As you are planning your garden, hidden away, pouring over your stash of newly arrived seed catalogs. You are staring at vegetables, flowers, fruits, and all things “seeds”. Don’t even bother to deny it; I know how it is because I’m doing it, too.
In fairness to you, if everyone would leave you alone with your obsession and not expect you to make lunch or fold laundry, you wouldn’t have to resort to hiding.
Well, you’re among friends here and while you’re scribbling away at your seed list for the coming year, I would like to make a suggestion for something to try in your garden. You should grow Russian Mammoth sunflowers.
Russian Mammoth Sunflower Specs
|Zones 2 through 11
|10 – 12 feet (3 – 3.6 meters)
|1 inch depth
|5.5 – 7.5
|downy mildew, rust, wilt, and rot
|3 – 4 inches (7 – 10 centimeters)
What Are Russian Mammoth Sunflowers?
Russian Mammoth sunflowers, also known as common sunflowers and Helianthus annuus, are large flowers that go by many names. They are sometimes referred to as St. Bartholomew’s Star and Golden Flower as well.
Whatever you call them, these gorgeous flowers are some of the largest you can grow in your garden. Each flower on this tall, annual plant is about 8 to 14 inches (20 to 35 cm) in diameter, boasting bright golden petals surrounding a chocolate disk.
They have sturdy stalks (so sturdy you’ll likely have to knock them down with chainsaws at the end of the growing season!) and are attractive to butterflies, birds, bees, and more.
These flowers make a serious statement in the landscape or garden! They’re easy to grow – in fact, once you get the seeds started, you probably won’t have to do anything at all in the way of maintenance.
They look wonderful as part of a border and you can even harvest the plump seeds if you choose!
Russian Mammoth sunflowers are deer resistant and perfect for cottage or cutting gardens. They are best planted in a somewhat sheltered location where they won’t get too much wind, but your soil doesn’t need to be exceptional in order to grow these annuals.
You can grow them in just about any growing zone, though they bloom best in mid- to late-summer. They are low-maintenance with minimal watering needs but do require plenty of space – you’ll need about four feet between individual plants.
Why Grow Russian Mammoth Sunflowers
Sunflowers have their obvious delights but these ones we originally decided to try because of the fond memories I had of them from my time living in Russia as a missionary.
I’ll never forget the first time I saw a Russian mammoth sunflower, its huge head dangling over the side of a fence looking for all the world like it was trying to choke itself on the fence post.
- A Russian mammoth sunflower is visually stunning not just for its size (they get to be about 8-10 feet and their head diameter can be over 12 inches), but because of its bright, happy color and large, umbrella-like leaves.
- The stalks are a good 3-4 inches in diameter when the soil is good and we have to saw them down at the end of the season; they make great kindling because they burn fast and hot when dried. Sometimes the heads get so large that the stalk begins to bend but quite often they grow up straight and tall and cut down into orderly shapes for your kindling pile.
- We discovered upon growing them that, apart from beauty, Russian Mammoth sunflowers are practical additions to the homestead. In fact, they can produce over one thousand seeds per head, making them a great supplement for your backyard flock.
- They do take up space, I’m not going to lie, but if you have it, I believe it will be space well used. When drying them, be extra sure to flip the heads repeatedly in order to avoid mildew.
What Does the Mammoth Russian Sunflower Need to Grow?
It’s a very low-maintenance plant, perfect for beginner gardeners. You can start the seeds indoors, or plant directly into the soil when it’s warmed, 1-2 weeks after the last frost date.
If starting seeds indoors, you should plant seeds 1/2 inch deep, 3-6 inches apart. I recommend planting in individual peat pots so that you don’t disturb their roots when you transplant. This can help reduce the likelihood of transplant shock and other issues.
Grow in an open area, as they will need lots of space. Russian mammoth sunflowers need lots of sun, so plan for an open sunny area.
Also keep in mind that these plants will easily grow to ten feet tall, so they will shade out anything growing around them – don’t plant them near other crops that aren’t fond of shade!
Before you plant, take the time to work three or four inches of compost or aged manure into the top six inches of soil. Sunflowers are heavy feeders and will use up any available nutrients rapidly!
Also, keep in mind that sunflowers prefer soil that is somewhat acidic to neutral. It’s worth doing a thorough soil test before you plant to make sure your pH is in the range of 5.5 to 7.5. If it’s too low, you can add limestone, and if it’s too high, you can add sulfur.
It may make sense to do your soil test in the fall and add these amendments then, since limestone, in particular, takes some time to work its magic in the garden.
Before you sow seeds or transplant the plants you started indoors, you might want to install some stakes into the ground, and put these in these oils about two feet apart to give your sunflowers the support they need without having to disturb them once they’ve already started to grow.
Wait to sow seeds outdoors (or to transplant) until soil temperatures are at least 50 degrees. All danger of frost should have passed, as a sudden frost will kill these plants quicker than anything else!
After seedlings emerge (it will take about one to two weeks), you can thin your sunflowers to about two feet apart. This will accommodate their large heads and can be done when the seedlings are about six inches tall.
