Planting Bulbs for Spring Flowers
- by R. Lieber
Over the decades I have heard many pearls of wisdom about planting bulbs. Some were based on experience, handed down over the generations, others were no better than superstition. Some garden truisms are falling by the wayside, as our seasons have trended to warmer winters compared to previous decades. However, the same questions and myths come at this time every year, and as we Master Gardeners get asked these questions we have become unsure about the truth ourselves. Which gardening pearls of wisdom do we hold dear and which do we ignore? The really big questions are: what do we do, and when do we do it, to have that gorgeous spring display?
The Best of the Bulb Myths (and there are many more!)
It is too warm for bulbs here in the upper south or We can't grow bulbs that come back here - "Nonsense and poppycock" as my old English teacher loved to say. All it takes is to look around in spring to know that isn't true, but there are some varieties and types of bulbs that don't do well in our warm (zone 7) county. There are plenty of bulbs that thrive on warmer winters, so the first myth to pitch in the compost bin is the all or nothing "We can't grow bulbs here." Many bulbs and corms can be perennial if planted in good growing conditions. Some reliable sources for bulbs now specify which will do better in zones 7 and 8 (and sometimes even further south). My personal favorites are Brent and Becky's and Old House Gardens but there are plenty more. I invite our BCMGs to send in their favorites so I can update the blog with a longer list of good sources.
Tulips don't grow well and tulips don't come back - Another popular myth, often coming with the observation that, at most, you can have them bloom for a year or two. Admittedly, until fairly recently, the heat of the summer and cold of the winter made common tulips iffy for southern gardeners, unless they had "cheats" and substitutes. Warm soils of the southern gardeners meant either grow them as annuals, replanting every fall with new bulbs, or learning about vernalization (see below). Sometimes it isn't the climate. For years I had no tulips but it was because I had deer and squirrel galore. That part of myth will be true anywhere in the USA! My current garden is deer free and I have had two tulip types return year after year, multiplying happily as they go. One is a range of "species" tulips and the other are Darwin tulips. Species tulips are smaller and less showy until growing in bigger clumps but the Darwins are as showy as any other Dutch tulip.
Fertilizer, bone meal, or high phosphorous additives are needed when planting bulbs - Bone meal is always a contentious subject among gardeners who plant bulbs. Some swear by it but the scientists, who have tested it rigorously with years of plant studies, find at best it doesn't help and more often actually hinder bulbs growth when put in the hole and around a bulb you are planting. It can actually create problems in most home gardens by making for toxic levels of phosphorus for the very fungi that occur naturally and help roots grow. You also are more likely to burn roots with concentrated fertilizer in the hole and often materials, not already completely composted, can temporarily deplete nitrogen levels as they decompose in the warming soils of spring. Special bulb fertilizers are also not needed. Unless a soil test shows something missing from your soil good top dressing of mature compost or very light application of an all purpose organic fertilizer with a smaller phosphorus content (e.g. Epsoma's Plant-Tone) will be enough. Apply after blooming starts, NOT in the fall.
There is a "perfect time" to plant bulbs and if you miss that perfect window of opportunity they won't grow or won't bloom -This myth is especially important to debunk in light of this year's high summer like temperatures right into November. For 2016 buying early but planting late is probably the best rule of thumb, as long as you find a cool place to keep them until you are ready. Bulbs don't know a thing about our calendar, and probably don't register one or two cooler nights. Their growth cycle is related to changes in how warm the fall and spring soil temperatures are, NOT air temperatures over a period of time. Most will do fine if planted sometime between Halloween and Christmas (if one needs a calendar reference). I managed to plant forgotten bulbs in late January and had most still bloom every year after the first. Of course late planting carries the risk of failure more than planting before Christmas but many of us have so much to do beforehand that forgotten bulbs always seem to be found come January 1st! The only rule is: as long as you can dig in the ground you can still plant.
Mulching myths, which is it? Cover or Don't? - There are two opposing schools of thought for mulch and bulbs. Some feel you should plant and immediately mulch to protect the bulbs and other believe you should leave the soil "bare" so critters aren't able to hide while digging or gnawing away at the growing bulbs. Once bulbs are planted and watered in, mulch will not deter critters or "insulate" the bulbs in warm autumn days. It's best to keep the ground bare to spot signs of trouble and let the soil cool down with the colder nights. The soil needs to fully cool down before insulation from desiccating cold winds is helpful and many bulbs deal better with cold than warm weather. Delaying the mulch will not hurt. We often see growth from bulbs that have stayed in the ground when we go through warm spells in the winter. Mulch added in January before we get the first thawing cycle helps keep the soil chilled and retards premature sprouting. Keep an eagle eye out for voles tunneling at this time. They like using mulch and snow as cover so disturbing the upper layers of mulch around any sprouted bulb helps to deter them.
Vernalization: The "Magic" Behind Dutch Bulbs
The Dutch have over the years developed the secret recipe of growing tulips and other bulbs, despite having a climate not at all like the original home of many bulb. It truly is a *secret* process, although we can make very educated guesses! Bulbs must be kept in just the right kind of dry and cold at just the right times to make the magic happen. The newest tulips no longer bear a close resemblance to the original plants that came from the dry and cold regions of the Middle East, or the arid steppes and mountains of central Asia stretching through Mongolia and into China. Bulbs have been changed by selection and breeding to be bigger and showier and grow in a wider variety of climates but the old native chill time is still required. Like tulips, daffodils also came from a drier climate like the one that can still be found in the Ukraine, high in a mountain valley where there is a fantastic preserve for them.
That chill time, or Vernalization, is another "trick" that has been used by our southern garden forerunners as well as commercially grown forced bulbs for early winter display. For gardeners in the warm south it is not for the lazy plant-once-and-forget gardener. Vernalization gives bulbs a dose of dry cold just like the very harsh and cold soil conditions of their origins. The only place to chill tulips like that is in a refrigerator. Basements are a distant second best and aren't always as successful. Most bulbs will need to be chilled for a minimum period of 8-10 weeks and cannot be allowed to get warmed up. To vernalize new bulbs buy as soon as they are for sale in September and keeping them in a cool place (at or below 50 degrees) and waiting until the soils have cooled down to at least 55 degrees or cooler before planting to be sure they have gotten the proper signal for growth. For existing bulbs dig up your bulbs when dormant, placing them in a cool but not really cold refrigerator, and plan on waiting a minimum of 2 months before thinking about putting them back. For many of us impatient and forgetful gardeners vernalization is no easier than getting a poinsettia to bloom in winter!
Further reading and some sources of bulbs:
Many bulbs and bulb-like plants are usually treated just like the daffodils and tulips. At some point in this blog we'll do more on other favorite bulbs, corms and rhizomes. From Alliums (onions) to Gladiolii (big and small) to Zantedeschia (Calla lily), tell us which ones you want to know about!