The four main types of bulbs
|While fall is the main planting time for bulbs that bloom in spring, the basics apply to summer and fall blooming bulbs too. Here is a summary of bulb planting for displays that will really "turn on" your garden in spring.|
See the planting guide for common bulbs by type. Summer blooming bulbs are highlighted in Green
|Types of Bulbs|
True Bulbs have a complete (or nearly complete) miniature of the plant encased in a fleshy set of modified leaves called "scales". These usually have a papery covering called a tunic. They have a basal plate where the bottoms of the scales join together. The roots grow from this basal plate. Tulips, daffodils, lilies, and hyacinths are examples of true bulbs.
Corms are the bases of stems that become swollen and solid. There are no scales. They are often covered by tunics like the true bulbs, and also have a basal plate. Corms completely expend themselves during the growth cycles, and a new one develops from buds that appear on top of or or beside the old one. Freesia, gladiolas, crocus, and acidanthera are examples of corms.
Tubers have no tunic or basal plate, but do have a tough skin that generates roots from many parts of its surface. Corms usually have a knobby surface with growth buds or eyes from which the shoots of the plant emerge. Some tubers grow larger each growing season (e.g. begonia), and other produce new ones from the sides of the original ones (e.g. caladium). Begonia, gloxinia, caladium, and anemone are examples of tubers.
The tuberous root is a fleshy root. The food supply is in the root, not the stem or leaf as in other bulbs. The roots do not take up water themselves, they send out a system of fibrous roots that take in moisture and nutrients. They produce buds from which new plants grow, and most buds are restricted to the neck of the root where they grow on the base of the old stem. This area is called the crown. Ranunculus and daylilies are example of tuberous roots.
A Rhizome is a thickened stem that grows horizontally along or below the surface of the soil, sending stems up at intervals. They contain buds with small scale-like leaves that appear on the top or sides of the rhizome. Some like lily of the valley send up small upright detachable growths called pips which have their own roots. Canna, lily of the valley and calla are examples of rhizomes.
Buying bulbs from garden center displays can be tricky. Ordering them online is even trickier! So stick with reputable companies that guarantee their stock. You can increase your stock of bulbs by propagation methods like chipping and scaling - see the "Bulb Division" section in Plant Division and Layering.
At first, bulbs all look the same, but a discerning eye can spot the good bulbs and avoid the bad. The bigger the bulb, the better the display next spring, so look for top size bulbs, which are the largest commercial grade. The bulb should feel very firm. Lily bulbs should not have very loose scales, they should be very fleshy and tightly packed. Tuberous roots should not be shriveled, except for their fibrous feeder roots which may be attached, but fleshy as well.
Avoid bulbs that show any signs of disease or damage. The skins or tunics should be intact. Missing papery covering on some bulbs like gladiolas and tulips are not a problem. I often remove the papery coverings to check for damage or disease signs.
When selecting bulbs in fall for spring bloom, avoid any that have sprouted. In spring, when purchasing summer blooming bulbs, it is often difficult to find those that have no signs of sprouting. Select the ones with the least growth showing, and get them into the soil as soon as possible.
There are two key things to consider when arranging your bulbs for best planting displays: plant height and time of bloom.
Arranging by height avoids hiding the small plants behind larger ones. Small, front-of-the-border bulbs: garden snowdrop, dwarf iris and Siberan squill. Mid-range (12 to 24 inches tall) bulbs: allium, hyacinth, narcissus and tulips. Back-of-the-border bulbs (reaching heights of more than 24 inches): tulips (single and double lates and Darwins), crown imperial 'Rubra Maxima' and allium, giant ornamental.
To ensure a long display of bloom, plant a variety of early, mid-season and late bloomers.
Early bloomers: crocus, eranthis, anemones, muscari, early-blooming narcissus such as 'February Gold' and Iris reticulata. These tiny but mighty bulbs can even be planted under deciduous trees because they bloom before the trees leaf out and shade the garden.
Midseason bloomers: mid-season narcissus and tulips, with a colorful and fragrant backup by the sturdy hyacinth.
Late bloomers: Dutch iris blooms in striking blues and purples and forms lovely clumps of lance-like foliage, star of Bethlehem's starry white blooms look great paired with the blue-hued Spanish blue bells, Allium christophii and ornamental allium with their purple, round heads.
|Depth and Spacing|
The rule of thumb is to plant the bulb 3 to 5 times deeper than its height. Large bulbs can go in at 3 times deeper and small ones at the 4 or 5 times deeper range. There are a few exceptions to this rule. Check the bulb chart for more information.
Dig an appropriately sized hole to hold your bulbs. Place your bulbs in the hole with the growing tip facing up. Place the bulbs in a random fashion so they will they look more natural when they start to grow. If one or two bulbs fail to grow, there won't be obvious holes in your design. Planting them in clumps of 3-7 is very effective. Space them at least twice as far apart as their diameter.
Add superphosphate or bonemeal at the time of planting to the bottom of the planting hole or area. Work this into the top inch or two of soil in the base of the hole with a hand fork gardening tool. Superphosphate is more immediately taken up by the bulbs' roots in spring.
Tools for Planting
Depending on the size of bulb and where you are planting them, you may use a number of tools and methods. For new beds, use a shovel to dig out the planting area. For a few larger bulbs here and there, use a hand bulb planter, or a long handled one (to save your back and wrist). For small bulbs, use a hand trowel or dibble to make the holes. Better quality versions of these tools come with the inch depth markings on the digging surfaces, so look for that when selecting tools.
When planting a new bulb bed in the open garden, use galvanized or aluminum chicken wire fencing over the planted area. I prefer to put this near the surface rather than right over the bulbs before covering them with soil. This makes it easier to get at the bulbs when division is required, because it won't get entangled with them. If you are naturalizing your bulbs, then go ahead and lay the wire right above the bulbs.
For your most precious bulbs, and to protect from burrowing moles and voles, create a chicken wire basket in which you lay the bulbs and then lower this into the planting hole. For more tips on protecting bulbs, check out the Critter Problems page.
Covering with Soil and Firming
Cover the bulbs with soil and firm into place with the flat side of a rake. Water well and mark the area where they are. This is important if you plan to do transplanting in the area later in fall, and to know where they should be come spring!
|Planting Bulbs in Lawns|
To plant single bulbs in your lawn for naturalizing, use a dibble for small ones or a bulb planter for larger ones. Arrange the bulbs on the lawn in the places where you will plant them. Remove the plug of sod from the hole to be dug first, and set it aside, then make the hole. Place the bulb in the hole and refill the planting hole with soil. Replace the sod plug and water in well.
To plant a collection of bulbs in an area in your lawn, cut through the sod in the shape of the area you wish to plant. Peel back the sod to the sides. Dig out the soil to the depth required for the bulbs you are planting, and pile it on some plastic beside you. Place the bulbs as described above and refill the planting area with soil. Water in well. Replace the sod, tamp it down and water again.
|Planting Bulbs in Layers|
Planting bulbs in 2 or 3 layers is effective for a long period of bloom. Think of it as a lasagna! Bulbs of the same type when planted deeper will come up later than the ones planted more shallowly. Layers can also be used to plant smaller bulbs so they come up between the larger ones planted more deeply. When planting in layers, leave at least 4 times their diameter in space between the bulbs. See how to layer bulbs in containers too!
Place your largest bulbs in the deepest layer. Cover with a layer of soil, and place the second layer. Cover these with another layer of soil and place the last layer. Cover all with soil, firm and water in well.