What Not to Grow Next to Marigolds: Cultivating a Harmonious Garden Ecosystem

As a seasoned gardener, I've seen my fair share of triumphs and tribulations in the soil. One of the most common gardening quandaries I encounter, and that many folks grapple with, is understanding companion planting. We all know marigolds are fantastic plants. Their bright, cheerful blooms can instantly lift spirits, and many gardeners swear by their pest-repelling prowess. I certainly rely on them to keep the aphids off my tomatoes! However, just as some plants are natural allies, others can be detrimental neighbors. That's why understanding what not to grow next to marigolds is just as crucial as knowing what to plant alongside them. Getting this wrong can lead to stunted growth, increased pest problems, and a generally unhappy garden. Let's dig into how to create a truly symbiotic relationship between your marigolds and their garden companions.

Understanding the Marigold's Role in the Garden

Before we delve into the specifics of what not to grow next to marigolds, it's essential to appreciate why we plant them in the first place. Marigolds (Tagetes spp.) are celebrated for their ability to deter a surprising array of garden pests. Their roots, particularly those of French marigolds (Tagetes patula), exude a substance called alpha-terthienyl, which is a nematicide. This means they can help control populations of harmful nematodes in the soil, which often attack the roots of vegetables like tomatoes, potatoes, and carrots. Beyond nematodes, marigolds are also known to repel whiteflies, Mexican bean beetles, and even some aphids. Their fragrant foliage, while pleasant to us, is often off-putting to these unwelcome visitors.

Furthermore, the vibrant colors of marigolds can attract beneficial insects like ladybugs and hoverflies, which themselves are natural predators of common garden pests. They also act as a living mulch, suppressing weeds and retaining soil moisture when planted densely. Their relatively short stature and long blooming period make them versatile additions to almost any garden bed, border, or container. However, their potent natural compounds and growth habits aren't universally beneficial. Some plants simply don't tolerate their presence, and forcing them together can create a host of problems.

The Core Principle: Avoiding Competition and Chemical Interference

The fundamental reason certain plants shouldn't be neighbors to marigolds boils down to two main factors: competition for resources and potential chemical interference. Marigolds, like all plants, require sunlight, water, and nutrients from the soil to thrive. If planted too close to a vigorous grower, they can be outcompeted, leading to stunted marigolds and, potentially, reduced yields from the neighboring plant.

More significantly, the root exudates that make marigolds such excellent pest deterrents can, in some cases, negatively impact the growth of other plants. While beneficial for some, these same compounds can be phytotoxic (toxic to plants) for others, inhibiting their development or even causing them to wither. It’s a delicate balance, and understanding the specific needs and sensitivities of each plant is key to successful companion planting.

What Not to Grow Next to Marigolds: Specific Plants to Avoid

Now, let's get down to brass tacks. Based on extensive garden observations and common gardening wisdom, here are the primary plants you should consider giving some breathing room to when planting marigolds:

1. Beans (Bush and Pole Varieties)

This might come as a surprise to some, as beans are often mentioned in companion planting guides. However, when it comes to marigolds, it's generally best to keep them apart. My own experience has shown that while marigolds can deter some bean pests, the relationship isn't always reciprocal. Some gardeners have reported that marigolds can stunt the growth of bush beans and pole beans. The exact reason is debated, but it's thought that the nematicidal properties of marigold roots might interfere with the beneficial nitrogen-fixing bacteria that beans rely on.

Why Avoid Beans with Marigolds?

Root Interference: Marigold root exudates are believed to disrupt the symbiotic relationship between bean roots and nitrogen-fixing rhizobia bacteria. This can lead to nitrogen deficiency in the beans, resulting in pale, stunted plants and reduced pod production.
Competition: Both beans and marigolds can be relatively heavy feeders. Planting them in close proximity can lead to them competing for essential nutrients in the soil, especially in smaller or less fertile garden beds.
Reduced Yields: Anecdotal evidence from countless gardeners suggests that planting beans too close to marigolds often results in smaller, less productive bean plants.

My Take: I learned this the hard way one year. I’d planted a row of bush beans right alongside my vibrant French marigold border, thinking I was being clever about pest control. By mid-season, the beans were noticeably less robust than those in a different part of the garden where they were planted further away from the marigolds. The leaves were a lighter green, and the yield was significantly lower. Since then, I've made it a point to give my beans a generous buffer zone from my marigold plantings.

