There are a few common bushes that produce blue flowers. To identify a mystery bush with blue blooms, it helps to consider the bush’s characteristics and growth habits. The time of year the flowers appear can offer clues, as can leaf shape and plant size. With some sleuthing and process of elimination, it’s often possible to put a name to an unknown blue-flowered bush.
When Are the Blue Flowers in Bloom?
Paying attention to bloom time is often the first step in identifying an unfamiliar bush. Many bushes have relatively short seasons of bloom, so the time of year narrows options. Here are some of the main shrubbery suspects for each season:
- Early spring: Forsythia, viburnum, hydrangea
- Late spring: Bluebeard, blue mist spirea, rose of Sharon
- Early summer: Butterfly bush, bluebeard, rose of Sharon
- Late summer: Bluebeard, rose of Sharon
- Fall: Blue mist spirea
As the list shows, a few bushes with blue flowers bloom for extended periods, making identification trickier. But most have a peak bloom time of just a few weeks or months. Timing is often the first clue to start the identification process.
What Are the Plant’s Other Identifying Features?
Once you know around when the flowers appear, examining other plant traits helps pin down possibilities. Here are key details to take note of:
Plant Size and Shape
Is the bush a large, sprawling shrub, or more compact and tidy? Does it have an upright or fountain-like form, or is it a vine? Observing growth habit rules out some options. For example, a 5-foot wide, 3-foot tall mound covered in blue blooms could be a blue mist spirea or butterfly bush, while a rambling 8-foot vine is likely a plumbago.
Leaf Shape and Color
Leaf details provide more clues. Are the leaves rounded, long and thin, or lobed? What color are they? Blue-green, deep green, purple, variegated? Leaf shape can point to hydrangea (lobed leaves) or rose of Sharon (long, thin leaves). Variegated leaves may mean hydrangea or viburnum.
Flowers
Examining the blooms themselves provides specifics like flower size, cluster shape, petal appearance, and so on. Lupe blossoms, for instance, have fluted petals, while hydrangea blooms can be cone-shaped or round mopheads.
Here’s a quick visual reference for common blue-flowered bushes and their features:
| Plant | Size | Leaves | Flowers |
|---|---|---|---|
| Butterfly bush | 5-8 feet tall, 4-6 feet wide | Narrow, grayish | Cone-shaped blooms in summer |
| Bluebeard | 5-8 feet tall and wide | Grayish green | Tubular blue blooms in late spring/summer |
| Blue mist spirea | 3-4 feet tall and wide | Green, small | Clusters of small blue blooms in spring/fall |
Most Common Blue-Flowering Bushes
Beyond when it blooms and physical traits, being familiar with likely blue-blooming bush suspects helps identify an unknown plant. Here are some of the top choices:
Butterfly Bush
One of the most popular blue-flowering bushes is butterfly bush (Buddleia davidii). It produces abundant conical flowers ranging from deep blue to violet. The blooms appear beginning in midsummer, and continue into fall in warm climates. Butterfly bushes grow quickly, reaching 5-8 feet tall and 4-6 feet wide. Their narrow gray-green leaves have a fuzzy texture.
Bluebeard
Bluebeard (Caryopteris x clandonensis) is prized for its weeks-long bloom period beginning in late summer. It reaches 5-8 feet tall and wide, with grayish green leaves and clusters of small blue tubular flowers. ‘Dark Knight’ is a popular dark blue variety. Pruning in late winter promotes abundant blooms.
Rose of Sharon
Rose of Sharon (Hibiscus syriacus) can take bush or small tree form. It flowers prolifically with large, showy blue blooms from midsummer into fall. Flowers can be single or double. Popular blue varieties include ‘Blue Bird,’ ‘Blue Chiffon,’ and ‘Blue Satin.’ Rose of Sharon grows 8-12 feet tall with long, thin green or variegated leaves.
Hydrangea
Many hydrangea shrubs produce blue blooms, especially mophead and lacecap types. Their color is influenced by soil pH. Alkaline soils result in pink flowers, while acidic conditions make hydrangea blossoms blue. Popular blue-flowering selections include ‘Nikko Blue’ and ‘Blue Wave.’ Hydrangeas reach 3-6 feet tall with large, lobed leaves.
Blue Mist Spirea
For a petite bush with blue flowers, look for blue mist spirea (Caryopteris x clandonensis ‘Blue Mist’). It grows just 2-3 feet tall and wide, with clusters of small blue flowers appearing in spring and again in fall. Its green leaves are small and rounded. Blue mist spirea thrives with minimal care, though pruning out old wood in late winter ensures abundant blooming.
Viburnum
Certain viburnum shrubs produce blue berry-like drupe flowers in spring, followed by clusters of blue berries in fall. Arrowwood viburnum (Viburnum dentatum) and Burkwood viburnum (V. x burkwoodii) are two examples. These bushes grow 6-10 feet tall and wide with green or variegated leaves. Pruning after flowering avoids sacrificing next year’s flower buds.
Bluebeard Bush
Like the more commonly known bluebeard shrub, bluebeard bush (Caryopteris x clandonensis) offers weeks of blue blooms in summer and fall. It reaches a larger size, up to 10 feet tall, with gray-green leaves. ‘Longwood Blue’ is a popular variety with deep blue flowers. Bluebeard bush does best in full sun and well-drained soil.
Grape Hyacinth
Grape hyacinth (Muscari) produces vibrant blue flower spikes in early spring. The compact plants reach just 4-8 inches tall. Leave foliage intact after blooming until it dies back naturally. Grape hyacinth grows well in beds, borders, and containers, and spreads slowly by bulb offsets.
Caring for Blue-Flowering Bushes
Most bushes with blue flowers are relatively easy care once established. Here are some general tips to keep them healthy and floriferous:
- Choose an appropriate site with full sun for most varieties.
- Provide average but consistent water, avoiding soggy soil.
- Apply a balanced fertilizer in early spring and midsummer.
- Prune old stems and shape plants after flowering.
- Watch for common pests like aphids, spider mites, and Japanese beetles.
- Mulch around the root zone to conserve moisture and suppress weeds.
- Divide overcrowded plants in fall or early spring every few years.
With proper care, bushes with blue blossoms will thrive for years of stunning color. Pay attention to each variety’s specific needs for the healthiest growth and maximum flowers.
Conclusion
Identifying a mystery bush is a fun challenge for keen gardeners. When it produces eyecatching blue blooms, look for clues based on bloom time, plant size and shape, leaf features, and flower details. Compare these observable traits to likely candidates like butterfly bush, bluebeard, rose of Sharon, hydrangea, viburnum, and more. With some deductive reasoning, the bush’s name should reveal itself.
Caring for blue-flowering bushes is fairly straightforward. Give them appropriate growing conditions, prune at the right time, watch for pests, and fertilize occasionally. The reward for proper care will be stunning swathes of colorful blue in the garden year after year.