Companion plants - Ask Extension
If this is out of the scope of what you help with, I understand. I have attached a PDF with the proposed layout of my garden this year. The carrots an...
Knowledgebase
Companion plants #923702
Asked January 16, 2026, 4:33 PM EST
If this is out of the scope of what you help with, I understand. I have attached a PDF with the proposed layout of my garden this year. The carrots and spinach are new and I'm having trouble with companion plants - there is so much conflicting information on the internet. Would you be able to tell me if I have plants paired correctly? A few notes: Purple outlined garden is new this year and therefore does not have established soil yet. I will be putting horse manure compost there along with my backyard compost. Green outlined garden will be on its 4th year. The sun shows its location at its highest point in the summer. My garden only gets about 6-8 hours of direct sunlight because we have a lot of trees. The blue lines inside the garden areas are trellis's. I read that spinach does well behind tomatoes because of the shade - which is the reason for the new trellis in the purple area.
Any help is appreciated! And again - if this is outside of the realm of things you help with, I completely understand!
Baltimore County Maryland
Expert Response
Although we aren't able to provide detailed garden design or layout guidance, we can provide some basic feedback, and your local Master Gardeners may also be able to help with tips for placement and combinations.
As a generalization, as long as each crop gets the conditions it needs (summer sunlight exposure, soil drainage, and room to mature without crowding), any layout can work. Proper spacing between plants can be critical for maintaining good air circulation (one way to suppress disease outbreaks) as well as giving each plant the full potential for growth and harvest yield. For crops that prefer cooler weather (many leafy greens), siting them where they'll be shaded by taller plants when the summer heat begins can be helpful to extend their season and reduce plant stress. Layout can also take into account which crops may benefit from being covered with either row cover (for frost protection), shade cloth (for heat protection), and/or insect netting (for pest exclusion). How you'll be covering them, such as with short hoops in a single row or scattered smaller cloche-like domes, may dictate which layout is easiest to work with so they remain easy to access to lift the cover off when needed. Row cover and insect netting are great ways to prevent most insect damage without the need for insecticide.
Regarding manure, make sure it's well-composted, and you may want to test a batch of it first with seeds to determine if it's contaminated with any long-residue herbicides. (Some of those chemicals can survive animal digestion and still impact plants growing in areas where that compost was applied.) If seedlings emerge normally in soil mixed with that manure, then it's probably fine to incorporate into the new garden. (As long as compost didn't have lawn clippings in it from a lawn treated with pesticides, it's probably fine.)
If you haven't already, it would be good to have the soil from both the established beds and the new bed area tested. Laboratory testing every few years can measure nutrient content (in case you need to supplement), organic matter content (which can guide you with regards to how much compost/manure to add), and soil acidity (pH), which impacts how easily roots can access soil nutrients. Organic matter (compost, manure) is a great soil additive, but you don't want to overdo it, since overly-rich soil can lead to some problems like pest outbreaks and plants producing more leafy growth when they need to be flowering and fruiting. The linked page has more information about soil testing. If you haven't tested the soil in the veggie garden yet, you can also consider lead testing.
There are different reasons for "companion planting." It could be used to make efficient use of space and combine crops that use different layers of the garden (something tall near something short, especially if the short plant benefits from cooling shade), or it could be used to have one plant help to discourage problems for another (such as using marigolds to repel soil nematodes or other pests near tomatoes). Companion planting can also include mixing-in flowering annuals or herbs that draw in pollinators, both to help pollinate the vegetable crops and to support beneficial insects that will eat pests like aphids. For example, the larvae of aptly-named flower flies eat aphids, and the adults visit flowers. Sometimes certain plant pairings are suggested as companions to purportedly boost each other's growth or have some other general benefit simply by being near each other, but those such pairings are not usually supported by research.