It can be heartbreaking to pinch off these massive beauties before they even get to their full size, but it must be done if you want the rest of your plants to thrive.
Russian Mammoth Sunflower Care
Here are some tips on caring for your Russian Mammoth sunflowers once they’ve germinated…
Water weekly, at least to 1 inch depth. These flowers need a fair amount of water during dry spells – you may have to water twice per week during prolonged droughts. Ideally, you should provide each plant with about a gallon of water.
Weeding and Maintenance
Pull weeds as needed but keep in mind that, as your sunflowers get taller, you likely won’t need to weed as much since they’ll shade out anything growing below.
You will, however, need to tie the stalks to the stakes you installed earlier as the flower heads grow. This can prevent the top-heavy plants from tipping over and snapping, something that is common during heavy rainfall and windstorms.
Most Mammoth sunflowers only produce one bloom, so once the plant has bloomed and the petals start to die back you can remove the plant if desired. Of course, you’ll want to remove the plant at the end of the season, too.
Mulch isn’t necessary but it can help the soil retain moisture and a proper temperature. Use an organic mulch, like shredded leaves, compost, or wood chips, if you want the soil to absorb some nutrients while also improving moisture retention.
When applying mulch, do so at a depth of one to two inches, and be sure to keep the mulch away from the stem of the plant. This can prevent rot.
You will also need to fertilize your plants. This can be done around midseason but only is necessary if the growth seems to be stunted, your soil is not very fertile, or the foliage has turned a light green color.
To fertilize, add a shovelful of compost in a circle around the plant – then water deeply to make sure it soaks all the way in.
Pests and Diseases
Growing Russian Mammoth Sunflowers is a great way to attract all kinds of wildlife to your garden, including birds that want to harvest the flowers’ tasty seeds. If you don’t want them to do this, you can fasten a bit of cheesecloth or bird netting around the heads.
After the season has ended and the heads have hardened and turned brown, you should cut the stalks and remove any debris from your garden. Although sunflowers aren’t prone to very many diseases and pests, they can attract scavengers at the end of the year.
Again, there aren’t many diseases you’ll need to watch out for. Most are fungal in nature and can easily be prevented by providing adequate spacing between plants (again, this is where thinning your weakest plants can be beneficial!) and adequate amounts of water.
Fungal diseases are far more common in wet, humid conditions. Cut down on the water and you’ll likely find that the disease goes away.
The most common sunflower diseases are downy mildew, rust, wilt, and rot.
Most pests will leave sunflowers alone. However, you may have to watch out for sunflower-specific pests like banded sunflower moths, sunflower beetles, sunflower stem weevils, and wireworms.
Cutworms tend to be the most detrimental to sunflowers. The good news about cutworms is that once your sunflowers have reached a certain size, you shouldn’t have to worry too much about them damaging your plants.
They will damage the leaves and stems of young sunflowers, often leaving notches or holes or causing severe wilting.
More often than not, though, cutworms target sunflower stems, biting them completely and severing the plant, killing it before it has a chance to get started.
Since sunflower stems become hard and woody once the plants have reached a certain height, this is only really a problem you’ll have to deal with when your plants are in the seedling stage.
You can protect sunflowers from cutworms by installing collars around your plants – you can buy these at farm and garden stores or easily make them by cutting rings out of toilet paper tubes. This will keep the cutworms away from your sunflowers when they are in their most fragile state of growth.
While most people grow Russian Mammoth Sunflowers strictly for their ornamental value, it’s important to note that you can also harvest seeds from the heads if you choose (some people even harvest the fullhead, throwing it on the grill just like they would corn on the cob!).
On average, Russian Mammoth sunflowers mature sometime between 55 and 100 days after planting. That’s when you’ll get the most gorgeous blooms. However, it will take a bit longer for your seeds to mature.
To harvest the seeds, cut off the flower heads along with 12 inches of the stalk still attached. The heads should be drooping and have turned a gray color on the back.
You can hang the heads up by the stalks until the seeds have dried. Then you can enjoy them or put them in dry storage for the winter!
Should I Grow Russian Mammoth Sunflowers?
There are multiple benefits to growing Russian Mammoth sunflowers. Not only do they add intense interest to your garden, but they also attract all kinds of pollinators – perfect for keeping your vegetables healthy and growing well!
There are very few reasons not to grow these flowers – except, perhaps, if you are limited by space.
If that’s the case, you might want to consider smaller or dwarf species like autumn Beauty, Suntastic Pink, Little Becka, Sunny Bunch, Tiger Eye, Teddy Bear, Chianti Hybrid, Elegance, or Lemon Queen.
While many of these do still offer the height and beauty you might be looking for, very few are quite as gargantuan as Russian Mammoth sunflowers!
Have you grown sunflowers before? Will you grow Russian mammoth sunflowers in your garden? Be sure to pin this on your favorite Pinterest board.
Heather’s homesteading journey started in 2006, with baby steps: first, she got a few raised beds, some chickens, and rabbits. Over the years, she amassed a wealth of homesteading knowledge, knowledge that you can find in the articles of this blog.
Learn more about Heather and the rest of the writers on this page.