Yes, will brunnera spread is a fair question and the short answer is yes, but at a slow and steady pace. This plant spreads in a moderate way, not in a wild or aggressive form. You will not see it take over your beds the way mint or ivy might in just one season.
In my experience, brunnera spread is slow but sure. When I first put a Jack Frost in my front bed about four years ago, I found a small clump of just 18 inches across. Now I have a plant that sits at about 30 inches wide and looks great. I learned the growth was slow but steady each year.
The way this plant spreads comes from its root system. Brunnera rhizomes are short, fat root stems that grow just under the soil. These stems push out a bit each year. They send up new leaves at the edge of the clump as they grow.
Each spring, the rhizomes wake up and push out a few inches of new growth. The clump gets a bit wider but stays in one spot. The plant will not send runners across your yard. It will not pop up in places you did not plant it through root spread alone.
Mature clumps reach 18 to 30 inches (45 to 75 centimeters) wide at full size. Most plants hit this size in three to four years from a one gallon pot. Some big-leaf forms like Looking Glass can spread a touch wider. The growth slows down once the clump hits this mature size.
Brunnera ground cover effect works well in shade beds where you want full leaf coverage. Plant clumps about two feet apart for a solid cover in three to four years. The big heart shaped leaves will fill in the space and block out most weeds. This makes brunnera a top choice for shady spots that need both beauty and weed control.
Some forms of brunnera can spread through seed too. Brunnera self seeding happens with the older non patented types like the plain green species. The named cultivars such as Jack Frost rarely set viable seed. Even when they do, the seedlings come up plain green and not silver.
To keep spread in check, just divide your clumps every three to four years in early spring. Use a sharp spade to cut the clump into chunks and replant them. You can also share these divisions with friends or fill in other shady spots in your yard.
Deadhead the flower stems after bloom to stop any self seeding. Cut the spent stems down to the base of the plant in late spring. This keeps your bed tidy and stops random seedlings from popping up. Your brunnera will give you years of slow, easy growth without ever taking over.
I always tell new gardeners to plant brunnera with full trust. You will not regret the choice in five or ten years from now. The clumps stay where you put them and look better each year. I have found brunnera to be one of the best behaved plants in my whole shade garden.
Plan your bed with the 30 inch mature size in mind from day one. Give each plant enough room to fill out without crowding its neighbors. Pair brunnera with hostas, ferns, and astilbe for a lush mix of shade plants. Your bed will look full within a few short years.
Read the full article: Brunnera Plant Growing and Care Guide
