The four main types of bulbs
True Bulb |
Rhizome |
Corm |
Tuber |
Depth
Chart |
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. |
Selecting
Bulbs
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. |
Arranging
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. |
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Feeding
Bulbs
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.
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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.
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Protecting
Bulbs
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.
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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.
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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.
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Avoid
diseased or damaged bulbs.
Avoid sprouted bulbs.
Plant
tall bulbs at the back of the border and shorter ones in
front. Use a nice mix of early, mid-season and late
bloomers.
Plant
bulbs 3-5 times deeper than their heights and in random patterns
and space at least twice as far apart as they are wide.
Add
super-phosphate or bonemeal to the base of the planting hole and
work into the soil.
Down
the left are the hand trowel, dibble and hand bulb
planter. The long handled bulb planter is at right.
Cover
newly planted bulbs and container plants with 1-inch mesh
poultry wire over the plantings. Soak bulbs in squirrel
repellent before planting. Apply repellents to tops and sides of
containers.
Cover bulbs with soil.
Firm soil with rake and water in well.
Arrange the bulbs and plant one at a time.
Peel
back the sod to plant.
Return
the sod, tamp down and water. 
Arrange the bulbs and cover with layer of soil.
Add
layers and cover with soil.