Cold-Treated Allium, Caesium

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COLD-TREATED ALLIUM, Caesium

Allium caesium which is also known as Allium urceolatum produces sky-blue globes that range in diameter from 2 to 4 inches. Each globe is made up of pale blue florets. Each petal of the individual florets has a dark blue midvein. The overall impression is of a vividly blue flower. The plants can reach a height of 10-16 inches.
Allium caesium is hardy from Hardiness Zone 4 to Hardiness Zone 7. It should be grown in full sun. Because its ancestors endured and even flourished, sometimes, in some of the harshest conditions on earth, it is truly forgiving of poor, dry soil, but it loves rich, loose loam. It blooms mid to late season and shows best when planted in groups of 10-25 bulbs. It should not be forced, because it does not do well, but it can be planted in containers.

Cold-Treated Allium, Caesium

The Allium family includes an enormous collection of plants including leeks, onions, elephant garlic and shallots. There are more than 200 species and thousands of cultivars. In the wild, they are found all over the Northern Hemisphere including North America, the Middle East, western China, the Pyrenees, the Alps and the Mediterranean. They flourish with exposure to full sun, in rugged mountainous areas where the ground drains quickly and completely. They also love bonemeal, so add a generous helping of bonemeal (1/4 cup) to the hole where you plant each bulb.

Of all the ‘critter resistant’ bulbs, the Alliums are the most ‘critter resistant’. Deer, rabbits, squirrels, mice, moles and voles cannot stand the smell of Alliums. The fragrance is so strong and so offensive to critters that Alliums can be used to deter the critters from tulips and other more vulnerable bulbs. A critter has to be really desperate to eat an Allium.

Allium caesium was introduced into Europe in 1830. As many of you know, true blue flowers are rarely found in Nature. When the Europeans saw Allium caesium and its truly blue flowers, they became very excited and for a short time, Allium caesium enjoyed popularity in Europe and the British Isles.

This Allium blooms for a long time, sometimes as long as 6 weeks. It cannot be dried like some other alliums, but it still leaves a lasting impression in the late spring garden. It is rarely offered. Harvesting History is delighted to have found a reliable source of these truly blue Alliums.

Plant Allium caesium bulbs at least 8-10 inches deep and 6 inches apart and don’t forget to add a quarter cup of bonemeal to each bulb hole. They need full sun and do best when grown in loamy soil.

Planting Bulbs in the Fall for Glorious Spring Color
Bulbs are some of the easiest plants to grow. Fundamentally the process requires four steps.
1. Dig a hole.
2. Dust the hole with bonemeal.
3. Place the bulb in the hole.
4. Fill the hole with soil.

There are, however, some additional refinements which help produce even more lavish results and enhance protection from critters.

First, bulbs can and should be planted deeper than the instructions you receive on the package labels. An easy way to remember how deep to plant the bulb is to think of a quarter. If the bulb you are planting has the same diameter as a quarter or less, plant the bulb 4 inches deep. If the bulb is broader than a quarter, plant it 6-10 inches deep. Large bulbs like some alliums, camassias, standard tulips and fritillaries can easily be planted 10 inches deep. As the soil compacts days, weeks and months after planting, it produces a thinner layer of soil on top of the bulb. Planting bulbs deep helps with critter control. Moles, voles, chipmunks and squirrels are lazy little creatures, and they don’t like doing a lot of digging to reach their food.

Second, bonemeal is a must. It is an excellent source of calcium and phosphorus which help the bulbs to form a strong root system and healthy stems. For large bulbs (those bigger than a quarter), use ¼ cup per bulb. For small bulbs, dust the entire surface or hole where the bulbs will reside.

Third, small bulbs should be planted in clusters of 10 or more – 1 inch apart. Large bulbs, like allium, can stand along, but create a much more pleasing presence in the garden when planted is clusters of 3-5. They should be separated by no more than 4-6 inches.

Fourth, bulbs usually multiply fairly quickly and once crowded will not produce blossoms. Plan to divide your bulbs in mid-summer to fall when the top growth has dried out.

These simple, easy, quick tasks are all that is required to produce a lovely bulb display year after year.

Planting Bulbs in Containers

If you live in Hardiness Zones 5 and higher all you need to do is mix some soil. . Check out the soil mix described in detail in our Harvesting History YouTube video. Do not use prepared soil mixes.

The Best Soil Mix for Containers

Always plant bulbs more densely in containers than in the ground. Pots as small as 6-inches in diameter can have a showy presence on a deck, porch or patio. You can use much larger pots and plant several kinds of bulbs.

Fill the pot half full, dust the soil surface with bonemeal, arrange the bulbs on top of the bone meal and fill the pot with the rest of the soil. Dust the surface of the soil with more bonemeal. Water thoroughly, but do not let the pot stand in a saucer of water.

If you live in Hardiness Zones 1-4, you must protect the pots by bringing them into an unheated garage or surrounding them with bales of straw. If you do not do this, the bulbs usually freeze and turn to mush.

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