How to Grow Amaranthus for the Cutting Garden
Amaranthus - also known as the shortened ‘amaranth’ is a really cool cut flower. Grown originally as a food source (the leaves, young stems and shoots, flowers and seeds are all edible), it has recently come into vogue for being one of the ‘ancient grains’ - a non-wheat related grain that is very nutritious and also naturally gluten free.
However, it’s not the garden variety of amaranthus that we’re after (which is actually similar to Palmer amaranth aka pigweed - a noxious and pokey species that does particularly well here). We are instead interested in the amaranthus that have giant plumes, tassels and spikes of burgundy, gold, lime green and faded coral that look excellent in the vase and in the garden.
Distantly related to celosia and gomphrena, amaranthus is also similar in that it loves the heat and full sun and is a very vigorous plant - growing well above your head with giant flowers that are three to four feet in length sometimes! It’s a very fantastic plant.
Selecting Your Variety
Amaranthus comes in three forms:
Plume (such as ‘Hot Biscuits’ or ‘Velvet Curtains’)
Hanging or tassels (such as the quintessential red ‘Love-Lies-Bleeding’)
Spike (such as ‘Elephant Head’)
Personally I don’t find the spike forms to be very attractive, nor easy to use in floral designs, but to each their own! I instead prefer the plumes and hanging varieties to be much more attractive and useful in design, so we grow solely those two varieties.
PLUME VARIETIES
Plume varieties grow mostly upright, forming a giant broomstick-like stalk that is topped by a giant plume that is anywhere from 24-36” in height. This is quite the spectacular sight to see in the garden, and is a lot of fun to use in floral arrangements. Our favorite variety is ‘Hot Biscuits’ for the lovely golden-rust tone of its seedheads and elegant foamy texture of its plume, but we also like ‘Velvet Curtains’ that is the deep red-burgundy version.
HANGING VARIETIES
Hanging or trailing amaranthus varieties also form a big stem, but then the flower heads start to form. Instead of developing into upright plumes, the flower heads then continue to grow, extending downwards sometimes as long as four feet in length, weighing down the plant in their beautiful draping flowerheads. An old florist standby is the light-green ‘Emerald Tassels’ along with the regular ‘Love Lies Bleeding’ but
our personal favorite is ‘Coral Fountain’ - a lovely faded rust-pink coloration that is a stunning muted shade that goes well with soft, muted color palettes.
2. How to Start Amaranthus from Seed
Amaranthus is very very easy to start from seed as long as you give it two things that it loves - light and heat.
Start amaranthus on top of the soil (and don’t cover since it does need light to germinate). And as far as heat, amaranthus sprouts very quickly if you keep it warm at 70+ F, usually around 24-48 hours for us.
Now here’s the tricky part - you want to make sure you get amaranthus into full sun as quickly as possible, otherwise you’ll end up with leggy, thread-like sprouts that will flop and do terribly. Generally speaking, plants that are warm season annuals should be in as much light as possible as early on as possible, otherwise they get leggy and unruly.
The best way to start amaranthus is to direct sow it where you want it- but I realize that’s not feasible for everyone, so if you are starting them in plugs or soil blocks I would recommend starting them off in full direct sun if you can - this will make it similar to direct sowing on the soil and help to keep your seedlings small, stocky and healthy.
3. Cultivating Amaranthus
Amaranthus is pretty easy after you’ve got seedlings in the ground - with enough heat and sunlight, it will be one of the lowest maintenance plants you can grow in the garden. Seriously, it will just start shooting up into a big and tall plant, seemingly rocketing up overnight to take advantage of the warm growing season, and if you keep giving it water and nutrients it will continue to grow just as explosively.
If growing in the garden, we place amaranthus at the back of the border because they get so large and tall. If we’re growing in a row for cut flowers, it’s advisable to stake or net the plants to prevent them from toppling over when they get larger. We recommend spacing 12-18” apart to give the amaranthus room to grow and spread out - and don’t plant them by anything that might get shaded out.
If you want a few large and fabulous flower heads you don’t need to do anything - just let amaranthus do its thing. However if you are planning on using them in floral design (or selling them to florists) you may want to consider pinching your plants. Pinching - when you take off the top of the growing tip of a young plant - forces the plant to start putting energy into sideshoots as opposed to the one single stem that they were growing previously.
