Love-hate relationships in the vege patch are something not all gardeners dwell on, but if your putting in crops this spring, a little extra thought and planning could return greater rewards.

It's nearly time for planting out plenty of veges as the weather warms, but do you plant tomatoes next to your garilic, lettuces by legumes, pile peas by potatoes or site silverbeet by your strawberries? Companion planting has been practised for eons by gardeners keen to get the best results possible from their crops and to stop plagues of pests the easy way.

While some planting combinations may be little more than old wives' tales, others have been scientifically proven. Most people know that planting basil by tomatoes is supposed to enhance the flavour of tomatoes, that marigolds or calendula can be helpful in repelling bugs from vege crops, and that garlic planted by roses apparently brings out the flavour of roses and helps deter aphids, but combination planting can get far more complex and interesting than that.

Like us, plants have their likes and dislikes, but it makes more sense that having a greater mix of plants in the garden will be beneficial by creating diversity. This helps to avoid monoculture - bulk planting the same type of crop - which pests and disease love because the can go from one plant to the next without stumbling across roadblocks.

"Diversity is the key," says organic gardener and educator Sol Morgan. "One of the core principals of organics is copying whats happening in nature." As Sol - New Zealand Gardener magazine's Nelson regional gardener of the year - explains, there are several types of combination planting. Gardeners can companion plant for the physical attributes of plants, such as planting tall plants to provide shade for lower growing plants. An example of this is growing corn to help shade pumpkin plants, which can otherwise be burned by the sun. In return, the pumpkin plants, with thier big leaves and low-growing nature, help to keep the corn roots moist.

Most salad plants like shade, so they love being grown below tomatoes in summer, he adds. "That slows them down so they don't bolt." Then there are combinations to help enhance the taste of certain produce, such as planting basil and tomatoes together. Marjoram, oregano and sage can be planted among all plants, and are supposed to enhance the flavour of the product they are next to, Sol says.

Variety is the key, but it's important not to go overboard. "Putting marjoram between all the different plants you are growing can be a complete nightmare because it can take over." Along with plants that simply like to grow next to each other, gardeners can outwit unwanted bugs by growing certain plants that will attract or repel them as desired.

Planting onions or garlic either side of a row of carrots deters carrot fly, because the flies can't smell the carrots over the strong smell of the onion or garlic.  However, to be effective, you'll need to grow alot of onions - up to ten rows to every row of carrots. Flowering cleome is one plant that will attract pesky shield bugs away from beans, which they love, says Sol. "You plant them to the side as a diversion." Gardeners can then collect the bugs and dispose of them.

Other strong-smelling flowering plants such as African or French marigolds deter many pests with their odour, working on pests both above ground and in the soil. "Especially things like nematodes that attack the roots of other plants - they will repel them," Sol says.

Mustard is another repellent, and can be planted to make a "cleaner" bed before starting to plant crops again, he says. Some plants are grown for the various nutrients they provide each other when sited together. An example of this is a technique known as the Three Sisters, in which corn is grown and then squash, pumpkins, and then climbing beans are added later around it. The beans, being nitrogen fixing legumes, grow up the corn, providing them and the corn with extra nutrients. The squash leaves act as mulch to retain moisture in the soil and prevent weeds, and the prickly hair of its vine also deter pests.

Then theres the bug eater approach. This method involves having edging or garden corners of flowering plants such as calendula, daisies and borage to attract beneficial predators to eat pests, and to attract beneficial parasites, such as some types of wasp, which lay their eggs inside pests such as caterpillars and kill them.

Phacelia is said to control white butterfly and aphids because it attracts the hoverfly, a predator of scale insects, aphids, and caterpillars and thier eggs. It also attracts predatory insects such as lacewings and aphid hungry ladybirds. Allowing vegetables such as brassicas to flower also attracts beneficial predatory insects, and "you can get the added benefit of waiting a little longer and getting a seed," Sol says.

While there are not many plants that create big problems if planted beside each other, one pairing commonly discouraged is tomatoes and potatoes together. This is because they are from the same family and are prone to blight and similar pest problems. "When you grow them side by side, it's kind of asking for it," Sol says. Other plant combinations are said not to do so well together because they compete for nutrients, such as pairings of asparagus and potatoes, or of brassica, tomatoes and strawberries.

As well as introducing flowers into the vegetable and herb garden, why not try switching things around and planting summer veges such as salad greens and courgettes in your ornamental garden? While the jury is still out on some love-hate relationships, in the plant world, with science yet to establish the effectiveness of  some companion plantings, if nothing else, diversity with flowers, herbs and veges growing in close proximity to each other makes for an attractive garden, and one the good guys of the insect world love.

Crop - Beneficial combinations - combinations to avoid
Beans - carrots, celery, lettuce - onions, garlic
Cucumbers - beans, radish, lettuce, corn - potatoes
Asparagus - tomatoes, parsley, basil - potatoes
Lettuce - carrots, radishes, strawberries, beetroot
Brassicas - potatoes, celery - tomatoes, strawberries
Carrots - peas, tomatoes, lettuce, radish - dill
Celery - leaks, tomatoes, brassicas - silverbeet
Corn - potatoes, peas, beans - tomatoes
Potatoes - corn, beans, cabbage, eggplant - squash, cucumbers, tomatoes
Tomatoes - onions, asparagus - potato, broccoli, cabbage
Courgettes - nasturtiums - potatoes

Not all of these combinations have been yet scientifically proven, but they are the common belief among gardeners.

Article sourced from Fairfax Media -  October 10, 2008