It’s hard to believe it’s already the first day of autumn. The season has been so cool that it feels like we should have two more months to garden yet! While there’s still time left to enjoy your gardens, this is the time of year that people come in or call with lots of questions about what to cut back and what they need to do before winter.
For annual gardens I pull all the dead annuals out of the ground and get rid of the debris. I don’t want pests or diseases overwintering in the debris and I want a clean start for spring. Soil can erode over winter so I mulch with a thin layer of straw or leaves at this time. Straw breaks down fairly quickly so in spring I will either plant new annuals right through it or work it into the soil when I prep the bed. I do this in vegetable garden areas that I don’t plant fall cover crops on as well.
Fall is an important time for plants to get ready for winter. They are busy storing nutrients in their root systems and in the case of woody plants also their wood. It’s important to let plants go dormant naturally. If you cut them back too early, you deprive them of energy to get through the winter. You can do perennial clean up in late October to late November. Cut any perennials that don’t offer winter interest back to ground level. Grasses, butterfly bush, mums, russian sage, perennial hibiscus, and Caryopteris all benefit from being left alone for the winter. Cut those plants back in early April.
While it’s just fine to do perennial garden clean up in fall, I actually do mine in spring. Many animals including insects, birds, and mammals will use a well planted perennial garden for cover or food in the winter. So I like to leave my perennials alone until April. The exception is if I had a serious pest or disease problem on certain plants. I will clean up those plants in fall and dispose of the debris in the trash to minimize those problems next season.
“Fall” pruning is often recommended; but it would be better to call it “late summer” pruning. Plants need to heal from pruning before winter sets in; if you prune too late they can suffer winter injury and you will need to do more pruning in spring. You generally want to finish any pruning by mid-August. The exception would be any spring blooming plants, which should be pruned by mid-June to allow them time to form new flower buds for next spring..
We get a lot of questions about Hydrangea pruning. Different types of Hydrangea need to be pruned differently. The macrophylla types that have colorful flowers like pink or blue should be pruned in spring when they start to leaf out. Only remove dead wood; they will leaf out on old stems and bloom best on that growth. The old fashioned ‘Annabelle’ types that look like giant snowballs can be left to leaf out on old wood or get cut back to the ground in spring. This includes newer varieties like ‘Incrediball’, ‘Bella Anna’, and ‘Invincibelle Spirit’ as well. The paniculata types like ‘Limelight’, ‘Strawberry Vanilla’, ‘Quick Fire’, ‘Limelight’, etc and the oak-leaf hydrangeas don’t need much pruning. I only prune for structure and to remove spent blooms, which I typically do in spring as the dried flowers offer winter interest.
Roses are another one that I get a lot of questions about. The hardy shrub roses such as the Knockout series, Carefree series, Easy Elegance series, rugosas etc don’t need to be pruned until spring. At that time I only remove dead wood and anything very weak. If I need to prune for size control I will cut the plants half way back before they leaf out in spring and remove any very thin or crowded stems. Most of these roses need little winter protection. The most I do to protect them is to mound some mulch 8-10 inches up around the base around Thanksgiving. Make sure to pull this mulch away in spring as we thaw out to prevent stem rot.
For roses that need winter protection such as the hybrid tea, grandiflora, or floribunda types I will prune off only what I need to in order to protect them for the winter. The goal with protecting your roses isn’t to keep them warm, but to protect them from temperature fluctuations and dry winter air.
The most common method of winter protection is the old-fashioned rose cone. If you haven’t seen these, they are styrofoam covers to go over your roses for the winter. They should be put on when we start to stay frozen, usually around Thanksgiving. It’s important to make sure your rose cones are vented; the ones we sell have vent holes in the top for warm air to escape on sunny winter days.
Like other shrubs, pruning roses late in the season can lead to winter injury so I don’t like to prune roses to get a rose cone on them. A good method I use is to build a cage around the rose bush with hardware cloth and fill it with oak leaves, mulch, or compost. What I like about this method is it allows you to protect more of your rose without pruning any stems off. If some stems stick out of the top of the cage that’s ok. They may get winter damage, but that can be pruned off in spring.
A third method for protecting roses in winter is to not even plant them in the ground. Instead, plant them in a 12-14 inch pot and sink that pot in the ground for the summer. Around Thanksgiving, pull them out of the ground, pot and all, and place them in the garage. Give them 1 cup of water every month starting in December. This keeps them from drying out over winter and the garage will keep the temperature cold but stable. This is a great method to use for rose trees which are otherwise difficult to protect for winter. I’ve also been known to do this for roses I buy late in the season that may not have enough time to get established in the garden.
Another important task for fall is weed control. Just like the perennial plants in your garden, perennial weeds are storing a lot of nutrients for winter. This makes it an excellent time to spray herbicides, as the plants take in more chemical than usual. It’s also important to hand pull any weeds before they go to seed at this time.
Fall is also a great time to renew your mulch. A fresh layer of mulch not only looks great but helps conserve moisture, cut down on weeds, and insulate your plants for winter. It’s important to continue watering your plants through fall until we freeze. Even though deciduous plants aren’t actively growing, they do continue to store water and nutrients until the soil freezes. And evergreens will continue to photosythesize and grow anytime the temperature is above freezing. Going into winter with the proper amound of moisture helps minimize winter damage. If rainfall is scarce this autumn, make sure to irrigate. Plants won’t use as much water, but the soil should never be very dry. A good rule of thumb is to irrigate 1 inch of water per week.
For more fall garden information, come see me at our customer appreciation day on Saturday September 27th. I’ll be giving a fall garden task presentation here at Caan’s; I’ll show you how to cut plants back, which tools to use, and talk a bit about fall planting and garden winterization. My friend Brent Horvath will also be giving a great talk about Sedums and selling and signing his new book, “A Plant Lovers Guide to Sedums”. All the info can be found here: https://caanfloral.com/special.html