Science communication


My acorn obsession

Watching an acorn grow into a seedling helps to pass the long, dark winter

I blame Estrid Ericson for my obsession. An art teacher and pewter artist, Ericson founded the interior furnishing store Svenskt Tenn in 1924. She later partnered with Josef Frank, an Austrian architect who fled to Sweden before World War II, to create what is now known as Swedish Modern design. Frank designed amazing fabrics and furniture that are still sold today. (Tip: If you come to Stockholm, Svenskt Tenn is worth a stop. I always take visitors there).

One of the more affordable items for purchase is a small vase that Ericson designed to hold an acorn. When I saw it, I knew I had to have it. And once I had the vase, I was on a quest for acorns. It was February at the time and I searched for acorns on the frozen ground beneath oak trees. Unfortunately, the only ones I found had been partially eaten or were crushed. So, I had to wait until autumn.

Once summer passed and it was finally acorn season, the next step was to get at least one to “hatch”. I found out the hard way that you cannot put a freshly collected acorn in the vase. The acorn first needs to have a bit of root production. After some more trial, error, and web searches, I found a method that works.


The root structure is quite fascinating and the vase is a great way to appreciate it


Grow your own oak tree

  1. Collect ripened acorns from the ground during autumn. Small holes indicate that an insect has likely eaten the contents of the acorn – avoid these. (Tip: don’t collect more acorns than you think you will plant. My hatching rate was quite high, and I ended up with a small forest of tiny oak trees.)
  2. Float test: put all the acorns in a bowl of water; discard the ones that float.
  3. Put the acorns in a container/plastic bag with potting soil. The soil should be slightly moist but not damp. Place the container/bag in the refrigerator.
  4. After 2-3 weeks, check the acorns to see if a root has emerged. If not, put back in the fridge and check in a week or so. If you do see a root, you can transfer the acorn to the vase (or find a bottle with a small opening). You can also plant the acorn directly in a pot with soil.
  5. Enjoy!

Acorn fun facts

acornA page from a 1920's tree field guide

  • There are about 600 species of oak that produce acorns, in the genus Quercus.
  • Oak trees are pollinated by the wind.
  • A common motif in home decorating and heraldry, acorns symbolize strength, honor, longevity, life, and fertility.
  • Acorns contain tannins, which are bitter tasting and interfere with an animal's ability to metabolize protein. Acorns can be toxic to horses and cows.
  • In early human history, acorns were an important food source. Today, they have largely been replaced by grains.
  • Oak trees produce acorns annually. Trees in a region synchronize their acorn production, and the volume of acorns can vary dramatically between years.*

*This variation affects animals, such as deer, mice, squirrels, and jay birds, that rely on acorns for food and causes “boom and bust” cycles in their populations. While weather conditions, such as drought, can affect acorn production, research suggests other possible reasons. One hypothesis is that variable acorn production is a strategy that evolved in response to seed predation. In “boom” years, more acorns are produced than can be eaten or stored by animals, allowing some acorns to grow into trees. Another hypothesis is that oaks are trying to maximize pollination efficiency by flowering and releasing pollen at the same time (which results in greater acorn production). I noticed there were substantially fewer acorns on the Stockholm University campus this year compared to last year.

oakI have a forest of oak trees in my office

Michelle McCrackin