic tips for growing greens successfully in both cold and hot weather.

You can listen in here, or donload for later:




Managing Temperature Swings and Extreme Garden Weather

Temperature Dictates the length of your Planting Season – 0:57
Finding Your First and Last Frost Days – 2:09
Finding your Plant Hardiness Zones – 4:24
Selecting the Best Varieties – 8:05
Managing Heat in the Garden – 9:40
Managing Cold in the Garden – 12:50
Why Do You Grow Food? – 19:20


Season Extension is the Act of Going Above and Beyond in the Garden

That’s because our ‘regular’ gardening season is determined by how much good planting weather we have in store for us each year, depending upon where we live. Plants have some specific requirements in terms of temperature, and plenty of us live in places where we have to bow out of growing due to extreme heat or extreme cold.

So, what’s too hot for a plant and what’s too cold?

Check out this chart, adapted from the book Four-Season Harvest by Eliot Coleman, which shows some of the problems that plants face when we ask them to continuing growing into inhospitable weather.

Effects of Temperature on Plants PDF Download

Plants, as it turns out, really prefer a ‘sweet spot’ of between 50 and 90 degree Fahrenheit. But with a little clever thinking, we can do our best to keep them close to that sweet spot, even when the thermometer says otherwise!

First though, it helps to know exactly when the regular season begins and ends, so that we can be ready to act as soon as any abnormal weather sets in.


Finding Your First and Last Frost Days

The best way to determine the length and exact dates of your regular growing season is by doing some basic math. To start, you’ll need to know the very last day that you can expect a frost as winter turns to spring. This would be the average recorded date that the temperature dips below 32 F in your area.

For me, the last frost occurs sometime around May 10, meaning that anything I plant before that date should be able to withstand frost on its leaves!

Next, you’ll need to track the first date in the Fall when frosts typically return to your zip code. For me, that’s around October 20. By counting the days between my last spring frost (May 10) and my first Fall frost (October 20) I can calculate that I have about 165 days to grow a garden – within the realm of what a plant can tolerate!

Now, Let’s Make That Math Easy…

The easiest way to calculate the dates and length of your regular growing season is to punch your zip code into a website like the one below, and sit back while it does all of the work for you!

Click here to get your First and Last Frost Dates from the Old Farmer’s Almanac

A teeny bit of advice here: it’s important to develop your own understanding of how the season may be different on your own property! My growing season is 2 – 3 weeks longer than what’s listed on the Farmer’s Almanac site, and a full 40 days longer than what I’ve seen on other websites.




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Finding Your Garden Hardiness Zone

Okay, so now you know how long your growing season is. This is great info to have, especially when you’re reading the back of a seed packet that tells you the ‘Days to Maturity’ of the veggie seeds inside. Parsnips, carrots, pumpkins – do you even have time to plant and harvest those within your season?

But there’s another vital piece of information to have at the ready, and that’s your Plant Hardiness Zone. This information let’s you know exactly how cold you can expect things to get at your place. Knowing how cold the thermometer can dip down to will allow you to plant smartly. There’s no sense in buying a tree, shrub, or perennial flower that will be killed off at minus ten degrees when you know that it can get as cold as minus twenty where you live.

Understanding your Plant Hardiness Zone and the limitations it brings will help you figure out a few things:

  • Which species and varieties will survive in your garden
  • Which species and varieties don’t stand a chance in your garden!
  • Which species and varieties might survive in your garden, with a little help from you

You can find your Garden Hardiness Zone by entering your zip code in the link below.

Click here to find your USDA Plant Hardiness Zone.

Again, this is a general guide – you may notice differences between your property and what’s listed. My house is listed as Zone 5a (big deal in VT – so tropical we call it the Banana Belt!) but I know better. Because the lake in my area always freezes solid, winds in January and February bring icy cold temps, down to -30F. That makes me a full two zones lower – a 4a.

Therefore, trees that can’t survive 30 below won’t last here unless I can offer them some protection from the cold. But that’s definitely a possibility! Let’s turn this conversation towards what you can do to manage extreme temperatures in your garden.


Selecting the Best Varieties

To start, knowing your Plant Hardiness Zone will make you a better shopper. As you’re browsing plants at the garden center or farmers’ market, you should notice that they’re all clearly marked by Zone. Typically, the plant tag that’s telling you the variety name and care requirements will also tell you which Zones the plant is appropriate for.

