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When Is The Last Spring Frost And When Should I Start Planting

15 years ago

Good evening,

I know that this may sound like a stupid to ask but I live in IL or the zone number listed above. I would like to know when is the last spring frost and when would it be safe to start planting. I have seeds that are annuals and perrinal bulbs. Some seeds are going into pots too.

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Comments (2)

ken_adrian Adrian MI cold Z5
15 years ago
it depends what you are planting ....

but even then.. mother nature is a cruel mistress ... and it is impossible to give you a specific date ....

for my zone 5 .... we are about 85% safe by 5/15 ... and USUALLY 100% safe by 5/25 .... but there is always that one freak year when stuff happens ...

all that said... seeds .. in the ground... arent affected by frost.. until they come up.. which takes 7 to 14 days or so depending on soil temps.. so you can actually plant.. a week or two ahead of last frost ...

perennial bulbs???... probably can be planted immediately .. depending on what you have and mean ... since perennials dont have bulbs ....

more info for more specific answers .. we love to teach.. fire away ... the ONLY stupid question.. is the un-asked question.. otherwise.. we will lead you down the garden path .. get it.. garden ... lol ..

ken
zen_man
15 years ago
emptysgirl,

"I would like to know when is the last spring frost and when would it be safe to start planting."

The best source of freeze data I have seen is from the National Climatic Data Center. This is the Freeze / Frost Occurrence Data for the State of Illinois. In order to apply the data for your use, you need to decide what constitutes a harmful freeze for you. The freeze thresholds available are 36, 32, and 28 degrees. A "hard freeze" would be 28Â°F. Only very tender plants would be killed by 36Â°F.

Then, look in the tables and find a weather station near to you. If none are right in your area, you could choose two towns on either side of you and interpolate their results for you.

Then, you decide on your gambling odds, and how much risk you want to take. The weather is a gamble and the best you can hope for is to know the odds. For Albion, IL the table says there is a 90% chance of a 28Â°F or lower freeze after March 16, so planting your stuff on that date would have a 90% chance of experiencing a killing frost. Not good odds. The table says there is a 50% chance of a 28Â°F freeze after March 31 in Albion. If you felt lucky you might plant on that date. The table says there is only a 10% chance of a 28Â°F frost after April 14 in Albion. That is a fairly safe bet, but still, 10% of the time you could lose that bet. That is how you would use that table, using Albion as an example.

ZM
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