You have a grape trellis on the map...if it's established and not new, you may already be aware of this, but grapes tend to require yearly pesticide (usually fungicide) sprays to preventatively manage issues like disease outbreaks. Drift wafting over a nearby vegetable garden may be undesirable, especially if certain products are not intended for use on other crops, or if certain crops are sensitive to the residues settling on their leaves or developing fruits. If you spray the grapes, you may want to make sure the nearby veggie plot is several feet away to reduce the risk of drift impacting those plants. (Even if a spray doesn't damage them, it may have a PHI [preharvest interval], where there needs to be a delay in harvesting so any spray residues have time to start breaking down.)
If you haven't come across them already, we have many web pages which may be helpful for growing vegetables, which include topics like selection, care, and troubleshooting.
Miri
As a generalization, as long as each crop gets the conditions it needs (summer sunlight exposure, soil drainage, and room to mature without crowding), any layout can work. Proper spacing between plants can be critical for maintaining good air circulation (one way to suppress disease outbreaks) as well as giving each plant the full potential for growth and harvest yield. For crops that prefer cooler weather (many leafy greens), siting them where they'll be shaded by taller plants when the summer heat begins can be helpful to extend their season and reduce plant stress. Layout can also take into account which crops may benefit from being covered with either row cover (for frost protection), shade cloth (for heat protection), and/or insect netting (for pest exclusion). How you'll be covering them, such as with short hoops in a single row or scattered smaller cloche-like domes, may dictate which layout is easiest to work with so they remain easy to access to lift the cover off when needed. Row cover and insect netting are great ways to prevent most insect damage without the need for insecticide.
Regarding manure, make sure it's well-composted, and you may want to test a batch of it first with seeds to determine if it's contaminated with any long-residue herbicides. (Some of those chemicals can survive animal digestion and still impact plants growing in areas where that compost was applied.) If seedlings emerge normally in soil mixed with that manure, then it's probably fine to incorporate into the new garden. (As long as compost didn't have lawn clippings in it from a lawn treated with pesticides, it's probably fine.)
If you haven't already, it would be good to have the soil from both the established beds and the new bed area tested. Laboratory testing every few years can measure nutrient content (in case you need to supplement), organic matter content (which can guide you with regards to how much compost/manure to add), and soil acidity (pH), which impacts how easily roots can access soil nutrients. Organic matter (compost, manure) is a great soil additive, but you don't want to overdo it, since overly-rich soil can lead to some problems like pest outbreaks and plants producing more leafy growth when they need to be flowering and fruiting. The linked page has more information about soil testing. If you haven't tested the soil in the veggie garden yet, you can also consider lead testing.
There are different reasons for "companion planting." It could be used to make efficient use of space and combine crops that use different layers of the garden (something tall near something short, especially if the short plant benefits from cooling shade), or it could be used to have one plant help to discourage problems for another (such as using marigolds to repel soil nematodes or other pests near tomatoes). Companion planting can also include mixing-in flowering annuals or herbs that draw in pollinators, both to help pollinate the vegetable crops and to support beneficial insects that will eat pests like aphids. For example, the larvae of aptly-named flower flies eat aphids, and the adults visit flowers. Sometimes certain plant pairings are suggested as companions to purportedly boost each other's growth or have some other general benefit simply by being near each other, but those such pairings are not usually supported by research.
You have a grape trellis on the map...if it's established and not new, you may already be aware of this, but grapes tend to require yearly pesticide (usually fungicide) sprays to preventatively manage issues like disease outbreaks. Drift wafting over a nearby vegetable garden may be undesirable, especially if certain products are not intended for use on other crops, or if certain crops are sensitive to the residues settling on their leaves or developing fruits. If you spray the grapes, you may want to make sure the nearby veggie plot is several feet away to reduce the risk of drift impacting those plants. (Even if a spray doesn't damage them, it may have a PHI [preharvest interval], where there needs to be a delay in harvesting so any spray residues have time to start breaking down.)
If you haven't come across them already, we have many web pages which may be helpful for growing vegetables, which include topics like selection, care, and troubleshooting.
Miri
