You might have noticed cool nights, colorful foliage and shorter days and wondered, “Should I be doing anything with these plants now that it’s fall?” The answer depends upon what types of plants you have in your yard. Some plants have very specific needs and if you know exactly what types of plants you have then it is easy to determine exactly how to care for them. This article lays out general care for your yard in case you don’t know what you have, and since I garden in the Denver area, it will be more relevant to temperate areas with distinct seasons.
While I have broken this article in sections for trees, perennials, etc., the one thing almost all types of plants need throughout the fall (except for succulents) is consistent moisture so that they’re not stressed going into winter. If you live in an area where you need to water your plants in the summer, make sure to continue to give them a good drink occasionally throughout the fall.
What do I do with my trees in the fall?
Most trees don’t need much attention in the fall and, as a rule, should be left alone at this time of year. Trimming a tree often encourages it to push new growth which we want to avoid as it is directing its energy into preparing for winter. However, if your tree has some large dead branches, these pose a hazard, especially once they get the weight of snow on them in the winter. Dead branches should be removed as soon as possible, regardless of the time of year.
However, fall is a good time to take stock of all your trees (maybe take a photo or two) before they go into dormancy. Make note of or mark dead branches or those that look diseased, so that you’ll remember which ones will need to be pruned out during the winter (which is a great time to prune many trees). Diseases can be evidenced by a tree or branches that lack vigor, or have areas of sunken or different-colored bark, e.g., reddish or blackened. Diseased leaves might be prematurely yellow, wilt, or fail to fall off like they normally have in previous years. Also, be aware of leaves or branches that have black, red, or orange spots, or have a white powdery mildew,
If you have large trees, suspect that a tree is diseased, or are unsure of which kind of trees you have, take time in the fall to find a reputable arborist. Many arborists will walk around your property with you, identify trees that have problems and give you a free estimate to care for them. Trees are your largest and longest-term plant assets and a prudent time to bring in professional help.
If you have a newly planted, young tree, you might have to wrap its trunk for the winter if sunscald is a problem in your area. Sunscald can be very damaging in areas of the country that have radical temperature swings and intense winter sun, like where I garden in Colorado. If that applies to you, wrap young, thin-barked trees in a paper wrap for a few winters after planting until their bark starts to thicken to help protect them from sunscald. If you put wrap on in the fall, make sure you take it off mid-spring. (I’ll explain more about sunscald and how to wrap trees in another blog post.)
What do I do with all these leaves?
Cleaning up the leaves and deciding how many of them to take or leave on the ground is usually your biggest concern with trees in the fall. Conventional suburban etiquette dictates that it’s your responsibility to tidy up your yard by raking and hauling away all the leaves in it. However, if you look at leaves through a wider lens, you might see them as more of a gift than a chore. Many pollinators and other beneficial insects overwinter in and under fallen leaves. Leaving them in your shrub beds and gardens can help give these vital parts of our ecosystem the opportunity to survive. These insects help to improve our soil, break down debris, pollinate our plants, feed birds, amphibians, mammals, and bring balance to the garden.
Leaves left in garden and shrub beds can add organic matter and nutrients back into the soil. Leaf mulch also helps to retain soil moisture and insulate plants from extreme cold and temperature fluctuations over the winter. Therefore, leaving some leaves in the garden beds can be beneficial.
Be aware, however, that leaves can also harbor diseases over the winter. If you have a plant that you suspect might be diseased throw those leaves away to help control the disease.
There is also a balance between benefits and problems due to the number of leaves left in the beds. Large piles of leaves are unproductive as they can smother small plants, mat together limiting water infiltration, restrict airflow or trap too much moisture in the soil. Leaves piled up against the stems of shrubs and trees can lead to disease and rot. A good general rule is to leave about 3” of leaves in the beds. If you have more than that, move some to your compost bin, give them to a neighbor that composts or haul them to a city/county compost area, as opposed to throwing them into the landfill.
In Colorado, where I garden, it is relatively dry, and I don’t have copious amounts of leaves. So, once I have filled my compost bins full, I will haul extra leaves to my designated leaf litter area where they catch between a row of evergreens and my back fence. I spread them out here in a thicker layer where they eventually break down and help to suppress weeds in the meantime.
You’ll probably want to remove leaves entirely from areas that are covered in rock or gravel, particularly if that rock is on top of a weed barrier. When leaves decompose on top of a weed barrier it creates pockets of organic matter, which make nice spots for shallow-rooted weeds to grow in your rock mulch. Blow or haul your leaves to a bed with bare soil or wood mulch whenever possible. Again, if you do have to get rid of some leaves, try to find a source that will compost them,
Do I need to clear the leaves off my lawn?
The short answer is yes; leaves should not be left on the lawn over the winter. Even small mounds of leaves can kill the grass underneath or cause mold or other diseases. However, running your lawn mower over leaves before they get wet or matted can turn them into a fine, top-dressing mulch that you can leave on your lawn. To do this, outfit your lawn mower with a mulching blade (and/or with a mulching kit that plugs up your mower’s discharge chute, or just take off the grass catch bag) which will chop up the leaves and deposit them back on your lawn. Finely chopped organic matter should break down quickly enough to feed your lawn without causing problems, but know that there is a limit as to how many leaves can be on the lawn when trying to mulch them into a fine top-dressing. The leaves should be scattered over the lawn. If your lawn is completely covered, you’ll need to haul some to your compost pile before attempting to mulch the rest onto your lawn. If your mower is making piles of shredded-leaf mulch, you are producing too much to leave on the lawn. Gently disperse the piles with a leaf blower or rake.
