When and How to Fertilize Amaryllis
Amaryllis (Amaryllis hippeastrum) are prized for their sumptuous, trumpet-like flowers, adding glorious color to our winter decor when forced to bloom indoors or grown in garden beds in regions with mild winters.
Although they’re often treated as a one-and-done flower, tossed out when they’ve finished blooming, these bulbs actually get better with age.
And with the right care, like fertilizing, these tropical bulbs grow larger and produce more of those sensational flowers with each growing season!
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But the timing for nourishing your plants is important. Feeding them too much or at the wrong time can result in nutrient burn, stunted growth, or yellowing foliage.
And not feeding them enough when they need nutrients can cause lackluster performance when they should be reblooming.
So if you’d like robust plants with large, vigorous bulbs that develop multiple show-stopping flowers, let’s get into the easy steps of when and how to fertilize amaryllis plants.
Start With Strong Roots
Whether you’re potting up bulbs to force them indoors or growing amaryllis out in the garden, you can feed your bulbs at planting time by mixing in a bit of bone meal to their growing medium.
Adding bone meal at planting time isn’t mandatory and your bulbs will grow fine without it, but I like to give my bulbs the best start possible.
Bone meal is ideal for encouraging the development of strong, healthy roots, as it has high levels of phosphorus.
With an NPK (nitrogen, phosphorus, potassium) ratio of around 3-15-0, bone meal not only helps with root development but it also encourages flowering – exactly what you want with these showy bulbs!
Use one teaspoon of bone meal mixed into the soil when potting up bulbs in small indoor pots and one tablespoon for larger planters or when planting outdoors.
Wait for New Growth
After the bulbs are planted, the active fertilizing phase for indoor potted plants starts with the emergence of new growth, and not before.
When you first notice new growth sprouting from the top of the bulb, I suggest using a balanced liquid fertilizer but diluted to half-strength.
I’m a big fan of the convenience of slow release fertilizers, but for bulbs planted in pots – especially small ones – I prefer liquid applications.
With liquid fertilizer, it’s easier to regulate the dosage amounts, to prevent overfertilization.
And these products provide plants with nutrients quickly, which is important for bulbs forced to bloom out of season and out of their natural environment.
After the first feeding, wait three or four weeks or when the growth is six to eight inches tall, before fertilizing for a second time, using the same half-strength solution.
When all the flowers are spent and removed, start fertilizing again following the feeding schedule outlined below in the next section.
Amaryllis can be fed a balanced fertilizer with equal NPK ratio, like 10-10-10, or a flower-boosting formula with higher phosphorus levels, such as 4-6-2 NPK.
I like to use Gardenwise Liquid Fertilizer 10-10-10, available in eight-ounce bottles from Walmart.
Water your amaryllis before feeding so the soil is moist, but not wet – plants are better able to uptake nutrients in lightly moist soil than in a dry growing medium.
Feed After Flowering
The period after flowering and before dormancy is crucial for the health of the bulb and its ability to reflower.
It’s during this post-bloom period that the leaves are actively processing sunlight into energy through photosynthesis, with the bulbs growing larger as they convert energy into sugars to store as food.
During this “green plant” phase, potted specimens should be fed regularly every two or three weeks with a liquid or water soluble fertilizer.
Water lightly to moisten the soil before feeding, then use a half-strength application of a mild, balanced fertilizer such as 5-5-5, or a flower boosting mix similar to 5-10-10.
You can also use the product recommended above, just be sure to dilute it to half-strength.
Continue to feed your plants regularly until it’s time to let them enter dormancy.
Stop fertilizing container-grown amaryllis around the start to middle of August so they stop growing in preparation for their rest period.
You can learn more about how to care for amaryllis after flowering in our guide.
In the Garden
For amaryllis in the garden, feeding starts as for indoor plants, or as soon as new growth emerges.
When your plants start growing in spring, apply a two-inch layer of compost as a top dressing over the root zone.
Or they can be fed with a slow release formula with a balanced NPK ratio similar to 10-10-10 or a flower boosting ratio like 4-6-2, scratching the granules into the surface of the soil.
Down to Earth has an excellent organic product with an NPK ratio of 4-6-2 that’s ideal for outdoor-grown amaryllis bulbs.
You can find it available from Arbico Organics in a variety of package sizes to suit your needs.
Plants can be given a second application of compost or slow release granules in early summer after the spent blooms have been deadheaded.
You can also use a liquid fertilizer if that’s what you prefer.
For liquid feeds, use a full strength application after new growth emerges and once again when the plants are six to eight inches tall.
Don’t feed again until after the flowers are spent and faded, then fertilize monthly until the beginning of August – withhold fertilizers after this point to ensure your plants stop growing before their dormancy period.
Blooming Brilliance
With their fantastic, trumpet-like flowers, amaryllis are a winter treat when forced indoors or a spring delight out in the garden!
And with the right fertilizing regime, you can enjoy their blooming brilliance for many years to come.
Remember to wait until new growth appears before you start to feed your plants and give them another dose about a month later.
After that, wait until after flowering to feed them again, then provide regular applications until it’s time for them to prepare for dormancy.
Are you growing amaryllis? Do you fertilize your bulbs? Let us know in the comments section below!
And for more information about growing amaryllis, check out some of these guides next: