I like to use the analogy of cooks vs. bakers when providing advice on annual artichoke culture. The fact is that artichoke culture isn’t exactly easy, at least in the north where few, if any of us have been able to grow artichokes as they can in California, but things have changed given new methods and new varieties. It’s going to take some time to catch on, but expect your local farmer’s markets and farm stands to start featuring artichokes as more and more local growers are discovering the potential given new methods.
The best part here is home gardeners don’t need to wait, you can start right now as artichoke seed must be started early (January or February) and grown on under light, but never in a cold environment so skip winter-germination or anything like that as exposure to cold temperatures while young is the trick (or hack?) you will use in April to get your young plants to bloom in the first year. More on that later.
HISTORY The Globe Artichoke (not to be confused with the Jerusalem Artichoke, which is a tuberous relative of the sunflower) are large, attractive thistle-like plants with sharp spines and silvery leaves. Botanically they are closely related to the ornamental and edible plant Cardoon) . Old, biblical plants, humans have been eating the stems, leaf stalks and the immature large flower buds since biblical times. Yet while scholars cannot agree on the exact origin of the plant, most believe that it likely was introduced by the Arabs into Europe.
The globe artichoke came to the United States earlier than you might think. In the 17th century Thomas Jefferson grew it at Monticello, but it wasn’t until 1920 when the veg started to become popular as Italian immigrants introduced better selections of one called ‘Green Globe’ to California. It was then when the artichoke started to became a significant agricultural crop in North America.
CULTURAL INFO Artochokes are botanically perennials, but you’ll see later that the new methods for growing crops in the north come with a trick that allows one to treat them as annuals. For nearly a century if a home gardener wanted to raise globe artichokes, they would have had to move to California and purchase root stock, or vegetative divisions or potted nursery plants. This is still the commercial method for propagating plants on artichoke farms as seed-raised varieties are variable.
NOTE: Since you will need to use seed-strains, this variability is not a bad thing, as today, purple, pointed or round buds from one field is considered diversity and provides interest. Commercial growers want uniformity and consistency as they are producing a product.
Artichokes cannot survive in soil which drops below 25° F, so as a true perennial, it required at least two years before plants could produce buds which has kept their culture to primarily mild-winter climates.
NEW ARTICHOKE OPPORTUNITIES Everything changed in the mid-1990s when plant breeding efforts in California developed an entirely new way to raise perennial artichokes. Still botanically perennial, new varieties could be now be grown in a single growing season as an annual crop. Practically overnight commercial farmers and even home gardeners could grow globe artichokes of very fine quality – from seed with no worries about wintering over because one could restart new seeds in the following season, which is the recommended now.
Today commercial growers in more northern markets are beginning to master these annual crop varieties bringing high-quality artichokes to local specialty markets in regions where artichokes could never have been planted before. Local artichokes are appearing at farmers markets, in CSA boxes, and at premium markets, yet the home gardener has been slow to pick up on the trend.
MANAGING EXPECTATIONS Before undertaking all the work required, I must be honest about a couple of significant points.
Artichoke plants are big. First, a healthy, mature artichoke plant can be too large for most raised beds. If you are thinking about raising one in a pot it sulks as a container plant. If an artichoke plant finds itself in a challenging environment, it will just produce leaves and appear stunted. Lovely foliage, but nothing to eat. Plan on planting 3 artichoke plants in a 4 x 8 foot bed.
Expect only a few full-sized buds per plant. This may be the biggest disappointment for first-time growers discover. A single plant will produce only one or two full-sized globe artichokes. There are smaller buds that come later, but if you are expecting harvests of full, 6-8 inch artichoke buds, plan on 2-3 per plant and 6-10 smaller ones. In full sun and with plenty of room, you may get 4-6 buds per plant. Really, to get a decent crop you should plant many plants. If you have the room, I would set out 12 – 20 plants, but I understand most gardeners will not have such space. But hey, if you reallllyyyy love artichokes…
In the end, globe artichokes are best suited for the larger vegetable garden where one can set out one or two long rows with a dozen plants each to keep the home cook happy and well supplied with this luxury crop. Given all of this fuss, for the hardcore artichoke fan, nothing beats a homegrown bud.
MOVING AHEAD WITH THE RIGHT VARIETY
Annual crops begin with sourcing seed of varieties which have been bred for annual production. While still botanically considered perennial in nature, these are varieties which respond well to the special techniques like vernalization (chilling) and then produce large, full-sized buds of a very high quality. Culturally the crops are recommended to be treated as annuals, turned under each autumn by commercial growers who sow fresh seed every year.
The flagship annual variety is ‘Imperial Star’ the result of an extensive breeding program at the University of California, Irvine during the late 1980’s (1). Introduced into the trade in 1992, ‘Imperial Star’ forever changed the annual artichoke production opening a new niche market for growers by offering a variety which will produce large, high-quality buds. (4).
Most home gardeners will be limited as to what varieties they can grow in the annual method from seed, with three varieties recommended for North American gardeners (‘Imperial Star’, ‘Improved Green Globe’ and ‘Colorado Star’). If you like in a traditional artichoke growing area there are many named selections both regionally unique or culturally significant.
The classic old commercial variety is ‘Green Globe’. You’ll see that an ‘Improved Green Globe now exists introduced in 1989 which is more resistant to disease and is better in production, but be certain that you order the later and not the old strain which many seed catalogs still carry. Large-scale commercial growers prefer vegetatively propagated stock as these are essentially clonal which ensures consistency and uniformity.
The seed-raised stock however while quicker to market, is less consistent with more diversity occurring in the field. Savvy consumers seem to enjoy multi-colored buds as well as the important fact that it is far easier to produce an organic product with annual varieties which reduce pathogens passed on in traditional vegetatively propagated stock. WE love all of the diversity and colors.
RAISING FROM SEED
There seems to exist conflicting advice on how to properly germinate globe artichoke seed even trusted retail seed suppliers can’t seem to agree particularly on pre-chilling the seed, a process known as stratification when seed is subjected to moist and cold temperatures for a specific period to induce germination. This is a treatment not uncommon for most perennials, trees and woody plants which typically would spend a winter in the soil.
Artichoke seed if procured from a reputable seed house shouldn’t need pre-chilling, as fresh seed will germinate quickly. Reputable seed suppliers test their seed (or they store their artichoke seeds cold). Always check the growing guide for artichokes available on most seed company websites your seed supplier and see if they suggest pre-chilling or not.
Seeds need be started early often as early as late January or 8-10 weeks before your frost-free date as you’ll need time to set young transplants outdoors to properly vernalize the seedlings when temperatures are still w 55° F.
It is helpful to use the right containers with artichoke seedlings, as you will want large and robust transplants which will perform best in the garden. Deep root-training types of cell containers are ideal as artichokes are tap rooted. The deeper the pot, the better to avoid roots encircling at the bottom of the pot. An unhealthy or stressed seedling is obvious, with weak foliage and rootbound.
If you cant find root trainers, a 3 or 4-inch container will suffice. I prefer to sow in a larger container to avoid at least one more chance to damage roots, but if you don’t have the room do take care when using plug trays, be sure to choose deep cells and transplant plus as soon as leaves appear to avoid root damage. I often use 3 or 4-inch pots when my root trainers are in use for cut flower sweet peas and they work well. Now there are 6 inch deep cell trays available from many supply sources.
Soil is always a controversial matter, but soiless mix is safest to avoid pathogens. I use a commercial grade sterile soil mix called ProMixBX (it’s what the big growers use), and I have never found an acceptable substitute at retail. If you prefer to use a peat-free mix, a homemade mix comprised of 1/3 compost or composted wood bark, 1.3 garden loam mix with 1.3 perlite or sharp sand will do. Be sure to pasteurize it in the oven following the directions outlined in the ‘Soils and potting mix’ section.
Germination temperature can be confusing if not misleading if you are looking on-line. While it is true that artichokes like bottom heat and warmer soil early when they are germinating, they are rather specific about how hot they want it. Failure often occurs when a heating mat is set too warm as that too can delay germination as much as cold soil can. Those sowing in cool environments will only get thistle plants.
The ideal range for daytime temperature germination is between 70 and 80° F. Sow seed 1/4 inch deep and cover. As soon as seedlings emerge, adjust the temperature to be slightly cooler, (60 – 70° F) to help seedlings grow more sturdy. A temperature shift to even cooler drops night helps many plants but particularly artichokes. Professional growers call this a differential. A slight differential (temp drop) to 55 – 60° F will stimulate healthier growth overall, but this can happen naturally if you are using a greenhouse or an artificial lighting system. Use a timer and set it for the lights to turn on for 16 hours of daylight and 8 hours of darkness. This should work for most other vegetable seedlings as well as most plants appreciate a differential.
FERTILITY Artichokes appreciate fertility and a healthy seedling is more likely to be more resistant to insects and disease. Artichokes are one crop where I am not afraid to use a chemical based water soluble fertilizer (the blue kind) but one with a balanced analysis. If you prefer to use only organic chemical fertilzer, be sure to look for a balanced feed (i.e. not just seaweed or fish emulsion). You’ll need once which the plants can access quickly so a slow release one won’t work.
