new seedlings, plants, hardening off plants

In Minnesota, April brings the new welcoming of season and an eagerness to get outdoors. While we are all anxious to jump into Spring, we should practice the patience of a gardener, carefully and cautiously when starting our gardening outdoors.  There are steps to take to appropriately harden off your plants and seedlings to prepare them for the unpredictable nighttime freezing temperatures, or the occasional April blizzards.

Here at Heidi’s Growhaus and Lifestyle Gardens, we commit proper routine practice of hardening off our products. We would like to share our knowledge with you on the importance of acclimating your plants to new environments along with the steps to do so.

Hardening off plants is the process of acclimating your plants to new conditions other than indoors or the greenhouse they came from. Your new seedlings and plants are delicate and can quickly be harmed when put outside to face the elements. Wind, drastic changing temperatures, sun and rain, can cause your plants to be shocked and potentially stunt their growth.

There are a variety of actions to take when planning to harden off your plants. Follow these steps to best harden off your plants and get them ready for the full season of growth ahead.

Hardening Off Plants Steps:

  1. Be mindful of your transplant date. Set a date when you’d like to plant your seedlings into your garden. Hardening off should start at least ten days before your planting date. Note, it is recommended soil temperatures reach 50 degrees before planting any new plants in the ground outdoors.
  2. Set three to four hours a day for your plants and seedlings to acclimate. Do this by placing them outside in an enclosed place of shade and shelter from the wind. As the days go by gradually increase the hours of exposure outside.
  3. Bring your plants back inside each night. Place them somewhere warm, whether it be a heated garage or heated patio.
  4. After the first three days, place your plants and seedlings in the morning sun. In the afternoon place them back into the shade as leaving them in the sun too long can scorch their leaves.
  5. Once temperatures consistently stay in the fifties during the day and overnight, your plants are able to remain outside.
  6. After about a week to ten days of full exposure, it is time to transplant your plants and seedlings into the garden, remember to water thoroughly once planted.

Gardeing with tools, hardening off plants

Some important things to consider during the hardening off process is to make sure your plants are watered only when they need to be watered. You will also want to protect your plants and seedlings from animals and pests when outdoors. It is important to be mindful of what type of plants and seedlings you are planning to transplant when hardening off. Below is a guide to help determine when is the best time to begin the hardening off process.

Very Hardy Plants

These plants can withstand more drastic frosts.

Vegetable Garden

  • Asparagus
  • Collards
  • Endive
  • Kale
  • Kohlrabi
  • Lettuce
  • Mustard
  • Onion
  • Peas
  • Potatoes
  • Rhubarb
  • Rutabaga
  • Salsify
  • Spinach
  • Turnips

Annual Ornamental Plants (Up to 28 inches)

  • Alysum
  • Ivy
  • Lemon Cypress
  • Lobelia
  • Lysimachia
  • Pansies
  • Snapdragon
  • Viola

These plants and seedlings are recommended to be planted four to six weeks before frost-free dates. We offer a variety of plants for your gardenscapes, see Annuals here.

Frost Tolerant Plants

These plants and seedlings can withstand a light frost.

  • Beets
  • Broccoli
  • Brussel Spouts
  • Cabbage
  • Carrots
  • Cauliflower
  • Celeriac
  • Celcery
  • Chard
  • Chinese Cabbage
  • Jerusalem Artichoke
  • Onion
  • Parsnips
  • Radishes

These plants and seedlings are recommended to be planted two to three weeks before the last average frost.

Tender Plants

These plants and seedlings do not germinate in cold soil and can be injured or killed by any frost.

  • Snap Peas
  • Sweet Corn
  • Tomato

Tender plants need to be planted on or after the frost-free date.

Warm Plants

These plants and seedlings love and thrive in warmer temperatures.

  • Lima Beans
  • Cucumber
  • Eggplant
  • Muskmelon
  • Okra
  • Pepper
  • Pumpkin
  • Summer Squash
  • Winter Squash
  • Sweet Potatoes
  • Watermelon

Warm plants cannot withstand cold temperatures and need warm soil to germinate. The recommend period to plant these plants and seedlings is one to two weeks after the last average frost-free date.

You can find many of these different kinds of seeds, seedlings and plants at our Growhaus. You can shop our online shop here, we offer curbside pickup and delivery (terms of service apply). Our offerings are always changing, if you don’t see what you’re looking for please give us a call at 763-420-2909 or email

It is so important to take these hardening off steps for your plants to properly acclimate to their new home. As we all know Minnesota weather can change drastically, especially during April months, it is especially important to take into consideration temperature and weather changes that occur from day to day, and sometimes even hour by hour.

planting in a garden, hardening of plants

We hope this guide helps you to achieve your Spring gardening goals in preparation for an amazing summer of growing! Remember we are here for all your gardening needs and essentials. We carry everything from plants, gardening equipment, pots, décor, and more! Get out and play and enjoy this time getting to know your plants and nature!