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Gardening - Plant Alchemy

Monday, 10 May 2010

Adam and Eve, Laurel and Hardy, Tom and Jerry, John and Edward.. Some companions were just made for each other!
Likewise in the plant world some combinations work better than others. Eugene will be discussing plant alchemy or companion planting - growing plants together that benefit one another.
What plant provides a protective odour, what plant keeps insects away and what plant protects your garden bed from aphids?
Eugene reveals all!!

Eugene Higgins - Plant Protector / Gardening Guru

1. French Marigolds and Potatoes

Plant Pals: Marigolds protect potatoes from the potato beetle.
Other benefits of Marigold: Pest deterrent. Keeps soil free of bad nematodes; supposed to discourage many insects. The marigolds you choose must be a scented variety for them to work.

French Marigold (T. patula) has roots that exude a substance which spreads in their immediate vicinity killing nematodes. These marigolds also help to deter whiteflies when planted around tomatoes and can be used in greenhouses for the same purpose. Whiteflies hate the smell of marigolds. Do not plant French marigolds next to bean plants.

Mexican marigold (T. minuta) is the most powerful of the insect repelling marigolds and may also overwhelm weed roots such as bind weed! It is said to repel the Mexican bean beetle and wild bunnies! Be careful it can have an herbicidal effect on some plants like beans and cabbage.

Other companions for potatoes: Companions for potatoes are bush bean, members of the cabbage family, carrot, celery, corn, dead nettle, flax, horseradish, marigold, peas, petunia, onion and Tagetes marigold. Protect them from scab by putting comfrey leaves in with your potato sets at planting time. Horseradish, planted at the corners of the potato patch, provides general protection. Keep potatoes and tomatoes apart as they both can get early and late blight contaminating each other.

2. Nasturtiums and Radish

Plant Pals: Nasturtiums improve radish growth and flavour.
Benefits of Nasturtiums: Nasturtium is an excellent companion for many plants. It is a companion to radishes and cabbage family plants. It deters aphids, squash bugs, and striped pumpkin beetles, and improves growth and flavour. Plant as a barrier around tomatoes, cabbage, cucumbers, and under fruit trees. Deters wooly aphids, whiteflies, cucumber beetles and other pests of the cucurbit family. Great trap crop for aphids (in particular the black aphids) which it does attract, especially the yellow flowering varieties. It likes poor soil with low moisture and no fertilizer. It has been the practice of some fruit growers that planting nasturtiums every year in the root zone of fruit trees allow the trees to take up the pungent odour of the plants and repel bugs.

Fact: The leaves, flowers and seeds of nasturtiums are all edible and wonderful in salads!

Benefits of Radish: Radishes are a deterrent against cucumber beetles and rust flies. Chervil and nasturtium improve radish growth and flavour. Planting them around corn and letting them go to seed will also help fight corn borers. Chinese Daikon and Snow Belle radishes are favourites of flea beetles. Plant these at 6 to 12 inch intervals amongst broccoli. In one trial, this measurably reduced damage to broccoli. Radishes will lure leaf miners away from spinach. The damage the leaf miners do to radish leaves does not stop the radish roots from growing, a win-win situation. Keep radishes away from hyssop plants, cabbage, cauliflower, Brussels sprouts and turnips.

3. Onions and Cabbage

Plant Pals: Any member of the cabbage family can be planted with onions, which are aromatic plants, and therefore deter cabbage worms.
Cabbage butterfly is repelled by planting rosemary or sage with cabbages.

Benefits of onion: Intercropping onions and leeks with your carrots confuses the carrot and onion flies! Onions planted with strawberries help the berries fight disease. Keep onions away from peas and asparagus.
Other cabbage companion: Celery, dill, onions and potatoes are good companion plants.

Other Helpful Plants in the Garden


Benefits of garlic: Plant near roses to repel aphids. It also benefits apple trees, pear trees, cucumbers, peas, lettuce and celery. Garlic accumulates sulfur: a naturally occurring fungicide which will help in the garden with disease prevention. Garlic is systemic in action as it is taken up the plants through their pores and when garlic tea is used as a soil drench it is also taken up by the plant roots. Has value in offending codling moths, Japanese beetles, root maggots, snails, and carrot root fly. Concentrated garlic sprays have been observed to repel and kill whiteflies, aphids and fungus gnats among others with as little as a 6-8% concentration! It is safe for use on orchids too.

Recipe for Garlic Spray

This protects against aphids and slugs too!

. 1 garlic bulb
. 1 quart of water
. 1 medium onion
. 1 tablespoon of cayenne pepper
. 1 tablespoon liquid dish soap


1. Crush the garlic, mincing it fine.
2. Add finely chopped onion to the mixture, while adding the rest of the ingredients except the soap.
3. Wait an hour before adding the soap to the mixture.
4. The spicy ingredients must sort of stew or steep, almost like tea. After an hour, add the soap and your non-toxic spray is ready to use! This can be stored in the fridge for a week.


Deters white cabbage moths, ants, rodents, flea beetles, fleas, aphids and improves the health of cabbage and tomatoes. Use cuttings as a mulch around members of the brassica family. Mint flowers attract hoverflies and predatory wasps. Earthworms are quite attracted to mint plantings. Be careful where you plant it as mint is an incredibly invasive perennial. We have found that placing peppermint cuttings (fresh or dried) where mice are a problem is very effective in driving them off!


Repels fleas and moths. Prolific flowering lavender nourishes many nectar feeding and beneficial insects. Lavenders can protect nearby plants from insects such as whitefly, and lavender planted under and near fruit trees can deter codling moth. Use dried sprigs of lavender to repel moths. Start plants in winter from cuttings, setting out in spring.

Other good companions:

. Broad Beans like to be with carrot, potatoes and lettuce

. Tomatoes like to be with celery, parsley and marigolds

. Birch Tree leaves help composts ferment better

. Chives grown beneath apple trees help prevent apple scab and Chives beneath roses help keep blackspot away.

Update on our GYO (Grow your Own) Vegetable garden!!

Every week we will be updating you on our TAS vegetable garden!

At the end of March we grew some Spring vegetables in some unusual places!!
We used everything from tyres, sinks and even teapots to house our new vegetable patch!

Every week we'll see how our vegetables are coming along and show you that it is possible to grow your own veg no matter how much space you have or what unusual objects you pick up along the way!!

Update Week 6: Our garden is coming along and loving the mixture of warm periods with bursts of heavy rain. As we saw last week the onions and potatoes are sprouting but our beans have also begun to flower! This week Eugene added some protective and complimentary measures and partnered our potatoes with marigolds and onions with cabbage!

Questions & comments from viewers about the TAS vegetable garden

Jenny Gaffney: I got a Rosemary plant in the shop, it's sitting on the kitchen windowsill but doesn't seem to be growing or anything? Any tips to help it?

Carol from Dublin: I would like to ask Eugene how I can get rid of Ivy as it has taken over my House and Shed.

Plants were kindly supplied by Balckbanks Gerdening Centre - 754 Howth Road, Raheny, Dublin 5. Contact Blackbanks Garden Centre on 01 832 7047 for further details.

Contact Eugene through his website

Image of onions and carrots was kindly supplied by Victoriana Nursery Gardens:

Image of radish was kindly supplied by the Sustainable Seed Company:

Image of Nasturtium was kindly supplied by Moosey's Country Garden: