Cardoon (Cynara cardunculus)

Dramatic plant of many uses. Produces large silver blue deep cut leaves that make a wonderful accent to any flower bed although they do need a lot of space. For this reason many people grow them just for the splendid foliage. If you live in a warm zone the plants may flower, sometimes but rarely in the first year so plants need to be in zone 8 maybe 7 for this to happen. When it does it produces large lavender/purple flowers up to 3 inches (7.6cm) cross on prickly stiff branched stems. The are beloved by butterflies bees and humming birds.
Many grow cardoon as a vegetable for its delicious edible stems. They take a little more work as plants need to be blanched before they are harvested but since Cardoon is rarely available for sale its the only way this delectable vegetable can be enjoyed. Easy to grow from seed, grown as an annual for food or decoration in most of the country. Will live as a perennial in warmer zones. Its very prickly so wildlife don't eat it. Needs full sun and good rich soil.

Large perennial plant hardy to zone 8 can be grown as an annual in colder zones and is unlikely to flower. This large member of the thistle family is closely related to artichokes. During its first year it will produce a very large single urn shaped rosette of leaves. These begin a shining silver blue color due to the multitude of tiny hairs covering the leaves they mature into a grey green and can be up to 3 feet (1m) long and up to 2 feet (61ccm) wide. Leaves are deeply cut into large lobes all of which have deep lobed margins that are rounded on the ends with heavy yellow spines along the edges and the petioles (leaf stalk). Mounds can reach 3 feet (1m) in height and are produced from the center of the rosette continuously throughout the season while older ones tend to die down and become matted and will smother close plants if not removed.
For zones where it can overwinter the second year will produce one or more likely several smaller rosettes that have denser foliage. Each one will produce a single thick stem that in ideal conditions can reach 6 feet (1.8m) in height but in meadowlands is more likely to be just over 3 feet (1m). These stems produce multiple branches from about half way up and each branchlet produces a single large thistle bloom. These can be up to 5 inches (13cm) in diameter are mostly a globular calyx with tough spiny exterior from the top sprouts a large collection of thin needle like purple to lilac 'petals' above a deeper dark maroon base of stamens and stigma. Seeds are fairly large and can be prolific, in some areas of America especially California it is considered an invasive pest.
While there are report of Cardoons being hardy to zone 7 this seems to be mostly a repetition of data rather than fact. The few places that have actually tried to grow them report hardy only to zone 8.

Best started inside at the beginning of the year to obtain plants large enough to harvest. outdoor seeding is not recommended above zone 8.
Not all Cardoon seeds are created equal some will produce good strong plants other will produce weaker ones or even albino (white) plants, some wont germinate at all 65% is usual.
So plant seeds in individual 3 inch (7.6cm) pots placing 3-4 seeds in each. After germination evaluate your seedlings are remove any weak or albino ones leaving the strongest seedling to grow. Best germination temperatures are between 70-75 F (21-23C).

Seedlings are slow starters and grow slowly to begin with so need nurture. Grow on indoors or a cool greenhouse where temperatures do not dip below around 50F (10C).

Transplant as soon after danger of frost is past as possible. Cool temperatures help to harden off plants but frost can inhibit them. While some sources suggest you plant before the frost date we do not recommend this as weather conditions are too unpredictable in recent years so it may drop too low and kill plants. Transplanting early is supposed to help increase likelihood of blooms forming but most Cardoons establish their roots in the first year and will not flower so should be grown for their ornamental foliage or as a vegetable (or both).
If temperatures are going to drop more than expected plants will need to be covered to protect them. If only a few plants plastic shopping bags can cover each plant, for more plants a plastic sheet held up by wire coat hangers and weighed down with stones works well, any color will do, if using black or transparent ensure it is removed before the sun hit them as this could damage plants. It is not guaranteed that first year seedlings will flower as they often spend the time building a tap root so if you are above zone 7 just grow it for the foliage.
Space plants 18-24 inches (46-61cm) apart in rows 36-48 inches (91-122cm) apart.

For zones 8 and warmer only. Seed when temperatures reach the at least 51 F (10.5C) overnight. Dig a good amount of organic material into soil and plant thickly. If temperatures are lower than this then cover with a cloche or plastic low tunnel until seedlings are larger Sow thickly are remove all weak or albino plants leaving only strongest at about 18 inches (46cm) apart.

Bed needs to be well prepared before transplanting. Cardoons like a lot of well rotted organic material so dig a good quantity into the bed beforehand. If growing as a vegetable some sources suggest digging a trench and adding the compost in the bottom and planting in the trench. This way soil can be added to the plant as it grows which aids with the blanching process (see below).
Space plants 18-24 inches (46-61cm) apart in rows 36-48 inches (91-122cm) apart.

Which ever method you choose good compost will produce the best plants.
Light. Cardoons need full sun they need at least 6 hours to make the best plants. If you are in zones 8 and more then some light shade mostly from noon sun would be useful as if it gets too hot the cardoons may go dormant and deleaf returning when temperatures reduce in late summer.

