Herb of the Week - Companion Plants

I've written on companion planting before, but I came across several new articles and resources on the subject, that I thought some updated info would serve everyone.

For a while it was believed that Companion Planting was only folklore and had no basis in science, however experts now call the interaction of plants allelopathy or "growth inhibition as the consequence of the influence of one organism on another."  The scents or air interactions as well as root excretions of certain plants will effect others.  Here are some examples of what I mean:

1. Legumes, such as peas and beans take nitrogen from the air and fix it for their own use, which will in turn benefit neighboring plants.
2. Some plants exude chemical from the root that repel insects, like the African marigold. This plant will give off a chemical called thiopene which repels soil nematodes.
3. Other plants may attract beneficial insects which in turn keep pests in check, like mint that attracts hoverflies.

Herb Companions

I have always known that tomatoes and basil enhance each other, so this year in my community garden I planted three varieties in the tomato bed to see which one has the best effect.

basil planted between the two rows of tomatoes

Chamomile, German variety (Matricaria chamomilla) improves the flavor of cabbages, cucumbers and onions.  The plant also accumulates calcium, potassium and sulfur which it returns to the soil.  These minerals are good for lowering the pH of the soil (making it more acidic) which vegetables like.

chervil

Chervil improves the growth and flavor of radishes and keeps aphids off lettuce.  Good to plant near dill and cilantro too.

chives 2014

Chives will improve the flavor and growth of carrots and a tea made from chives can be used to treat downy mildew on cucumbers.  I tried it on my rosemary for the same issue and it worked!

Geraniums will repel Japanese beetles and are a nice low growing addition to a rose garden.

Mint deters white cabbage moths, aphids and ant.  It improves the health of tomatoes and cabbages when grown near them.  It also attracts hoverflies and predatory wasps, but keep it away from your parsley.

Nasturtiums by tomatoes in cages.

Nasturtiums with work on wooly aphids, whiteflies and cucumber beetles.  Whitefly is a bug that likes lemon verbena, so I often plant nasturtiums in my lemon verbena pots. If I had known about the cucumber beetle thing, I think I would have ringed my community garden with nasturtiums before I planted anything.  As it is, I set in some seed only after the cucumber beetles ate alot!

purple sage

Sage is used as a companion for broccoli, cauliflower, rosemary and cabbage and carrots as it will deter moths and beetles because of its strong scent, but don't place it too close to the cucumbers.

marigolds encircling tomatoes

Scented marigolds (sometimes called Mexican or French marigolds) are the best at repelling soil nematodes, but remember a dense planting is needed, not a random plant here and there.

scented marigolds

Stinging Nettle helps neighboring plants to grow more resistant to spoiling. It also increases the essential oil in other herbs.  And a tea made with the leaves can be sprayed on plants to help them grow strong stems.

nettle

Summer Savory should be placed near the beans and onions to improve the flavor. I just discovered a midget variety that I think will work great around these plants.

Midget Summer Savory (Saturejus hortensis 'midget')

Tansy will keep away leaf borers and is very good companion in the fruit orchard or among the grape vines.

Resources: 

The Practical Organic Gardener by Brenda Little

How to Grow More Vegetables by John Jeavons

The Essential Herbal magazine - several recent editions from 2013 and 2014