Annuals that Star in Perennial Borders

By Marilyn Barlow. First published in Fine Gardening Magazine Issue #180 (March-April 2018)

More and more lawns are disappearing, but the endangered lawn is one thing we need not worry about! Shovels are slicing through sod, green deserts replaced with the many native and non-native perennials that welcome local and migrating songbirds, butterflies, bees and enrich your local habitat.

Most perennials take three years or more to become full specimens and forlorn patches of earth or bark mulch are all too common. Annual fillers including some tender perennials that are grown as annuals north of Zone 8 are perfect for filling in that first year, and perhaps every year thereafter, for who can resist their long-blooming colorful ways?

Some annuals to use in perennial beds are airy weavers, stunning when grown in drifts or ribbons of a dozen or more plants. Many of these self-sow onto bare earth and will happily grow every year among your perennials for they take up little ground space. Others are plants with more substance and height that bring needed structure while your perennials are establishing plus an unrivaled variety of color and form. Shorter annuals edging the borders complete the summer long show.

Give your annuals what they need!

Annuals are programmed to grow quickly, bloom and set seed in one year, and it is important to give them everything they need to do this without any check in their growth. The below are generalities, there are annuals that do well in shade and grow in any soil, but for the most part they need the following.

  • Annuals need a sunny spot- at least 6 hours of direct sun
  • Annuals need fertile, humus rich, well-drained soil to develop healthy plants full of flowers. Get a soil test to guide you from your local Cooperative Extension office.
  • Annuals need ample room to develop to their full potential so thin seedlings out early and keep all the weeds out by a weekly light cultivation.
  • Annuals need regular water, one good soak a week rather than daily light sprinklings.
  • Annual seedlings need protection from slugs, rabbits and more so use an organic repellant and handpick pests. 
  • Annuals need a pinch when 6” tall to develop branching and more flowers
  • Annuals need fertilizing with compost topdressing or organic fertilizers twice a season, early in growth and when setting buds.
  • Annuals need deadheading to keep the bloom going so cut often for bouquets.

Many annuals can be started in rows in a nursery bed outdoors and transplanted to their final spots. Some resent disturbance and should be started in pots, or sown direct in place, making sure any mulch in that area is removed and the soil deeply dug and then raked smooth. These outdoor sown annuals can outstrip the ones started indoors, especially if you do not have an area devoted to starting seeds with a bank of grow lights delivering the amount of light they need to grow strong and stocky.

See-Through Weavers

Queen Anne's Lace 'Dara'

Botanical Name: Daucus carota
Height & Width: 3' h x 1.5' w
Light: Full Sun
Soil: Rich, well-drained

Although closely related to the biennial Queen’s Anne’s Lace, this showy annual shares non of the weediness of the former, self-sowing only mildly in zone 5b. Its large flower clusters, composed of groups of identical smaller flowers grow up to 8” across and are held aloft by an armature of curving stems or rays, visible if you peak underneath. The developing buds are nestled in a lacy collar of bracts and the ferny leaves add to the overall impression of a graceful “see through” plant. Easy to grow by direct sowing in early spring, it makes a great cut flower, which will help it produce more blooms. Site in the middle of the border, with a backdrop of rose and white Cleome, and a shorter cosmos, such as Rubinato in front.

Ridolfia 'Goldspray'

Botanical Name: Ridolfia segetum
Height & Width: 3-4’ h x 2' w
Light: Full Sun
Soil: Regular, moist, well-drained

This uncommon annual has flower heads that at first glance seem similar to fennel or dill but are more substantial and bloom longer on tall stems perfect for cutting. A seemingly phosphorescent acid green under sunny skies, this “see-through” variety looks great with hot colored summer perennials, weaving easily among these more structured plants. Sow direct in mid spring at last frost date and provide some twiggy brush or crossed bamboo canes at the base of the plants to give them a little support.

Tall Verbena

Botanical Name: Verbena bonariensis
Height and Width: 4' h x 10" w
Light: Full sun
Soil: Regular, moist, well-drained

The flowers of this popular heirloom from Brazil are made of many clustered violet and rose pink tubes forming a corymb. Wiry stems hold the plant stiffly upright and. it branches readily, which can be enhanced by a pinch when 6” tall or so for maximum flower power. In any case, it is always wonderfully airy in effect and can be placed near the front of the border, or weaving in drifts among your perennial plantings. It really comes into its own in late summer when it attracts migrating Monarchs and bloom continues well past the first frost. A tender perennial grown as an annual North of zone 7, start indoors 8 weeks before setting out into warm soil. Be sure to cover with vermiculite or a sheet of newspaper to exclude light for the best germination. Self sows to the delight of most if not all gardeners!

