Most people smile when they see the big, spherical flowers of globe thistle. They’re visually-striking and just so cheerful. They’ve become a staple in arboretums, cottage gardens, or other garden settings.
The foliage is a bit weedlike in appearance until those giant globes of color appear. Leaves from this plant are a little prickly as they’re covered with a myriad of fine, stiff hairs. Like other thistles, they can be a little hard on the hands, but they’re great as cut flowers.
But the flowers make these large plants worthwhile, and so too does its drought tolerance. It’s very popular in areas like southern California where summer water levels are low. With just occasional watering, these can thrive where other plants don’t.
Let’s discuss the best ways to grow this herbaceous perennial today! With a little know-how, you’ll find this an easy and fun plant to grow.
Quick Care Guide
|Scientific Name||Echinops spp., specifically ritro, bannaticus, etc.|
|Common Name(s)||Globe thistle, southern globethistle, blue globe-thistle, blue glow|
|Height & Spread||24″ to 72″ tall, with similar spread|
|Soil||Well-draining a must. Tolerates poor soils. Loam ideal.|
|Water||Low water, drought-resistant|
|Pests & Diseases||Aphids, root rot if overwatered, rarely powdery mildew, four lined plant bug|
All About Globe Thistle
The Echinops genus comprises the globe thistles, all 120 or so of them. Surprisingly few of these make their way into regular garden use.
Of those, the most popular is Echinops ritro, or the southern globethistle. It’s won the Royal Horticultural Society’s Award of Garden merit. So has one of the subspecies of this plant.
Echinops ritro produces steely-blue flowers that can reach up to 2″ across and have a misty blue glow. The plant itself rarely gets much taller than two feet. Prickly grey-green foliage sets off the vivid blooms.
Another close relative is Echinops bannaticus, the blue globe-thistle. This much larger globe thistle grows to 4 feet tall on average. Due to its size, it’s much less common in garden usage, although it can be a dramatic centerpiece.
Not all globe thistle types produce those blue flowers. Other forms of echinops, such as Echinops exaltatus, produce white flowers. In fact, Echniops exaltatus (sometimes called Russian globe thistle) is the largest of the genus. It can reach staggering heights of 6 feet.
As a general rule, the blue flowering species are preferred to white ones, especially as cut flowers. This is not because the white ones are unattractive – they’re actually just as pretty! But the white ones tend to be less suitable in smaller gardens.
Globe Thistle Care
Caring for your blue glow thistle plant is relatively easy. It requires no elaborate techniques or fancy soil blends. Let’s talk about the perfect conditions for this perennial flowering plant.
Light & Temperature
Full sun is perfect for your globe thistle plant. While it’s possible to grow in partial shade conditions, it won’t grow to full size nor flower as much as it would grown in full sun. Looking for something for that bed that gets the summer heat? This is a great choice.
Their natural environment ranges from Europe to central Asia. A Mediterranean climate is preferable, but they can tolerate high heat conditions too. Most grow in USDA zones from 4-8. The blue globe thistle species often tolerate zone 9 and 10 conditions as well.
Water & Humidity
Drought-tolerant, the blue glow plant prefers dry soils. It has a long taproot which can get very deep into the soil in search of water. Too moist soil throughout the growing season can create conditions that cause root rot.
Because of that, it’s better to water your globe thistles sparingly, but deeply when you water. Use a soaker hose or other soil-surface irrigation. This allows the soil to slowly soak up the moisture and drain off excess.
Mulching around the base of your plants will prevent evaporation as you’re growing globe thistle. Avoid watering until the soil is dry.
Very young plants may need a little extra water to get established. For these, keep the soil evenly damp but not muddy. Opt on the side of under-watering if you’re uncertain of the watering frequency.
While your plant can tolerate humidity, it may be slightly more susceptible to powdery mildew in humid climates. Arid regions will find this plant has little to no problem in their environment.
In the best possible conditions, the soil for your blue glow plant should be loamy but well-draining. You should avoid poorly-drained soils whenever possible. However, globe thistle plants are tolerant of a wide variety of soil types. If you’ve got poor soil, they can handle it.
Avoid extremely rich soils. Your plant’s foliage will explode into growth, but they don’t put out nearly as many flowers. These plants are accustomed to wild conditions and are more than willing to rough it out on their own! If you’re springing for a commercial mix, try a cactus potting soil.
Neutral pH is ideal, but they will tolerate slightly-acidic or slightly-alkaline soils. Try to maintain a neutral pH as much as possible if you can, but don’t panic if it slides a little off balance. Your plant will likely handle it just fine.
