Confidently Forcing Bulbs - The Best Ever!
Professional growers' tips & step-by-step instructions for incredible results - EVERY TIME!
You're in luck, because it's still not too late to force some flower bulbs! There isn't too much time left, but you can still have fabulous color for your home and office if you start now.
Happily, this article is very different from your usual "forcing bulbs" article, because in typical Weekend Gardener Monthly Web Magazine style, we are going to go through all the steps from purchasing, sorting, planting, and cooling, to finally forcing the plants.
Each step will give specific, detailed tips and insights, so you get the most out of the experience.
But you may ask, "Why, force bulbs?"
The answer is: because it's easy, it's fun, and it brings magnificent color, and in some cases fragrance, into your home or office.
Plus, once you get the hang of this you can experience growing and forcing many different kinds of bulbs that you normally can't grow in your climate zone and it really is exhilarating.
Now, if you have done this before but didn't like your results, or if you have never done this before, follow along, because we've added in several professional growers' tips so you'll experience stunning results, and forcing bulbs will become a project you'll want to do every year.
Admittedly, we are writing this article at the tail end of the spring "bulb" season, but there is still plenty of time to do this project.
Next year, if you want to start earlier, we recommend that you print or save this article, and you can start forcing your bulbs in October for January flowers, November for February flowers, and December for March-April flowers.
Forcing really just means that we are going get a plant to flower at a time or under conditions that are not natural to its normal life-cycle.
We will be working with hardy bulbs that can take this kind of treatment, and depending upon when you start, you can have a succession of indoor color from January to April.
Now before we go any father, we will be using the term "Bulbs" very loosely. Many of the plants we talk about may actually be a true bulb, but others may be a tuber, a tuberous root, or a corm.
So, for clarification, we have a list below telling you which plant is what kind of "bulb".
Professional Tip: We will be forcing our bulbs in pots, but, you can also force bulbs in flats. Using flats is a great way to get huge amounts of flowers if you are planning to use them in cut flower arrangements. Some peoples' objective is to have winter cut flowers. If you had to buy winter cut flowers, the cost would be huge, so keep in mind, if flower arrangements are appealing to you, plant in flats. |
Most Common Bulbs For Forcing
Pictures of each to the right
Amaryllis - true bulb
Brodiaea - corm
Crocus - corm
Eranthus - tuber
Erythronium - corm
Fritillaria - true bulb
Galanthus- true bulb
Hyacinth- true bulb
Iris reticulata - true bulb
Leucojum vernum - true bulb
Muscari - true bulb
Narcissus - true bulb
Ornithogalum - true bulb
Oxalis adenophylla - true bulb
Scilla tubergeniana - true bulb
Tulip- true bulb
Hard to Force: Because the following bulbs require specialized techniques, and are usually greenhouse grown, we are not going to talk about growing:
Allium - true bulb
Camassia - true bulb
Scilla campanulata - true bulb
Lilies - true bulb
4 Basic Steps
Here are the four steps we will be going over:
Purchasing and maybe preliminary storage
Forcing into Flower
The key to each step is appropriate timing!
When you buy your bulbs, be picky! It's OK to demand quality because let's face it, bulbs can be pricey and you want the best you can get for your money. There is always going to be a wide variation in the quality and size of bulbs available commercially so look carefully before you buy.
Different types of bulbs are available at different times of the year, but for our purposes, we want spring flowering bulbs, because they are available in the fall from around October to December. Try and buy bulbs that are as fresh as possible and that are healthy and firm with strong growing points.
Avoid any bulbs with soft or diseased areas or insect damage. Also, keep in mind any bulbs that are much smaller than they normally should be, may not produce flowers in their first season.
Tulips should have intact skins (also called tunics) or they may be vulnerable to disease.
When purchasing, also check the label or bulb catalogs, because sometimes there will be a notation that says "good for forcing".
If you're going to work with tulips, hyacinths, and daffodils since such a wide number of varieties are available, make sure you are buying similar types, because they can be early-flowering or late-flowering, and you'll want to plant similar types together.
You can purchase at a garden center, or through catalogs, it doesn't matter as long as they are offering quality plant material.
If after purchasing your bulbs, for some reason if you can't plant them up right away, store them in a cool place 35 to 55° F (1.7 to 12.8° C). Your refrigerator is ideal for this.
If they are packed in boxes or paper bags, open them up to give them some ventilation while they rest in your refrigerator. You can store bulbs like this for several weeks, but it's better to plant them as soon as possible.
