Forcing Bulbs Indoors

By: Brent, Co-Owner, Brent & Becky's Bulbs

How to Force Bulbs Indoors
How to Cool Bulbs for Forcing Indoors
Growing Bulbs Indoors
How to Keep Your Bulbs From Getting Too Tall
Best Bulbs for Forcing Indoors

Some of our favorite plants in the gardening world are those started from bulbs. With brilliant displays of beautiful blooms and unique appearances, we love adding them to our gardenscape, so it’s no wonder that we want to bring them into our homes, too.

How to Force Bulbs Indoors

There are two ways to look at forcing bulbs, and it all comes down to the two different types of bulbs: those that require cooling and those that don’t.

Bulbs that require a cooling period to grow will typically come from mountain climates in the Northern Hemisphere with cold winters before they grow, and need a cold sleep before growing. Bulbs that don’t require cooling will natively come from warmer climates that don’t naturally see a frosty winter, so they won’t need to cool to grow.

How to Cool Bulbs for Forcing Indoors

This starts with vernalization - the cold winter hibernation that comes just before the growing season. To replicate this, we’ll need to equip them for the cold by getting them rooted. They’ll root best and quickest in soil between 50-60℉. Give them about 2 weeks to fill the pot with roots, and they will be all set for their cold slumber.

Once rooted, bring the soil temperature down to about 35℉ or below for as long as they need - 8-12 weeks for early season bloomers, 12-14 for mid-season, and 16 for late. This cooling can be done in a cold storage room or garage, or even in the refrigerator - as long as it’s the beer fridge. Remember, the ethylene gases given off by fruits and veggies can cause bulbs to abort their blooms.

If your fridge space is at a premium, you can also try dry cooling. This process is actually quite simple - simply place your dry bulbs straight into mesh bags and drop them in the crisper drawer. When they’ve had their time to cool off, take them out to root (again, at 50-60℉), and they should be ready to force!

If the cooling process doesn’t sound like your thing, don’t worry, you can still grow your favorites at home. Pre-cooled bulbs can be purchased from our online store and can be forced quite easily. Just remember to pot them quite quickly after you get them or they’ll lose the effect of their cooling.

Growing Bulbs Indoors

You’ll want to plant your large bulbs about 10 to a pot and your smaller bulbs shoulder to shoulder for best visual appeal. Plant them with about 3x their height in soil underneath them and cover them about ¾ of the way with the pointed tip exposed.

Temperature: Bulbs will typically root best in soil temperatures between 50-60℉. Once rooted, to get them to bloom quickly, you’ll want to raise the soil temperature to about 70℉ to encourage growth. A great way to do this is to place your pot on a seedling heat mat. You can also try turning up the thermostat, but this can make the air quite dry, so that’s better left at 68℉ for longer-lasting performance.

Water: To get your plant ready to grow, you’ll want to get the soil good and moist with slightly warm water so as not to shock the roots. Don’t water again until the soil either dries out quite significantly about an inch deep or it actively starts growing. Then, you’ll want to water a tad more frequently - about once a week - and when your plant is ready to bloom, you’ll want to increase that to about once every day or two.

Fertilizer: Too much nitrogen is like an energy drink for a bulb that causes them to grow more foliage and fewer blooms. It also causes cellular stress, which makes them more susceptible to fungal diseases and more interesting to insects and pests. When it comes to fertilizing bulbs, you want to use an all-natural soil fertilizer that is bulb-related, like Espoma Bulb-tone. Spread it on the soil just after blooming to add a boost to next year’s blooms.

If you want to keep your bulbs going, you can plant them out in the garden after the danger of freezing has passed. This adventure back into nature will allow their leaves to soak up the sun to recharge their batteries. Spring bulbs can stay out for next season, but warmer climate bulbs will need to return inside to bloom again. Dig them up in September and let them dry off. After their leaves have dried and fallen, give them a 2-month rest in a cool place - about 50-60℉ - and they’ll be ready to start again!

How to Keep Your Bulbs From Getting Too Tall

The biggest issue with forcing bulbs indoors is that we are forcing plants that like to grow in sunlight out in nature to now grow in the heavy shade of the indoors, instead. This often creates an issue where they grow too tall or lopsided as they stretch toward light sources that are too far away from them. To prevent this, you’ll need to substitute in a good light source. The best lights are cool fluorescent, LED, or grow lights kept about 1 foot above the pot to keep them nice and short.

In nature, these plants are used to having air movement, which also prevents them from overgrowing. To mimic this in the house, place a small fan nearby to blow on them while they’re growing and that should help them to hunker down.

I once had a customer tell me that the best way to keep your indoor bulbs from growing too tall was to “just given them some gin.” At first, I just thought maybe she had just nipped a bit that morning, but then I became curious - so I tried it on my bulbs at home. Sure enough, I killed them - but only because I gave them too much. A study done at Cornell actually has proven that a 10% solution of alcohol can stunt a bulb plant’s growth. It does this, though, by burning tender root hairs, which makes for a less durable plant that won’t last as long. Although it’s an interesting experiment, I’ll stick to my cool lights and fans.

Best Bulbs for Forcing Indoors

Tulips are, as Becky calls them, “the parrots of the bulb world”. They are incredibly beautiful and come in so many amazing colors, shapes, and sizes. Early blooming varieties will perform much better when forced than late, and as spring bloomers, they will require cooling to grow.

Hyacinths are spring bloomers that perform quite well when forced and can even be grown in specialized vases that don’t require soil. Set them atop a bed of pebbles or seashells and fill with water just to the very tip of the root hairs and watch them grow!

Narcissus, also known as paperwhites, are excellent bulbs to force indoors and don’t require any cooling. Paperwhite ziva is a particularly popular variety with brilliant white buttercup blooms on tall stems. They bloom quite quickly - as soon as 2-3 weeks after starting - and are the most fragrant (which some people love, but others will check the bottom of their shoes to see what they’ve stepped in).

Hippeastrums, also known as amaryllis, are a popular bulb in the holiday season, as they are quite easy to force by Christmas time - perfect for gifting. Growing the fall season of the Southern Hemisphere (our spring), they are quite ready to get going at this time of year. So, while they don’t require cooling, you may wish to keep them refrigerated to prevent them from sprouting sooner than you’d like.

Oxalis, which we might know better as shamrocks, are great choices for forcing indoors that don’t need any cooling. As natural shade-lovers, they make wonderful houseplants, lasting most of the year, so long as they aren’t overwatered.

As beautiful as our bulb blooms are, it’s easy to see why we’d want to capture that beauty indoors, as well. To learn more about forcing bulbs or to get an idea of how to plan your bulb arrangement, check out the Living Flower Arrangement workshop on our site for care instructions, recipes, or to find a class happening near you!

- Brent, Co-Owner, Brent & Becky's Bulbs

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