Bulbs are capable of growing in nearly any soil, but you can help them produce great blooms by providing soil ideally suited to their needs. Three aspects of soil should be considered: porosity (how dense or loose it is), fertility (what nutrients it contains) and pH (its acid-alkaline balance). Most bulbs perform best in loose soil, balanced fertility and conditions that range from slightly acidic to neutral. You can take a few simple steps to ensure optimum soil quality:
Before you set your bulbs for underground hibernation, make sure your soil has been properly prepared.
Photo Credit: ©2002 Dolezal Publishing/John M. Rickard
Choices of fertilizers abound, including organic or inorganic, natural and synthetic, liquid or dry, foliar or water-soluble formulations. Note their nutrient contents rather than the names they’re given.
Photo Credit: ©2002 Dolezal Publishing/John M. Rickard
Begin by eliminating soil-need questions by testing samples of your soil with an at-home test kit (available at garden centers) or by sending a sample to a soil lab. Once the results are in, it’s easy to improve your soil by adding recommended fertilizers or amendments.
After testing, cultivate the beds at least 1 foot deep, removing any rocks, debris and deep-rooted weeds. Use a mechanical tiller or double dig the bed – turning the earth two blade-lengths deep with a spade or shovel. Most tillers cultivate only 6-8 inches deep, so it’s important to till once, then a second time at right angles to the first pass. If you’re determined to achieve the best results, remember that deep cultivation requires considerable effort when the area to be turned is large, but it thoroughly mixes the soil.
Following cultivation, adjust the pH balance of the soil. Most bulbs prefer slightly acidic soils, in the range of 6.0-6.5 pH, and few bulbs except iris can tolerate alkaline conditions. Lower pH by adding garden sulfur; raise pH by adding garden lime. Apply pH amendments by carefully following the package-recommended rates.
The next step is to apply fertilizer and amendments, working them into the loosened soil. Bulbs need three nutrients: nitrogen (N) for foliage growth, phosphorus (P) for vitality and strength, and potassium (K) for intercellular transport of nutrients. Their content in fertilizer is expressed numerically on the package (represented as N-P-K). Use fertilizer with a 4-10-10 formulation when planting; you’ll need extra nitrogen only if it’s present in insufficient quantities. Bulbs also require micronutrients and trace minerals, including iron, magnesium and zinc, best provided through amending and mulching with organic compost.
Nitrogen is water-soluble and travels down through the soil, while phosphorus and potassium tend to become fixed where applied; for best results, mix fertilizers deeply into the soil. While traditionally used for bulbs, avoid fertilizers containing bonemeal; several scientific studies suggest that bonemeal could be hazardous and may contain infectious proteins called prions capable of causing fatal nerve disease in humans or animals. Bonemeal also may lure animal pests by its scent.
Bulbs tolerate many different soil types and compositions. The best soils are loams – roughly equal mixtures of sand, silt, clay and organic matter – with a slightly acidic pH. Regardless of the additives you may have to bring into your planting bed, the process of cultivating the soil is the same. Just take the easy steps shown in the following pictures and described in their captions.
