Now that spring is here and the ground is thawing, it's time to get out in the garden and inspect any winter damage. It can be tricky to tell from first glance whether a plant has died from frost or is simply still dormant. But, there's a 10-second trick pro gardeners use to get an immediate answer: the plant scratch test.
It's something to stick at the top of your spring gardening checklist, even if you followed all precautions to protect your plants from frost. By simply scratching plant stems (you can use a garden knife, like this one from Amazon), you can see if they're green inside, indicating good health, or brown, indicating dead plant matter.
It's particularly useful for trees, shrubs, and woody perennials that are transitioning out of dormancy, so you can figure out the right next steps for them. Here, the experts explain why this test works, how to do it, and what to do if the results show brown – spoiler: it doesn't mean you have to throw away the whole plant.
What Is the Plant Scratch Test?
If you live in the coldest US hardiness zones or had a particularly brutal winter, then the plant scratch test is a useful thing to do before getting stuck in with spring gardening.
'I'm in Northern Michigan where we have very long winters. The scratch test is common practice for us at this time of year,' says Anna Ohler, owner of Bright Lane Gardens.
'The scratch test is one of the easiest ways to check if a woody plant is dead or just dormant after a frost.
'I gently scrape a small bit of bark with my fingernail or pruners (you can also use this garden knife from Burpee) to expose the tissue underneath,' she explains.
It's the color beneath the newly exposed area that determines the status of your plant.
'If it’s green and slightly moist, the plant is still alive. If it’s brown and dry, that section is dead,' Anna says.
'This works because you’re checking the 'cambium' layer, which is the living growth tissue just under the bark.
'Frost can damage the outer growth, but the inside can still be perfectly healthy,' she explains.
'This works because it gives you a peak inside the stems to see what the plant is doing,' adds Staci Hill from Gooseberry Bridge Farm.
'Dormant plants can look dead to us from the outside but really they’re just sleeping and waiting for spring,' she says.
What to Do If the Results Are Brown
If the plant scratch test revealed green tissue beneath your plant, then the good news is it hasn't experienced severe damage from frost and is likely to emerge from dormancy with the right spring care – specific to the plant of course.
'If a side branch appears to be brown after preforming the test, move down the plant and try again,' suggests Staci.
'Sometimes the outer branches are dead but the main stems are still alive,' she explains.
'Often there’s still green tissue lower on the branch, and that’s where I prune back to,' Anna adds.
As Staci and Anna explain, it might be that just certain branches or stems have taken a beating from frost, with plenty of healthy tissue on your plant to still work with.
You should use essential pruning tools (like these Fiskars bypass pruning shears from Amazon) to remove the dead pant material and encourage new growth for recovery.
However, if you've used the plant scratch test on varying points, it has shown brown every time, and it appears extremely brittle and dry, then it's unlikely to recover and it might be best to remove it.
'My biggest tip is don't rush to rip plants out. Some shrubs just wake up slowly, especially after a cold spring or extended winter. Patience saves a lot of plants,' Anna advises.
FAQs
Can You Use the Plant Scratch Test After Extreme Heat?
While the plant scratch test is primarily associated with checking plant health after extreme winters, it can be used after exposure to any extreme weather. If you've had an unusually hot summer, for example, the scratch test will quickly tell you if your plants have died back as a result or if there is hope of reviving them.
One of the best ways to help your plants cope with freezing winters is by boosting your yard's resilience to extreme weather.
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