Hostas are beloved for their lush foliage, low maintenance needs, and ability to brighten up shady corners of the garden. They thrive in cool, moist environments and get along with many other plants.
But not all garden neighbors are created equal. Some plants don’t just compete with hostas, they overwhelm them.
Whether it’s stealing moisture, hogging space, attracting pests, or loving way too much sun, the wrong companion can cause real trouble. If your hostas aren’t thriving the way they should, their neighbors might be to blame.
To help you create a healthier, more harmonious shade garden, here are five specific plants you should avoid planting near hostas and the reasons why they just don’t get along.
Black Walnut
If there’s one tree that causes more garden drama than any other, it’s the black walnut. This towering beauty might look harmless, but beneath the surface, it’s hiding a toxic secret.
Black walnut trees produce a chemical called juglone, and hostas want nothing to do with it. Juglone is released by the roots, leaves, and even the nuts of the tree. It seeps into the soil and affects many other plants nearby, including hostas.
This chemical can disrupt your hostas’ ability to take up water and nutrients, leading to yellowing leaves, stunted growth, or even total collapse. And the worst part is that once juglone is in the soil, it’s difficult to remove.
If you’re noticing that hostas near a black walnut tree look droopy, discolored, or are struggling to grow, your watering routine likely isn’t the issue. The damage may be slow and subtle, but over time, it adds up.
The root system of a mature black walnut tree can extend 50 to 80 feet in every direction. That means even if your hostas aren’t right next to the trunk, they could still be in danger.
The simplest solution is to avoid planting hostas anywhere near a black walnut tree. If you’ve already made that mistake, consider relocating your hostas to a fresh area with uncontaminated soil.
Also be cautious about using compost made from any part of a black walnut tree. Leaves, bark, and husks can all carry juglone into your garden beds.
In short, black walnut might be majestic, but it makes a terrible companion for hostas. Keep your distance and your shade garden will be better off.
Ferns
Ferns and hostas might seem like natural partners. They both love shady spots, focus on foliage, and are often featured together in garden displays.
But their similarities can lead to competition. Many fern varieties are incredibly aggressive below the surface.
Ferns form thick, spreading root systems that quietly take over the soil. While their tops seem calm and well-behaved, underground they can squeeze out other plants before you even notice.
In mixed beds, ferns often absorb more than their share of moisture. That leaves hostas with dry roots, especially during warmer weeks.
Hostas thrive on consistent moisture. When ferns dominate, hostas often start looking thin, droopy, or washed out.
To make matters worse, many ferns grow tall and bushy. That full upper growth can block the light hostas do need, reducing leaf size or causing patchy growth.
Some of the fastest spreading varieties, like ostrich fern or lady fern, can completely invade a hosta bed. Their runners pop up between hosta clumps, making them hard to remove without disturbing the roots you want to protect.
This doesn’t mean you can’t have both plants in the same garden. Just give them their own space.
Try planting ferns in their own containers or beds, where their roots can’t mix with your hostas. That way, both plants get what they need without stepping on each other’s toes.
Ferns are undeniably beautiful. But near hostas, they can become the kind of neighbor that quietly takes over the whole block.
Mint
Mint might be delightful in a drink or dessert, but in the garden, it behaves like a menace. It smells sweet and looks tidy, but behind that charm is a plant that doesn’t know when to stop.
Mint spreads fast through a network of underground runners. These creeping roots travel just beneath the soil’s surface, sneaking into any nearby open space.
Once mint reaches your hostas, it doesn’t stop. It competes for moisture, light, and nutrients, often overpowering the more delicate root systems of nearby plants.
Hostas rely on shallow roots and steady moisture. Mint drains the soil faster and dominates the space, leaving hostas thirsty and stressed.
You may start to notice your hostas fading, drooping, or growing less than they did before. That’s a strong sign they’re losing the underground battle.
Trying to remove mint after it has spread can be incredibly frustrating. Even the tiniest root fragment left behind can grow back with force.
If you love mint and still want to grow it, give it boundaries. Plant it in containers or use buried pots to prevent it from spreading into your hosta beds.
Another option is to place it far away in a sunny herb section of the yard. That way, you can still enjoy the aroma and flavor without threatening your shade garden.
Mint is refreshing in a glass but overpowering in the soil. Keep it away from your hostas if you want to avoid a creeping takeover.
Russian Sage
Russian Sage brings airy texture and soft color to sunny borders. It’s a tough, drought-resistant plant that thrives in open, dry, well-lit locations.
That description alone should make it clear why it clashes with hostas.
Hostas prefer rich, damp soil and low light. Russian Sage craves dry roots and full sun. Put them together, and neither will be happy.
When you try to meet the water needs of a hosta, Russian Sage may suffer from root rot. If you back off watering to suit the sage, your hostas will quickly start to sag and suffer.
Sunlight is another issue. Russian Sage needs six or more hours of direct sun each day. That’s far more exposure than most hostas can handle.
Bright light can scorch hosta leaves, turning them brown around the edges or fading their signature color.
Trying to compromise with a partly shaded area usually backfires. Both plants end up outside their comfort zone.
A better strategy is to plant Russian Sage in its own sunny corner. It pairs beautifully with lavender, salvia, or ornamental grasses, plants that enjoy similar dry conditions.
Keep your hostas tucked into cooler, shaded garden beds where they can soak up moisture and thrive. Both plants can be stunning, but not when they’re forced to live side by side.
Barberry
Barberry looks like an easy-care shrub. Its colorful foliage, compact shape, and resilience make it tempting for gardeners.
But don’t let the surface charm fool you. It brings more harm than good when planted near hostas.
For starters, barberry is covered in sharp little thorns. Reaching in to water or weed around it can leave you scratched and frustrated.
Worse than the physical challenge is how barberry changes the space around it. It grows thick and low, creating a dense canopy that blocks airflow and sun.
Hostas thrive on good circulation and cool, moist soil. Barberry creates a pocket of dry, shaded air that keeps moisture out and raises stress levels for any plant nearby.
Invasive barberry varieties have also been linked to soil imbalance. Over time, they can alter the chemical structure of the soil, making it harder for moisture-loving plants to thrive.
But perhaps the most concerning fact is its effect on garden pests. Barberry provides ideal shelter for ticks.
It creates a hiding place for deer mice and other tick carriers, increasing the risk of tick bites in areas where it grows.
This makes it a real concern for gardeners who enjoy spending time close to their beds. Hostas may be low maintenance, but barberry adds an unwelcome layer of danger.
If you want shrubs that work well with hostas, consider dwarf fothergilla, hydrangea, or heuchera instead. These options bring color without causing conflict or inviting pests.
Barberry may look appealing, but for a shade garden built around hostas, it’s best left off the guest list.
Final Thoughts
Hostas are forgiving, but they still need the right company to flourish. Planting them next to aggressive or incompatible neighbors leads to stress, stunted growth, and disappointing displays.
By steering clear of black walnut, ferns, mint, Russian Sage, and barberry, you give your hostas the space and environment they need to thrive.
Plan your combinations carefully. With the right mix of companions, your hostas will reward you with beautiful foliage and a calm, healthy garden that only gets better year after year.