A is for aggressive.
B is for bully.
C is for colonizer.
The ABC set of descriptors are synonymous with invasive species. Invasive species are very successful exotics, i.e., colonizers that have been for the most part released of what keeps them in check. They are damaging to the environment.
But the ABCs could also be easily ascribed to a number of native species, too. And it is those species that we have to be careful about when gardening, particularly in a small garden on the boulevard. It really pays to research what you introduce and invite to stay as a resident in your garden.
Besides dealing with the usual parameters in your garden: type of soil (fine to coarse), light level (sun/shade), and moisture regime (dry to wet), other considerations should include height and spread. Proportion is important. In a small garden, a couple of really large plants will only emphasize how small the garden is. Even though in your mind your garden is limitless, reality hits when the clearly defined limits to your plantings are laid out – when the garden meets the house, driveway, paths, fences, or roads. Although, sometimes these limits are ignored to varying degrees by both plants and people. Everyone has seen houses and fences engulfed by vines and plants spilling out across sidewalks.
I don’t have a prairie or a meadow, but I would like to have some semblance with native plants appropriate to the site which is partly sunny and very dry owing to the boulevard slope and the Norway maple which sucks every bit of moisture from the earth.
A small patch of goldenrod came with my property, so as it spread, I’ve had to pull it to keep it under control, which is very easy to do. Now, my New England aster has established and is moving closer to the sidewalk, so it too, gets pulled on occasion. I don’t need to incur the wrath of neighbours and then bylaw officers.
I like sunflowers and other asters like cup plant (Silphium perfoliatum), but at 3.5 m (about 12 ft.) and a wide root-print, my front garden would have consisted of a large, aging Norway maple, the dominating feature, and a couple of mammoth cup plants – not a great scenario proportion-wise or when one is trying to maximize a wildlife garden for 3 seasons, i.e., succession in flowering. The 4th season usually buries the garden when the accumulation of snow is shovelled and piled in the only viable spot which is at the base of the tree.
I had success with a woodland cousin, a true sunflower (Helianthus divaricatus), which seemed well behaved along an edge in the backyard under the cedars.
Why not try a false sunflower?
According to the fact sheet from the USDA plant database fact sheet smooth oxeye or false sunflower (Heliopsis helianthoides) grows a little over a metre (3 to 4 feet). Also, it has no serious insect or disease problems. But, it has been observed to have some susceptibility to aphids.
So, I settled on two plants.
In reality, sometimes plants don’t follow the script. Not only did they grow quite well on an unforgiving site, they thrived like crazy, reaching 2 m (6.5 ft.).
I guess I missed the part about its tendency to become weedy in landscapes. They built up enough nerve to spread both by rhizomes and seed.
After a couple of years, I found it to be thuggish. It started to bully other plants, even those that are aggressive themselves!
The bully bullies another bully. Was the yarrow getting pushed out? Apparently, it is an aggressive plant, too. According to the USDA fact sheet it likes poor, well-drained soil. But to prolong its relatively short life, they have to be divided every other year and planted 12-18 in. apart.
Yes, but not right away. Like invasive plants, sometimes aggressive native plants can fly under the radar for a couple of years and then sneak up on you later, popping up everywhere. I planted two smooth oxeye in 2007 and they behaved themselves for a number of years. Little did I know they were building up reserves in their roots and conspiring to invade the rest of the garden.
Smooth oxeye moved itself from two places I put it and seeded everywhere because I didn’t deadhead it. It started to bully by stealth and targeted the weaker push-overs. It pushed out a few of my plants like horsemint and pearly everlasting. And then it started to push out my whorled milkweed and yarrow. That was enough! I needed to take control of the situation before I ended up with a monoculture of sunflowers towering over the sidewalk, or worse, falling all over themselves on the sidewalk after a hard rain.
The whorled milkweed is skinny enough to evade the pushy tactics of false sunflower. A deep taproot might help it side step the ever-expanding root ball of the sunflower. It’s hanging on and doing better now that the sunflower has been evicted. However, it did lose the support of the rigid stems of the sunflower and now tends to flop over. The introduction of some new plantings of other robust native species should help keep the milkweed as an upstanding citizen in the garden.
Everything is not going to hell in a hand basket. False sunflower has its good points, if you can get a handle on its thuggishness.
It’s a tall, erect, imposing plant and makes quite the statement. Stems are robust enough to support other weaker-stemmed plants. Cut stems have a small hollow and might be used by cavity-nesting insects.
This plant is for you if you are a control freak beyond the usual vigilance with invasive species (remove as they move in). And if you have fun deadheading, this plant is for you, too.
It is drought resistant, but it can look very droopy during the heat of the day under full sun exposure, much like other wide-leaved asters, such as black-eyed susans.
It is a source of pollen, nectar, seeds and habitat for wildlife.
It is one of the earliest flowering sunflowers starting in May and flowering through September, providing a nectar and pollen source. In my area, it doesn’t bloom until July. I’m sure if I deadheaded it, I could extend the flowering season beyond August. But there are plenty of other asters ready to take over the duty of blooming.
Is the false sunflower an aphid attractant? I scored the mother lode with aphids coating the entire top half of main stems in 2010. I was ready to put out a work order for lady beetles. This year the aphid population was down and I’m not sure if it is related to the high rainfall not stressing out the plants or making the aphids less thirsty.
Probably – it is not really suited for a small yard, as it is a crafty species, adept at moving around. It’s amazing how much of a crater is left when you remove a large root ball. I have some work ahead of me to fill it in. I’m inclined to replace the pearly everlasting and horsemint and add more Liatris spp.
However, I won’t take out all the smooth oxeye. I’ll keep a couple of clumps to tower over the other asters of even-height.
I’m going to keep the smooth oxeye as a source of seedlings for guerrilla gardening. Wouldn’t it be great to see a slope of false sunflower rather than invasive dog-strangling vine along our local roadways?
In retrospect, I should have kept an eye on it and have deadheaded it, but it seemed so conventional in gardening circles. The whole idea about gardening with native plants is to provide for wildlife. If I deadhead the flowers, I deprive wildlife of a source of seeds.
Another reason to plant with natives is to reduce maintenance for the gardener. That’s why we choose the right plant for the situation, so we’re not watering like crazy after the initial establishment period or constantly pruning or deadheading.
Definitely, if I had a large property with meadows, I would include smooth oxeye as it has many fine attributes.
Heliopsis spp. facts:
About 18 species: Canada, U.S., Mexico, Central America, South America (to Bolivia). Most Heliopsis spp. are known only from Mexico. According to the USDA plant database there are only two native Heliopsis spp. H. helianthoides with four varieties has taken most of the continent while the only other Heliopsis sp. is the mountain oxeye (H. parvifolia) which is confined to Arizona, New Mexico, Texas, and Mexico (Chihuahua, Coahuila, Durango, Sonora, Tamaulipas). The Flora of North America elevates one of the varieties to the status of species: H. gracilis.