Try and remember, however, that bulbs are living plants, so handle them carefully, and try and avoid putting them anywhere they can freeze.
If you store them in the fridge, just make sure there are NO apples. Apples produce ethylene gas that can cause flowers to abort. So during preliminary cooling and later, don't have apples around!
Professional Tip: If you end up storing your bulbs for 2 or 3 weeks, remember to subtract that time from your cooling period. So for example, you have bulbs that will require 12 weeks of cooling, they will really only need 9 or 10 more weeks of cooling once you pot them up, because 2 to 3 weeks of that cooling are done.|
Deterioration of Bulb Tissue:
Use a good general potting mix; one that is has good organic content and drains really well. A good basic potting mix will have 2 parts peat, 3 parts sand, and 4 parts compost or soil.
The most important thing is having soil that has great drainage, since we don't want the bulbs to rot.
You can use either clay or plastic pots, both are good as long as they have drainage holes in the bottom. I have always used plastic because they are easier to find than clay, just keep in mind they won't dry out as quickly as a clay pot, so don't water your bulbs as often, only as needed, when the soil mix dries out.
Correct Planting Depths
The rule of thumb is that planting depth depends on the size of the bulb.
Outdoors: we would use the height of the bulb as a rough guide and plant the bulb 3 to 5 times deeper than that height, but we're not doing that.
In Pots: Ideally, bulbs should be planted in pots at the same depth as bulbs grown outside, but this isn't always possible with larger bulbs.
The solution to this problem is simple: just make sure the pot is deep enough to allow at least 1 inch (2.5 cm) of moist soil mix beneath the bulb.
I use standard 6 inch (15 cm) pots, because they allow enough room for most bulbs and can take at least 3 daffodils and up to 5 or 6 tulip bulbs, depending upon their size.
In fact, tulips and hyacinths can have their tips poking through the surface and they'll still be just fine.
When filling the pot, allow about 1/2 inch (1 cm) of space below the rim of the pot to allow for watering.
Outdoor Planting Depth:
This 6 inch (15 cm) is OK:
This 6 inch (15 cm) is OK:
Both deep enough to allow
at least 1 inch (2.5 cm)
soil beneath the bulbs:
Choose bulbs of a similar size and the same variety when you are forcing so you get regular and similar sized flowers. For crocus and other small bulbs, a 6 inch (15 cm) pot can hold up to 10 to 12 bulbs.
Place a minimum of 1 inch (2.5 cm) of soil in the bottom of the pot, and space the bulbs evenly on this. If we were planting in the ground, spacing would be the 2 to 3 widths of the bulb apart, but in pots they can be a finger width apart.
Don't press the bulbs into the soil mix, just place them, because you want to avoid compressing the soil beneath so you don't hinder root formation later.
Leave about 1 finger-width between each bulb.
Professional Tip: Position tulip bulbs with the flat side facing out; the first leaf will grow out over the edge of the pot making it look more natural.|
Continue to work soil between the bulbs and firm very gently. Small bulbs should be covered completely, but tulips and daffodils may be left with the tip of the bulbs showing if your pots are small.
Some people at this point suggest putting a layer of sand or "grit" over the top layer of soil to help with water retention or to make the pot look better - I say forget it! You don't need it, but if you want to, go ahead, it's just another step.
None! Bulbs contain enough food in them for developing their roots and flowers, so don't fertilize during the forcing process.
This is important if you intend to stagger your planting!
Many people start planting up bulbs in October for January flowers, and then continue to pot up bulbs through December for April flowers.
If you do this, great, but label your pots! Include:
The plant name
The date of planting
The date you intend to bring it indoors for forcing
This really is the critical point here, because timing is everything.
Finger Width Apart:
Most bulbs require a chilling period of about 14 to 15 weeks. You can cool them from 13 to 18 weeks depending upon the varieties you have, but keep in mind if you don't cool a late-flowering variety long enough, the stems will be short, and if you cool an early-flowering variety too long, you can develop long stems.
So read your bulb labels carefully, and clearly label your pots after planting them.
Don't worry! We'll give you a rule of thumb about this further in the article to help with this process.
Don't allow the soil to dry out completely, so check frequently. As the bulbs begin to root and grow, you will probably need to start regularly watering - remember these are living plants.
Cold Storage of Your Pots
There are 2 ways to do this, and both work great.
If you have the room, or a second fridge you can store your pots in the refrigerator. A root cellar, or a cool corner of a basement work great too. As long as the temperature remains between 35 to 45° F (2-4° C), and there is very little light, you will be just fine.
