You’ve likely have heard the promotion “Leave the Leaves” to protect beneficial insects like pollinators during winter. While it is a good idea to leave fallen tree leaves in garden beds and shrub borders, it is not be the best idea for lawns or other turfgrass areas.
A thick layer of leaves on lawns, especially if snow accumulates on top of the leaves, can suffocate turfgrass leaving thin or bare areas in spring. While these areas can be reseeded in spring and recover quickly, avoid this by raking tree leaves into flower or shrub beds rather than leaving them on the lawn.
In plant beds, a layer of leaves protects beneficial insects during winter, conserves soil moisture, and in the absence of snow protects plant crowns and roots from winter weather extremes.
Many of our solitary bees, of which there are 100s of species, overwinter in soil or inside of plant stems. Leaving leaves in plant beds and waiting until spring to cut back herbaceous perennials, or only cutting them to 12 to 18 inches tall, can help protect these pollinators and other beneficial insects.
While it is recommended to leave plants overwinter, this applies to flower gardens and not vegetable gardens. It is wise to remove dead vegetable plants and weeds from gardens due to the number of disease and insect pests that attack vegetables.
If a plant in a flower bed had a disease or insect pest during the growing season, it would also be wise to cut back the tops of these plants and remove the debris from the garden in fall instead of spring.
Fall sanitation reduces carryover of diseases, insects and weeds to next year’s garden. Debris from vegetable plants that did not have a disease or insect problem during the growing season, and weeds that have not gone to seed, can be added to compost piles or tilled into garden soil.
A light fall tilling of garden debris, except in erosion-prone areas, can improve soil structure and lead to soil warming and faster drying in spring. This allows vegetables to be planted earlier and reduces the need to work soil in spring when it may be wet, which damages soil structure and causes compaction.
Weeds that have gone to seed and diseased vegetable plants are best removed from vegetable gardens and recycled elsewhere, such as taken to yard waste recycling, rather than tilling them into soil.
On another note, as shrubs and other plants drop their leaves tree seedling may be noticed growing amongst the plants. If weedy trees are cut to the ground for control, the majority will re-sprout and continue to grow next season. Treating cut stumps with an herbicide can reduce resprouting.
When a weedy tree is growing amongst landscape plants, it is best to use the herbicide glyphosate, such as a Roundup product, to treat cut stumps. Glyphosate has little to no soil residual and risk to nearby plants is low if used correctly and kept off of desirable plants.
Read Roundup labels before buying to be sure the product contains only the active ingredient glyphosate. Do not use products with picloram (Tordon) or imazypyr to treat cut stumps in shrub or flower beds or near other trees or shrubs. Both will kill other plants. When treating cut stumps, do so within 5 minutes of cutting the tree and know that spring application is most effective.
If you prefer not to use an herbicide, frequent and repeated cutting to the ground of nuisance trees as they re-sprout will eventually kill roots and the tree. Note the location of the weedy tree and check it every other week during the growing season for the need to cut it back to the ground.