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  4. How to Force Bulbs Indoors (including Hyacinths and Narcissi)

How to Force Bulbs Indoors (including Hyacinths and Narcissi)

Indulge in the beauty of classic hyacinths, stunning amaryllis, fragrant daffodils, and intricate double tulips by growing them from bulbs indoors. This allows you to relish spring’s vibrant hues and delightful scents, even when it’s far on the horizon. Successful indoor bulb growing requires careful planning. It’s important to note that there are two categories of bulbs for indoor cultivation: those requiring chilling and those that don’t.

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Types of Bulbs to be Forced

Bulbs That Don’t Need Chilling

Bulbs originating from tropical regions don’t necessitate a chilling phase to initiate flowering. Amaryllis and Paperwhite Narcissus fall into this group.

Bulbs That Need Chilling

Certain bulbs that bloom in spring need a period of chilling before they can flower. This category includes tulips, daffodils, hyacinths, crocus, Dutch iris, and scilla. Exposure to extended cool temperatures triggers a biochemical response within the bulb, initiating the development of the embryonic flower. Most bulbs necessitate 16 to 18 weeks of cold for the flower to fully form. Once this stage is reached, they are prepared for exposure to light and warmth. Cutting short the chilling period may result in the emergence of flowers, but they are likely to be stunted and deformed.

This method of encouraging early indoor bloom in bulbs is commonly referred to as “forcing.” The easiest bulbs for this process are crocus, hyacinths, muscari, and mini-daffodils. Tulips and standard daffodils can also be forced, but they require more careful attention.

Chill in SeptemberBloom in January
Chill in OctoberBloom in February
Chill in NovemberBloom in March
Chill in DecemberBloom in April

How do you force indoor bulbs?

Accelerate the blooming of your spring-flowering bulbs by manipulating their exposure to light and temperature. Place the bulbs in the refrigerator, ensuring they chill at around 4 degrees for approximately 10 to 15 weeks. This chilling period mimics winter, providing the necessary cold for proper flowering. Store the spring bulbs in darkness, using an opaque bag to contain them. Similarly, you can force summer-flowering bulbs, but refrain from chilling them before potting up, as they do not require a cold period for flowering or growth.

Pro Tip: When handling bulbs, consider wearing gloves to avoid potential skin irritation from certain varieties.

Where should I plant my forced indoor bulbs?

Plant your forced indoor bulbs in decorative pots with a sturdy base, using peat-free bulb compost. A dense potting mix, enriched with grit, will provide stability and support as your bulbs grow top-heavy with flowers. It also enhances drainage, preventing the bulbs from sitting in waterlogged soil. Unlike outdoor planting, the depth is less critical for forced indoor bulbs, so feel free to expose the bulb slightly or opt for a shallower container. For pots with drainage holes, use peat-free multipurpose compost, while containers without drainage benefit from bulb fibre, designed to retain water without becoming overly soggy.

After planting, water the bulbs and relocate the containers to a cool, dark, sheltered space. Cover the surface with newspaper to block any light from reaching the soil. Once shoots emerge, transfer the containers to a well-lit indoor area. Ensure that the bulbs establish robust root growth at the pot’s base before moving them into warmer conditions. Underdeveloped roots can lead to stunted top growth and undersized blooms. When displaying your bulbs, avoid areas near dry heat sources such as radiators, and monitor soil moisture levels to prevent the compost from drying out.

Forcing Flower Bulbs In Water

Cultivating bulbs indoors in water offers a simple method to relish early spring blossoms. While the process is straightforward, ensuring the right chilling duration and selecting robust, sizable bulbs are essential for success. A handful of materials, fresh water, and your preferred bulbs are all you need. Keep in mind that not all spring bulbs are suitable for forcing, but experimenting with daffodils, tulips, hyacinths, and crocuses can yield delightful results.

Even when growing flower bulbs in water, subjecting the plant to cold is crucial to prompting the embryo to break dormancy as temperatures rise. Place the bulbs in a paper bag in the refrigerator to simulate an early release from dormancy.

Bulbs growing without the supportive structure of soil may tend to droop, diminishing the visual appeal. To prevent this, use a container with a height equal to or greater than the anticipated flower stalk length. While a transparent container adds a fun element, allowing observation of root and shoot development, any vessel that supports leaves and stems while holding water will suffice. Hourglass-shaped vases designed for facilitating bulb growth provide stability and an attractive presentation.

