All posts by Katherine Tracey

Summer Hardiness–which plants survive the heat?

Yucca 'Color Guard', Vernonia lettermanii and Crambe maritima have performed despite the heat and drought .

Yucca ‘Color Guard’, Vernonia lettermanii and Crambe maritima have performed despite the heat and drought .

Well, we know we’re not alone, but here in southern New England, we’ve had an exceptionally hot dry summer. The amount of precipitation in our area has varied due to isolated showers, but I would guess here at Avant Gardens we have totaled less than 1 inch during the past 75 days. Lack of rainfall plus high humidity, coupled with daily temperatures in the high 80s and 90‘s can have an effect on plants. (Many plants begin to suffer physiological damage when temperatures remain above 86F or 30C)

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This brings up the classification of plants rated for Summer Hardiness. The American Horticultural Society (AHS) has created a Summer Heat Zone map of the US.  Regions having less than 1 day with temperatures above 86F (30C)  are classified as zone 1, and on the other end of the spectrum, the areas having the most days with high temperatures are classified as zone 12. This may correlate with the familiar USDA Winter Hardiness Zone Map (which rates average lowest temperatures) but in some cases it does not. Folks in the southern US have learned that Summer Heat Zone Hardiness is definitely a criteria when selecting plants. The above map will need regular adjustments now that global warming is causing extreme temperatures worldwide, and northern gardeners will have to pay heed to which plants will survive/perform with higher summer temperatures.

We’ll be ruling out more plants that do well in our gardens in the future, I’m afraid, as climate change continues to affect what we can and cannot happily grow.

Have you come to the conclusion that some plants, which once thrived in your gardens,  no longer will? Which plants have you found best withstand our ever warmer drier summers?

The Blue Garden

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Newport RI.  The middle of a cloudless summer day is usually not the best time for landscape photography….but a garden so elegantly composed with formal beds, pottery, pergolas, and pools, mirroring the sky above and lined with exquisite blue/green tiles, is a photo op waiting to happen. And here I was, courtesy of Candace Morgenstern and the Tiverton Garden Club, delighted with the opportunity to walk the grounds of The Blue Garden, a private property not open to the general public.

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Originally created in the years1911-1913, the legendary Blue Garden was designed by The Olmstead Brothers firm for  Arthur Curtiss and Harriet Parsons James. The James’ left no heirs, and the property, willed to the Catholic Diocese of Providence, fell into disrepair over the years. In the 1970’s the large property was subdivided into several large lots.

In 2012, the property where the Blue Garden once thrived was purchased by philanthropist Dorrance Hamilton. She commissioned the landscape architectural firm of Reed Hilderbrand to undertake restoration plans based on the Olmstead original drawings.

Many firms and individuals were involved with the success of this project, including Landscape Historian Arleyn Levee, and Sarah Vance, who is now the property director.  Much more information is available on The Blue Garden website.

All images taken by Katherine Tracey

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Conoclinium coelestinum ‘Cory’

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A new name for the Hardy Ageratum. Formerly Eupatorium coelestinum, the plant taxonomists have bestowed the name Con-oh-clin-i-um on this late summer into fall blooming plant. The species name co-el-est-in-um means heavenly. Clusters of heavenly sky blue flowers atop 18-30″ stems bloom in August and September, attracting butterflies and pollinators. Conoclinium enjoy average, evenly moist soil conditions and spreads by stolons, creating a healthy patch where happy. It makes a lovely cut flower and is hardy in zones 5-8.

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Summer Meadow Rues

As the 4th of July rolls around, the early June show of Baptisia, Peonies, Iris and Cranesbill is fading, and its time to focus on high summer performers. I could not be without the dreamy clouds of  the summer blooming Meadow Rues, or botanically speaking Thalictrum, with their sprays of dainty small blossoms on tall stems, creating a seductive haze above the knee high plants in the garden.

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Thalictrum ‘Splendide’

First there is ‘Splendide’, the first of the French breeder Thierry Delabroye’s introductions with its slightly larger soft lavender flowers. ‘Splendide’ is statuesque…it can reach 7′ in a rich soil, and may need staking when the branched stems are heavy with buds.

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Thalictrum ‘Splendide ‘White’

Thalictrum ‘Splendide Whiteis perhaps my favorite. Another selection from Thierry Delabroye, this white selection takes the place of Baby’s Breath in the border with its 3′ to 4 .5′ stems above delicate Columbine like foliage. Sprays of pearly buds  burst into 1/2″ 5 petaled blossoms with greenish white stamens. Blossoms continue for weeks, and make exquisite cut flowers.

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Thalcitrum delavayi ”Hewitt’s Double’

And then there is this older form of the species, T. delavayi,  ‘Hewitt’s Double’, which bears its inflorescence on 3-4′ stems above dainty Maidenhair fern like foliage. It has shown a preference for excellent soil drainage in winter, but enjoys an evenly moist soil during the summer months.