Pinching amaranthus at about 6” will allow for it to produce multiple smaller flowerheads that are better incorporated into designs and bouquets, with stems more like pencil-thickness as opposed to broomstick-thickness. You will also have far more flower heads as well, giving you an even larger harvest from each plant.
The main issues we have with growing amaranthus are two.
First, flea beetles love amaranthus for some reason. They will specifically target amaranthus it seems, chewing multiple little holes all over the leaves and turning them into lace-like leaves. Luckily the flea beetles don’t effect the flowerheads at all, and when harvesting you’ll strip the leaves off the stems anyway since they don’t keep well. However, you can help to prevent this by covering your amaranthus when young with row cover to physically prevent the flea beetles from getting to them.
Secondly, amaranthus is a major major allergen for me - it will cause my hayfever allergies to become very severe, very quickly. It’s one of the reasons why we grow less of it now, as it is seriously so bad for me that I have issues breathing if I’m outside and the pollen blows into my face. I’ve actually harvested using a paint respirator before, which seems silly but helped a lot, so if you’re one of those people who are allergic to amaranthus, use a mask or bandana to cover your face.
4. Harvesting Amaranthus
Amaranthus grows pretty quickly, soon sending out its flower heads. The flower will start to emerge from the center of the stem in the the leaves and will grow larger with time - either into a large plume or a trailing head depending on the variety.
The nice part about the flower heads is that they will continue to grow and get longer until you harvest them. For example, if you’re growing a hanging amaranthus, let it continue to grow until it reaches your desired length.
To harvest, we recommend harvesting in the early morning or late evening when the temperature is coolest and the sun is not directly shining on them. If you’re cutting a single large head, I recommend cutting it back to about to two feet from the ground so that it can grow a few smaller, shorter heads (you can do this alternatively instead of pinching it back). If you’re cutting a single, smaller stem, just cut it back to the main trunk of the plant.
Make sure that you strip the leaves off - the leaves will get wilty very quickly, and can actually cause the entire stem to go floppy if you allow them to remain. I also don’t really enjoy the look of the leaves - it looks weedy in a bad way, so just get rid of them and get a clean stem for designing with.
Designing with Amaranthus
Amaranthus really adds a fun dimension to arrangements. Neither a filler nor a spike nor a trailing element but somewhere in between all of those, they can really add some drama to arrangements. Amaranthus is also pretty long-lived in the vase of usually about 5 days or so - just be careful because the big-flowered and thick-stemmed flower heads can really suck up water very quickly!
If using plume varieties, we utilize them usually as filler. The golden-hued ‘Hot Biscuits’ works very well for this, appearing as an elegantly curving cloud coming from arrangements, tucking in neatly between other floral materials. You can also use it as a vertical spikey element too, depending on the shape of the flower plume - strip off some of the lower parts of the flower to expose the stem and highlight the linear form.
If using hanging varieties, we use them as a cascading, trailing element that works fabulously off the side of a compote or urn arrangement. Footed, tall containers show these off very nicely, with the amaranthus spilling over the sides and falling through the flowers like cascading water or streamers.
You can also use them in installations - one of the most stunning hanging arrangements I’ve ever seen was a single bar of red and green hanging amaranthus that formed a very striking and structurally powerful display. If you’re using the hanging amaranthus they technically don’t need a water source, which means you can treat them as a grass seedhead and place them in situations that you might not be able to compared to materials that need a water source.
Amaranthus also dries wonderfully, and so long as you keep it out of direct sunlight it will keep its color, albeit a bit faded and less intense. Make sure to hang it upside down to get a straight form from the plume varieties, while if you’re wanting to capture the hanging or cascading form make sure to drape it down into the direction you want first.
I hope you’re as excited about amarathus as I am
Whether you’re growing it for the back of the border or to use in floral arrangements, amaranthus is such a hardy and easy plant to grow that really lends a texture and presence that is quite unlike anything else in the cutting garden or flower farm. So long as you give it heat and light, it will grow well for you, giving you plenty of enjoyment and beauty all season long.
How to Grow Castor Bean (Ricinus) in the Garden and for Floral Design
The Glory of Zinnia Haageana (Aztec, Jazzy and Other Small Zinnias)
How to Grow Gomphrena (Globe Amaranth) for the Cutting Garden
And if you’re interested in growing cut flowers as a business - whether that’s selling at a roadside stand, a CSA, at a farmer’s market, to florists or for your own design work, check out our eBook bundle for flower farmers!
