Fall Pruning 101: DON'T!

Q. We just purchased a new home with some nice azalea bushes in the yard.  However they are too large for our taste, and we'd like to prune them back from their current six foot height to around four feet. Can you provide tips on how to do this?

---Gardening Challenged Carolyn in Delaware county PA

I have over-grown climbing roses and would like to make them more managed looking.  How far back can I safely cut the branches and when is the best time to do so?

---Rebecca; ALSO in Delaware County

Last fall I ruthlessly pruned my lilac bushes. They now look awful. Can you please tell me what, if anything, I can do to help make them look good again?

---Maryin Wyndmoor, PA

Mike: I would like to know which flowers or shrubs should be left standing through the winter and then cut back at the beginning of Spring, and which should be cut back now and mulched over for the winter? Thank You.

---Lauriann in Germantown

A. Well, thank you all ladies—this is the perfect time of year for me to hold forth on the wonderful ‘garden cleanup’ people perform in the fall that keeps so many nurseries busy selling replacement plants in the Spring! You heard that right—in almost every instance, your garden would be much happier if you just disappeared for the next three months.

Carolyn with the new home with the big azaleas—you’re the easiest. Don’t dare touch them now! Take a close look at the branches—those nubby things you see are all flower buds. All of our fabulous Spring blooming plants—azaleas, rhododendrons, camellias, magnolias, forsythia, dogwood and all of the flowering fruit trees—have already formed next year’s buds so they can be ready to bloom right after winter. The only safe time to prune Spring bloomers is in the couple of months right after their flowers fade.  

Prune those azaleas lightly right after they flower, removing a foot all around. Let them recover for a month; then you can take off another six inches or so. It’s always better to go slow, remove more than less, and to work in stages. Take it from The Old Perfesser—duct tape and crazy glue will not put Humpty together again after you take him on a trip down to Stump town. Reducing a big plant’s size over several years is your best bet at achieving the shape you desire—and at not killing the plant, which is always a good idea. Stop pruning and shaping Spring bloomers two months after they finish flowering

Don’t prune other woody plants like those out-of–control climbing roses now either. Pruning stimulates new growth, and all plants want to go to sleep for the winter—even down South. And, if like over-caned Rebecca, you live where winter means bitter cold, that tender new growth will freeze, killing it—and perhaps the entire plant as well.  

The safest times to prune non-Spring bloomers are in the dead of winter, when the plants are dormant, or in early Spring when they show the first signs of new growth. Winter pruning is like carrying a four year old in asleep from the car—they are SO sound out, they’ll never know what happened (even if you bang their little heads on the doorjamb a couple of times). In Spring, the plants are actively growing and have the strength to readily replace what you trim. Winter or Spring, never remove more than a third of any plant over the course of a single season unless you’re SURE it’s the right thing to do. (An example of a plant that can really take a big whackin’ is butterfly bush (Buddelia), which is often cut back to the ground in Spring to control its rampant growth.)

Oh, and don’t prune maples, birches, grapes, hardy kiwi and other “Chuck Wepner” plants in early Spring; these bleeders lose a lot of sap if they’re cut at that time of year—better to do them in the dead of winter or later in the Spring.

Mary: Your lilac-loping tale of woe illustrates the serious negative long-term effects Fall pruning can have on the health of plants. The best thing you can do for those lilacs right now is to shovel an inch of compost around their base, apologize for that assault last Fall and explain that you will now only prune them after they finish blooming in the Spring.

 The only pruning of any kind that should be done at this time of year is to remove dead or diseased plant parts. Yes, I realize that the weather’s nice, we can see exactly what needs to be done, we finally have time on our hands, and we really WANT to prune now. This is Nature’s way of trying to teach us the benefits of knowledge over passion. Or, as Garrison Keillor would say,“Well, you knew not to do it and know you know why”.

Garden cleanup? If it’s a herbaceous perennial (a plant that dies back to the ground every winter only to re merge in Spring) that doesn’t have big seed pods (like peonies, for instance), go ahead and clean up the dead stuff on top of the soil; these plants are long done collecting solar energy for the season. Wait to apply an inch or two of mulch until AFTER the ground freezes hard for the season. (You’re prevent winter heaving, not keeping the plant warm.) If your ground doesn’t freeze, you don’t have to mulch. (And pppfffttt on you; I’ll send you an ice storm in January.)

Leave plants that DO have big seedpods (like hostas) in place for winter interest, natural bird feeding and surprise volunteers (“hey is that a host a up in your gutters?”). Leave ornamental grasses alone too. That plant mass on top insulates the crown down in the soil, and in areas with snow, holds that wonderful insulating white stuff in place. Clear out the old growth when you see new growth appear in the Spring.   

Upright, non-climbing roses can bet ricky. They often show lots of disease this time of year, but they’ll survive winter much better if they aren’t pruned back till Spring. I pick the worst looking leaves off mine by hand in the Fall, remove the worst looking canes mid-winter and then prune for real as soon as I see new growth in the Spring.