If your soil is still “cold”, it is possible to move and divide bulbs this month, but you must do it very carefully. A better plan might be to wait until this fall, but if you have a construction project scheduled for this summer or otherwise need to move your lilies out of harm’s way you can move them this month.
The lily stems on the left side of this photo are nicely spaced and the flowers will open fully with the maximum number of buds. However, the “clump” on the right side needs dividing because the bulbs have become overcrowded, with each stem exhibiting fewer flowers.
- Pull away any loose mulch and pile up to save for later. As a general rule of thumb, "summer" mulch should not be more than 2 inches deep, "winter" mulch in cold climates is more substantial. (See Guidelines for Winter Protection.) If you are thinking of moving bulbs now—and the soil has thawed—you can do so, but remember that you should not leave more than the bare minimum of mulch, especially if you live in an area with lots of cool weather rainfall. Whether established bulbs or newly transplanted ones, too much mulch and the bulbs will rot should the soil be able to dry quickly between storms in spring.
- Sink a garden fork (preferred) or sharp shovel into the soil about 4 inches away from the old stems to avoid slicing through the underground lilies. If the soil is hard, then start further away and go a full shovel deep. You want to dig under the bulbs and lift them up. We find a good spading fork best for the job. Should the old browned stems not be present from last year, your task will be much harder, so proceed slowly or wait until the sprouts have emerged.
- Carefully loosen bulbs, soil, plus any weeds—do not dump over the contents of your shovel above ground—we aren’t digging potatoes or clams! Lily bulbs do not have tough outer shells like tulips and can be easily damaged if dropped or crushed, plus you do not want to risk breaking off emerging sprouts. Broken sprout = no flowers.
- With your hands, pick through the soil to extract the bulbs being mindful of soft sprouts or
—and if you can gently pry them apart with your fingers—then you now have two nice flowering size bulbs to plant separately in the garden. If the lily resists being divided, re-plant as-is and wait until this fall to divide the plant for sharing or creating another lily bed. Smaller bulbs attached to the bottom sides of the main lily that are fully formed (see photo below) can be snapped off and planted a bit more shallow than you would bury the large bulbs. 2-1/2 times the size of the bulb is the golden rule for planting lilies.
- If you are unable to plant the newly harvested bulbs right away, then layer them in a cardboard box with pet bedding (shavings), dry peat or potting soil in a protected area of the garage or garden shed until you can plant. Do not let the bulbs either become too dry in the storage box. Lily bulbs (and sprouts) will dehydrate quickly when out of the soil. You can also "pot them up" for the summer, choosing a container with good drainage holes and at least eight inches deep. (Also see: Emergency Transplanting)
Photo on left: If you choose, gently break off the offsets (basal plate bulblets), planting them with no more than two inches of soil over the top. For the specimen shown, the larger bulb would go back into the garden with 4 to 6 inches of soil covering the top of the bulb.
(The bulb shown is 'Candlestick', a Longiflorum-Oriental Hybrid.)