Flex-wrap does not wrap items in IE11

Add flex: auto to the first child.

For image scaling, add img { width: 100%; height: auto; }

.d1 {
  display: flex;
  flex-wrap: wrap;
  padding: 4%;
}

.image-container {
  align-items: center;
  display: flex;
  flex: auto; /* adjustment */
  justify-content: center;
  max-width: 250px; /* optional; limits image size */
}


/* image scaling */
img {
  width: 100%;
  height: auto;
}

.d1 .text {
  flex: 1;
  padding: 2%;
}
<div class="d1">
  <div class="image-container">
    <img src="https://emilythompsonflowers.com/wp-content/uploads/2016/08/hippie-flower-300x300.jpg">
  </div>
  <div class="text">
    Lorem ipsum dolor sit amet, consectetur adipisicing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua. Ut enim ad minim veniam, quis nostrud exercitation ullamco laboris nisi ut aliquip ex ea commodo consequat. Duis aute irure dolor
    in reprehenderit in voluptate velit esse cillum dolore eu fugiat nulla pariatur. Excepteur sint occaecat cupidatat non proident, sunt in culpa qui officia deserunt mollit anim id est laborum.
  </div>
</div>


You could refer to this code sample. The image is original size at first and the left and right parts are of the same width. It works well in IE 11 :

.d1 {
  display: flex;
  flex-wrap: wrap;
  padding: 4%;
}

.image-container {
  align-items: center;
  display: flex;
  flex: 1;
  justify-content: center;
  min-width: 200px;
}

.d1 .text {
  flex: 1;
  padding: 2%;
}

/* adjustment */
img {
  width: 100%;
  height: auto;
  max-width: 300px;
}
<div class="d1">
  <div class="image-container">
    <img src="https://emilythompsonflowers.com/wp-content/uploads/2016/08/hippie-flower-300x300.jpg">
  </div>
  <div class="text">
    Lorem ipsum dolor sit amet, consectetur adipisicing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua. Ut enim ad minim veniam, quis nostrud exercitation ullamco laboris nisi ut aliquip ex ea commodo consequat. Duis aute irure dolor
    in reprehenderit in voluptate velit esse cillum dolore eu fugiat nulla pariatur. Excepteur sint occaecat cupidatat non proident, sunt in culpa qui officia deserunt mollit anim id est laborum.
  </div>
</div>

Result in IE:

enter image description here