Langsdorff's Tobacco

Botanical Name: Nicotiana langsdorffii
Height & Width: 3-5’ h x 1-3’ w
Light: Full sun to partial shade
Soil: Rich, moist, well-drained

Its amazing the way hummingbirds love the floral wind chimes of this Nicotiana, their beaks a perfect match to the dangling vibrant green blooms. Introduced from Brazil in 1819, N. langsdorffii grows from a tiny seed very quickly once it gets going, its fairly narrow leaves and sturdy upright stems support the cascades of bloom that follow. Lovely with perennial grasses, or against a dark leaved perennial or shrub.

Mid-Garden Must Haves

Cosmos 'Rubinato'

Botanical Name: Cosmos bipinnatus
Height & Width: 1.5-2' h x 1.5' w
Light: Full Sun
Soil: Regular, well-drained

All the charm of the old-fashioned cottage garden cosmos, but more compact and floriferous, Rubinato has softly pleated flowers with gold crested centers. Native to Mexico, it comes into its own as summer heat increases, growing quickly into a cloud of ferny green foliage, blooming at the height of summer to first frost. We love its varied old rose to claret hues in bouquets, which enjoyably lessens the need to deadhead. A showy addition to the front to middle of the garden, it is easily grown, just sow direct after frost for blooming plants in 8 weeks. A pollinator friendly variety that attracts bees in particular, in later summer as nights cool, it’s wide petaled flowers become the refuge of drowsy bumblebees.

Sweet Scabious 'Black Knight'

Botanical Name: Scabiosa atropurpurea
Height & Width: 3' h x 1.5' w
Light: Full sun
Soil: Rich, moist, well-drained

We love scabiosas, for as summer wanes and the garden gets a bit tired looking they come into their own, their "pincushion" flowers looking fresh and perfect. Long lasting in the vase and a midsummer to fall delight in the border, especially if grown in large drifts. Beloved since the early 1600s in England, when this variety was called Blackamoor's Beauty and Mournful Widow. The sumptuous dark maroon flowers resemble a dark satin pincushion studded with white-tipped pins. Honey-scented flowers attract bees and butterflies.

Back Border Stars

Sunset Hibiscus

Botanical name: Abelmoschus manihot
Height & Width: 6’h x 3’w
Light: Full sun to partial shade
Soil: Rich, moist, well-drained

Sunset hibiscus has brushed-silk flowers in creamy yellow with burgundy eyes that give depth and richness to the 6” blooms. Unfurling from tear-drop shaped buds during the height of summer until frost, this tropical heat lover also offers attractive palmate leaves with burgundy washed stems and veining. It mixes well with tall verbena and cleome and adds structure and eye-catching bloom to developing perennial borders. A tender perennial in zones 8-10, grown as an annual further North. Sow indoors 6-8 weeks before setting out into the warmer soils of June in zone 5b.


Botanical Name: Cleome hassleriana
Height &Width: 3-5' h x 1.5' w
Light: Full sun
Soil: Regular, well-drained

Hardly any annual blooms as long as Cleome, or looks as good for as long, all summer until frost in fact. The flowers open from the bottom of the large flower heads to the top, its individual flowers seem to cascade from a never-ending supply of tightly furled buds, their looping “whiskers” soon to be set free as the flower opens. They make great cuts, but beware the short sharp thorns found on the stem under each leaf axil. Naturally branching and with attractive palmate leaves, they are perfect for the rear to middle of the perennial bed and are best in groups. Sow outdoors on the surface of the soil, just pressing for firm contact. Cleome tolerates heat and drought and poorer soils, but the best plants are grown in fertile well-drained loam.

Mexican Sunflower 'Torch'

Botanical Name: Tithonia rotundifolia
Height & Width: 6' h x 3' w
Light: Full sun
Soil: Regular to rich, well-drained

This South of the border shrubby native has scarlet orange daisy flowers blooming at the ends of the long fluted stems. Mixing effortlessly with perennial heleniums, heliopsis and more, it is perfectly suited to the back of the border and is heat and drought tolerant when established and blooming. Easy to grow from seed sown direct after frost, it grows in leaps and bounds to flower full summer to frost. A popular rest and refuel stop for migrating Monarchs.

