First frost dates in the fall and last frost dates in the spring are based on recorded historical data - but remember - everyone will need to watch that ten-day forecast! (Then remember to keep checking it daily since even the ten-day forecast can change!)
Changing weather patterns can affect temperature swings from one day to the next, and have become increasingly common or more frequent. So, even though your zip code may produce dates that are considered "frost-free", you will still need to pay attention to the predicted weather in your immediate area!
We’re all itching to get outdoors and get planting and playing in the soil! But when life and death for your plants can depend on just a few degrees, it’s vital you pay attention and don’t get ahead of yourself and the weather.
- Frosts and FreezesHow Chill Damages Plants
- Types of Frost Damage
- When Should I Cover My Plants?
- Spring Planting Guidelines
- How to Tell When It’s Safe To Plant Seeds and Seedlings
- How to Tell When It’s Safe To Plant Annuals, Vegetables & Bedding Plants
- How to Tell When It’s Safe To Plant Dormant Plants & Bareroot
- What to Expect for Dormant Plant Delivery
- How to Tell When It’s Safe To Plant Container Perennials, Shrubs & Trees
- Get Planting This Spring Without Worry!
First and last frost dates are simply a suggested guide to assist you when you start growing seeds, and for you to purchase plants that will eventually be planted outdoors. Save yourself time, money, and heartache by paying close attention to what mother nature has in store for you and your garden!
Frosts and Freezes
Frost is essentially frozen dew and water vapor in the air that collects onto leaves, the ground, your cars windshields, and other surfaces like condensation does on a cold beverage. But when the temperatures drop, these droplets freeze. When the temperatures dip into the mid to upper 30s and wind remains calm, frost forms. A freeze occurs when temperatures are at or below 32 degrees, and winds prevent the formation of frost.
Weather Terminology:
- Cold Weather Advisory - Typically 32°- 45°F
- Frost Advisory - Light frost warnings are between 29°-32°F
- Freeze Warning - Moderate freeze between 25°-28°F
- Hard Freeze - Temperatures 25°F and below. The ground is frozen solid
Remember, it is not just the temperature to be concerned about - but the length of time during which temperatures remain at or below freezing!
How Chill Damages Plants
One of the most difficult things for all plants to tolerate is wild temperature swings! Spring's early warm patches may push out plant growth or flower buds prematurely - then suffer when a frost hits. Autumn can have warm bouts of weather followed by drastic temperature drops at night and the damage won’t show until the following spring! These changes in temperatures are more common in the turbulent weather of today, so pay close attention to the forecast in spring and fall.
Increased and more frequent temperature swings, increasingly severe and unpredictable weather, drought, and flooding are all being seen in some areas - more than often occurring all in the same year!
Types of Frost Damage
Frosts can either break cell walls due to swelling and expansion or evaporate moisture right out of the plant like wilted spinach. While there are many scientific names like advection frost, radiation frost, and evaporation frost, gardeners need to worry about:
- White frost - Ice forming on the plant's exterior because of humid air, calm winds, and clear skies.
- Black frost - no ice forms on the plant due to low air humidity and low soil moisture. Named for the color the plant turns.
Most wild temperature swings occur in both the fall and the spring. Many of the southern states have experienced extremely warm periods and then a quick sharp drop in temperatures of 50 or 60 degrees is one of the hardest things on plants. Northern states have the opposite, stretches of cool to cold weather with brief warm-ups that can sometimes trigger plants to bloom or sprout leaves prematurely.
Different sources will offer different ranges and that is because no one can predict with any accuracy those frost-free dates. Unusually early spring warm temperatures may cause plants to prematurely begin to grow - and then delayed cold snaps that may freeze off the tender new growth is also something that is being seen across the US.
When Should I Cover My Plants?
Frost and freezing occur when temperatures are at or below 32°F (0°C). Frost-tender plants are damaged under 40°F if the plants are in low areas where cold air sinks. Plus the weatherman isn’t always 100% correct, so any time it could possibly dip near your plant's tolerance range is when you should act.
