This week, a little behind schedule, the first fragrant purple flowers have begun to adorn the lavender plants in the master-gardener Herb Demonstration garden. Lavender flowers typically appear in June and July, but the plants in the demonstration garden, located on the Illinois State Fairgrounds, were planted this spring and are therefore flowering later in the season.
There are more than 15 species of lavender. Flower color ranges from white to pale pink to clear violet-blue to dark purple. The 2-inch-long leaves are smooth and narrow, gray-green to silver-gray. Plant height ranges from 1.5 to 3 feet tall.
Although both the flowers and foliage are fragrant, lavender flowers are more useful, adding beauty and fragrance to fresh and dried arrangements. For dried flowers, harvest when the flowers buds are just showing color but before they fully open. For dried cut flowers, cut the stem at least 6 inches long. Hang the lavender in small bunches of eight to 10 stems or lay them on screens, and place them in a cool, dark location. Flowers can also be used in sachets and potpourris.
Lavender is a little fussy about its growing conditions. Cultivars of Lavandula angustifolia and Lavandula x intermedia are best suited to our area. “Munstead” and “Hidcote” are the most easily obtainable cultivars of L. angustifolia. Popular cultivars of L. x intermedia are “Grosso” and “Provence.” Many cultivars are suitable for zone 5.
The more sunshine lavender gets, the more the plant will flourish and bloom. At the very least lavender requires four hours of direct sunlight a day. Any less, and the plants will begin to look straggly and produce few flowers.
In addition to full sun, lavender needs a dry, somewhat infertile soil with a pH range of 6.4 to 8.3 to look its best. Good drainage is a must, so consider planting lavender on a raised mound. To make a mound, take one part garden soil, one part sand, and one part compost; mix well and add a third as much pea gravel. Shape this mixture into a mound 8 to 18 inches high, depending on how wet the area is. The mound will eventually settle to about half its original height. To plant the lavender, make a cone of the soil, using mostly soil and brushing any gravel away. Spread the roots of the plant over the cone, cover them with the soil mix, and water thoroughly.
Lavender generally shouldn’t need additional fertilizer. In its native habitat, lavender grows in relatively poor rocky soil, so too much fertilizer may render the foliage more vulnerable to fungal attack.
In central Illinois, lavender requires about an inch of water per week during the summer. You’ll find a soaker hose useful in this regard.
Lavender does not tolerate “wet feet”: Planted in a heavy clay soil or watered too heavily near the crown (top) of the root system, lavender may succumb to root rot, the major killer of this plant. Mildews and rusts, indications of too much watering of the foliage, can be prevented with a change in watering method.
The best mulch for lavender is white sand. If you use wood chips or other organic mulch, keep it away from the stem and spread it in a thin layer.
Although lavender is particular about its growing conditions, a well-placed plant can provide years of beauty and fragrance in your garden.