Alternative Companion Plants for Beans: Consider planting beans with rosemary, potatoes, cucumbers, or strawberries. These tend to have more harmonious relationships.

2. Cabbage Family Vegetables (Brassicas)

This broad category includes broccoli, cauliflower, Brussels sprouts, kale, cabbage, and their relatives. While marigolds are excellent at deterring many pests that plague vegetables, they don't always play well with the Brassica family. Some gardeners have noted that marigolds can inhibit the growth of these cruciferous crops. It’s speculated that the allelopathic properties of marigolds might be too strong for these sensitive plants.

Why Avoid Brassicas with Marigolds?

Growth Inhibition: Similar to beans, Brassicas can exhibit stunted growth when planted in close proximity to marigolds. The exact chemical interactions are not fully understood, but the results are consistently observed by many growers.
Pestular Conflict: While marigolds deter some pests, they don’t necessarily ward off the specific pests that plague Brassicas, like cabbage worms or aphids. In fact, some gardeners theorize that the presence of marigolds might even attract other insects that then go on to bother the Brassicas. This is less about direct chemical warfare and more about creating an unbalanced ecosystem.
Nutrient Competition: Brassicas are also known for being heavy feeders, requiring rich soil and ample nutrients. Competing with marigolds for these resources can lead to suboptimal growth for both.

My Take: I remember a particularly frustrating season where my prized broccoli heads were small and malformed, while the cabbages struggled to even form proper heads. The marigolds planted at the end of the row were flourishing, but the Brassicas looked miserable. It took a bit of research and talking to seasoned growers to realize the marigold-Brassica conflict might be the culprit. Now, I ensure my broccoli and cabbage patches are entirely separate from my marigold displays.

Alternative Companion Plants for Brassicas: Consider planting dill, rosemary, sage, thyme, or chamomile near your Brassicas. These herbs are generally considered beneficial companions.

3. Carrots (in certain contexts)

This is a nuanced one. While marigolds are often recommended for planting near carrots because their roots are said to deter nematodes that attack carrots, there's a caveat. The positive effect is often more pronounced when marigolds are planted *around* a carrot bed, or at a distance, rather than directly interplanted. If you're planting dense rows of both, you might run into issues.

Why Exercise Caution with Carrots and Marigolds?

Root Exudate Sensitivity: While marigolds target nematodes, their root secretions can also affect the delicate root systems of young carrot seedlings, potentially inhibiting their growth and development.
Competition for Space: Both plants need room for their roots to spread. Interplanting too densely can lead to a battle for soil volume, water, and nutrients, impacting the carrot's ability to develop those signature long, straight roots.
Over-reliance on Nematicidal Properties: If nematodes are a severe problem, relying solely on interplanted marigolds might not be sufficient, and the negative impacts on carrot growth could outweigh the benefits.

My Take: I've experimented with this quite a bit. When I plant marigolds in a general border a few feet away from my carrot rows, I do notice fewer carrot rust fly issues and generally healthy roots. However, when I've tried tucking marigolds directly between rows of carrots, the carrots tend to be smaller and less abundant. The key, it seems, is distance and allowing both plants their own space to establish their root systems without direct interference.

Best Practices for Marigolds and Carrots: If you want the benefits of marigolds for your carrots, plant them in a border several feet away from the carrot patch. This provides a protective zone without direct competition or chemical interference.

Alternative Companion Plants for Carrots: Rosemary, chives, radishes, lettuce, and onions are often excellent companions for carrots.

4. Fennel

Fennel is famously known for being a bit of a loner in the garden. It’s often said to inhibit the growth of many other plants, and marigolds are not an exception. While marigolds might benefit from the potential pest-repelling qualities of fennel, the reverse is not necessarily true, and fennel can actively suppress the growth of nearby plants, including marigolds.

Why Avoid Fennel with Marigolds?

Allelopathic Properties: Fennel releases compounds, particularly from its roots and seeds, that are known to inhibit the growth of many other plants. This is a classic example of a plant actively suppressing its neighbors.
Growth Stunting: Planting marigolds too close to fennel can lead to significantly stunted marigold plants, with fewer blooms and less vigor.
Unbalanced Ecosystem: The strong allelopathic effect of fennel can create an unfavorable environment for many other plants, marigolds included.

