Zinnias are easy to grow, attract pollinators and look great. They’ll brighten any garden with their beautiful flowers.
So it’s not a shock that they’re very popular. Everyone loves a Zinnia!
But it isn’t the case that every plant loves them. In fact some flowers and plants are terrible companions for zinnias.
They can outcompete them, attract pests that hurt them or just negatively affect how they grow.
So to make sure your zinnias grow and do well you’ll want to avoid planting them with the following plants.
Why Compatibility Matters in the Garden
How compatible plants are together will decide how successful a garden is. Some plants just work together. They share their resources, keep away bad pests and insects and can even help each other to grow better.
But there are others that compete hard with them or attract insects that do damage. And ultimately your garden or area you’re growing your flowers and plants fails.
Zinnias are generally easygoing and don’t mind what they’re planted with. But if you get it wrong it can result in poor growth, issues with pests and just a lot of wasted effort.
So knowing what not to plant with zinnias can save you a lot of time and frustration.
1. Cucumbers
Cucumbers and zinnias are a bad pairing because they compete for resources and have problems with pests.
Why Cucumbers are a Problem:
- Competition for Nutrients: Both cucumbers and zinnias like a lot of feeding, especially for nitrogen, which can leave both plants struggling.
- Pest Attraction: Cucumbers being in pests like cucumber beetles and these can also hurt zinnias.
- Vine Sprawl: Cucumbers’ vines can overtake zinnias, blocking the sun out and crowding them too much.
- Humidity Issues: When cucumbers grow their leaves/foliage can trap moisture and this can cause the zinnias to develop fungal infections.
- Shading: If your cucumber grows tall it can overshadow zinnias and stop them getting enough sunlight.
- Space Hogging: Cucumbers grow large and will compete with zinnias on the ground for space.
- Root Competition: Cucumber roots grow pretty widely and will steal a lot of the nutrients zinnias need.
- Attracts Mildew: Cucumbers are prone to powdery mildew which can then spread to zinnias.
- Moisture Imbalance: Cucumbers need to be watered consistently which is different to what zinnias like.
- Weed Harboring: Cucumber foliage can have lots of weeds growing in it that will wreck your zinnias.
2. Tomatoes
They make look harmless but can cause some problems for zinnias.
Why Tomatoes are a Problem:
- Nutrient Depletion: Tomatoes need lots of phosphorus and potassium, which they take from the soil and that leaves less for zinnias.
- Pest Magnet: Tomatoes attract pests like whiteflies and aphids and these will hurt zinnias.
- Disease Spread: Fungal diseases that affect tomatoes, like blight, can easily spread to zinnias.
- Shade Issues: Tomato plants grow tall and can block sunlight from reaching zinnias.
- Space Competition: The way tomatoes grow can overcrowd zinnias.
- Water Competition: Tomatoes like a lot of water and will take it leaving zinnias dehydrated.
- Root Crowding: Tomato roots grow aggressively, stealing the nutrients in the soil and meaning zinnias won’t get what they need.
- Chemical Sensitivity: Tomatoes release chemicals that can have a real negative affect on how zinnia grow.
- Pruning Needs: You have to prune tomatoes fairly often and this can disturb nearby zinnias.
- Soil Imbalance: Tomatoes alter the acidity of the soil and it might not suit zinnias.
3. Pumpkins
Pumpkins and zinnias clash over the nutrients they need and the available space.
Why Pumpkins are a Problem:
- Vine Encroachment: Pumpkins vines can be too much for zinnias and overwhelm them.
- Nutrient Hogging: Pumpkins need a lot of nitrogen and that leaves less for your zinnias.
- Shading: Large pumpkin leaves will block the sun from getting to zinnias and stop them from growing.
- Moisture Issues: Pumpkin leaves hold on to humidity and that can make fungal diseases more likely for the zinnias.
- Pest Problems: Squash bugs and beetles that affect pumpkins can harm zinnias too.
- Root Crowding: Pumpkins’ roots take a lot of the nutrients form the soil and leave little for the zinnias.
- Growth Suppression: Pumpkins can outcompete zinnias for space and light.
- Weed Creation: Pumpkin vines can have weeds growing in them that affect zinnias.
- Soil Exhaustion: As pumpkins deplete the soil quickly it leaves it without enough for zinnias to grow properly.
- Climbing Interference: When or if pumpkins climb it can then overshadow zinnias.
4. Potatoes
Potatoes can cause a few challenges if you want to plant them with zinnias.
Why Potatoes are a Problem:
- Pest Attraction: Potatoes bring in pests like aphids and beetles that can do harm to zinnias.
- Nutrient Competition: Potatoes steal nitrogen and other nutrients from the soil.
- Disease Risk: Potatoes are likely to get blight which can then spread to zinnias.
- Space Conflict: Potatoes need a lot of space to grow and can crowd zinnias.
- Shading Issues: Potato leaves and growth will block zinnias from getting the light they need.
- Root Spread: Potatoes roots will compete hard for the nutrients in the soil and steal what zinnias need.
- Water Needs: Potatoes need to be moist for the most part and zinnias might not like this.
- Chemical Sensitivity: Potatoes release chemicals into the soil that can affect how zinnias grow.
- Fungal Problems: Potatoes can get fungal problems that may spread to zinnias.
- Soil Disturbance: When you harvest potatoes it can upset the roots for the zinnias close by.
5. Mint
Mint is a poor companion with virtually everything! Zinnias included.
Why Mint is a Problem:
- Invasive Growth: Mint grows quickly and will choke out zinnias.
- Allelopathic Effects: Mint releases chemicals that really mess up and stop the growth any plants near to them.
- Nutrient Depletion: Mint is aggressive and will take all the nutrients from the soil.
- Space Encroachment: The way mint grows will crowd zinnias.
- Moisture Competition: Mint absorbs water quickly which leaves little for zinnias.
- Shade Issues: Mint can grow so densely that it blocks the sun from the zinnias.
- Weed Like Behavior: Mint acts like a weed and will grow into every space in your garden.
- Root Spread: The roots of mint grow fast and wide and will steal the space that zinnias need.
- Difficult Removal: Once mint has got itself established it’s hard to remove, especially without upsetting zinnias.
- Fungal Risk: mint holds on to moist and that can make fungus more likely to grow on zinnias.
6. Fennel
Fennel is one of the worst neighbors for zinnias because of the allelopathic nature.
Why Fennel is a Problem:
- Allelopathic Compounds: Fennel releases these chemicals that will stop any plants planted close to them from growing.
- Nutrient Competition: Fennel takes a lot of nutrients from the soil that zinnias need.
- Root Spread: Fennel roots grow aggressively and take up a lot space zinnias will need.
- Pest Attraction: Fennel will bring in pests to gardens that can hurt zinnias.
- Shading Issues: Fennel grows tall and doing so will block the sun from getting to the zinnias.
- Moisture Conflict: what Fennel needs in the way of water is different to zinnias and they can clash over this.
- Growth Suppression: Fennel stops other plants growing that are near to it.
- Space Competition: How big it grows and spreads out can overcrowd zinnias.
- Soil Imbalance: Fennel changes the chemistry in the soil and that makes it less suitable for zinnias to grow in.
- Pollinator Interference: Fennel and zinnias competes with each other for pollinators.
Good Companions for Zinnias
As we’ve just been through there are doing plants that are bad when planted with zinnias. But there are others that actually work well.
- Marigolds: Keep away pests and do really well with zinnias.
- Lettuce: Doesn’t compete for nutrients with zinnias.
- Sunflowers: Attract pollinators that help zinnias to do well.
Tips for Successful Companion Planting
- Match Nutrient Needs: Try to pair plants with others that need the same sort of nutrients and take them from the soil at the same amount so they don’t compete.
- Group by Sunlight: Pick plants that need the same amount of light.
- Control Pests: Use companion plants that keep pests away but that don’t damage their neighbors.
Zinnias look great and are worth putting the effort in to grow. But you need to make sure you avoid the wrong sorts of plants to plant won’t them. Otherwise that hard work will all be a waste.
So keep these recommendations in mind when planting and growing your zinnias and you can be confident they will do well and not struggle because of their neighbors.