Saturday, October 5, 2013

Planting Lily Bulbs on their side... for Water Control?

Has anyone ever suggested to you that lily bulbs should be planted on their sides to "keep them from filling up with water" over winter in heavy clay soil?  Does it work?

Physiology of a Lily Bulb

When lily bulbs are dug, and where the old flowering stem was located, you can see a neat and tidy "hole".  Lily bulbs are composed of overlapping "scales" attached at the basal plate (bottom of bulb).  Water washes through the lily bulb to the roots, which is sort of like a kitchen bowl with a crack in the bottom—it holds water for a period of time, but eventually the water completely leaks away. 

Lily Bulbs do not swim well.
  • Your goal is to have water move freely and quickly from the soil immediately surrounding the bulbs, so they will not be subject to rotting over winter and early spring. 
  • Sluggish drainage—caused by tightly packed clay soil—creates saturated soil for an extended period of time, which results in a depletion of oxygen and danger of loss over winter/spring.  
  • Frequent heavy rainfall with fast draining soil provides oxygen to the plant tissues, which is not a problem in sandy loam because the water drains quickly away from the bulb itself.  
  • Planting lilies on their sides into clay-based soil still doesn't do anything to improve the drainage, you will still have over-saturated soil. 
  • Digging a larger-than normal hole in clay soil, then refilling it with commercial potting soil doesn't work either—the hole acts as a slump and quickly fills with water. 

The solution for clay-based soil is a slightly raised wide mound or berm, where the bulb is above natural ground level.  The lily roots may penetrate further below and into the natural clay, but the bulb itself stays drier.

What is going on underground?

There's more going on under the soil surface than most people ever suspect.  While being tractor-planted, many bulbs will either land upside down in the soft soil, or sideways.  Lilies have "contractile roots" on the bottom of the bulb, which helps to anchor the lily from upheaval by wind.  They will frequently turn themselves right side up as the new roots grow deeper into the soil, but some may take another year to become fully upright. 

In the photo below, the roots on the left are contractile basal plate roots.  Do you see how thick they are?  The ones growing above the bulb are stem roots, which being just under the soil surface, take up nutrients, the reason why fertilizer is spread on top of the soil, not mixed into the bottom of the planting hole.  Basel plate roots can persist from year to year, stem roots are grown new each year with the new stem.  By the way, there is no need to wash transplanted bulbs before planting, this photo was just to clearly show the two kinds of roots.  Tiny bulblets—offshoots of the original—will nest within the tangle of roots, if that variety is so inclined and make new, full-sized bulbs for you within a few years.

Not all lily bulbs produce stem bulblets.  Some, like this Orienpet, just keep getting bigger until they divide into two.

The next photo shows an Asiatic lily that was laying on its side when planted (in spring), and the sprout traveled underground for over a foot before turning up to make a stem above ground.  The rock on the right is there to prop it up and show how the now-browned stem emerged from the soil. Had it been planted upright to begin with, the plant would not have expended as much energy underground, and would probably have had a taller stem with more flowers that year. 

Digging this one was a chore, the stem just kept going off into its neighbors.

The Bottom Line

Correct any poor draining soil and put the bulb, so the roots are downward, with no need to put them on their sides.  Even if you make a mistake and accidentally plant them upside down, the stems will still find their way to the sunshine.

Related Blog Postings: 
Semi-automated Planting of Lily Bulbs
Clay Soil and Lily Bulbs
Bulbs planting upside down?  No Worries.
When Mother Nature is Generous with Rainfall

1 comment:

  1. Dianne, when I transplanted Lesotho the root ball nearer the surface was 12" around with a fully formed bulb within the mass of roots. Strangely though, below that was a huge bare stem 1.5 inches in diameter going straight down into the soil another 12+". It appears to be broken. I dug even deeper to about 18" but found nothing else below. Did I kill the bulb?