Most piedmont gardeners recognize Sweet Alyssum — an annual often used to edge flower beds. This low-growing, ever-blooming flower exudes a delicate sweet fragrance, but that’s not why I grow it. I grow this reliable friend because it is a pollinator magnet, attracting many species of nectar-loving insects.
Although I have planted this annual in my formal flowerbed in the past, that’s not where it will be going this year. As with many past growing seasons, I’ll interplant it with my spring vegetables, because of its propensity to attract lacewing insects — voracious eaters of aphids. Aphids are generally the only insects that bother my spring vegetables. They are especially fond of pea plants, multiplying and covering stems rapidly.
Green Lacewings — very pretty delicate green insects — eat even more aphids than Lady Bugs devour. The Lady Bugs will show up in my spring garden too, but they take longer to generate a population large enough to counter the aphid invaders.
Lacewings, on the other hand, seem to show up as soon as my Sweet Alyssums begin to bloom. These beneficial insects dine on the nectar of the flowers and then disperse among the aphid-plagued veggies. The lacewings are well-fed, my peas flourish, and I have a productive, healthy garden.
Companion planting is a practice followed by many, usually organic, gardeners. Over many years, gardeners have compiled lists of which plants seem to help each other when planted together, and which plants actually hamper each other when interplanted.
For example, planting alliums (members of the onion family) near fruit trees is supposed to enhance the health of the trees. Tomatoes do better when interplanted with basil, and, according to the charts I perused, basil near rosemary will kill the rosemary. I’ve never intentionally planted those herbs close together, so I can’t attest to the accuracy of that last claim.
If you search on “companion planting” on the internet, you’ll find an abundance of information on this topic. I think companion planting makes a lot of sense, and I can explain much of it from what I know of botany and ecology.
The most obvious reason for the success of companion planting is that gardens planted according to this notion are much more diverse than traditional vegetable gardens. Instead of whole beds of tomatoes or beans or whatever, beds are interplanted. Species diversity almost always makes for healthier ecosystems, whether they are naturally occurring forests or human-made gardens.
In the vegetable garden, pole beans and squash do well together. Basil attracts pollinators to tomato plants, and the chemicals responsible for their delicious scents may well deter some tomato varmints. Marigold roots have been shown to exude chemicals that repel damaging soil nematodes.
Today, I’ll be planting Sweet Alyssum seeds in my greenhouse. From past experience, I know they will germinate quickly, and I’ll urge them along with dilute doses of a fish emulsion/seaweed extract mix that encourages strong, rapid growth of roots and leaves. They should be ready to transplant among the peas, lettuces, and spinach just about the time the aphids mount serious attacks.
My money’s on the siren scent of Sweet Alyssums and the beneficial insects they attract.