Friday, October 28, 2011

Mulching Lily Bulbs for Winter

Whew, we are 99% caught up with fall lily bulb shipping.  Only the orders that came in this week are outstanding and those will be going in Monday's mail.  Be sure to consult your planting guide and the extra 1/2 sheet of paper regarding winter mulch.  The past two winters have been surprising for most folks and so a little tweaking might be order for your area.  In case you've misplaced the instructions, both sets (Cold Winter & Wet Winter) are reviewed below.

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Avoid these 3 Mistakes in Colder Climates 
  1. Not using a thick winter mulch over Oriental, Trumpet, and Orienpet (OT) Hybrids each winter in more severe climates (below -10 F.).
  2. Mulching before the soil is well frozen which gives rodents a winter home (with food). Wait until the soil is frozen at least several inches.
  3. Leaving a thick mulch on the garden too long, which does not allow the soil to dry quickly between rainfalls in spring.
Although more moderate climates only require enough mulch (one to two inches) to reduce winter weed germination, colder climates need a bit more attention, in the same way that roses and other "softer" perennials are protected. During a recent winter, some areas of Wisconsin, Minnesota and Illinois experienced very cold temperatures, with frost levels greater than 5 feet, and without enough snow
cover for many plants. The loss of rose bushes, trees, shrubs and other "above ground" plants is a tough one to avoid, but protecting lily bulbs under such conditions is easy if the ground is mulched. You MUST place an insulating layer of mulch over all Trumpet, Oriental, OT Hybrids or species where gardens are subject to deep freezes, especially if a good snow cover is lacking or not expected.

Asiatic lilies do not generally need extra protection, but all other lily bulbs in the Midwest, or Mountain states should to be covered. SPRING: Remove the mulch in layers, as the ground thaws and warms to evaporate rainfall (or snow melt) fast enough in spring or your bulbs or sprouts will rot.  If lilies are planted at the top of a ridge or small hill, the cold will not settle around them as much, so those areas may get by on a lesser amount of mulch, but soggy, wet areas are to be avoided.

A good layer of mulch may consist of 8 to 12 inches of straw or hay, tree boughs or other fluffy material. Avoid compacted leaves or grass clippings, these have the potential to hold too much moisture in the soil and around the bulbs and can rot the sprouts in spring if you do not remove the mulch fast enough. Shredded leaves are better because they allow air movement and are easier to remove in spring.

“Wet Winter” Instructions - Rain, rain and more rain, interspersed with slush.

Be CAREFUL about mulching your newly planted bulbs if you were affected by an unusual amount of
rainfall resulting in your garden becoming saturated this past winter or spring - especially important if
your soil surface was unable to dry between storms - as many states had the past two years. Lily Bulbs by
their very nature are designed to store water for times of drought; plant on a slope or in a slightly raised bed to avoid flooding - they do not swim well and will suffocate if the soil stays constantly soggy over winter - moisture replenished on a daily basis is OK just as long as it is draining away quickly and not sitting stagnant.

During cold and wet springs a too thick mulch over lily bulbs may cause the sprouts to decompose while still underground or as they emerge. See Fungus: Stump Rot (Phytophthora) on our website under “Problem solving (Animals to Weeds)”.

In moderate/mild Southern and Coastal areas, use only enough mulch (one or two inches) to suppress winter weed germination, especially since this winter is again expected to be wetter than normal. During wet winters if the soil surface is not allowed to dry between rainfalls and the garden remains saturated, you risk losing even established bulbs. Use of porous mulch (e.g. straw or large nuggets of bark) allows soil to breathe and dry faster. Go easy on spreading compost; only an inch or two on top of the soil is recommended per year.

Your goal is not deep freeze protection as in the Midwest or Northern states, but rather a tidier garden.  Maritime areas of the Pacific Northwest should also go very easy on mulch this winter. Additional bark, shredded leaves or other decorative materials should only be added in late spring after wet snow and/or heavy rainfall has diminished and just before the new weed seeds begin to germinate, which will keep the garden looking good all next summer. It is important to allow the soil surface to dry properly between storms.

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