(Author of The Bulb-o-licious Garden) If you're new to gardening, you may not be familiar with the term indicator plant. What the heck is this, you ask. Simply put an indicator plant is one that can be added to the garden, oftentimes as a sacrificial specimen, which can help "indicate" or determine when pests or disease are likely more prevalent. Some of these plants can also pinpoint nutrient deficiencies in the soil or even when it's time to plant or water the garden. Here are the top 5 indicator plants that can be added to the garden: 1. Petunia - Petunias are commonly used in greenhouses to detect the presence of thrips. Certain cultivars of petunia, like 'Red Cloud,' 'Summer Madness' and 'Super Magic Coral,' have been found to be highly attractive to these pests and are also susceptible to viruses. 2. Saucer Magnolia - The saucer magnolia is a common indicator plant for early spring pests, such as the ever-annoying eastern tent caterpillar. While the tree itself is not typically bothered by these defoliating pests, when your magnolia begins blooming, it indicates the right time to treat for tentworms in the garden. 3. Impatiens - Along with ajuga and coleus plants, impatiens make excellent indicator plants for watering. Since the plants are highly susceptible to water loss, they will exhibit signs of wilting and browning leaf tips whenever the soil becomes too dry, indicating that it is time to water your garden. 4. Lilac - You may not be aware but the common lilac is commonly used as an indicator plant for phenological observations. One example of this is following the plant's life cycle. For instance, when the lilac is in full bloom, this typically indicates it's a good time for planting tender garden crops such as beans, cucumbers and squash. 5. Chicory - Chicory is more than just a common weed or garden addition (depending on who you talk to). This summer-flowering plant can be crucial to gardeners as an indicator plant. As soon as chicory starts blooming, it signals that it's a good time to begin treating the vegetable garden for dreaded squash vine borers.

Nikki Tilley
Senior Editor

Nikki Tilley has been gardening for nearly three decades. The former Senior Editor and Archivist of Gardening Know How, Nikki has also authored six gardening books.