How to harden off your plants

One of the most important parts of growing a successful garden is getting your plats hardened off.

What plants do you need to harden off?

Not all plants need hardening.

If you’re growing in a greenhouse, any plants going in there don’t need to go through this process.

Direct seeded plants don’t need hardening (maybe this is obvious). If you’re seeding directly into your garden beds, your seedlings will pop up all ready to deal head-on with the elements. This is a big benefit of direct seeding.

ALL other plants will need some hardening off.

Stock, snapdragons and other cool-hardy flowers getting hardened off under shade cloth.

Plants need some sort of gradual adjustment to outdoor conditions. After being cozy and warm indoors for their entire lives, it can be stressful to get popped directly outdoors.

The first plants I harden off in the spring are all the “cool-hardy’s”. These are plants that can survive a light frost and include the following:

• Most salad greens

• Spinach

• Kale

• Broccoli

• Peas

• Onions

• Snapdragons

• Bupleurum

• Poppies

• Rudbeckia

• Calendula

• Ammi

• Strawflower

• Campanula

• Nigella

• Most perennial flowers that are suited to your zone.

In general, to get fully hardened off, plants need about 3-5 days in the shade.

When nighttime temps are steadily in the 30s, the above varieties can be set out in a shady spot. In previous years I was moving my plants all over the place, from shady spot to shady spot.

This year I finally streamlined my process and started using hoops (made of thick wire and then stuck in the ground) and draping 30% shade cloth over the top.

My cool loving plants go in here and in 3-5 days we’re good for planting!

For warm-season plants, I’m a little more cautious. Ideally, before hardening these crops, our night temperatures would be in the 45 + zone. In Alaska, this can be a tall order!

So for these, I watch the weather and put them in their shade hoop when temps are in the 40s or higher. Using past last frost dates can work but since each spring is so different sometimes it’s hard to predict.

To help any early-planting anxiety you may have about cold temps, you can always add extra protection by putting a layer of Agribon over the hoop as well.

In fact, this would have helped me this season as I pushed it a little with a few varieties and killed off a few trays during a spotty frost that struck our neighborhood last week.

(sigh)

I guess it’s just a good reminder that a good fail is always the best way to be successful in the end!

30% shade cloth hooped over my cool-hardy flowers.