Explore Plants

Share

Ask Mr. Smarty Plants

Ask Mr. Smarty Plants is a free service provided by the staff and volunteers at the Lady Bird Johnson Wildflower Center.

Search Smarty Plants
    
 

Can't find the answer in our existing FAQs, submit a question to Mr. Smarty Plants.
Need help with plant identification, visit the plant identification page.

rate this answer
11 ratings

Wednesday - October 31, 2007

From: Harrisso twp., MI
Region: Midwest
Topic: General Botany
Title: Plants killed by frost
Answered by: Barbara Medford

QUESTION:

In a frost why do flowers etc. die where grass will not die?

ANSWER:

To quote from one of our favorite books, Botany for Gardeners, Revised Edition, by Brian Capon:

"In winter, when the leaves of deciduous species have fallen, water movement comes to a standstill in the plant. If the remaining water freezes in its cells, its expansion ruptures the delicate cell membranes-a condition from which there is no recovery."

Very generally speaking, plants die without water in their systems. In a quick frost, some of the top blooms or leaves might get brown or fall off, but if the water in the stems is not frozen hard, the plant itself will survive. A longer frost, a real freeze, can freeze that stem moisture to the point that the plant dies from dehydration, as well as the damage from expansion of remaining water, as cited above. Many plants, especially what you might refer to as "flowers", are annuals. They really are only programmed to live one season, bloom, make seeds after blooming, spread the seeds, and then their purpose in life, which is to make other plants just like them, is finished. If they're still getting water and sunlight, they may linger on for the warm months of fall, perhaps even put out a few unenthusiastic blooms, but it doesn't take much cold to convince them it's time to fold the tent. Their seeds will sleep, insulated by the earth, until warmth, water and sunlight in the spring cause them to sprout and rise again.

Other plants, usually referred to as perennials, which can include flowering plants, shrubs and trees, have deep root systems, again kept warmer by the earth. In its dormancy, and often without leaves, the plant is able to draw nutrients from the root material. The plant may drop leaves and blossoms, twigs die on the end and the whole plant can look like it's dead but, again, warmth and moisture will call them back to life after several months of dormancy.

More specifically, lots of grasses have still more protection, in that they already are growing low to the ground, where there is a thin layer of air warmed by the reflection of the sun on the earth. Decomposing organic material in the soil causes warmth to be generated year-round, which protects roots from freezing. There are parts of the world, of course, where even the soil freezes, and the plants that survive from year to year there have even more sturdy survival tactics. In parts of the world where it gets that cold, even grasses often have to be replanted every year. However, in the more temperate parts of the world, many grasses have rhizomes, underground root systems, really tubers, that can go as much as 18" deep in the dirt, ride out the cold, and pop up, usually where you don't want them, at the first sign of warm air.

 

More General Botany Questions

Correct spelling of Passiflora caerulea
August 07, 2007 - What is correct, passiflora coerulea or caerulea ?
view the full question and answer

Comments on article in Austin paper
January 22, 2012 - Why can't we comment on your piece in the Statesman? It says no comments possible at the bottom.
view the full question and answer

Century plant dying after bloom
August 12, 2007 - My century plant is so tall that it is up to the top of the telephone pole top lines that carry our streets electric. I was wanting to know if you knew if I cut the stock off would it save the plant ...
view the full question and answer

How does Styrax youngiae differ from other Texas Styrax species?
August 18, 2013 - How does the Styrax youngae differ from other Texas styrax? Where can I find a description of all the Texas styrax trees?
view the full question and answer

Can foxglove poison be transmitted to the soil and taken up by another plant
May 29, 2012 - Hi Mr. Smarty Plants, Recently I discovered a Foxglove that had come up after being planted 2 or 3 yrs ago. Next to it I have some medicinal Feverfew growing. (They were so close together I suspec...
view the full question and answer

Smarty Plants's Facebook profile Support the Wildflower Center by Donating Online or Becoming a Member today.

Mr. Smarty Plants wants you to be his Facebook friend. Click the Facebook icon to add yourself to Mr. Smarty Plants list of friends.