That is to say the May day that they finish blooming.

“Prune after bloom” is a fairly reliable mantra for spring flowering shrubs. The other good one is George Aiken’s “I generally prune when the saw is sharp”.

Shrubs that bloom in the spring set their next-spring flower buds, covered by cold hardy bud scales, by midsummer. Thus pruning needs to be done soon after the spring bloom (to enjoy the maximum of bloom) and before the plant begins to form the new buds. By pruning immediately after blooms fade the plant doesn’t waste any energy on setting seeds or on growth that will be cut off, thus maximizing the amount of energy devoted to bud production. That said, you can prune shrubs if you need to almost any time through the
year, although late summer pruning may result in new growth that will probably winter-kill, and late fall into winter when the shrub is going dormant can leave the cuts unhealed and losing moisture.

Forsythia’s gold glory illuminates the drab early spring landscape. Preliminary pruning is accomplished by cutting as many branches to force as you like in late February, and blooming stems for arrangements in late March and April. After bloomtime shape the bush by cutting out a few of the oldest stems at ground level, removing crossing or damaged
wood, and trimming top growth as you feel necessary. Always cut back to a bud or side
shoot heading in the direction you want the stem to grow. Don’t leave stubs.

If you want a shrub to grow only to a specific height prune branches about 2 feet lower to allow for growth. To avoid the “haircut” look, cut branches at varying heights.

Our forsythia cultivar ‘New Hampshire Gold’, developed in Cornish, NH, is one of the bud-hardiest forsythias with full-stem bloom after -33 degree weather. Forsythia
‘Week End’ is a more compact, upright bush that bloomed for a good month last spring.
We were impressed by its tidy form and its abundance of flowers. If you would like even earlier gold in your landscape now is the time to plant the March blooming witchhazel, Hamamelis vernalis, or cornelian cherry dogwood, Cornus mas.

Lilacs should have spent flower heads, extra sucker growth, and any other pruning for shape done right away after bloom. The flower buds for next year will be mature by early July. If the lilac is one that suckers profusely cut out all but 2 or 3 strong replacement shoots so that the strength goes to existing mature wood for next year’s bloom. Some lilacs
do not sucker, developing only one or two main stems that become fascinatingly twisted and gnarled with age.

Check out our grown-in-our fields lilacs (we are sure to have your favorite fragrance) and be sure to attend Shelburne Museum’s Lilac Sunday. Charlie Proutt will be there to give his
annual talk on lilac varieties, planting and care.

Spireas come in two types. The bridalwreath spireas bloom once in mid-spring, on last year’s wood, with white flower clusters along the stems. Little pruning is needed beyond cutting out some of the oldest wood at ground level to rejuvenate the shrub and keep its
distinctive, graceful shape. This is why they are known as the “lazy man’s hedge”.
Instead of trimming back an old-fashioned, 6 foot Vanhoutte spirea to keep it within bounds, consider moving it to a bigger space (see Transplanting a Large Shrub coming in our next leaflet) and replacing it with the more compact cultivar ‘Renaissance’, or the 3 foot
‘Halward’s Silver’. All of these have lovely fall color.

The shorter (1-3 foot) Japanese spireas bloom white, pink or red in early summer on new wood. Some have recurring bloom, and the cultivar ‘Neon Flash’ continues to bloom all summer long. ‘Mt. Fuji’ has delicate, white variegated leaves and white flowers, lovely in front of darker green-leafed shrubs. ‘Pink Parasol’ really resembles a Victorian doll’s parasol with its fluffy, pink flower cluster. ‘Fire Light’ has rich orange spring foliage and
flame-red fall color. ‘Fire Light, plus ‘Little Princess’ with flame-yellow foliage, and ‘Mt
Fuji’ with paler yellow-green fall color would be wonderful planted together. All of these
should be pruned as growth begins in the spring, cutting out the oldest wood and heading back the rest to stimulate plentiful new growth. Some deadheading through the summer helps produce more flowers.

Most shrubs that bloom in mid to late summer on new wood should be pruned as they start into growth in the spring.

Rhododendrons look better and have more energy with their spent flowers removed. Snap the flower stalk carefully at the wrinkled place just above the new leaf buds. Any shaping or dead wood removal should be done at this time. Always cut back to a side shoot or bud headed in the right direction and don’t leave stubs -they are ugly and cause dieback into the plant.

We highly recommend the new ‘PJM’ cultivars ‘PJM Compact’ and ‘PJM Elite’. They are among the hardiest rhodos in the world, with-standing cold and exposed sites (make sure they have plentiful moisture going into winter). The leaves are aromatic and have wonderful winter color. New Mezitt introductions that we carry, having the same stellar qualities, are the ‘April Mist’, ‘April Rose’ and ‘April Snow’ rhodos.

‘Annabelle’ hydrangeas should be cut back to 8-10 inches. This spring pruning will promote more larger blooms on a tighter shrub.

The Horsford catalog has a good section on tools and techniques for pruning. Stop in and talk to any of Horsford’s gardeners if you have plant care questions.