What do I do with my shrubs in the fall?
Like trees, shrubs should be left alone while going dormant for the winter. Cutting them back while they are losing their leaves might cause them to put their energy to the wrong area. Also, if your shrubs are native to your area, they’re likely to provide habitat
and their seeds or berries may be an important food source to the birds and other wildlife over the winter. Therefore, leaving them be until the end of winter is a good choice for both the plant and wildlife.
What do I do with my perennials and annuals in the fall?
Once temperatures descend in the fall to below a plant’s hardiness tolerance, they will die. (If you need a refresher on Annuals,
Biennials, Perennials and Hardiness Zones click on the button below to see my blog on the subject.)
After annuals, second-year biennials and non-hardy perennials die, they can be pulled out or cut off at the base and composted. They’re not coming back, but you may be able to harvest their seed to respread or start indoors over the winter for replanting next year.
If the perennials in your yard are hardy, they will likely die down to the ground in the fall, but their roots will remain alive allowing the plants to regrow in the spring. If your plants have been growing for over a year, they are possibly a biennial or most likely, a perennial. If you don’t know if a plant is an annual or if it is hardy, then leave it and wait until spring to see if it comes back. Be patient, you might have to wait until early summer to know for sure if it is coming back or not.
As is the case with leaves, suburban etiquette tends to dictate that the proper thing to do with perennials in the fall is cut the foliage down once it looks dead, to neaten up the gardens for the winter. I personally spent much of my career “cleaning up” homeowners’ gardens in the fall, but over the years I began to weigh the norm against what I considered to be important. Cutting perennials down in the fall will make the garden look neater, but it can have a negative impact on plants and animals. Butterflies, native bees and other beneficial insects overwinter on undersides of leaves, and in and on stalks left standing through the winter.
Many plants also have “winter interest” meaning their standing, dormant foliage and seed heads add interesting structure to the winter garden, especially while kissed with frost or blanketed in snow.
Seed heads, and overwintering insects, particularly if your plants are natives, can provide a food source for birds and mammals throughout the winter.
If a perennial is not cut down in the fall, its dead foliage can create a protective dome over the base of the plant which helps to insulate it from fluctuating and extreme temperatures. Some short-lived, hardy perennials also tend to live longer if their stalks are left up over the winter, providing them access to more stored nutrients. Therefore, leaving perennials be until spring can be a good strategy to adopt.
Are there some perennials I should cut down in the fall?
There might be reasons to cut a perennial down in the fall. If you have any that look diseased then it is a good idea to cut them back and throw away the cuttings because diseases can overwinter on the dead foliage. Another reason to cut a perennial down in the fall, is if you have an infestation of bugs on a plant. If bugs have caused severe problems with a plant, cutting down the foliage in the fall and throwing it away might help set the bugs back next year. If you do decide to cut down a perennial because of bugs or disease, cut it to 2-4” high.
Another reason, to cut a plant back in the fall is because it’s an aggressive re-seeder. If you notice that a certain type of plant seems to have a lot of separate baby plants around it, it might be an indication that the plant reseeds aggressively. In which case, it could be prudent to cut off the seed heads (or at least most of them) to keep new plants from sprouting to the point where they are a problem. If the plant has stiff stalks, cut the seed heads off leaving the stalks 8 – 15” tall to help create beneficial insect habit.
While it is possible to compost seed heads or cuttings from diseased, infested, or aggressive plants, if your compost pile is not hot enough for long enough, these seeds, bugs or diseases won’t die or break down and you could end up spreading them back over your soil when you spread compost. So, you might want to throw diseased cuttings into the trash or share the seeds with a fellow gardener or a seed exchange.
What do I do with broad-leaved, evergreen perennials in the fall?
If you have a perennial that is evergreen, as in the leaves didn’t die and it is still green (or some form of grayish-green, reddish-green or purplish-green) after all the other perennials’ tops have turned brown and crispy, then leave it be for the winter. Wait until spring to cut it back and shape it if you think it looks scraggly or overgrown. If you are happy with the size and shape, you can just continue let it be.
What do I do with my ornamental grasses in the fall?
One of the benefits of ornamental grasses is their winter interest. It is often their time to shine. Grasses will continue to give the garden movement and life when the other plants have become brown and stiff.
Let yourself be captivated by the way they continue to dance in the wind and enjoy how their inflorescence sparkles under a frost. If you live in an area that gets snow, it will take a toll on the grasses throughout the winter and break them down. They can be cut to 8 - 15" tall at any time they look start to look messy, but bumble bees and other invertebrates like to nest at the base of bunch grasses and leaving a cover of the broken grass might help protect them throughout the winter. So, leaving them be until right before they start to green up in the spring is a good strategy to adopt.
Don’t over-stress yourself worrying about the right way to take care of things in your yard. If you ask 5 different gardeners what to do with your plants in the fall, you’ll get 6 different answers. Every “rule” has almost as many exceptions and what “always” works for someone “never” works for someone else. The good news is that most of the plants that you already have growing in your yard should be resilient and survive your efforts at care. Remember though that you are less likely to do lethal damage to your plants if you wade in cautiously. If in doubt, leave it and see what it does. What you lack in control and tidiness, you often gain in life and wonderment. I’ll keep creating more blogs to help you navigate your way through caring for your yard, including one on how to take care of it in the spring. In the meantime, relax, take pictures, makes notes and experiment with a child-like curiosity. This will help turn your yard into a fun, new adventure instead of a chore.