Bulbs for Naturalizing: A Toronto Master Gardeners Guide

 

The pagoda-like flower of Erythronium or dog’s tooth violet. (Photo: Helen Battersby)

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.

Location

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

Fritillaria melaegris is the checkered or snake’s head lily. (Photo: Helen Battersby)

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. It should be noted that bone meal which contains 20-22% phosphorous should be used with caution as high levels of phosphorous are damaging to the beneficial mycorrhizal fungi in gardens with trees and shrubs. It is advisable to periodically test your soil using either a home test kit, or a professional soil testing service and add fertilizers only if the soil test indicates a deficiency.

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.

Cultural Conditions

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 a layer of compost to the surface to improve the structue of your soil.

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.

Anemone blanda, or Grecian windflower, can be found in white, mauve-pink or blue. (Photo: Helen Battersby)

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.  Be sure to replenish this after rain. Cayenne pepper, which contains capsaicin, has also be used, but as it irritates the eyes and mucous membranes of animals and humans and may harm beneficial insects, it is not recommended.

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.

Recommended Species

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

Glory-of-the-snow (Chionodoxa) reliably naturalizes and gently increases by self-seeding in the garden. (Photo: Helen Battersby)

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

Merrybells or bellwort (Uvularia grandiflora) is an under-used North American native. (Photo: Helen Battersby)

References

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

Halton Master Gardeners.  An informed approach to animal ‘pests’ in the garden. May 2020. https://haltonmastergardeners.com/2020/05/08/an-informed-approach-to-animal-pests-in-the-garden/ [see “use of cayenne pepper (capsaicin products)]

Date revised: March 2022

Prepared by the Toronto Master Gardeners, these Gardening Guides provide introductory information on a variety of gardening topics.  Toronto Master Gardeners are part of a large, international volunteer community committed to providing the public with horticultural information, education and inspiration.  Our goal is to help Toronto residents use safe, effective, proven and sustainable horticultural practices to create gardens, landscapes and communities that are both vibrant and healthy.

Statement on Invasive Plants: When choosing plants, avoid invasive plants, which can spread quickly and dominate gardens.  Invasive plants are sold by nurseries, big box stores or even at community plant sales.  Invasives may already be present in your garden.  They can invade gardens by spreading from under a neighbour’s fence or may be transported by wildlife.  For beautiful, sustainable options to invasive plants, see the Ontario Invasive Plant Council’s “Grow Me Instead – Beautiful Non-Invasive Plants for your Garden” at https://www.ontarioinvasiveplants.ca/resources/grow-me-instead/ before purchasing or accepting “gifts” of plants.

Statement on Home Remedies: The Toronto Master Gardeners do not recommend home remedies, as these have not been proven effective through scientific investigation, and may even damage other living organisms in the soil or plants in your garden.  There are other garden friendly options you can use.

If you have further gardening questions, reach us at our gardening advice line 416 397 1345 or by posting your question here in the Ask a Master Gardener section.  To book Toronto Master Gardener volunteers for talks, demonstrations, advice clinics, or other services, please contact us at 416 397 1345  or bookamg@torontomastergardeners.ca