Tip: if you use a refrigerator or root cellar, just make sure you do NOT store your pots with apples! Apples produce ethylene gas which can inhibit flower development, not a good thing since we are doing everything here to get our bulbs to flower!
You can use a cold frame or cold greenhouse in a shady location.
Keep in mind, bulbs in pots are very vulnerable to cold damage, so if you live in an area that gets severe winters, pots in a cold frame or unheated greenhouse may freeze solid. You will need to take a few extra steps to protect your pots.
The best way is called "plunging" or burying your pots. Simply bury your pots in a bed of good soil mix, or bury them in a straw-lined trench in the garden covered amply with more straw for insulation. You can also insulate with loosely packed leaves.
Basically what you want is the lining and covering to be thick enough (3 to 4 inches (7.4 to 10 cm)) to prevent the pots from freezing in the middle of winter, and also to give them a dark location to allow them to form their roots.
If you intend to keep your pots outdoors, before you cover them with insulating mulch, you may want to cover the containers with fine wire mesh to keep any rodents or mice from eating your bulbs.
Plunging The Pot:
Cover with Mesh:
Bring Indoors To Force
After about 10 weeks, begin checking to see if any pots are ready to bring indoors. Early-flowering varieties typically need fewer hours of cold treatment than late-flowering varieties which can need up to 16 weeks.
So when purchasing, planting and labeling, read the plant tag and make a note in your calendar when certain pots will be ready to bring indoors.
Rule of Thumb: Typically, when pots are ready, new shoots are visible and you can see roots at the base of the container.
At this time, bring your pots into a cool room or greenhouse between 50-55° F (10-12° C), and keep them out of direct sunlight initially.
Once the shoots turn green and start to grow, move them into direct light and warmer conditions, about 60° F (15.6° C). You'll still need to water, but just keep the soil moist, not wet. It will take between 3 or 4 weeks for the flowers to appear.
Rotate your pots regularly so that all the leaves get equal light and you don't get a lopsided plant.
When the flower buds start to form and color, you can move your plants out of direct light and into bright indirect light. This will help prolong the bloom period.
At this point, you can even take some of your pots to the office for your desk so you can enjoy them at work too.
Professional Tip: If you're aiming to a specific date for your plants to be in flower and they are growing too fast, you can delay flowering by moving the plants into a cool room (40 to 50° F or 4.4 to 10° C) out of direct sunlight (but not total dark). Bring them gradually back into sunlight and warmth when you want them to start growing again.|
Professional Tip: Flowers will last longer if the containers are moved into a cool room at night.
After a bulb has been forced, you'll want to keep them, so don't throw them out.
It's true, you really can't force bulbs twice, but that doesn't mean they will never flower again. On the contrary, bulbs will naturalize in your garden, and they will flower again for many years to come.
The only difference is that they will flower on their own schedule, not yours, and they may take a year or 2 to regain their energy, but they will eventually flower for you again.
Tip: Obviously if you live in a climate that is no where near what the bulbs will need to naturalize, like a tropical environment for tulips, then they will not naturalize. Be realistic about your expectations.
Move Bulbs To Your Garden
After the bulbs have flowered in their pots, allow the flowers to turn brown, and then remove them. Meanwhile, keep the soil moist and allow the leaves to turn brown and die back.
The plant is still alive, and you need to allow the energy from the leaves to drain back into the bulb so it has energy to flower next year.
Once all the foliage has completely died back, cut it all off. Carefully dig up the bulbs out of their pots. Now you can plant them out into the garden. Just keep in mind whether the bubs need full sun or shade, and plant them in the appropriate place.
If you love to garden, and feel deprived during the colder weather, forcing bulbs indoors is definitely the way to go.
You can experience a whole new group of plants, colors, shapes and sizes that are not normally available at any other time of the year.
While tulips and hyacinths are nice, get bold and grow some fritillaria or muscari, they are stunning!
Also, don't forget to take some of your containers to the office for your desk. Nothing brightens the day like a table full of colorful spring flowers.
Good luck and have fun!
Hilary Rinaldi is a member of the National Garden Writers Association, a nationally published writer, and a certified organic grower. She regularly speaks and writes about all gardening related topics, with an emphasis on making gardening a successful and enjoyable process for anyone who wants to learn. Weekend Gardener Monthly Web Magazine concentrates of giving detailed gardening tips and gardening advice to all levels of gardeners.
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This work is licensed under a Creative Commons Attribution-NoDerivs 2.5 License.