My Take: I learned to respect fennel's solitary nature early in my gardening journey. I once planted a beautiful dill and fennel combination in a large pot, with marigolds around the edges. The fennel took over, while the dill and marigolds struggled to produce. It was a clear demonstration of fennel’s dominance. Since then, I always give fennel its own space or plant it in a location where its allelopathic effects won’t harm other desirable plants.

Alternative Companion Plants for Fennel: Fennel generally does best planted on its own or with plants that are known to be resistant to its allelopathic effects. Some sources suggest basil, but caution is still advised.

5. Certain Ornamental Flowers (Depending on Variety and Space)

While marigolds are often grouped with other flowers in garden beds, it's worth noting that not all ornamental flowers are ideal companions. The main concerns here are competition for resources and, in some cases, shared susceptibility to certain pests or diseases.

Why Consider Spacing with Other Ornamentals?

Resource Competition: Just like with vegetables, dense planting of various flowers can lead to competition for sunlight, water, and nutrients. This can result in weaker blooms and overall less healthy plants.
Pest and Disease Transmission: While marigolds deter some pests, they don't deter all. If other ornamental plants in the vicinity are susceptible to the same pests or diseases that marigolds *don't* repel, planting them too closely can facilitate the spread. For example, if both marigolds and a neighboring flower are prone to powdery mildew, overcrowding can exacerbate the problem.
Aesthetic Overcrowding: Sometimes, it’s simply about visual harmony. Overcrowding flowers can make a garden bed look messy and chaotic, rather than a well-designed tapestry of color and form.

My Take: I often use marigolds as a border for my perennial beds. I’ve found that planting them a few inches away from more delicate perennials like delphiniums or foxgloves works best. This allows the marigolds to offer some protection from ground-dwelling pests without their roots getting tangled or competing too aggressively with the perennials’ established root systems. It’s a visual and practical win-win when done thoughtfully.

Best Practices for Marigolds and Ornamentals: Aim for thoughtful spacing. Use marigolds to edge beds or fill gaps, but avoid planting them directly against the main stems or root balls of more sensitive or established ornamental plants. Consider their mature size and growth habit.

The Nuances of Companion Planting: It's Not Always Black and White

It's important to remember that companion planting is not an exact science. Many factors can influence how well or poorly two plants coexist, including:

Soil Type and Fertility: Rich, well-amended soil can better support multiple plants in close proximity than poor, sandy soil.
Climate and Weather Conditions: Prolonged drought or excessive rain can stress plants and make them more susceptible to negative interactions.
Specific Cultivar: Different varieties within the same species can have slightly different tolerances and needs.
Planting Density: Simply put, how much space each plant has is critical.
Individual Plant Health: A strong, healthy plant is more likely to withstand minor competition or negative interactions than a weak one.

Therefore, while the general guidelines for what not to grow next to marigolds are valuable, always observe your own garden. If you notice signs of stress, stunting, or increased pest problems on plants near your marigolds, it might be time to reconsider their placement. Your plants will tell you if they’re happy or not.

Creating Your Marigold Companion Planting Chart

To help visualize these relationships, consider creating a simple chart. This can be a quick reference when you’re planning your garden layout each season. You can even keep a gardening journal to track your observations.

Marigold Companion Planting: What to Avoid
Plant Category	Specific Examples to Avoid Near Marigolds	Reason for Avoidance
Legumes	Bush Beans, Pole Beans, Lima Beans	Potential interference with nitrogen fixation; growth stunting.
Brassicas	Broccoli, Cauliflower, Cabbage, Kale, Brussels Sprouts	Growth inhibition; potential for unbalanced pest attraction.
Root Vegetables (with caution)	Carrots (especially when interplanted closely)	Root exudate sensitivity; competition for root space.
Alliums (with caution)	Onions, Garlic, Shallots (some reports of negative interaction)	Potential for allelopathic effects or competition.
Fennel	All varieties of Fennel	Strong allelopathic properties; suppresses growth of neighbors.
Cucurbits (with caution)	Cucumbers, Squash, Melons (some reports of stunted growth)	Potential for competition for nutrients and space.

Note: The "with caution" categories highlight interactions that are debated or depend heavily on specific garden conditions and planting density. Always observe your plants.

