Great migration (of pots) is a sure sign of spring

You know spring is on the way because the great migration started last weekend.

I’m not talking about an avian migration, such as the one that carries Sandhill cranes overhead with their telltale screechy rattle. The big spring migration that truly indicates that we’re on the cusp of warm weather is the relocation of pots from the garage to their spots in the garden.

Shrubs grown in containers don’t generally fair well in winter in our harsh Wisconsin climate. The rule of thumb is that containerized plants should be rated for two hardiness zones lower than the one you live in. (Ozaukee County is zone 5, which corresponds to an average annual minimum winter temperature of -20 degrees.) But you can cheat the rule by offering containers some protection in winter.

My containerized shrubs winter in my unheated garage, which is not exactly the plant equivalent of Florida, but it provides enough protection to let them go dormant and keep them alive. I give them a little help by adding mulch on the top of the soil and some burlap wrapped around rose canes, which serves the additional purpose of reducing the chances of an eye being poked out when you attempt to fetch the snowblower. I water them a bit every six weeks or so.

Now with nighttime temperatures consistently above 25 degrees, it’s safe for the containers to come out of hiding.

The moving process requires an industrial handtruck (borrowed twice a year for the migration) and two people. Shrubs are not content to grow in small pots for long.

Two 24-inch diameter pots house cream-colored David Austin roses that are underplanted with annuals and anchor the corners of the driveway apron. When their burlap shrouds were removed they looked to be in good shape, with green stems and lots of swelling leaf buds.

Another pot is home to a ‘Green Mountain’ boxwood, which has been residing there for well over five years. In a few weeks I’ll carefully tip it out of its pot and freshen up the soil. I expect that will be a messy job, which is probably why I’m at least two years late in doing it.

Other pots grow shrubs that look great tucked around the garden, including the dwarf stahorn sumac (Rhus typhina) cultivar ‘Tiger Eyes’.

All are now in their summer locations, but protected from the wind, cold and sun, which they’ve only seen through a small window for the last several months, by a layer of fabric usually used for covering vegetable rows. I have learned not to rush the process of exposing them to the elements, and more than one plant has ended up in the compost heap thanks to my impatience for this process.

With that job done, there’s one more rite of spring sure to come for these containers — the one where we accidentally back into them with our cars.