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Don't Plant these in 2016!


Alternatives to Invasive Species by Bill Cullina (Original text copyright © New England Wild Flower Society 2003) 

Of the 2814 species of plants growing wild in Massachusetts, fully 45% (1276 species) have been introduced (either on purpose or by accident) from other parts of the globe.  Many of these are agricultural weeds that began arriving in grain or ship’s ballast soon after European colonists came here in the early 1600’s. Others were introduced by horticulturists or the federal government for use in gardens or soil stabilization, reforestation, and the like. It is impossible to know what effect this monumental immigration has had on native plants and animals. Certainly, of the thousands and thousands of plants introduced in the US and Canada from abroad, only a small number (estimates range from 3-7%) are thought to pose a serious threat to native ecosystems. These problem few are quite a problem, however. These invasive exotics have few if any natural predators to keep them in check, instead running rampant and displacing entire communities of native plants as well as the insects, fungi, birds, mammals, reptiles, bacteria, etc that have come to depend on them…. Invasive species have the potential to completely alter habitats, disrupt natural cycles of disturbance and succession, and most importantly, greatly decrease overall biodiversity, pushing rare species to the brink of extinction. Many ecologists now feel that invasive species represent the greatest current and future threat to native plant and animal species worldwide – greater even than human population growth, land development, and pollution.


It is high time that we horticulturists recognize our responsibility to both cease the importation and introduction of new and potentially invasive exotic plants and to stop growing and planting known or suspected invasives regardless of their ornamentality or consumer demand. I believe that we need to adopt the precautionary principle as far as plant introductions are concerned, and assume a species (including all of its cultivars) is invasive until proven otherwise (rather than the current approach of “innocent until proven guilty”). At least let’s not make this situation any worse.

Let's make a pact - let's try to avoid planting these plants this year. 

1. Akebia quinata (Akebia).  Anyone who has planted this vine heartily regrets it within a couple of years. Luckily, its not quite as tenacious as some of the invasive vines, so if you catch it early before it becomes too woody you can pull it out of trees and shrubs.        

Instead, plant a vine on the pergola that’s an annual.  Most vines grow fast enough to give some coverage by the summer.  And, after all, the pergola is meant to provide shade in and of itself.  If you want a perennial vine, its best to stick with Wisteria frutescens (American Wisteria). 

2. Berberis thunbergii (Japanese Barberry) and Berberis vulgaris (European Barberry).  Yes, its on the NYS Invasives list now, and already was considered to be invasive in CT.  And yes, lots of people including old-school landscapers, nursery personnel and even at least one of my friends claim that the cultivars that have colored foliage (burgundy; gold; red) are not invasive.  I’m skeptical, and favor the Bill Cullina approach of assuming they’re invasive until proven otherwise.  There’s a fair amount of money and effort in NYS going into studies of some of the nicer barberry cultivars to show that they are not invasive so they can be grown and sold again. 

People use barberry for a few reasons, mainly because it’s deer-resistant and has colored foliage.  Plus some of the burgundy cultivars, like ‘Concorde’, remain small and compact – others, including ones with gold foliage, are pillar-shaped providing uprights in the design.   And barberry was inexpensive.

 I admit, it's hard to beat the impact of purple barberry in this landscape!

To substitute for burgundy-colored barberry we tend to use either smokebush or ninebark.  Neither of those is as reliably deer-resistant as barberry was, in my experience.  Both can be cut back hard if needed – so you can keep them small.  A more deer-resistant purple foliage plant is ornamental grass.  There are some cultivars of Panicum that read “purple” throughout most of the season – they’re upright and as an added bonus they add motion to the garden.  But if your intent was to have groups of small shrubs with purple foliage near the front of a fairly formal border or on the ends, none of these choices will really satisfy you.  You may have to turn to purple-leaved Heuchera cultivars – although of course those have their own brand of finicky as well.  Other perennial suggestions are burgundy-leaved Ajuga cultivars, Penstemon digitalis ‘Husker Red’ or ‘Dark Towers’, Actaea simplex atropurpurea cultivars like ‘Brunette’ or ‘Hillside Black Beauty’, Lobelia cardinalis ‘Fried Green Tomatoes’ or Hypericum androsaemum ‘Albury Purple’.

Penstemon digitalis 'Husker Red'

3. Buddleia davidii (Butterfly Bush) and B. alternifolia (Alternate-leaved Butterfly Bush).  It’s a beautiful shrub when it’s in flower, there’s usually a butterfly on every single flower and it grows fast and flowers on new wood so you can cut it back every single spring.  Chickadees eat the seeds in winter.  Its inexpensive and takes up a fair amount of space – excellent bang-for-buck in summer gardens.  But it’s also invasive.  And if you look at the “Bringing Nature Home” information, you’ll see that it serves as a host plant for only one species of butterfly.  Compare and contrast – clover serves as a host plant for 122 species of butterfly.  Better to leave a little clover in your lawn and plant some nectar-rich perennials.

If you want a summer-flowering shrub with excellent flower power try Lagerstromia or Hibiscus syriacus.  Most of the newer Rose-of-Sharon cultivars are triploid – meaning they can’t set seed so you won’t have a forest of R of S like in the olden days.  Other ideas include Hypericum (shrub form), Hibiscus moscheutos, Heliopsis helianthoides, Aster and Goat’s Beard.  Of course, ornamental grasses can also be used for late summer interest.