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Thalictrum rochebrunanium

Last but not least, is the most familiar form Thalictrum rochebrunanum ‘Lavender Mist’ which can easily grow 4-6′ tall in a rich somewhat moist soil.  Sprays of lavender buds open to show 4-5 petaled blossoms with prominent yellow stamens in July and August.  T. rochebrunianum can self sow where it is content.

Thalictrum are members of the Ranunculus family which includes, Anemones and Buttercups. They enjoy average to rich soil with ample moisture during the growing season and full or half day sun. T. delavayi is hardy in zones 5-8, and the rest are more cold tolerant and are hardy in zones 4-8.  And oh, yes, they are not favored by deer or bunnies.

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Containers 2016, the Before Shots

iron_urn_detail-1I always think I’ll get my containers planted by Memorial Day, but that doesn’t happen often, so I shoot for the Fourth of July. My goal each season is to come up with fresh combinations that are easy care and will still be looking sweet in September.  Of course, I use a lot of succulents because they always deliver. Here are the end of June images. Check back for the end of September shots.

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Grasses gone wild pot…Stipa tenuissima, Carex flagellifera , Chocolate Cosmos, Heuchera ‘Champagne’, Oregano ‘Kent Beauty’ and Sedum ‘Angelina’

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Iron urns…succulent mix of Beschorneria, Aeonium, Sedum mackinoi ‘Ogon’, Crassula and String of Pearls Senecio

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Succulents in Embossed Terra Cotta: Crassula argentea variegata, Sedum adolphi, Graptosedum ‘Alpenglow’ and Senecio ‘MIni Blue’ with sedum mackinoi ‘Ogon’

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Hypertufa Low Planter with Succulents: Echeveria imbricata and ‘Black Prince’, Senecio lineare, Sedum mackinoi, and x Sedeveria ‘Hummelli’

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Under the Sign Pot (a hot neglected area): Succulent mix…Aeonium ‘Kiwi’, Sticks on Fire Euphorbia, Senecio cylindricus, Aeonium ‘Zwartkopf’ and ‘Lilypad’, String of Bananas Senecio and Sedum mackinoi ‘Ogon’

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Drum pot with Phormium ‘Evening Glow’and assorted succulents

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Succulent Detail: Echeveria ‘Swirl’ with Aeonium , x Graptoveria ‘Debby , Graptopetalum hybrid and Blue Leaved String of Bananas

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Tall Pot with Melianthus major, Kalanchoe behartii, Senecio cylindricus, Echeveria hybrid, Aeonium urbicum and Dichondra ‘Silver Falls’

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Out of the way pot  (always forget to water!): Sansevieria, Aeoniums ‘Kiwi’ and ‘Tip Top’ with Tradescantia ‘Pale Puma’

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35″ Zen Bowl with Succulents (as always.)..but with a new mix.

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For hummers and part shade: Abutilon ‘Kentish Bell’, Fuchsia ‘Debron ‘Black Cherry’, Phygelius ‘Sunshine’, Euphorbia ‘Ascot Rainbow’, Heuchera ‘Steel City’ and Hedera ‘Amber Waves’

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Also for pt. shade: a new white Begonia boliviensis from seed, plus Eyelash Begonia and Asparagus Fern (Plumosa)

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For a Shady spot (gets a little early morning sun) Asparagus densiflorus myersii and densiflorus ‘Cwebe’ with a short Silver Sansevieria, Begonia ‘Concorde’ and trailing purple Alternanthera….

Allium ‘Millenium’

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Allium ‘Millenium’ in the early morning light.

What’s not to love? This Allium hybrid from Mark McDonough is one of the key plants for solid bloom in July and August in our perennial and mixed beds. 2″ lavender orbs on sturdy 12-18″ stems provide color for weeks. It doesn’t mind the heat and dry soil, and  bulks up quickly, and can be divided in the spring if you want to spread it around. Of course it is attractive to butterflies and pollinators. When blooming fades, cut back the stems, or leave the heads on to dry and add textural interest. Deer and rabbit resistant and it is perfectly hardy in zones 5-9.

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Blue Plumbago…Problem or Not?

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Blue shades, clockwise from the top: Clematis, Lavender, Baptisia, Nepeta, Geranium ‘Rozanne’, Campanula ‘Sarastro’, Wisterla ‘Amethyst Falls, and Plumbago auriculata

Funny thing…this favorite color, the color of the sky above… true blue-baby blue is not the easiest color to mix and match. Think of the blues in the garden…most shades have red in them…the violets have a darker red, lavenders can have that pinkish tint. Blue flowers also look so different depending on the light…take a picture of a blue flower on a cloudy day, or at  midday, and at dusk and notice how the hue changes.

I have a challenge here…I’m trying to decide which plants I can use to complement a lovely blue Plumbago auriculata in one of my containers. My aim, as always, is to have the container look great now through September, and have it be pretty easy care.

First if you are unfamiliar with Plumbago,  it is a tender perennial/shrub producing powder blue phlox like blossoms endlessly all sumer.  Plumbago forms sizable shrubs where it is hardy, but for those of us growing here in the northeast, expect plants to grow to 2’-2 1/2’ in a season in our gardens or pots.

