Beneficial insectary is a term that refers to plants that attract and host beneficial insects. In other words they are the plants that provide a habitat for predatory insects. Beneficial insectary plants often have nectar and pollen to offer to the good insects. Their flowers offer a flat landing place for insects and sometimes they exude an unusual scent as an attractant. The list of beneficial insectary plants continues to expand with the increasing research work and interest in organic farming.
Beneficial insects on the other hand are insect predators that prey on many common garden pests. Indirectly they benefit gardening by helping eliminate the destructive plant-feeding insects. For example lady bugs don't eat plants; instead they feed on aphids that are destroying plants in the garden. For the gardener, beneficial insects offer a biological control of pests. Effective biological pest control is a safer alternative to pesticides.
In My Garden. There are some plants growing in my garden right now that are known to be beneficial insectary. The Santa Barbara daisy (Erigeron karvinskianus) as I mentioned before is a very versatile perennial. In addition to its aesthetic contribution in the garden, itis also valued for the role it plays in biological control of pests. Among the herbs that double as insectary are spearmint (Menta spicata), coriander or cilantro (Coriandrum sativum), flat-leaf parsley (Petroselinum crispum). Although my marigolds (Tagetes patula) are newly planted and recently damaged by birds, they are also known to harbor some beneficial bugs including lady beetles. Hence, they are recommended to be planted near tomato plants. Even English ivy (Hedera spp.) is supposed to harbor some beneficial wasps.
What then? Not all insects are gardeners' enemies. In fact some of them are our allies. They eliminate the real enemies. This is like having your own army protecting your plants while you sleep and play. However, their loyalty is dependent on the fringe benefits we give them. Some gardeners provide a dedicated habitat (Beneficial Insectary garden) for these allies. However, if your garden is small, you can diversify your plantings to include the ones that attract them.
Finally, do not be deceived - not all pests can be eradicated by biological means. An effective pest control involves an integrated approach based on numerous factors. Read more about integrated pest management approach (IPM).