 Hibiscus moscheutos

4. Hedera helix (English Ivy).  No, no, no!  Don’t do it!  Once its spread all over the whole landscape its virtually impossible to remove.  It will rot your fence, engulf your trees and grow into your brick façade.  In general, using vines as ground covers is usually not the greatest idea because they will be hard to keep in check.  If you want a beautiful ornamental vine that does somewhat less damage but is much easier to manage, try Hydrangea anomala ssp. petiolaris (Climbing hydrangea).  You can let it creep along the ground, and it makes a lovely ground-cover.  Its relatively easy to pull off the house if you want to.  It can make chain-link fence completely disappear – but don’t try to remove it from a chain-link fence because it is quite two-dimensional and will wind back and forth extensively.

5. Ligustrum species (Privet).  Yes, it’s invasive, so we need to stop planting privet hedges and use other types of plants instead.  Privet is “traditional” and “classic”, not eaten by deer and inexpensive.  It has an upright habit and is grown especially for use in making hedges, so its really easy to get a row of uniform plants of just about any height to create an “instant” hedge.  It can be readily renovated, so, again, you can keep it manageable. 

Almost any shrub can be made into a hedge, especially if you plan ahead – with the caveat that plants should be spaced so that they grow to be a hedge over time.  Page Dickey told us about using ‘Miss Kim’ lilac as a hedge.  We’ve seen lots of pictures where ornamental grasses are used as a hedge.  If you have no deer, you can use Taxus or Manhattan euonymus as a hedge.  Some shrub roses can be hedges.  Evergreen choices include Ilex glabra (Inkberry Holly, Prunus laurocerasus (Cherry Laurel), Leucothoe, Rhododendron and Leatherleaf Viburnum.

 Miss Kim Lilac Hedge along the top of the terrace



Native plants for challenging situations - 4 I love

Inspired by plant lists and lectures by William Cullina, Head of the Coastal Main Botanical Gardens - check out his website:
Sassafras (Sassafras albidum) can rival even sugar maples in the beauty of its fall display.  In the 
shade, the foliage becomes an intense golden yellow.  When the tree is in more sun, leaves become scarlet, orange, and maroon.
 Sassafras is an opportunistic tree found commonly along unmanaged fence lines and power line right of ways where it can compete with larger trees.  It sprouts readily from stumps and the sprouts grow rapidly, adding up to 3-4 feet in height each year for the first 
ten years.  You may have never even seen sassafras flowers in early spring – but they’re a good nectar source for early pollinating insects.  

Sassafras flowers in early spring
Sassafras fall color
There are two types of sumac that are nice additions to the landscape if you have good sun.  One is ‘Gro-Low’ fragrant sumac (Rhus aromatica).  ‘Gro-Low’ is a vigorous spreading groundcover (up to 2 ft tall with a spread of up to 8 ft), making it an excellent choice for stablizing a bank or smothering weeds.  It has interesting fruits and a gorgeous orange-red fall color, and is deer resistant.  

Rhus aromatica 'Gro-Low'

Rhus aromatica fruit
The other is ‘Tiger Eyes’ staghorn sumac (Rhus typhina ‘Tiger Eyes’ or ‘Bailtiger'), a dwarf, golden-leaved cultivar that typically matures to only 6’ tall and wide. It was discovered in a cultivated nursery setting as a whole plant mutation of R. typhina ‘Laciniata’ and is considered to be superior to both  ‘Laciniata’ and the species because of its dwarf size, quality yellow foliage and minimal suckering.  Deeply dissected compound leaves emerge chartreuse in spring, but quickly mature to bright yellow.  Fall foliage is a striking mixture of orange and scarlet.  It performs best in good sun.  Since it can tend to become a bit leggy and spreads via suckers, its a good candidate for the back of the border, a naturalized stream bank or the wild garden (but not so much as a specimen).

Rhus typhina 'Tiger Eyes'Rhus typhina fall color
Wavy Hair-grass
Wavy hair-grass (Deschampsia flexuosa) is a clump-forming cool-season native grass that is not too large, takes some shade and has relatively showy flowers - it can fit into a mixed border quite well without overwhelming it.  Like most ornamental grasses, it prefers well-drained soils.  Its foliage is semi-evergreen in a mild winter.  It's native to dry open woods, slopes, fields, grasslands and open areas, forming a low, dense tussock of very thin, arching green grass blades up to 2’ long.  Flower stems rise in summer above the foliage mound bearing wide, airy panicles of tiny, purple to bronze flowers which form a cloud over the foliage that is attractive when backlit.  Flower panicles turn gold after bloom as the seed ripens.

Smooth Witherod
Smooth Witherod (Viburnum nudum) is native to low woods, swamps and bogs in the east and southeast, from Connecticut south to Florida and Louisiana.  It can tolerate a wide variety of light conditions, from full sun to part shade and can also tolerate boggy conditions – a good candidate for a wettish area in the landscape.  It has showy white flowers in spring – they don’t smell very good though!  (For my nose, its definitely one of the “stinky” viburnums, but others don’t perceive it as smelling particularly bad).  Flowers are followed by clusters of berries in late summer that change color as they ripen from light pink to dark pink to blue to purply-black.  For best cross-pollination and subsequent fruit display, plant shrubs in groups rather than as single specimens.  The best cultivar is ‘Winterthur’ – now fairly commonly available in the Nursery trade - a compact version, growing to about 6’ X 6’, with a reliably beautiful fall foliage color – maroon, dark red, purple.   ‘Winterthur’, an introduction of Winterthur Gardens in Delaware, was a winner of the Pennsylvania Horticultural Society Gold Medal Award in 1991 – I guess that qualifies it as “tried and true” at this point!

Viburnum nudum 'Winterthur' flowers
'Winterthur' berries ripening'Winterthur' ripe berries look beautiful with the fall foliage color