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One thought I had was to play with complementary colors….light orange and light blue are color opposites. I found a consistent apricot in Heuchera ‘Champagne’, and I thought  of adding some light yellow/lime…perhaps the Helichrysum ‘Limelight’ or Oxalis ‘Copper Glow which has tints of orange too. A green ornamental grass like Hakonechloa macra can add a different texture and natural feeling. A possibility, but then I realized I didn’t have a pot this group works with.

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I did have this white handled jar. Blue and white is a classic combination. Gaura ‘So White’ adds a wispy vertical, Euphorbia ‘Diamond Frost is an all purpose filler with an aura of baby’s breath , and for bold punch, the glossy foliage of Angelica pachycarpa which can be set out in the garden in the fall. Needed something to trail so I tucked in a Teardrop Ivy.

What do you think? What would you pair Plumbago with?

Smitten by Solomon’s Seal

Polygonatum x hybridum 'Striatum'

Polygonatum x hybridum ‘Striatum’

Unfurling

Other forms….Unfurling

Dancing

Dancing

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Dangling

Just a few images to share….loving the various species and  forms in the genus Polygonatum (Solomon’s Seal).  We currently have about 15 selections, ranging in size from tiny 6″ Polygonatum humile to  6′ selections of P. biflorum. and are always seeking out more.

quick facts: Solomon Seals is in the family Asparagaceae. Most forms are hardy in zones 5-8, (a few in zones 3 & 4). They slowly spread by jointed rhizomes, and enjoy well drained soil in partial to full shade. Long lived and almost indestructible, Solomon’s Seal is one of those plants that holds its good looks with little care all season.

Asparagus Ferns to Know and Grow

Perhaps your grandmother had a big hanging basket of Asparagus Fern on her shady porch…you probably didn’t think much about it, but there it lived, thriving with little care, living in the same pot for what seemed to be years on end. Yes-sir-ree…a testimony to a plant which could thrive on neglect.

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Just planted….Asparagus setaceus plumosa, with 2 begonias in an 8″ square pot.

Despite their fernlike ambience, this group of foliage plants are not ferns at all, but members of the Lily family (Liliaceae). An inspection of the root system reveals a mass of bulb-like tubers, (think lily bulbs). Being pot bound doesn’t discourage their vigor and although they like bright light, Asparagus Ferns can exist satisfactorily with quite a bit of shade. They do not need a constant supply of moisture, and prefer a soil that is sharp draining. Take note: Asparagus Ferns make great companions to Begonia  which like similar conditions… bright light to shade, and a soil that doesn’t stay wet.

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Asparagus densiflorus ‘Sprengeri’ (L) and densiflorus ‘Myersi’ (R)

The most familiar species is A. densiflorus ‘Sprengeri’, known for it’s arching stems of apple green narrow leaves. (For those who need to be on top of all things botanical…the genus is now Protasparagus, but that may be too much information for some. ) The next most commonly encountered form is the Foxtail Asparagus, A. densiflorus ‘Myersi’, with its  gorgeous chunky plumes.

Now, let me introduce you to  a few siblings, which offer variety but require the same easy care, and of course are suitable as cut greenery for arrangements.

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Clockwise from upper left: A. densiflorus ‘Cwebe’, A. setaceus plumosa, A. setaceus pyramidalis, and A. macowanii

Asperagus densiflorus ‘Cwebe’ is not dissimilar to Grandma’s form, but ‘Cwebe’ tends to be more upright, growing, to 18-20″ tall, and has an interesting bronze tint to the new growth. Asparagus setaceus plumosa is  very lacy,  and is familiar to those who purchase cut greens for arranging.  Asparagus setaceus pyramidalis also has lacy, fine textured foliage with an upright thrust. Perhaps the sweetest of all is Asparagus macowanii, commonly called Ming Fern, with very delicate forest green foliage. As a young plant A. macowanii  is quite small in stature, but if grown in a conservatory or outdoors where it is hardy, it can reach a height of 5’ at maturity.

Anemone x ‘Wild Swan’

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Like everyone else, we have fallen for Anemone ‘Wild Swan’.  Exquisitely simple white petals reversed in periwinkle blue surround a boss of yellow stamens in anemone like fashion and are held on 18-20″ stems. A hybrid of Anemone rupicola and possibly hupehensis,  it was selected by British plantswoman Elizabeth MacGregor a decade ago, and took her years to build up stock.  At last it debuted at Chelsea Flower Show in 2011, and caught the eye of many a gardener on both sides of the pond.

We finally acquired some tissue culture propagated plants in 2015. In its first year in the garden, ‘Wild Swan’ began blooming  in late spring,  then rested once the summer heat set in.  We found that in September,cooler temperatures encouraged  a second round of flowering stems. (In cool summer climates, the show may in fact carry on all summer. ) All of last year’s plants have come back up in the garden, after inconstant winter weather. We’re hoping for a more robust show this year.

Anemone x ‘Wild Swan’ enjoys a soil with good drainage and full sun or partial shade. It is hardy in zones 5-8.

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