Spring flowering bulbs add colour and interest to an area as they often bloom earlier than other flowers. Some add fall colour. This gardening guide provides information related to choosing and growing ornamental bulbs that naturalize easily. The information applies to true bulbs, corms, rhizomes, tubers and tuberous roots. They are considered together because they all produce plants from swollen storage organs and all have the ability to naturalize, spreading readily from a single plant into many plants over time.
Plant bulbs in grass, meadows, in beds amongst later blooming plants, or around the base of deciduous trees. The chosen location should provide enough room for these plants to colonize.
If you mow your lawn frequently use early flowering spring or fall flowering bulbs. The grass grows more slowly in the early spring and fall so the bulbs and grass do not compete as much for nutrients and water. During this time the lawn also does not have to be mowed as often thus allowing the leaves of the bulbs to mature. The bulbs’ leaves supply them with nourishment that will enable growth the following year and generally should be left untouched for about six weeks. However, a few small bulbs complete their life cycle more rapidly (e.g. Eranthis byemalis, Chionodoxa, Scilla, Crocus and Galanthus). A shortened life cycle allows the grass to be cut within one month.
Plant large leaved bulb plants where the leaves will be hidden as they die down, particularly if used in an ornamental bed.
How to Plant
As a general rule bulbs should be planted at least two to three times as deep as the diameter of the bulb. This can vary with soil type. In heavy soils that are not amended it may be better to plant bulbs more shallowly and in light soils it might be wise to plant them more deeply. In colder areas plant more deeply and mulch.
Make sure that bulbs are planted in well-drained soil. After flowering bulbs need drier conditions and often excess moisture, necessary for other annuals and perennials in a border, may affect the development of next year’s flower buds, at the time when the bulbs should be drying out.
At planting time you can add bone meal (a natural phosphorus product that is mild and slow acting) or a fertilizer high in phosphorus (the middle number). It is a good idea to water if the soil is unduly dry.
Bulbs may be hand tossed and planted where they land to create a natural effect. It is not wise to do this with small bulbs, as they may be lost, nor is it wise to do this with a large number of bulbs because this can result in a haphazard planting with little visual appeal.
For larger numbers remove a strip of turf, place a group of small bulbs on the soil and recover them with the turf. Larger bulbs should be planted more deeply using a trowel or bulb planter either where the turf has been removed or directly through the turf.
Plant bulbs in groups to produce a solid block of colour. Avoid using too many different varieties in one location because this can create a somewhat chaotic effect.
Light requirements will vary but bulbs will not thrive in dense shade. Check preferred light conditions when choosing a bulb. The preferred light condition is noted for the species listed below.
Bulbs prefer a loamy well-drained soil but conditions must not be overly dry. Waterlogged soil leads to rotting of the bulb. Never plant in newly manured soil as the acidity in the manure could burn the newly emerging roots and shoots. If the soil is clay based, amend it by adding coarse sand and/or compost to improve the drainage.
Because bulbs are often planted in ‘natural’ or less formal locations their maintenance is similar to growing bulbs in the wild. No maintenance is necessary, assuming that their leaves are allowed to die down naturally.
Considerations Related to Choice
Strong and healthy bulbs are less likely to produce plants that succumb to bacterial and fungal infections. Healthy plants are also more able to withstand attack by pests. When buying a bulb make sure it has no soft spots, is hard to the touch, and has no outward signs of physical damage.
Colour, height and form are personal choices. If you are naturalizing in a mowed lawn, choose early, small spring flowering bulbs that will have matured before the lawn needs to be mowed in the spring. If you plan to plant an uncut meadow, larger bulbs, such as Narcissus species, may be chosen. If you plan to plant in a sunny border, you may wish to choose bulbs that will die down quickly or can be easily hidden by later emerging perennials. If you wish plant under a deciduous tree, choose bulbs that flower early before the tree leafs out, or choose ones that tolerate semi shade conditions.
Pests and Diseases
Bulbs used for naturalizing rarely have disease and viral problems.
Large pests such as squirrels, moles, voles, cats, dogs, and deer can be a problem. There are many recommended remedies. To repel rabbits sprinkle blood meal over areas where bulbs have been planted or have sprouted. This is a nitrogen fertilizer and quite harmless but this can attract carnivorous animals. Cayenne pepper can also be used but is an irritant to eyes and other mucous membranes of animals or humans. Both of these substances have to be replenished after rain.
Metal or plastic screening or mesh, often the most effective deterrent, can be placed around the bulbs or on top of the ground after planting, to prevent animal damage. Fishing line, strung around the planting area, fencing of adequate height or tomato cages placed over plants, may deter deer. There are also commercial products sold as deterrents for deer.
Following is a list of some bulb plants that naturalize well. The type of bulb, time of bloom and preferred light conditions is provided.
Anemone blanda (Windflower) tuberous root, early spring, sun
Camassia species (Camas) bulb, late spring, sun or partial shade
Chionodoxa (Glory-of-the-snow) bulb, early spring, sun or partial shade
Colchicum species (Meadow Saffron) corm, spring or fall, sun
Crocus species and hybrids (Crocus) corm, spring or fall, sun or light shade.
Eranthis species and hybrids (Winter aconite) tuber, early spring, sun or light shade
Erythronium species (Dog tooth violet, Trout lily) corm, early spring, semi shade
Fritillaria species, bulb, spring, partial shade
Galanthus (Snowdrop) bulb, early spring, sun or shade
Leucojum (Snowflake) bulb, spring, sun or partial shade
Muscari species (Grape hyacinth) bulb, spring, sun
Narcissus species and hybrids (Daffodil etc.) bulb, spring, sun
Ornithogalum species (Star of Bethlehem) bulb, spring, sun or partial shade
Scilla species (Siberian Squill) bulb, spring, sun or partial shade
Uvularia grandiflora (Merrybells) rhizome, spring, partial shade
Scheider, Alfred F. A Park’s Success with Bulbs. Greenwood, South Carolina, U.S. A.: George. W. Park Seed Company, 1981
Mathew, Brian. Growing Bulbs. Portland, Oregon, U.S.A.: Timber Press, 1997.
Rockwell, F.F., Grayson, Esther C., Dietz, Marjorie J. The Complete Book of Bulbs. J.B. Lippincott Company, Philadelphia & New York, U.S.A 1977
Date revised: November 17, 2007
For printable version, click: Bulbs for Naturalizing – A Toronto Master Gardeners Guide
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