Soil. Must be well drained. Adding the compost will aid with this but cardoons do not like wet feet it will rot the roots. Roots tend to go down deep so they need more than a few inches of drainage. They prefer a pH of 6.0 - 7.0. You may need to add some lime if the compost is acidic.

Water. Water in well when transplanting after that only occasionally to ensure even watering which will depend on rainfall. Water the soil around the plant not the leaves. Using a soaker hose running along the base of the plants is the best method, this can then deliver the amount of water required to keep them moist. Don't water or a regular schedule but on demand depending on when it rained.

Feeding. If growing as a vegetable feeding regularly with a high nitrogen fertilizer can help to increase leaf production and reduce likelihood of flowering.

In zone 7 and possibly 8 depending on location it may be possible to overwinter plants with some work. In late fall before temperatures get below 50 F (10c) but the plants down to about 8-10 inches (20-25cm) above the ground then pack straw and leaves around them. Ensure you have a large coating and mound for enough insulation. It may need to be covered with burlap and weigh down either with stones or branches. Christmas tree branches are ideal for this. With luck this will keep the stump from freezing over the winter. Remove the covering in April when the temperatures rise. with luck this will have protected some plants although some loss is always inevitable. Also covering in such a way can encourage voles who are now protected from predators and can attack and eat out the roots.

The large flowers are a delight to butterflies and humming birds love them.
Caution. In areas that are ideal for cardoon growth plants have escaped and become a invasive nuisance plant. This is especially true in some areas of Northern California where plants can grow on steep, hard to reach slopes and become seed sources that can infect crop and rangelands. Do not grow this plant in California unless very strictly controlled.

Medicinally the leaves are harvested before the flowers form, or in late summer for first year plants or annuals.

Now comes the hard part. Harvesting is not as easy as it sounds as Cardoon leaves need to be blanched before they are harvested to ensure they are tender and not stringy plus it is reported to improve the flavor and reduce the bitterness. This is why some gardeners choose to grow their plants in trenches.

Plants need to be at least 3 feet (1m) in height before they can be blanched.
First you need to remove all the dead and dying leaves from the base of the plant. Once done it should look like a head of celery.
Next the leaves are gathered together in a bunch and tied up either with one single piece of twine wrapped up in a spiral or in several pieces in sections up the leaf to make a cylindrical shape. Use soft twine or raffia to avoid damaging the leaves. The whole cylinder is then wrapped in burlap and sections of cardboard or pieces of weed barrier. The objective is to prevent light from reaching the cylinder of leaves. Once completed it should be a covered cylinder with a few green leaf sections poking out the top. This will then cause the chlorophyll (green bit) to vanish from the plant and many of the compounds that were stored in the leaves will be removed by the plant. This process takes around 4-6 weeks. Check plants regularly during this period as they are more prone to rotting and disease at this time especially if there is high rainfall.
If you have a series of plants blanch them in a staggered fashion so you always have plants preparing for harvest. Once the plant has been blanched it must be harvested.

If cardoons are grown in a trench plants can be covered with soil rather than wrapped. Once blanching has completed plants are dug up and harvested.

once the blanching period is complete the material can be removed and the plants are cut down using a sharp knife cut them off at ground level and trim off the outer leaves. If they need to be stored wrap in brown paper and store in a box of sand or peat to retain moisture.

Leaf ribs oxidize quickly so when preparing drop cut sections into water with some lemon juice - or other acidifying additive to keep them from going brown.
Ribs need to be removed from the leafy section then cut into sections before cooking. Cardoon is only eaten cooked where it tastes very similar to artichoke but with less preparation work (if you don't count the blanching).
Ribs can then be used in multitude of ways. Braising is a common method of cooking but they can also be deep fried, sautéed, slow cooked or added to soups and stews.
Flower buds can also be eaten and prepared in the same manner as traditional artichokes however they are smaller and more fiddly to deal with. Only the base of the bract and the 'heart' of base of the petals is eaten the flavor is reported as milder and more delicate that traditional artichokes
Roots. Can be cooked like parsnips. They are large, fleshy, tender and most agree they have an agreeable flavor.

Recent research has discovered the compound cynarin in the leaves or cardoon which has been shown to improve liver and gall bladder function. It can stimulate the secretion of bile and other digestive juices which helps to lover cholesterol levels. Tinctures are used internally for treatment of early stages of late-onset diabetes, chronic liver and gall bladder diseases, jaundice, hepatitis and arteriosclerosis.

Produces magnificent flower heads that can be cut and dried for arrangements. The dried flower heads contain a compound that can be used as a substitute for rennet in curdling plant milks for creation of vegetation cheeses. It does tend to give the products a earthy herbaceous taste.
Bio fuel research is investigating cardoon seeds as a source of oil.

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