When I was in graduate school I lived in a hillside apartment that had beautiful four o’clock flowers in the front yard. They came in different colors, mostly bright pink to magenta, and they self-seeded themselves every year. I liked them. Hummingbirds liked them too. Even the large shiny black seeds were pretty.
Every afternoon the flowers would open, and the front yard went from green to colorful. Generally, four o’clocks (Mirabilis jalapa) grow better in full sun, but this area was partially shaded.
The soil wasn’t overly fertile in that spot. These plants grow best in deep fertile soil, but they thrived anyway. I never watered them either, and I remember 1983 was a very dry year in West Virginia. Four o’clocks usually have few disease and insect problems, which makes for low maintenance.
Plants grow two to four feet tall, so they can be pruned into a hedge for the growing season. Four o’clocks bloom throughout the summer and fall, and the flowers are quite fragrant. They die to the ground in winter.
Four o’clocks are in the nightshade family along with potato, tomato, peppers, eggplant and tobacco. This one is bred for its flowers. I wouldn’t recommend eating it.
When I moved to North Carolina I learned to dislike this plant. They became a true perennial and developed huge tubers that virtually engulfed whole flowerbeds. In all but the sandiest soils they were nearly impossible to remove.
If that weren’t enough, the large black seeds spread everywhere. I never noticed this before in northern areas. Perhaps that’s because I lived in town. Birds eat the seeds, so this can be quite an invasive plant in warm climates like ours.
This nightshade family member is one of the plants deer and rabbits normally avoid. When plants are damaged they usually recover quickly. Deer, dogs and other animals may not eat landscaping, but they still trample it.
Speaking of dogs, four o’clock tubers and seeds are highly toxic to them. Dogs, especially puppies often like to dig up and chew on the tubers. Alkaloids are the likely toxicity culprit. Symptoms range from vomiting, diarrhea, skin rash and redness around the mouth. When detected early it isn’t fatal.
Regardless, it’s not a good idea to treat it yourself. If you suspect four o’clock poisoning, the smartest option is to take your animal to your local vet.
Many broadleaf weed killers will kill four o’clocks. This is probably the way to go when they spread into lawns. Round-up will control it too, but you must be careful to hit only the targeted plants.
As far as four o’clock culture goes, they are great north of zone seven. In warmer climates some thought is required. Eventually they will take over an area, and that is fine if you like them. Another option is to plant them in pots.
Likely they won’t overwinter in pots around here, but it wouldn’t matter if they did. I still have a soft spot for them, but I prefer to plant them away from other things.
Sorry, I posted the wrong picture earlier. That one was evening primrose and I’ll post that column next week.
Ted Manzer teaches agriculture at Northeastern High School (firstname.lastname@example.org).