Questions about Pruning and Non-blooming Daffodils
Now that the snow has finally melted enough, I can get into the Sunken Garden to prune the Sargent crabapple that grows in the center. I can also get out to prune other shrubs like my smokebush (Cotinus) and hydrangea. This is not a chore I enjoy. I was talking to a friend, a retired doctor, and confessed that I found it very difficult to make the necessary cuts because I was afraid of doing it incorrectly and killing the shrub. He laughed and said that as a doctor he was used to cutting, and as a gardener, he said most plants survive.
Several readers have asked me about pruning, so as we all set off with our sharp pruners, loppers, and little pruning saws, here are some general pruning principles.
There are essentially two reasons to prune a tree or shrub. The first is to maintain the health of the plant, and the second is to control growth and shape the plant.
To maintain the health of any plant cut out any broken branches that have been damaged over the winter. Also cut out any that are overcrowded or cross each other so that they rub each other damaging the bark. Also cut out any branches that are diseased.
Many shrubs do not need frequent pruning, but you might want to rejuvenate mature flowering bushes like lilacs. This is done by taking out no more than a third of the oldest trunks at ground level at one time. If more pruning is necessary, put it off til next year. A gradual rejuvenation is best for the plant’s health.
If you are cutting out old lilac trunks in the spring, stop there. Do not cut back old flower heads or other branches higher on the plant. Lilacs, like mock orange, weigela, forsythia, kolkwitzia, spirea, pieris and other shrubs, bloom on ‘old wood’ that is growth that is a year old or more. They should be pruned right after blooming. If you prune these bushes in the early spring you’ll be cutting off that season’s bloom. You won’t hurt the bush, but you will lose that season’s bloom.
Don’t worry about not deadheading lilacs in season, although feel free to take all the bouquets you want, because the newest thought is that deadheading is not necessary to good bloom the following year.
Flowering shrubs that bloom on ‘new wood’, new growth, can be pruned at the end of winter or very early in the spring. These include potentilla, St. John’s-wort (Hypericum) and some hydrangeas.
One reader complained the hydrangea she planted about three years ago has always bloomed poorly. The ugly truth is that some are not good plants and don’t always live up to the breeder’s or nursery’s promises. Endless Summer, a new hybrid was highly touted, but I have been hearing that it is not a good bloomer. It is more than possible hers is an Endless Summer.
Another reader asked about pruning roses. My own personal experience with roses is limited. I only grow old fashioned shrub roses, and hardy rugosa hybrids, neither of which require any more pruning than cutting out broken branches in the spring. No pruning is done in the fall. I deadhead throughout the season as I have time, but as with lilacs, whether I deadhead or not does not seem to affect the next season’s flowering.
Floribundas should be cut back hard in the spring, removing last year’s growth.
Hybrid tea roses are tender and pretty fussy. They should also be pruned in early spring because there is always going to be some winter kill, even if they are protected. I have no personal experience with these because I need tough hardy plants, partly because of my climate, and partly because I am not inclined to fuss too much with any plant.
Another question was about daffodils that do not bloom. The general needs of daffodils are for a half day of sun in well drained soil and fertilizer in the fall, very early spring, and at bloom time. Be sure not to use a high nitrogen fertilizer which will give strong foliage, but discourage flowers.
A common cause of poor bloom is that the foliage is cut off too soon after blooming. It takes at least six weeks after flowering for the bulb to replenish itself. When the leaves start to yellow and wither they can be cut back.
Sometimes a site can change while the gardener’s back is turned. Trees grow and throw more shade. Or it becomes wet and the bulbs become infected with basal rot resulting in malformed leaves and flowers. Those bulbs have to be dug and destroyed. There is no cure.
There are also viruses that can attack bulbs. Yellow stripe shows as yellow streaks on the leaves as they appear. The plant weakens over two years. Mosaic shows as pale blotches on the yellow flowers. Mosaic does not affect the vigor of the plant. Both are infectious and affected plants should be dug and destroyed.
Finally, it is possible that they are overcrowded. You can dig the bulbs, divide them and replant and water immediately.
There are many mysteries in the garden, but I welcome questions and comments from readers who can reach me by email at commonweeder@gmail.com.
April 12, 2008