Colours and fragrances to attract insects

Insects fascinate us with their colors, variety and fragility. They are mostly beneficial to the garden, with only 2 percent out of 2000 species of butterflies, native to Lithuania, being harmful. The good news is that these useful insects can be attracted into the garden with some simple techniques. Most butterflies are pollinators, especially of night-flowering plants, while their caterpillars feed mostly on plants of little value. Dragonflies, praying mantises, several grasshoppers, shield bugs, carabus beetles, lacewings, predatory wasps and ichneumons feed on other insects, supplementing their diet with nectar. The larvae of ladybirds and hoverflies are ravenous predators of garden pests such as aphids, while bees make themselves useful by producing honey.

Plants and insects are the best of neighbors. Insects need plants for food and shelter, while plants would not be able to reproduce without the help of insects. Plants attract insects offering nectar and pollen, which is very nutritious in proteins, fats, carbohydrates, enzymes and vitamins. Poppies, anemones, St. John’s Wort and wild roses provide pollen in abundance. Insects fly from flower to flower, thus cross-pollinating plants.

However, nectar is the most important source of nutrition. Nectar is produced by nectaries, which are located at the base of petals and a pistil. Nectar is a sweet liquid, which consists of fructose, glucose, saccharose and maltose, and is accumulated in calyces and spurs of long and narrow flowers. The amount of nectar exuded by [banner] the flower depends on the plant species, the time of the day, the development stage of the flower, temperature, etc. A single flower holds very little nectar, so insects have to visit many flowers. With some plant species, such as lilies, nectar is rather difficult to access. Their nectaries are so deep within the flower, that only butterflies with their long spiral proboscises can reach them.

 To attract insects, a flower has to be of a particular color or fragrance. Bees and bumblebees home in on yellow, mauve or white flowers.

Colors are as important to day-flying butterflies: cabbage whites or scarce swallowtails search for food in red, yellow or purple flowers, while mourning cloaks, painted ladies, tortoiseshells, marbled fritillaries and ringlets prefer yellow and blue blooms. The purplish red flowers of pinks are frequented by hawk moths with long proboscises. White, yellowish or light mauve flowers are more noticeable to the night-flying butterflies. Flies, hoverflies and beetles love bright yellow, blue, purple and white flowers. Various blotches, streaks and patters are also important in attracting the insects. A yellow eye on a blue flower of a forget-me-not, veined petals of a cranesbill or a spotted lower lip on any plant of the mint family draw attention of insects. Some flowers change their colour over time. Flowers of lungworts start of pinkish purple, eventually turning blue, and the everlasting sweet pea changes its bloom color from red to greenish blue.

Fragrance is very important, as well. Flowers exude fragrant (sometimes malodorous) substances, which are mostly aromatic oils. The flowers of hawthorns, viburnums, rowans, dogwoods and barberries are frequented by flies and beetles due to their special fragrance. The calyces, stamens, staminoids and nectaries of flowers are the source of fragrant oils. Some plants have developed special glands, which produce aromatic oils of particular smell. For example, the purple glands on stamens of dittany (Dictamnus) produce a characteristic citrus fragrance.

Plants have evolved to avoid any waste of nectar or fragrance. The flowers, such as soapwort, catchfly, evening primrose and sweet rocket, which are normally pollinated by night-flying butterflies, open their flowers in the evening, wafting around a heady fragrance. Flowers pollinated by day-flying butterflies and bumblebees are at their best during the day.

In order to attract beneficial insects, include a diversity of plants in the garden. Some annual flowers, most attractive to insects are: white mignonette (Reseda odorata L.), sweet allysum (Lobuliaria maritima (L.) Desv. sin. Alyssum maritimum (L.) Lam.), garden snapdragon (Antirrhinum majus L.), flossflower (Ageratum houstonianum Mill.), flowering tobacco (Nicotiana alata Link. et Otto), common wallflower (Cheiranthus cheiri L.), garden cosmos (Cosmos bipinnatus Cav.), sweet scabious (Scabiosa atropurpurea L.), zinnia (Zinnia elegans Jacq.), clarkia (Clarkia unquiculata Lindl.), garden balsam (Impatiens balsamina L.), Himalayan balsam (Impatiens glandulifera Royle), love-in-a-mist (Nigella damascena L.) and annual candytuft (Iberis amara L.).

Popular perennial plants for beneficial insects include: bergenia (Bergenia), ice plant (Sedum), cranesbill (Geranium), winter savory (Satureja montana L., hyssop (Hyssopus officinalis L.), Eastern purple coneflower (Echinacea purpurea (L.) Moench), yarrow (Achillea), English levander (Lavandula angustifolia Mill.), thyme (Thymus), peppermint (Mentha piperita L.), Canada goldenrod (Solidago canadensis L.), garden phlox (Phlox paniculata L.), globe thistle (Echinops sphaerocephalus L.), meadow clary (Salvia pratensis L.), wall rock cress (Arabis caucasica L.), oregano (Origanum vulgare L.), elecampane (Inula helenium L.) and common milkweed (Asclepias syriaca L.).

If you keep bees, or if you would like to attract more of them into your garden, consider sowing lacy phacelia (Phacelia tanacetifolia Benth.), viper’s bugloss (Echium vulgare L.) and borage (Borago officinalis L.). In addition to their honey-producing properties, they also make an attractive addition to your border. Some attention should be given to caterpillars of butterflies. Plants in the pea family (clover, sweet clover), as well as the cruciferous plants (field penny-cress, shepherd’s purse, bitter cress, brassicas) are most appealing to caterpillars of beneficial insects. Most insects are especially attracted by flowers of plants in the carrot family, such as dill, caraway and anise. A sizeable clump of nettles is sufficient to feed the caterpillars of the tortoiseshell, peacock and red admiral butterflies. And if you grow plants of the carrot family and rue, you may even have a chance to see the most exquisite butterfly of Lithuania – the swallowtail butterfly.

© Giedra Bartas, 2012

One Comment:

  1. Some good ideas on plants to attract insects. I will link to my blog

Leave a Reply

Your email address will not be published. Required fields are marked *