19 May When do I plant annual flowers in Minnesota?
Minnesota is a very mercurial weather state which makes it difficult to know when to plant annuals. It is incredibly hard to predict when the weather will turn warm for good. Just look at the current spring versus the spring last year. Last spring’s warm weather did not really start until June because we had our last snow storm in early May. This year was a much more drawn out spring where the last snow fall was in early April. However, the temperatures have fluctuated all over the place.
We’re going to discuss the factors that determine when to plant different types of annuals. The most important factor is the frost date but the type of annual flower also matters.
Why does the frost date matter?
The last frost date is crucial when planting annuals flowers and plants. These “one season” plants are not as hardy as perennials or shrubs so they are affected much more by cold temperatures. They are also not buried as deeply in the ground and do not have the same established root systems that perennials and shrubs have. When the weather turns cold, the water in the plants and around the plant can freeze and harm growth or even kill it. So it’s really important to know when the last frost date occurs.
When is the last frost date for Minnesota?
The average last frost date for the Twin Cities is May 21. It gets up to June 15 in the northern regions of Minnesota. Keep in mind that that’s an average so it can fluctuate between earlier and later. However, if at all possible, we try to plant our annuals in pots or displays after this date.
This year is a perfect example of why you should be patient and not overzealous with your annual plantings. Just this week (writing this on May 20 or so) the temperature will get down to 35° F in the Twin Cities and even colder in other parts of Minnesota. That spells doom for many annuals. Patience is a virtue, especially when it comes to annual planting.
Are different types of annuals hardier than other types?
Annuals are separated into three different kind of plants. Hardy annuals can survive quite cold weather (into the 20’s F). Some examples of hardy annuals include Sweet Pea, Bachelor’s Button, and Pot Marigold. These plants are resilient and actually do better in the cold weather than the hot summer sun.
Another type of annual is the half-hardy annual. These annuals can tolerate weather into the 30’s F. There are a ton of plants that fit into this category including marigolds, dusty miller, ageratum, petunias, cleome, and nicotiana. The most spectacular annuals are the tropical or exotic annuals like Begonias and Impatients. Unfortunately, these are also the most tender and popular type of annuals. You would not want these plants to hit any weather below 40°F. Make sure to wait until June to plant these, if at all possible.
If you need more information about annuals in Minnesota, check out this document from the University of Minnesota. You can also give us a call at 763-568-7251 for any of your annual planting needs. We love designing annual pots, window boxes, or annual planters for homes and businesses. We are a full service landscape design and installation company with over 10 years of experience.