Parsnips are not only nutritious and delicious on your plate, but can also be beneficial companion plants to other plants in your garden. Companion planting, also called interplanting, is a valuable tool that allows gardeners to garden more organically and grow strong, non-chemically treated produce -- including parsnips. When you interplant carefully, all of your plants benefit.
Attracting Beneficial Insects
Parsnip plants produce strong-smelling flowers in big clusters. These flowers attract beneficial insects to wherever they are planted, which can help anything planted in the area -- not just the parsnips. Beneficial insects are so-called because they either eat or parasitise other insects that might otherwise harm your garden. Ladybirds, spiders, most wasps and insects in the mantid family are all considered beneficial and essential in integrated pest management programs, as most organic gardeners use.
Interplanting is a more accurate term for the method by which the factual benefits of "companion planting" can best be achieved. Much writing on gardening and mass production of agriculture focuses on monocrops, or large areas featuring a single plant. Unfortunately, monocrops provide ideal conditions for harmful insects and diseases to thrive -- they are essentially all-you-can-eat buffets. Interplanting parsnips with other plants stymies pests, deters diseases and strengthens both your parsnips and the other plants.
Shared Pests and Diseases
When planning where to put this year's parsnips, remember where you had plants last year. If this is your first year gardening, such consideration is not necessary. However, if you planted carrots, tomatoes, legumes, lettuce or cabbage in an area last year, avoid planting parsnips there this year. Some of the same soilborne diseases and pests affect all of these crops, and crop rotation is essential to management of these problems.
Parsnips can safely be interplanted with any plants with which they do not share common pests or diseases. This group includes most herbs, cucurbits -- cucumbers, melons and squash -- and pest-deterrent flowers such as marigolds. Since parsnips have deep roots, choose companion plants that have smaller roots, so they do not interfere with each other -- such as broccoli or turnips. Interplant parsnips with plants that share watering requirements. Parsnips like frequent, regular watering, so avoid interplanting with anything that prefers drier soil. Sunflowers and Jerusalem artichokes (also called sunchokes) should not be planted with anything other than themselves, because they negatively affect other plants.
Since interplanting is not done in traditional rows, proper spacing takes more planning than row gardening. Look at the spacing requirements of both your parsnips and the plants you intend to interplant with them. Then measure your available garden space so you can plan. An easy way is to alternate the plants so that they are the equidistant from each other on all sides. Figure the correct distance by averaging parsnip spacing with whatever you interplant with them. Visualise a honeycomb to help you stagger your plants and make the best use of available space.