Plants That Generally Thrive Alongside Marigolds

While we’re focusing on what *not* to grow next to marigolds, it’s equally important to highlight plants that generally benefit from their presence. This reinforces the positive aspects of companion planting and helps create a balanced ecosystem:

Tomatoes: A classic pairing. Marigolds deter nematodes and other pests that can attack tomato roots and foliage.
Peppers: Similar to tomatoes, peppers benefit from the pest-repelling qualities of marigolds.
Eggplant: Another member of the nightshade family that appreciates marigold's protective presence.
Squash and Cucumbers (with distance): While some reports suggest caution with very close planting, generally, marigolds can deter squash bugs and cucumber beetles when planted at a reasonable distance.
Strawberries: Marigolds can deter lygus bugs and other pests that damage strawberry fruits.
Zucchini: Often planted with marigolds to keep away squash bugs.
Herbs: Many herbs, like rosemary, thyme, and sage, do well near marigolds and can even benefit from the pest deterrence.
Roses: Planting marigolds around rose bushes can help deter nematodes and other soil-borne pests, promoting healthier rose growth.

Frequently Asked Questions About Marigold Companion Planting

How do I know if my marigolds are negatively impacting another plant?

Observing your plants closely is the key. Look for these tell-tale signs:

Stunted Growth: If a plant that normally grows vigorously is consistently smaller, weaker, or slower to develop than expected, especially when compared to the same plant grown elsewhere in your garden, proximity to marigolds could be a factor.
Yellowing Leaves (Chlorosis): This can indicate a nutrient deficiency, which might arise from competition for resources or interference with nutrient uptake. While not solely indicative of marigold issues, it's a warning sign when plants are near them.
Lack of Flowering or Fruiting: If your plants are healthy enough to grow but fail to produce flowers or fruits, it could be a sign of stress or imbalance caused by neighboring plants. For example, beans that are struggling might produce very few pods.
Increased Susceptibility to Pests/Diseases: Paradoxically, while marigolds deter many pests, if a neighboring plant is *still* succumbing to common pests or diseases when planted near marigolds, it might mean the marigold's presence is creating an unbalanced environment, or that the neighbor is too stressed to fight off invaders.
Root Rot or Wilting: In extreme cases, severe root interference or chemical toxicity from root exudates can lead to wilting or root damage, even if the above-ground portion looks otherwise healthy initially.

When you notice these symptoms, try to isolate the cause. Are the plants getting enough water? Enough sun? Is there evidence of other pests or diseases? If the only variable seems to be the proximity to marigolds, it's a strong indication that you might need to relocate one or the other.

Why do marigolds deter pests, and which pests are they most effective against?

Marigolds are celebrated for their natural pest-repelling abilities due to their chemical compounds, primarily found in their roots and foliage. The most significant of these is **alpha-terthienyl**, a naturally occurring thiophene. This compound acts as a potent **nematicide**, meaning it is toxic to nematodes – microscopic roundworms that can infest plant roots, causing significant damage and reduced yields in many vegetables like tomatoes, potatoes, and carrots. When marigolds are planted, these compounds are released into the soil, creating a hostile environment for harmful nematodes.

Beyond nematodes, the strong, aromatic scent of marigold foliage is thought to confuse or repel various flying insects. They are particularly effective against:

Whiteflies: These tiny, sap-sucking insects can devastate many plants. The scent of marigolds can deter them from landing and feeding.
Mexican Bean Beetles: Marigolds are a traditional companion for beans, helping to keep these destructive beetles at bay.
Aphids: While not a foolproof solution for all aphid infestations, marigolds can help reduce their numbers by deterring them.
Tomato Hornworms: Some gardeners report fewer hornworm issues when marigolds are planted nearby.
Spider Mites: Their presence can make the environment less hospitable for spider mites.

It’s important to note that marigolds are not a silver bullet. They won't eliminate every single pest, and their effectiveness can vary. However, they are a valuable, natural tool in integrated pest management strategies. The key is to understand which pests they *do* work against and to avoid planting them next to plants that might be negatively affected by their chemical defenses.

Can I plant marigolds in containers next to other potted plants?

Yes, you absolutely can plant marigolds in containers alongside other potted plants, but the same principles of spacing and compatibility apply. In containers, resources like water, nutrients, and root space are even more limited than in the ground, so careful consideration is crucial.

Container Gardening Considerations:

Pot Size is Key: Ensure the pot is large enough to comfortably accommodate the root systems of both the marigold and its companion plant. Overcrowding a single pot is a recipe for disaster.
Companion Compatibility: Even in pots, you should avoid planting marigolds next to sensitive plants like beans or Brassicas. The risk of stunted growth or nutrient competition is amplified in a confined space.
Watering Needs: Different plants have different watering requirements. Group plants with similar needs together. Marigolds generally prefer well-drained soil and can tolerate some dryness, but they shouldn’t be left parched or waterlogged.
Nutrient Requirements: Container plants rely entirely on you for nutrients. If you’re planting heavy feeders, ensure you’re supplementing with adequate fertilizer. Be mindful that marigolds are not overly demanding, but they still need nourishment.
Visual Harmony and Pest Control: Container groupings can be very aesthetically pleasing. Use marigolds to add a splash of color and potentially deter pests from more vulnerable container plants like your herbs or smaller vegetables.

My Experience with Container Marigolds: I often tuck a few marigold plants into my larger pots of herbs or even around the base of a chili pepper plant. This works wonderfully. The marigolds fill in any bare spots, add color, and I've noticed fewer aphids on my basil when marigolds are nearby. The key is that the other plant in the pot (like basil or peppers) is generally considered a good companion for marigolds, and the pot is adequately sized.

What about the different types of marigolds? Do they have different companion planting needs?

That’s an excellent question, and yes, there can be some subtle differences, though the general principles remain the same. The two main types of marigolds gardeners commonly use are:

African Marigolds (Tagetes erecta): These are the taller, larger varieties, often with bold, pom-pom-like blooms. They can grow up to 3 feet tall. Their larger root systems and potentially stronger chemical output mean they might have a more pronounced effect on neighbors.
French Marigolds (Tagetes patula): These are smaller, more compact plants, typically growing 6 to 18 inches tall. They are prolific bloomers with often single or double, ruffled flowers in a wider range of colors. French marigolds are generally considered the most potent in terms of nematode-repelling properties due to their root exudates.

Implications for Companion Planting:

French Marigolds: Because of their concentrated nematicidal properties in the roots, it is particularly important to give French marigolds adequate space from sensitive plants like beans and Brassicas. Their allelopathic effect is often cited as more significant.
African Marigolds: While still possessing pest-deterring qualities, their primary impact might be more through their foliage scent and general space occupation. They might be slightly more forgiving in close proximity than their French counterparts, but caution is still advised with known incompatible plants.

Regardless of the type, the core advice to avoid beans, Brassicas, and fennel remains sound. The intensity of the interaction might vary, but the potential for negative effects is present with all marigolds. Always err on the side of caution and provide good spacing.

Can marigolds help deter pests from my vegetable garden in general, even if not planted directly next to every plant?

Absolutely! This is one of the most effective ways to utilize marigolds. You don’t need to interplant marigolds with every single vegetable to reap their benefits. Planting them in borders around your garden beds, in strategic locations throughout your vegetable patches, or even in key spots near susceptible crops can significantly contribute to a healthier garden ecosystem.

Strategies for General Pest Deterrence:

Border Planting: Create a ring of marigolds around your entire vegetable garden. This acts as a first line of defense, potentially deterring pests from entering the area altogether.
Corner Planting: Place marigolds in the corners of larger garden beds. This provides a buffer zone and can still influence pests in the vicinity.
Near Vulnerable Crops: If you have specific crops that are prone to certain pests (e.g., tomatoes to nematodes, cucumbers to cucumber beetles), plant a few marigolds within a few feet of them. This provides targeted protection without the risk of direct negative interaction.
Companion Planting with "Good Neighbors": As mentioned earlier, many plants are excellent companions for marigolds. By planting marigolds alongside these compatible plants (like tomatoes, peppers, or strawberries), you create a mutually beneficial arrangement that also offers broader pest deterrence for the entire bed.

The key is to leverage their natural pest-repelling qualities without creating competition or chemical conflicts. By strategically placing marigolds, you can create a more balanced and resilient garden that requires less intervention.

Are there any specific soil amendments or conditions that make marigolds more or less likely to cause problems for neighboring plants?