PESTS Any pest concerns indoors should be limited to easy to control but expect aphids if you are raising plants under lights. Fungus gnats can become a problem as you’ll be using fertilizer. A good regimen of allowing the soil to dry nearly complete between watering will help. Out in the garden there are few pests, however aphids can pose a problem during dry summers. If caught early, they can be washed off with a sponge.
THE TRICK – HOW TO VERNALIZE PLANTS
Vernalization sounds more complicated than it actually is. Basically you are just tricking these perennials into believing that they’ve survived a mild winter period. It’s just a metabolic process that stimulates, in this case, a perennial plant switching from a vegetative stage to a reproductive stage, which means simply that exposed to a brief cold period, artichoke plants will be induced to form flower buds.
What we are trying to attempt here is to trick the young plants into believing that they’ve survived what is essentially a ‘mini winter’. Vernalization occurs quickly, in just 7 – 10 days after exposing the plants to a few days where the temperatures don’t rise about 55° F. or below 33°. The process works best on young plants which have produced at least 7 or 8 leaves.
In the Northeastern US where I live, I simply set my plants outdoors for a week or so sometime before May 10th when they are most likely to experience a period of cooler weather. As weather varies from year to year, and since I don’t have the luxury of refrigerated rooms like the commercial growers use, I sometimes set plants out a bit earlier as long as they have seven leaves in some years, as early as late March.
Studies have recently shown that this treatment works with many varieties of artichokes, but it works best with those bred for annual production, with ‘Imperial Star’ performing the best, ever than ‘Green Globe Improved’.
Seedlings can handle a light frost as well, especially once set into the ground, and even more so once they are established. They will freeze if not hardened off though, so cover early plantings with a floating row cover for the first few weeks. While hard frosts won’t kill a plant, it will damage flower stalks if they are forming.
Seedlings can be set out in the open garden early if threats of hard freezes have passed, usually, immediately after the seedlings have been vernalized. Globe artichokes prefer fertile soil. Prepare beds before planting out with additional granular plant food (20-20-20), or well-rotted manure and compost if you are growing organic best applied in the previous autumn especially if you are using blood meal, bone meal, kelp and other slow-release minerals and organics.
MULCH AND WATER
Black plastic is the preferred mulch both for commercial growers and for home growers. It provides benefits such as warming the soil and it preserves moisture, not to mention weed suppression. It works best for us as organic mulches here in New England are encouraging an infestation of the highly invasive Asian Jumping Worm (Amynthas agrestis). A drip irrigation system applied under the mulch is also helpful.
FERTILITY REQUIREMENTS OUTSIDE
Globe artichokes are heavy feeders A high nitrogen formula is recomended at planting time, but later the use of one which is relatively evenly balanced such as a 10-10-10 or a 20-20-20. Most university studies advise rich, fertile soil. Conventional fertilizer should be applied as a granular side-dressing before the black plastic mulch is laid down. If you are looking for suggestions for organic feed,
CULTURE IN MILD CLIMATES
OK. if you are in California or in the British Isles, you are golden. While propagation for most home gardeners in the north is from seed, in mild-winter climates like California, the England and any Mediterranean country, artichokes are a natural crop. Here they are vegetatively propagated often by division ever 5 years which allows one to raise clones, often landrace varieties and older and heirloom perennial varieties. With these named selections, some of which are regional or nationally protected landrace strains, dividion remains as the only way to obtain a genetically pure variety.
Treatment is similar to other perennial crops like rhubarb or seakale. Root divisions should be taken from healthy plants in March or April, ideally with two or more shoots. Alternatively, in mild-winter areas, nursery grown container plants are often available of perennial producing varieties. Perennial selections should be divided every 2 or 3 years to maintain vitality and the sold amended to retain vigor. Plants can become very long lived.
WHY GROW YOUR OWN IN THE NORTH?
The real question here is ‘IS IT WORTH ALL OF THE TROUBLE” With all of this criticism, you may be wondering why one would bother to grow artichokes at all? I fear that I’ve been saying little to encourage its culture in the home garden.
Needless to say that if you love artichokes, no argument needs to be made. I was sceptical myself, but was shocked with the results. If you are still thinking about trying them I offer this encouragement – globe artichokes are not only fun to grow, they make beautiful plants in the garden – even a poorly raised plant will look nice in the border. Like cartoons, they are handsome specimen plants that will trigger comments from anyone who visits, especially if they are allowed to bloom (although the flowers are not as colorful as cardoon flowers are).
Best of all, and perhaps most importantly, I cannot overemphasize that a home raised artichoke is superior to anyone could buy at a market and potentially could convert even the most sophomoric of eaters. They are indeed the ‘Lobster of the Vegetable Kingdom.’