Monthly Archives: May 2012

       The next couple of weeks provide the last chance to get your perennial garden in order.  The beds should be weeded and mulched; summer and fall blooming perennials such as blackeyed Susan (rudbeckia), bee-balm (monarda), tall growing asters, sedum (particularly ‘Autumn Joy’), coneflower (echinacea), Shasta daisies (leucanthemum) and tall growing forms of goldenrod (solidago) must be pruned back before flowering to maintain their health, and to extend bloom time into late fall.

Pruning before flowering can strengthen perennials and prevent them from becoming “leggy”, and will encourage them to increase branching and achieve a fuller silhouette.  This will also help the plant to become healthier and fight off diseases such as black spot and powdery mildew. Pruning sections of a bed planted with perennials such as blackeyed Susan and bee balm can also create height variations as well as a staggered bloom time.

The June pruning should not be confused with the technique known as “pinching” in which the tip and first set of leaves are removed or “pinched off”.  The gardener needs to remove several inches of plant material when the plant reaches 8” or so in height. Those perennials most in need of pruning are:

• Bee balm (monarda) : the plant should be cut back to 6” when 12” tall.  It’s a bit late for this as most of the monarda in my garden are 2-3′ tall already.  If you just can’t bear the thought of losing 12” of plant material, prune the monarda in the front of the garden bed to 12″and work towards the back of the bed in stages, leaving taller plants in the back.

• Stonecrop (sedum ‘Autumn Joy’) should be cut back when the plant is between 8” and 12” tall.  This is really your last chance; some of my stonecrop have already set seed heads.  If your stonecrop has already set seed heads it is too late–just be prepared to stake the plants come September.  Prune or “pinch” about 4” from each stem, shaping the plant as you go.  Don’t be alarmed at the misshapen look—those lovely buds will grow back quickly.  And you will have prevented your sedum from flopping over in the fall.

• Coneflower (echinacea) should be cut back to 12” when the plant reaches about 24” in height.  Again, if your coneflower has already set flowers, wait until the bloom opens, and then follow this procedure–use the blooms in flower arrangements in your home.  If your coneflower has not set flower heads, prune back now.  Your plant will flower about 2 weeks later than usual (early July rather than late June), but it will also keep the plant flowering well into September.

• Shasta daisies (leucanthemum) can be cut back by half when they reach 12”; they also benefit from deadheading (pruning off the dead flowers) to encourage repeat bloom through the summer.

• Aster–Tall growing forms of aster should be cut in in half by late May; this will prevent them from becoming lanky and losing leaves towards the base of the plant.

• Blackeyed Susan (rudbeckia)  Both the hirta and the ‘Goldstrum’ varieties of rudbeckia will benefit from cutting back to 6” when the plants reach 12” in height.  As with bee balm, gardeners can add variety to the flower bed by cutting some plants back and leaving others in the same bed to bloom taller and earlier.

• Goldenrod (solidago) Tall growing forms of solidago such as ‘Golden Fleece’ or solidago rugosa tend to flop and get bedraggled by the end of the season.  Cutting back by one-half when the plants reach 12”-16” will result in a more compact growth that will flower in August and last through September.

If you have the chance, get up early before the heat sets in and take care of this essential late-May to early June chore.  Water the beds deeply once this is done.

I still see the eagles flying over Belle Haven, although they are no longer nesting between Edgewood Terrace and Grove Drive.  This morning a fox scampered through my side yard, pausing to investigate the dead bole under my stand of mock orange.

While watering the new salvia in my garden, I found a box turtle in my front bed.

Last night my cat Petal caught a skink in the garage–the skink escaped but she kept the tail.

And the bird feeder is visited by wood pigeons, robins, blue jays, mocking birds, sparrows, indigo buntings and wrens.

There is an amazing variety of wildlife living in our ‘hood.

I’ve come across a stunning color combination of native plants which will bring a lot of color to any spring garden year after year– blue star (amsonia) and mouse eared tickseed (coreopsis auriculata ‘Nana’).  Click on the photo for a more detailed enlargement.

Amsonia tabernaemontana and coreopsis auriculata ‘Nana’

If you are looking for yellow color once your daffodils are gone, Coreopsis auriculata ‘Nana” is a hardy little variety of coreopsis that adds a golden orange to the garden and comes back reliably year after year.  It can tolerate dry periods and sun/part shade and can be a great accent at the edge of your garden or in a rock garden.  It can also be used as a ground cover.  Like most coreopsis, you can sheer the flowers after the first bloom for an intermittent bloom the rest of the season.

The lovely native plant, Amsonia, or Blue Star, brings blue color and an interesting texture to the late-spring early summer garden and has the added benefit of spectacular yellow fall color.  Two varieties: Blue Star Willow, amsonia tabernaemontana, and Blue Star Arkansas, amsonia hubrichtii, are available in the local nurseries; of the two I prefer amsonia hubrichtii whose billowing needle-like leaves are silky soft.  This perennial grows about 3’ high and wide, and bears hundreds of light-blue star-shaped flowers at the top edges of its leaves.  Amsonia has no serious disease or insect problems, and deer don’t like it.  It was chosen as the 2011 Perennial Plant of the Year.

deutzia ‘Magician’

I’ve been anticipating this event all spring.  I’ve had a succession of shrubs bloom in the garden–forsythia, azaleas, rhododendron, roses –and now one of my favorites, the deutzia.  My cultivar is Deutzia Kalmifolia ‘Magician’,-  a hybrid that never fails to elicit gasps of astonished delight from my gardening friends.  This is a large shrub–mine has grown to 6’ in height with beautifully arching stems.  It is now decked out with numerous racemes of fragrant pink-and-white bell shaped flowers.  This plant adds a wonderful fragrance to the garden as well as color, and although it would probably appreciate a sunny location—mine does spectacularly well with 3 hours of afternoon sun.

Deutzia ‘Nikko’ at the National Arboretum

If you have a hillside garden, or a stone wall, you couldn’t go wrong with incorporating a  deutzia gracilis ‘Nikko’, introduced in the 1980s by the U.S. National Arboretum.  It’s  is a compact variety whose slightly arching branches are covered with white blossoms for about 2 weeks at this time of year.  ‘Nikko’ can be used in the front of a border, growing over low walls, or even in containers.

A new variety ‘Chardonnay Pearls’, has lime-yellow foliage which can brighten up shady areas in your garden, and the pearl-like buds give it its name.

deutzia ‘Chardonnay pearls’

In late April and May the flowers open as little stars and the fragrance attracts hummingbirds and other pollinators.  A plus for those of us who live along the Potomac River corridor—it is deer resistant!