Position the container in a well-lit, indirectly illuminated room, monitoring root development and adjusting water levels as needed for the root zone. As leaves and stems emerge over time, transfer the plant to a brighter area with temperatures at least 18 degrees Celsius. Rotate the vase periodically to encourage straight stem growth, preventing leaning towards the sun. In most cases, bulbs will bloom within 2 to 3 weeks following their chilling period.

What should I do once my forced indoor bulbs stop flowering?

Once the flowering period concludes, you have the option to transfer the bulbs to an outdoor garden for them to naturally recede and bloom again next year. Alternatively, if outdoor space is limited, you can dispose of them. It’s worth noting that, with the exception of Amaryllis, attempting to force these bulbs to bloom indoors for a second time is not feasible.

To encourage future outdoor blooming, remove the flowers before the plant invests energy in seed production. Allow the foliage to naturally wither completely. Once the foliage has turned brown, detach and relocate the bulbs to a dry, cool environment. Plant the matured bulbs in your garden and look forward to a vibrant display the following spring or summer. For more detailed information, refer to our guide on cultivating spring-flowering bulbs.

Which are the best bulbs to force indoors for a winter display?

Most common outdoor bulbs, whether spring or summer flowering, can be successfully forced indoors. Here are the top five spring-flowering bulbs recommended for forcing during the winter:

Hyacinths

Renowned as classic indoor bulbs, they feature attractive straplike leaves and highly fragrant, dense flowering spikes. Plant these bulbs with half of the tops exposed, utilizing moss or grit to pack around the bulb tops. If working with unprepared bulbs, store them in the fridge in a bag for 4 to 6 weeks before planting. Create aesthetically pleasing containers filled with hyacinths in white, ‘Delft Blue,’ and pink for a superb flowering display, emitting a delightful scent throughout the house.

Daffodils

Available in various shapes and sizes, serve as ideal indoor bulbs. Opt for a compact dwarf variety such as the popular ‘Tete a Tete’ for a neat and concise display. Plant prepared Narcissus papyraceus bulbs for a traditional display and intoxicating scent during the festive season – these ‘Paperwhites’ take half the time between planting and flowering compared to other narcissus. Chill ordinary daffodil bulbs for 9 weeks before potting up to ensure a robust flowering display.

Crocus

Boasting shorter foliage and flowers, making them a suitable choice for smaller spaces. Despite their compact size, these bulbs provide vibrant colors, enhancing your home during the winter. Plant the bulbs closely together in a wide and shallow decorative container for a dense flowering display. Chill unprepared bulbs for 8 to 10 weeks before planting them in their final containers.

Amaryllis

Producing an impressive display, with high-quality bulbs yielding 2 to 3 stems, each adorned with 4 or 5 flower heads. Amaryllis is easy to force indoors as it does not require a chilling period. Plant the bulbs in mid-September for a Christmas display, opting for classic velvety red or a variegated type like ‘Appleblossom’ with an RHS award of garden merit. Plant amaryllis in a snug container to compact the compost around the roots. Unlike other bulbs, amaryllis can be forced year after year for a recurring Christmas display.

Tulips

Tulips demand an extended period of cold before being forced indoors, necessitating chilling the bulbs for 14 to 20 weeks to ensure robust flowering. The wait is worthwhile, as tulips offer scented blooms, large double flower heads, and captivating color combinations. Consider a dwarf tulip variety for a compact display or experiment with mixing tulip bulbs for intriguing color combinations.

Bloom Time
Amaryllis
Crocus8-15 weeks2-3 weeks to bloom after chilling
Daffodil2-3 weeks2-3 weeks to bloom after chilling
Grape Hyacinth8-15 weeks2-3 weeks to bloom after chilling
Hyacinth12-15 weeks2-3 weeks to bloom after chilling
Iris13-15 weeks2-3 weeks to bloom after chilling
PaperwhiteNone3-5 weeks
Snowdrop15 weeks2 weeks to bloom after chilling
Tulip10-16 weeks2-3 weeks to bloom after chilling

Updated on February 7, 2024

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