For frost-free dates, use a trusted source. As a guide, check your area for frost-free dates, and then watch the forecasts! Look up your growing zones by zip code on the USDA website or here at Nature Hills, and use this info to find the first and last frost dates for your area. Or you can head over to your local County Extension Office, or check out morningchores.com Find the First and Last Frost Dates in Your Area by ZIP Code
Spring Planting Guidelines
Types of Plants to Protect From Cold
Factors to consider before you cover everything in your garden with your favorite linens:
- A plant or bulb that’s non-native or outside your growing zone
- Newly planted plants
- A plant that just leafed out or bloomed
- Sheltered -vs- exposed locations
- Seedlings or houseplants that are not hardened off yet
- Protect tender perennials in spring and fall
How to Tell When It’s Safe To Plant Seeds and Seedlings
Since seeds that you buy are usually already ready to be planted as soon as the ground is workable. Seeds you’ve gathered yourself should go through a chilling process called stratification, which triggers certain hormones that ready the seed to get ready to grow once temperatures are just right. You can find stratification information with a quick internet search.
So as soon as you can plant seeds in the ground outdoors in spring, go for it! Water them well and ensure they are covered with soil appropriately. They will stay safe under the ground until they are ready to grow at the right time based on that particular seeds temperature needs.
Seeds that have been started indoors and are actively growing should be ‘hardened off’ by moving them outdoors in the cool, but not freezing temperatures during the day, then brought back indoors for the night. This process should be done for a few weeks before they are planted outdoors permanently. You can also put your seedlings into a cold frame for the spring.
Once planted, however, be ready to run outside at night with a cover or cloche in the event of an unexpected frost or freeze.
How to Tell When It’s Safe To Plant Annuals, Vegetables & Bedding Plants
Vegetables and annual plants can be purchased before they get planted out so you have better availability, but you may have to hold these plants in an area where they are protected from frost.
This may mean keeping them in the flats or containers they were bought in so they can easily be moved outside in the sun when above freezing, but then easily moved in a garage or covered to protect from cold. Once that weather pattern changes and the temps are to remain above freezing - then you may decide it is time to plant them out
How to Tell When It’s Safe To Plant Dormant Plants & Bareroot
The nice thing about planting dormant plants or bareroot plants that Nature Hills have just delivered to your doorstep is that you can simply plant them right outdoors without much worry!
Dormant plants that have been planted will simply come out of dormancy naturally as the temperatures warm and plants will respond naturally by beginning to grow. Bareroot plants are coming from our coolers where they are held dormant until they are shipped and planted into warmer temps. The only thing you have to pay attention to is once those new shoots and leaves begin to develop, as they are very tender.
Watch the forecast to see when temps below freezing are suggested and cover them up with something to prevent damage to the new growth. Eventually, they will be in the clear.
What to Expect for Dormant Plant Delivery
With spring and fall shipments, please know that our plants can be in varying stages of being dormant to breaking dormancy. A tree or shrub may have some spotted, tired leaves that remain from last year in the elements. It’s completely normal in the autumn and early spring for fruit trees to arrive with no leaves at all!
Herbaceous Perennial plants are typically pruned down, perhaps all the way to the soil, so it may appear we’ve shipped you a pot of dirt with some stubble. Nope! You have a fully established, power-packed root system that is ready to leap out of the ground in spring once those roots warm up and have some wiggle room free of their pot!
Water your plants in very well and place a 3-4 inch thick layer of arborist mulch over the soil surface - extending a couple of feet from the trunk, but not piled up against the trunk or stems.
How to Tell When It’s Safe To Plant Container Perennials, Shrubs & Trees
Planting in the spring can be a tightrope walk with temperatures and timing. But as long as your container plants are not full of leaves and the ground is “workable” (no longer frozen and it is not too wet to work with) and you are past the suggested last-frost date. But mother nature always has some curveballs in the wings, so be ready to throw a protective cover over your plant for a light freeze, or be ready to add more protection should there be a storm.
If your plants froze overnight and you forgot to cover them, it may be beneficial to immediately spray the plants with cold water from the hose to bring the temperature above freezing.
Once planted, water them in well and keep them regularly watered as long as temps remain above freezing. Mulch well to help further hold in moisture and insulate the roots.
Get Planting This Spring Without Worry!
These frost-free dates are simply a guide. They are going to change yearly and weather patterns can change the planting dates overnight! Pay attention to your local extension offices and to your local weather forecasts before doing a lot of your planting.
So use those warm days for garden prep, and save the planting until a bit later. We are all itching to get out of doors and start planting, but a moment's hesitation will save you from the heartache of seeing those new plants frozen back or worse!
Happy Spring and Happy Planting!
