Q: I keep having trouble with Cardinal Flower in my garden… it disappears and I need to replace it every few years. Is it getting diseased, or am I not giving it what it needs? When it is growing, it seems healthy.
A: If the plant’s growth looks normal and vigorous, then it’s probably in the right conditions, and it’s just the ruderal trait of the plant you’re dealing with that’s causing the periodic vanishing act.
Ruderal plants are those that colonize disturbed habitats (think of “rubble,” the origin of the term in Latin). Examples of events promoting ruderal plant growth include wildfire, soil erosion or regrading, and clearings formed by storm-felled trees or deforestation for development. In garden settings, this can also include areas repeatedly disturbed by digging, like transplanting perennials or installing annuals.
Ruderal species tend to be short-lived. In the wild, ruderals germinate from the seed bank when conditions favor them and their colonization of a habitat that suddenly has less competition. Besides Cardinal Flower (Lobelia cardinalis), Columbine (Aquilegia), wild petunias (Ruellia, which isn’t a petunia relative), and blanket flower (Gaillardia) are other examples of ruderal species.
Ecologically, they fill an important niche, stabilizing soils to reduce erosion, supporting beneficial soil microbes and wildlife, and (when the ruderal species in question is native) competing with invasive species also vying to colonize available ground.
You may find that light soil disturbance every couple of years allows Cardinal Flower seeds already in the soil from prior generations to germinate. This can help perpetuate the planting without you having to buy more to refill their void in the garden. If you’d rather not depend on self-seeding (if plants pop up where you don’t want them), you can try collecting ripe seed and sowing it yourself so you can manage where the Lobelia grows once the seedlings are old enough to be planted out.
Q: Do I need to do anything to my aging strawberry bed? The plants are looking tired and scraggly.
A: Due to diseases and crowding from several seasons of growth, June-bearing strawberry cultivars typically decline after three to four years. You can start a new bed with fresh plants in a new location, or renovate the old bed. (Don’t move runners from an old bed if you had problems with insect pests and diseases, or else you’ll just contaminate that new planting.)
Our Growing Strawberries in a Home Garden web page guides this issue and includes a link to a video demonstration of bed renovation by the University of Maine. For novice strawberry growers, this technique may look brutal for the plants, but they rejuvenate well and the refreshing of growth is needed to keep them productive and vigorous.
After the end of the second-year harvest, mow or manually trim plants to a height of 2 to 3 inches, or just above the crowns. Apply fertilizer, then thin the “daughter” plants to 6 inches apart. Use a garden spade or other hand tool to turn under or remove runners that strayed beyond the 12- to 18-inch-wide growing bed, leaving a bed of mingled mother and daughter plants.
Repeat the third year: mow, fertilize, and thin daughter plants to 6 inches apart. In the fourth year, alter this process by turning under the mother plants and allow only the strongest daughter plants to form the 12- to 18-inch-wide beds. Plant new plants every three years if you’re growing strawberries in containers.
University of Maryland Extension’s Home and Garden Information Center offers free gardening and pest information at extension.umd.edu/hgic. Click “Ask Extension” to send questions and photos.