Most plant growth is obvious, even to the casual observer. In spring and summer, we can see shoots, leaves, and stems burgeoning. By this time of year, that growth appears to slow, even stop. But another cycle of growth is just beginning in preparation for winter. Tucked safely – and invisibly – beneath the soil, bulbs are growing fresh new roots.
Out of sight usually means out of mind. However, you can improve the performance of your bulbs if you take a few moments to fertilize in the fall, even though it feels as though nothing new is happening in the plant world. The ideal bulb fertilizer is slow-release, lower in nitrogen (which supports leaf growth) and higher in phosphorous and potassium (to enhance roots and flowers). For centuries, bone meal was the bulb fertilizer of choice, but it’s not a complete fertilizer and may have the unfortunate consequence of attracting dogs or rodents, who digs around to try to find the tasty “bone,” so we no longer recommend it.
Apply the fertilizer as a top-dressing to your existing bulbs, or after planting new ones. You can do this now, or later in the season after you’ve cleared away spent plants.
With fertilizers, it’s important to follow label directions and apply only as much as directed. Applying more than your plants can absorb doesn’t benefit the plants, and excess nutrients can wash off into waterways, disrupting aquatic life. The best practice is to apply fertilizer with a frugal hand.