BARBARA LEACH: Questions For The Fall Lawn / Garden

Can leaves hurt my grass?  Well, yes and no.  Leaves must not cover the grass to the point that the grass cannot receive the sunlight it needs, so leaves should be raked, mown, or blown regularly.  On the other hand, leaf particles can return a lot of nutrient to lawns and reduce the amount of fertilizer the lawn needs, as well as enrich and improve soil structure.  There is wonderful “magic” that happens when you add organic material to clay.  The particles stick together in balls and create air pockets and improve water percolation.  In addition, the decomposing material attracts worms and other healthy soil life.  Next thing you know you have a little army of soil workers tilling, moving, mixing and depositing their byproducts.  Mow your leaves and rake off the excess that doesn’t disappear into the grass blades. The chopped leaves can be composted and returned to the lawn later, or can be used in flowerbeds and gardens. Make the most of the resources that are free on your property and keep them out of the landfill.  It does take some management and planning on your part, but the rewards are great.  Perhaps you have a neighbor who cannot process their own leaves.  Maybe you can work out an exchange that will provide you with more compost, help them and the landfill!  You might even get cookies for your labor!

Can I use pine needles as mulch, or are they too acidic?  Pine needles make fine mulch.  I have three criteria for choosing mulch.  Will it help retain water and cool the roots, does it look good, and will it cost me a lot?  If you like the look of needles and they are free or cheap and available, you have a winning combination.  They are light to handle and drain well.  There are a couple of precautions, however.  Make sure they are not raked off an area that has been treated with weed killers.   Make sure they are from a healthy tree.  You may be able to see scale insects or other disorders in the tree.  Avoid those.  By the way, all organic mulches could change pH over time.  That is why it is so important to check your pH every few years and make adjustments, if needed.

Should I cut my plants back now?  Annuals and perennials that have gone dormant and have died back can be cut to the ground and debris removed now.  If mulching, it may be best to do that first.  You will be less likely to cover up plant crowns and rot your perennials.  Hostas, in particular, are sensitive to winter rot.  Keep mulch very thin.  1”-2” is plenty for flowers and small shrubs.  Plants that are still green should be left.  Since they can take the cool weather the tops are now feeding and developing new roots in an attempt to recover from the heat and drought of summer.  Give them all the time you can to catch up!  Remove foliage only after it has died back.   If they are evergreen (a few iris, daylilies, hellebores, ferns, etc. are), cut them back in the spring.  Trees that are “free-bleeders” (maples, elms, hornbeams, birch, mulberry, willows and others) can be pruned as soon as the leaves color or drop.  If you wait until late winter they will bleed profusely in the spring.  The idea behind early dormant pruning is to do it when the plant can heal over before sap rises.  Most non-flowering evergreen trees and shrubs can be pruned lightly in the fall.  If you must cut back into large wood you may be best to wait until Feb-March, after the worst if the winter is behind you and just before a flush of spring growth that will cover that “just pruned” look quickly.  Most deciduous non-flowering trees and shrubs are best left until Feb-March, since cuts can be relatively large.  This avoids winter damage.  Roses and shrubs with a pithy or hollow stem, like butterfly bush or caryopteris should be cut in early spring or moisture could get into the stems and damage them when it freezes.  For now, just remove errant branches that might break under a snow/ice load or high winds.

Barbara Leach, VCE Horticulture Technician, Roanoke

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