Blue Globe Thistle Fertilizer
Skip the fertilizer with your echinops plants. Thistle plants typically live in conditions where there’s poor soil quality. They thrive on a bit of neglect! In fact, these are great to start loosening up the soil in areas you plan on converting to gardens later. So don’t worry about fertilizing them… they find their food deep under the soil’s surface.
Your thistle plant’s long taproot makes it a poor candidate for root division. Cuttings don’t develop roots quickly enough to survive.
Because of this, your best bet for propagation is from seed. Those globe shaped flowers produce a large quantity of seed as the flowers begin to fade. If you place a paper bag over the flower head once it’s faded, you can usually cut off the head and allow it to dry out. Once dry, you can shake the seed from the bag.
Globe thistle seed is available both online and at local gardening centers. Somewhat more rarely, you may find live plants for sale.
Pruning Your Globe Thistles
Once the round flowers fade, cut back the long stems. Otherwise, most of your pruning will be for shaping and general maintenance.
This plant tends to a weed-like appearance, but doesn’t spread on its own. You can shape it for cosmetic purposes, but it will always have a somewhat weedy look when not blooming.
As the leaves have tiny little leaf spines and often jagged edges, wear gloves when pruning. The stems may also produce thorns, so be sure they’re sturdy gloves. A pair of rose pruning gloves may be your best bet.
Troubleshooting Blue Globe Thistles
Have you gotten the sense that your globe thistle’s a bit tough yet? Because these plants are quite determined to care for themselves.
Still, there are a few rare problems you might encounter while growing these. Let’s discuss those briefly.
As echinops plants grow, they can become top-heavy. This is especially true once they’re in flower. To keep your plants looking good and prevent stems breaking, stake as necessary.
Some species of thistle plants may start to decline after three or four years of growth. If this happens, replace the plant with a younger one. These are perennial, but only tend to look good for the first few years.
One pest you’re likely to encounter on your globe thistle is aphids. These little annoyances like to suck the juice out of thistle stems and leaves.
A good, hard spray of water will wash the aphids off your plant. Be careful not to hit a flower that’s starting to fade with your hose. If you do, you may send a shower of seeds to the ground below your plant.
Weekly mistings of diluted neem oil concentrate will deter aphids.
The four lined plant bug is another common pest on globe thistles and mint plants. It feeds on leaves and stems, laying eggs in the stem of the plant. Damage appears as very stark precise stippling. Most of the time damage from these pests is cosmetic, but encouraging predatory wasps in the garden will prevent that altogether.
Most diseases don’t bother your thistle plants. If the plant is already weakened, or if it’s overwatered, it may be susceptible to fungal root rot. Keep your plants healthy and the soil on the dry side to prevent this problem. Dispose of the entire plant if the rot moves to the crown, stems, and basal foliage of the plant.
In humid environments, it is possible that the leaves of your plant will develop powdery mildew. This generally will not harm the plant if treated rapidly. Weekly mistings of neem oil will prevent this whitish mildew from forming.
Frequently Asked Questions
Q. Is blue thistle invasive in nature?
A. Because of their tendency to spread seed quite easily, a few forms of echinops are invasive. Probably the best known of these is Echinops sphaerocephalus. That species is considered invasive in parts of the United States. It’s also a rapid spreader in its native regions of Europe and western Asia.
To prevent invasive spread, remove the flower before it can fully develop seeds. Alternately, place a paper bag over the flower as it starts to fade. Tie a string around the stem to prevent seeds from escaping, then trim off the stem.
Q: How drought-tolerant is this plant?
A: It’s become a very popular plant for xeriscaping in recent years. Very little actual care is required, and virtually no watering except during extreme heat. You can find globe thistle’s popularity rapidly spreading in southern California’s drought-tolerant garden scene!
Q: Is globe thistle a perennial?
A: Indeed, it is! It’s a hardy perennial in hardiness zone 4 through 10. In areas colder than zone 4, it can be a tender perennial.
Q: What is globe thistle used for?
A: It’s great for adding an interesting texture to your perennial garden, and to add a pop of lovely blue flower color. It’s also excellent for attracting bees to the yard.
Q: Is globe thistle poisonous to dogs?
A: Thankfully, globe thistles are not poisonous to dogs, even when ingested.
Q: When should I cut back globe thistle?
A: To control their spread, deadhead spent flowers or cut them at the base of the plant when they’re in full bloom to incorporate them in cut flower arrangements. An annual pruning to the base of the plant in fall will also keep it healthy.
Q: How long does it take globe thistle to bloom?
A: They sprout in early spring and bloom in summer, so just a few months!
Q: Do bees like globe thistle?
A: They adore it. Bring in those bumble bees and honeybees with this lovely plant.