A magnificent plant. The scotch thistle - the National flower of Scotland. Can reach 8-10 feet in height. It has large triangular stems and huge silver blue leaves that will stand out from a great distance. Add to this the lovely purple violet flowers and this makes a plant that attracts everyone to admire it. It makes a wonderful focal point plant and is very easy to grow. It needs sunlight and water but is happy on poor soil and due to the very nasty spines is not troubled by any animals. It's a biennial so to keep a display going it is necessary to plant every year but its well worth it. The flowers are loved by butterflies and bees and the goldfinches love the seeds.
Warning. Scotch thistles can get out of control and in some areas are considered a noxious weed, while in others a wonderful majestic plant that needs to be protected. Take care to control the seeds by deadheading your plant to ensure it does not drop seed and get away from your garden.
Mostly the Scotch thistle acts as a biennial. However in some case it will flower in one year and act as an annual.
In the first year the plant produces a flattened rosette of silvery leaves that can reach two feet long and a foot wide. These are broadly elliptic, coarsely lobed, sharply spined and covered with silver gray hairs that give the leaves a velvety appearance. During this first year the plant is producing a large fleshy tap root. The leaves will overwinter giving an interesting silvery appearance.
In the second year it puts up a central stem triangular stem that is silver gray in color and again covered with hairs and spines. The leaves are attached alternately on the stem without a stalks and form leaf wings that extend down the stem. The stalk becomes very branched with each branch ending in a solitary flower. These can be up to two inches across with spiny tipped bracts. The flowers are purple to violet in color and appear from July through September. Flower stalks can reach 8 feet in height in some conditions they can go as high as 10 feet. Flowers are attractive to butterflies and bees. The large seeds are a favorite of goldfinches.
Location and Care.
Scotch thistles need full sun and need reasonable water to reach their full height. They are not drought tolerant and will need to be water to flourish. - They are the national flower of Scotland, where it does rain quite a lot. However even though they need damp soils they don't tolerate waterlogged soils. They are quite happy on poor soil, even ones that have lots of stone or gravel, and often do less well on rich soils. They are very hardy plants up to zone 5 down to 8. They can stand heat, cold wind and rain, but they must have good sunlight. A sunny bank or field like area is a excellent setting for these plants. Solitarily they make magnificent focal point plants with their giant silver leaves and purple flowers. If placing in a back border make sure they have plenty of room. Water regularly. A soaker hose is an ideal watering method. Water at least once a week if insufficient rain, more in hot dry areas. Don't get too close the spines are vicious.
Once the plant is in the ground do not try to transplant. The large fleshy taproot is not easily removed without damage and the plants to not transplant well once they are larger. Pick your location carefully and stick with it.
Thistle rosettes are great for keeping down the weeds but do benefit from a little mulch at the end of their first year to ensure that they will grow large in their flowering year. This also helps keep the weeds away from around the plant, since these plants are so prickly going near it to weed can be an unpleasant experience.
Cut the plants down with loppers once the flowers have finished. You can use the lopper to pick up the stem and move to your compost heap or discard pile.
To keep the flowers coming and to prevent the plants from self seeding and taking over, deadhead your plants. Even though the goldfinches eat a lot of the seeds they can drop them in other areas and once spread this plant can be difficult to remove. In some areas it is classified as a noxious weed so take care of your plants and make sure they are contained.
The best way is to deadhead the plant once the flowers are finished. To do this put on the thickest pair of gloves you own. Use scissors, floral snips, or if you want to stay even further from the plant, small loppers to remove the dead flower heads from the plant. This will keep it flowering longer and prevent it from spreading. Keep some flowers to produce seeds if you want to keep the thistles each year. If using pruners with a little practice you can catch the pruned head on the pruners and place directly in a bucket to prevent them falling to the ground. IF they do fall pick them up with pruners or loppers, don't use even your gloved hands as they can get you even through gloves. The thistle head are great on the compost heap, just take care when turning your compost before the leaves have rotted down a bit.
Scotch thistles can be sown in situ, they germinate well and can be easily grown. Studies have suggested that they can germinate at any time of the year but do need a light/dark cycle of certain day lengths to do well. IF the day is long enough sometimes seeds sprouted in early spring will flower the first year and act as an annual.
If planting directly outside make sure there is plenty of space between seedlings. At least 24 - 30 inches.
IF planting indoors start seeds at least 30 days before last frost date, earlier is better to give them a good start. Use individual pots and grow plant to a small rosette of leaves before transplanting out. Harden off plants in the pots before planting out and ensure that the whole root ball is planted directly in a large enough hole. Try to disturb the roots as little as possible. We grow all our thistles from transplants and find this method works very well.
If you want to keep a display of thistles you will need to seed every year to ensure that you have plants in the rosette stage and the flowering stage each year. These plants do well in the same spot year after year. IF they start to get a little smaller add a little mulch in the fall around the plants and they will grow taller.
Surprise! These things are edible. The young stems were cooked like asparagus or rhubarb after the spines had been removed. The flowers buds can be used as a globe artichoke substitute although they are much smaller and very fiddly to work with.
The seeds have a very high oil content about 25%. This was used by the ancient Scottish people as lamp oil but it is also edible. The stem hairs were often collected to stuff pillows.
The flowering plant is used in some heart medications and there is some suggestions that the juice of the plant is effective in treating both cancers and ulcers.
Cotton Thistle, Scottish Thistle, Scotch Cottonthistle