7 Plants You Should Never Grow in a Rock Garden
As temperatures rise and heatwaves grow more common, drought-tolerant spaces, such as rock gardens, are becoming increasingly important. They use natural-style designs to encourage resilient and hardy plants. Although these gardens are alluring, not all plants thrive in them. Consider leaving these seven plants at the store instead of growing them in your rock garden.
Contents
What is a rock garden? Simply put, it’s a sun-filled garden with boulders, rocks, and gravel. These plantings originated as replicas of alpine zones, where perennials and annuals live in extreme conditions. Rocky crags and high altitudes create harsh conditions that most plants struggle to survive in, and these gardens were a way to recreate the scenes at lower altitudes.
Nowadays, a rock garden can be anything you want it to be! You may plant your favorite non-native ornamentals alongside drought-resistant native plants. Add manzanitas for height and dimension, and sow succulent sedums to fill the cracks between the boulders. Bulbs, low-growing perennials, and heat-loving annuals are also ideal.
These gardens, or rockeries as they’re also known, are best in sites with full sun. Excellent drainage is a must, and extra irrigation is necessary in the first two years to help the plants establish themselves. The specimens will be drought-tolerant and require little watering after the first two years.
While these seed selections work great for rock gardens, the list below describes some moisture-loving plants that are best avoided.
7 Plants to Avoid in a Rock Garden
The distinct, rocky conditions favor certain plant species, though they’re less than ideal for the following seven. Consider using alternatives like native annuals, grasses, and low-mounding perennials.
Vegetables
Vegetables love fertile, well-drained loam. They perform best when they have continuous access to nutrients, moisture, and sunlight. Though they like full sun, they dislike dry soil, making them poor choices for planting in a rockery.
Most vegetables are picky, as we’ve bred them for their size and flavor more so than for their hardiness or pest resilience. When they dry out in a rocky site, they’ll attract pests and diseases that cause further harm.
Though most vegetables are high feeders, some are resilient enough to grow in between rocks and boulders. Asparagus, sunchokes, and amaranth are some examples that may work well, though you’ll have to trim or harvest them annually to keep them tidy.
Leafy Greens
Like vegetables, leafy greens love nutrients, water, and sunlight. They’ll grow tough, bitter leaves if they receive too much sun and not enough moisture. Crops like lettuce, spinach, and arugula grow best in fall or spring when the weather is cool, mild, and sunny.
Other leafy greens, like the previously mentioned amaranth, may fare well in a rockery if they’re tolerant of heat and drought. Though they’ll survive, that doesn’t mean they’ll look great in your design! You’ll want complementary perennials that contrast or match well with the surrounding plant species.
Fruit Trees
Apples, pears, plums, persimmons, pluots, and dozens of other fruits grow off woody, deciduous trees. These specimens require less moisture than vegetables, though they still need more than is average for a rocky garden.
Fruit trees are also big—they fill empty spaces with their lush green leaves and juicy fruits. They’ll cast shade on the other plants in the area, which will cause them to grow poorly in the future.
Some fruiting shrubs may work well if you prune them to keep them small and prevent them from shading nearby plant species. If you want harvestable fruit from your rockery, consider using heat-tolerant shrubs like goji berries, pineapple guavas, or mulberries.
Rambling Berries
Though goji berries and pineapple guava are ideal for rocky sites, other berries that grow off canes and vines are not. These varieties, like raspberries, blackberries, and boysenberries, will take over the site and prevent other plants from growing.
Whether trailing or upright, cane-producing berries grow long, woody stems that often have thorns on them. The canes sprout from underground roots, spreading into new areas each spring. If you plant a trailing blackberry, it’ll overrun your low-growing perennials and snuff them out.
Upright berries won’t blanket the ground quite like trailing varieties, though they will cast shade and prove too unruly to manage. They also need consistent moisture to thrive, which is much more water than a yard of this style requires.
Invasive Species
In the same way that berries ramble, invasive species aggressively spread and have a similar potential to snuff out your tender annuals, perennials, and mounding shrubs. They tend to be hardy, vigorous, and readily self-propagating.
These are some of the most common invasive species to avoid:
- Himalayan Blackberry
- Kudzu
- Japanese Knotweed
- Giant Hogweed
- Cogongrass
- African Feathergrass
Many invasives exist throughout the U.S., and some retailers and nurseries still sell their seeds! A little research can tell you whether or not a plant is invasive. Consult the federal noxious weed list from the United States Department of Agriculture, or look to the individual states’ lists for local warnings.
A native plant cannot be invasive, only unruly. Native plants are superb choices for rock garden plantings, as they evolved to grow in your local region. Select heat, sun, and drought-loving varieties for a resilient garden.
Mint
An herbal, aromatic perennial, mint is not to be messed with! It uses free-rooting stems to anchor itself onto fresh soil patches. Though it’s useful, hardy, and free-spreading, it’s too vigorous for a rock garden. The stems will blanket the boulders and snuff out your smaller ornamentals.
Mints in the genus Mentha are problematic, but there are many other mint-like plants native to the U.S. that work well in rocky gardens. Try yerba buena, or “good herb” in English, on the West Coast. Opt for the mountain mints of the genus Pycnanthemum in the eastern and central states. Both of these types sprout leaves that make soothing herbal tea.
Carnivorous Species
Most carnivorous plants are bog-dwellers that live in unique conditions. They need lots of direct sunlight, though they also require consistent watering. They thrive in swampy, wet environments close to coastlines, rivers, and lakes.
You may still have these insect-eating carnivores in your rock garden; you’ll just need to supply them with moisture throughout the growing season while also maintaining a dry culture for your other specimens. One way to do this is with a basin below the roots that soaks water without seeping into the surrounding soil.
With some creative solutions, carnivorous species may survive in your rocky plantings. So long as they have full sun, consistent moisture on their roots, and infertile soil, they’ll fare well in your garden.
Key Takeaways
- Rock gardens are best in sites with full sun, ample drainage, and gritty soil. You may plant them in the shade, though you’ll have to use shade-loving plant species instead of sun-loving ones.
- The worst types to grow are invasive, spreading varieties. They require constant maintenance, weeding, and pruning, and they have the potential to invade nearby natural areas.
- Vegetables, fruits, and leafy greens are demanding plants; they’re best for a raised bed or separate area with plenty of moisture, nutrients, and loamy soil.
- Some of these plants can fare well with slight modifications. Plan, design, and prepare the rocky garden first before planting in it.
Frequently Asked Questions
Are rock gardens expensive?
They can be! It all depends on how many materials you source locally without purchasing them, and how many plants you have available to you. Using seeds, sourcing rocks from resellers, and planting over time instead of all at once can help lower the associated costs.
Can roses grow in rock gardens?
Yes, they can! Drought-tolerant roses are exceptional for rock gardens. Select non-spreading species like shrub types, or train climbers onto trellises, arbors, and supports near the site.
Are rock gardens hard to maintain?
They’re one of the easiest gardens to maintain, so long as you select low-maintenance plants to grow. Evergreen perennials require the least maintenance, while herbaceous perennials and shrubs may require pruning and trimming. Aside from that, all you’ll have to do is weed out unruly seedlings and water as needed.
