In the last article in this series, winterization of the lawn was discussed. Lawn winterization is important to take care of early in the fall season, because adequate water may be needed immediately after fall fertilization. Landscape plants, while equally in need of proper winterization, are not as time and precipitation sensitive, and winterizing can take place later in the fall season.
Landscape plants come in many different forms. The four major classifications are woody landscape plants, perennials, annuals, and ornamental grasses. All have unique features and needs, but all are fairly easy to winterize.
Fortunately, two of them are very easy to prepare for winter. Perennials and ornamental grasses, which are, in essence, perennial, die-back at the end of the growing season. Depending on the species, they will last different lengths of time into the cold season, and some may even have ornamental value during the winter. Regardless of how everything looks going into the last week of October, anything that is not expected to provide ornamental value during the winter needs to be cut back during the first week of November.
Depending on the plant, using loppers, shears, or whatever other tool is appropriate, most perennials will need to be cut as close to the ground as possible, without damaging the crown of the plant. Cutting into the crown can cause damage and have adverse effects when the plant begins growing again in the spring. Ornamental grasses are a bit different.
Many ornamental grasses do have winter value, but it really comes down to personal preference. Some people like the beige colors and forms that these grasses can carry through the winter months, but some people like the cleaner look of just cutting them back. One consideration when making this decision is snow load. If the region in question can get a lot of heavy-wet snow throughout the winter, these grasses can tend to look messy and should just be cut back in the fall. If they are not cut back in the fall, they will definitely have to be cut back in the spring to allow new growth to flourish.
Cutting back grasses is very easy to do with pruning shears and does not need to be as close to the ground as perennial flowers. Usually, most grasses will have between six and eighteen inches of plant material left, depending on the type of grass.
Ornamental grasses and perennials are fairly easy to winterize - just cut them back and let them rest. Annuals are a whole different ballgame.
Annual flowers are very rarely kept alive from one year to the next. When they die at the end of the season, most people just pull them and throw them away. However, there are people that like to keep potted annuals in the landscape during the growing season and bring them inside during the winter. In this case, the two most important things to remember are to get the plants inside before the first frost and make sure they have adequate sunlight throughout the winter. All too often, people bring their annuals inside from full sun to a partially sunny room in the house, and they can't figure out why they always die. Plants go into shock, just like people can, and without proper care, they may not make it. Adequate sunlight is key to a happy houseplant.
With the three easiest plant types covered, it's time to discuss woody landscape plants. These are going to be your typical trees and shrubs that have woody branches, stems and trunks.
Woody landscape plants come in many forms. There are deciduous plants, whose leaves fall off in the winter, and there are evergreens, which can come in the needle form or even broadleaf. Different types of trees and shrubs may or may not need some winterization, and the requirements can vary from region to region, so it's important to check with a reputable, local garden center or landscaper to see what is recommended for that area.
The most common items are going to be leaf clean-up, pruning, or, in the case of evergreens, an application of anti-dessicant. Leaf clean-up is fairly cut ad dry. It is important to clean up leaves that have fallen, because they can become a hotbed for insects, disease, and even fungus. Not to say that they shouldn't be composted properly and reapplied to the garden areas, but they should not be left on top of mulch, rock, or lawn. Leaves left in planting beds, even if there is weed fabric present, can break down in rock or mulch, and create a growing medium for future weed growth. Pruning is a little more calculated.
Tree and shrub pruning should take place after the plants have hardened off, and most, if not all, of the leaves have fallen off. Although, it is usually a good idea to mark the branches that are to be removed with a ribbon while the leaves are still on, because branches will hang lower with leaves on and can be deceiving during the winter months. Pruning cuts should be made at the base of the branch, but not into the collar, which is the thick ring where the branch meets the trunk. Cutting into the collar is unhealthy for the plant, and can cause openings to disease and insects.
The final step to winterization of woody landscape materials is the application of anti-dessicant, but this is only applicable to evergreen plants. Dessication is moisture loss that can take place in evergreens, because they still have foliage and are still transpiring, but are not receiving any supplemental irrigation. Anti-dessicant is especially important in climates that have long periods of warm, dry weather in the winter, such as the Rocky Mountain region.
Finally, in addition to the other winterization techniques, it is always important to throw down a little bit of fertilizer at the base of trees and shrubs, and, frankly, the same products that are used on the lawn are sufficient for woody materials. If it takes place as a part of broadcast application with a typical spreader, that will work just fine. Just as with turfgrass, woody plants don't "die" during the winter, hopefully, they just go dormant, but they are still evapo-transpiring, and that requires water and nutrients.
Speaking of water, winter watering is always important with any landscape plants. Water is just as important to plants as it is to humans, even though they use it at a much slower rate. During any periods of extended, dry weather, regardless of temperature, all plants will need to be hand watered to maintain proper health.
While there is never a guarantee that all woody plants will maintain optimal health from one year to the next, following these steps will greatly increase winter health and sustainability.
Next up is the final and most important step to winterizing the landscape - taking care of water features and irrigation systems.