This is especially important when you’re choosing Perennials – plants that go dormant during the winter months and come back to life each gardening season. Understanding this crucial info will help you decide if:

  • You can expect the plant to do well in your garden, year after year
  • You should plant it in a pot instead of the ground, so that you can take it indoors to overwinter
  • You can put the plant in the ground, but might need to create some shelter for it when winter comes
  • You can enjoy it as an annual plant this season, with no expectations that it will come back next year

Now, let’s talk about annual plants, like our garden veggies. In fact, let’s talk about greens specifically, and how you can make sure to choose a variety that thrives in heat during the hottest periods and cold during the coldest periods.

The best way to find out about these different varieties is to shop for seeds online. That’s because many seed company’s websites have evolved so much that you can shop for veggies by trait. Look for ‘heat tolerant’ or ‘cold weather’ sub-categories as you’re shopping for your favorite greens or other veggies. Two great sites that list their seeds this way are JohnnySeeds.com and HighMowingSeeds.com. From there its’ up to you whether you push ‘Add to Cart’ or just consider yourself a bit wiser for knowing which varieties you should be on the lookout for!


Managing Heat in the Garden or Hoop house!

One of the most interesting things to happen in my typically icy-cold northern region, is that many of us growers have had to learn to manage heat and humidity, just like our gardening friends way down south. This is because in an effort to extend our growing season into the winter months, many of us have invested in high tunnels and hoop houses (plastic greenhouses).

This means that throughout the regular growing season, we’ve created a microclimate under that plastic that is way, way hotter than what we’re used to. So, managing plants in the heat has become just as necessary as if we lived in the hot and humid Southeast.

When managing heat in your garden, you have 3 main goals:

1. Create airflow, which prevents diseases like mold from spreading. This can be done with fans (in a hoop house) or just by leaving extra space between plants.

2. Water plan – excess heat can mean that water will evaporate much faster, so making sure that you have drip tape or a soaker hose that is slowly trickling water directly onto the soil towards the roots is the best plan. Using sprinklers and other above-soil watering devices is risky, in that there’s no guarantee that water will make it to your plant roots. And don’t forget to mulch, which will help keep that water in place!

3. Create shade, which can drop the temperature. To do this, use bendable metal hoops draped with ‘shade cloth’ over your plants OR simply plant more sensitive varieties in the shade of a taller plant (like the horseradish below, that’s shading the colorful gomphrena from the hot afternoon sun).



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Want to Know More? Check Out These Resources for Managing Heat in the Garden:

Timber Press Guide to Gardening in the Southeast

Timber Press Guide to Gardening in the Southwest


Managing Cold in the Garden

While you might think that dealing with cold weather in the garden is just a reversal of our practices for managing heat, there’s actually something really major at play that we must consider.

If you live in an area that experiences below-freezing temperatures, that usually means that you’re a significant distance from the equator – so lack of sun is actually your biggest issue! It’s hard to grow anything with limited sunlight.

So, your winter management goal is not just to protect your plants from snow, ice and wind, but to get them planted and grown to a life stage that can tolerate the cold and that you, the eater, also find tasty.

The goal, specifically, is to grow to maturity and to allow the plant to go dormant so that you can protect and harvest.

Timing is everything.

In terms of protection, you’re usually providing some warmth, a defense against harsh and damaging winds, and you’re also limiting fluctuations in humidity, which is crucial. This looks different for everyone, depending upon where you live, what you’re growing, and what materials you have on hand.

Most of us will use hoops or tunnels with row covers (aka ‘garden quilt’, ‘agribon’, or ‘remay’) and also plastic. Often times, you’re creating multiple tunnels, preserving some space for airflow in between each layer.

If you’d like to pursue managing cold in the garden, I highly recommend that you peruse some of the resources below, so that you can identify exactly what kind of materials and system will work in your garden. Each resource has phenomenally helpful charts for planting dates, temperature shifts and more.

Want to Know More? Check Out These Resources for Managing Cold in the Garden:

The Winter Harvest Handbook by Eliot Coleman

Four-Season Harvest by Eliot Coleman

Also, check out Mother of a Hubbard.com, Cathy Rehmeyer’s blog largely about growing for winter in Zone 6b.



Why do you Grow Food?

In this section we ask our listeners to share why they are growing food. This week Vanessa B shares why she loves growing food.

Lucky Vanessa won a collection of Liz’s heirloom leafy green seeds, available on Amazon.

Thanks for reading my blog : ) We appreciate your time and wish you much success in growing healthy food!