Soil conditions and amendments play a significant role in how plants interact. While marigolds themselves are quite adaptable and can grow in a variety of soils, their impact on neighbors can be influenced:

Rich, Well-Composted Soil: When soil is rich and abundant in organic matter, there is generally less competition for nutrients. This can buffer the negative effects of marigold root exudates or competition for nutrients, making it easier for neighboring plants to thrive even when planted relatively close. More resources mean less stress for everyone.
Sandy or Poor Soil: In soils that are lacking in nutrients and organic matter, competition becomes a much bigger issue. Marigolds, if they are growing well, will be actively drawing nutrients and moisture. In such conditions, any negative allelopathic effects from their root secretions can be amplified, and competition for scarce resources will be more pronounced, leading to weaker growth in neighboring plants.
Soil pH: Marigolds generally prefer slightly acidic to neutral soil (pH 6.0-7.0). While they are tolerant, extreme pH levels can stress them, potentially making them less vigorous or, conversely, more prone to releasing stronger allelochemicals in an attempt to survive. If your soil pH is far from ideal, it might be wise to amend it to create a more balanced environment for all plants.
Drainage: Marigolds, like most plants, need well-drained soil. Waterlogged conditions can lead to root rot for marigolds and their neighbors. Ensuring good drainage will help prevent issues that could be mistakenly attributed to companion planting.

My Experience with Soil: I've found that in my garden, which I diligently amend with compost each year, the negative interactions between marigolds and plants that are *usually* incompatible are less severe than I read about. However, I still maintain a good buffer zone. The compost seems to provide a buffer, allowing plants to be more resilient. In contrast, when I've gardened in areas with very poor, sandy soil, I've seen the negative effects of marigolds on sensitive plants much more dramatically, even with careful spacing.

What are the practical steps for preparing a garden bed to avoid marigold conflicts?

Planning is your best friend when it comes to avoiding companion planting pitfalls. Here's a step-by-step approach:

Sketch Your Garden Layout: Before you even buy seeds or seedlings, draw a plan of your garden beds. This doesn't need to be fancy – a simple diagram on paper or a digital tool will suffice.
Identify Sensitive Plants: Make a list of the plants you intend to grow. For each plant, note its known companion planting needs. For example, list "Tomatoes (Good with Marigolds)" or "Beans (Avoid Marigolds)."
Map Out Marigold Locations: Decide where you want your marigolds. Are they for borders, filling in gaps, or deterring specific pests? Mark these locations on your map.
Create Buffer Zones: For plants that should not be near marigolds (beans, Brassicas, fennel, etc.), draw a clear buffer zone around them. This could be an empty space, a path, or a planting of a compatible plant (like herbs or strawberries) between the marigold and the sensitive plant. Aim for at least 1-2 feet of separation where possible, especially for the most sensitive pairings.
Group Compatible Plants: Place plants that are known to thrive near marigolds (tomatoes, peppers, etc.) in proximity. This creates harmonious zones within your garden.
Consider Mature Size: When drawing your map, think about how large the plants will get, both above ground and below. This ensures your buffer zones remain effective as plants mature and expand.
Soil Preparation: Before planting, amend your soil generously with compost and other organic matter. This creates a healthy foundation that supports robust growth and resilience for all your plants.
Observe and Adjust: Once planting is done, keep an eye on your garden throughout the season. If you notice any plants struggling near marigolds, don't hesitate to transplant them to a more suitable location, even if it's mid-season. Early intervention is key.

By following these steps, you can proactively design a garden layout that minimizes potential conflicts and maximizes the benefits of companion planting. It's about thoughtful placement, not just random planting.

In conclusion, what is the single most important takeaway regarding what not to grow next to marigolds?

The single most important takeaway regarding what not to grow next to marigolds is to **give known sensitive plants, particularly beans and Brassicas, a significant buffer zone.** While marigolds are fantastic for pest control, their potent root exudates can inhibit the growth of these specific vegetables. Understanding and respecting these key incompatibilities will help you cultivate a healthier, more productive garden, allowing both your marigolds and their neighbors to truly flourish.

Gardening is an ongoing learning process, and observing your plants is your best guide. By applying these principles and paying attention to your own garden's feedback, you'll be well on your way to creating a beautifully balanced and thriving ecosystem. Happy gardening!

What Not to Grow Next to Marigolds: Cultivating a Harmonious Garden Ecosystem