Dahlia ‘Bishop’s Children’ 

Botanical Name: Dahlia variablis
Height & Width: 3.5' h x 2' w
Light: Full sun to partial shade
Soil: Rich, moist, well-drained

Dahlias from seed? Yes, you can have glorious tall blooming dahlias from seed in as little as 12 weeks. Start indoors 6 weeks before your last frost and plant out 2 weeks after that date, when cool night temperatures are less likely. Dahlias soak up the sun and churn out buds and flowers from July onwards in rich, moist soils supplied with ample amounts of phosphorus and potassium and less nitrogen - a flower or tomato fertilizer to be exact. This variety has shiny chocolate foliage and downturned buds that open to pinwheel blooms of many warm and spicy colors. Lovely mixed with summer and fall perennials in the mid border, it resents high heat and drought, relishing the cooler nights of fall.

Colorful Edgers

Orlaya ‘White Lace’ 

Botanical Name: Orlaya grandiflora 
Height & Width: 2' h x 1' w
Light: Full Sun to Partial Shade
Soil: Regular to rich, well-drained

Often confused with Queen Anne’s Lace and Ammi, the related umbelifera Orlaya grandiflora goes by many variety names such as White Finch, White Lace, or Brussels Lace, names suggesting gentility and grace, a change from the much more to the point Bastard Parsley of the 18th century. It lives up to these newer names, however, for it offers masses of long blooming lace cap flowers and excellent dark green ferny foliage. Deadheading is necessary to keep it from going to seed, fortunately it makes an excellent cut flower, so you get to enjoy their clouds of white indoors and out. Self-sows in some gardens but not excessively, just enough to have a repeat show the following year.

Melampodium ‘Showstar’

Botanical Name: Melampodium paludosum
Height & Width: 10" h x 1.5' w
Preferred Conditions Full sun to partial shade
Soil: Rich, moist, well-drained

We are lazy gardeners in the summer and prefer, no, demand flowers that need little coddling during this time of heat and humidity. Under-appreciated Melampodium has an unfailing bloom of simple star shaped daisies in golden yellow all summer long on a compact tidy shrub. No deadheading needed, it is perfect for the front to middle of the border. Direct sow after frost or start indoors 6-8 weeks before setting out when nights have warmed, generally 2-3 weeks after last frost date. Tolerates drought when a mature plant and keeps on blooming until frost, self sowing in moderate climes.

Sweet Alyssum ‘Benthamii’

Botanical Name: Lobularia maritima
Height &Width: 10" h x 6" w
Light: Full sun to partial shade
Soil: Regular to rich, moist, well-drained

A scattering of spring sown seed that can be simply raked in results in a fragrant honey sweet border edge in as little as 6 weeks. A successive sowing in early July of this heirloom open-pollinated variety results in fresh pure white domed blooms through late summer and fall. In hot areas a little afternoon shade is beneficial. Perhaps under-appreciated, this sweet annual is an indispensable border edging and looks great hop scotching along the path with signet marigold and blue annual clary.

Salvia - Annual Clary ‘Blue’ 

Botanical Name: Salvia viridis
Height & Width: 1.5’ h x 1’ w
Light: Full sun to partial shade
Soil: Regular to rich, well-drained

Annual clary is an easy undemanding annual who's claim to fame is the colorful bracts that extend the show to almost impossible lengths. This variety has spikes of blue purple that bloom end of June to frost that can be easily started from a sowing direct into garden soil in spring. Nice mixed with
short grasses at the front of the border and effective in large drifts, perhaps contrasted with signet marigold or interspersed with sweet alyssum and cerinthe.

Zinnia ‘White Star’

Botanical Name: Zinnia angustifolia
Height & Width: 1-1.5’ h x 9”
Light: Full Sun
Soil: Rich, well-drained

Many of us are familiar with the tall large flowered zinnias. This sweet little daisy flowered annual is an overlooked gem, it’s mildew free as can be, requires little in the way of deadheading and is heat, humidity and drought tolerant too. The narrow foliage echoes the pure white long-lasting flowers for a refined display. Sow direct after frost.


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