Question
We are having a discussion here at work.  Some say the best time to plant annuals is Mother's Day and some say Memorial Day.  Due to the climate in Wisconsin, when do you think the best time is to plant annuals?

Answer
Lynn,
Since I started my gardening in Wisconsin, and frequently visit my mother, who is a great gardener in Stevens Point, I am pretty familiar with your state.  You don't say where in Wisconsin you live, and this makes a difference. You can plant a great deal earlier in Madison but might need to wait until the end of the month if you live in Superior!

Basically, our climate has been getting warmer. Although it was common in the 60's and 70's to have a freeze at the end of May, it hasn't happened lately, either in Wisconsin or Massachusetts, where I now garden.  So gardeners such as myself who started planting in the 60's have Memorial Day as our guidepost for the time to plant, where as newer gardeners haven't experienced a freeze past the middle of May.

It isn't as simple as the last frost date, however, and in this sense both sides of this discussion are right. Although it is unlikely (though not impossible) that there will be a frost from now until the end of May, it is very likely that the temps will dip below 50 at night. There are many annuals such as Marigolds, Zinnias and Impatiens that do NOT do well when the temperatures dip below 50...at best, these plants will sulk until the temperatures rise, and at worst they will die.

Other annuals such as allysum, pansies, million bells and petunias are less sensitive to these lower night time temperatures, and although they too won't grow gangbusters until June, they won't suffer much in the mean time.

No matter what you are planting, you can't lose by waiting until the end of the month, but if you do plant early there is a chance that you might have to replace some of your plants.

At this time of year we are all SO HUNGRY to get our summer annuals in, especially after the winter that you in Wisconsin and we in Massachusetts just went through!  So perhaps the best thing to do is to savor the spring and do a little planting every weekend from now until Memorial Day - start off with the more cold-tolerant things, or planting in containers that can be brought into the garage when the forecast is for below 50 at night, and move onto the more sensitive things later in the month.

Wishing you all a wonderful summer,
C.L.
www.gardenlady.com