More than any other garden crop, starting alliums from seed gets me enthusiastic. They announce the end of winter, which by February is the only story I want to hear. They are a brilliant green sign of spring.
The earliest seeds that can be grown indoors belong to this plant family, which also includes leeks, chives, garlic chives, onions, scallions, and many more less well-known species. In the Northeast, onions and leeks transplant best from February 1 through March 10 and produce the largest bulbs and shanks (but I’ve had outstanding crops from mid-March sowings and passable harvests from late-March to early-April direct sowings). More tolerant of starting times are scallions, chives, and garlic chives. Scallions in particular benefit from succession sowings in the spring and summer.
Allium seeds can be easily sown. The deeper the tray, the better. Fill it with potting soil that has been supplemented with compost. Then, create and firm down furrows along the length of the tray that are approximately 2″ apart. In these furrows, scatter the seeds thickly at a rate of 6 per inch. A different technique for growing onions and scallions is to fill six-packs with enriched potting soil, moisten it, and then make a dibble in the middle of each cell that is a quarter-inch deep. Each dibble should contain 6-8 onion seeds or 12–15 scallion seeds before being filled with potting soil. (This latter approach has the benefit that transplanting is simple. Simply extract the entire plug and transplant it after thinning the cells to 3-5 plants apiece. They will happily reach their full size in a clump that is simple to weed around if you place them in the bed about 12″ apart.)
At room temperature, alliums germinate most well. As long as you start them early enough, you should be able to wait the 7–10 days it takes for them to emerge at room temperature even if they pop a little faster with heat because the germ rate actually decreases. Unlike other seedlings, they prefer to be kept moist and grow most robustly when their feet are nearly continually wet. Rather tragically, these wet conditions also contribute to damping off, the primary issue that onion seedlings experience. Compared to almost any other seedling, onions are more susceptible to damping off and other fungal diseases. Growing onions indoors at room temperature in nicely moist soil with regular air flow is optimal. A little fan works wonders for this. As with other seedlings, make sure there is enough light available.
Alliums are typically advised to develop until they are pencil-thick before being transplanted. However, it is difficult to accomplish this by transplant time, which is roughly 6 weeks before the final frost, even with an early- to mid-February start date (early- to mid-April here in upstate New York). I believe that aiming for seedlings with a diameter of between 1/8 and 1/4 inch is a more practical objective. These size seedlings are simple to nurture, transplant well, and begin to grow within a day or two. They provide large onions, thick leeks, and quickly growing scallions. The wiry, thin seedlings are frequently successful; they are not useless. But before starting to grow again, they may waste days or even weeks appearing to be nearly lifeless. Tip: Start your seeds in a very deep tray—say, six to eight inches—if you want particularly thick seedlings. Some growers accomplish this using a window box.
The most challenging aspect of growing alliums from seed is locating the ingredients for quality potting soil in the bitter cold of winter. There are several closed garden centers. Most likely, your personal compost pile is frozen. And even though the outside garden centers at big-box home stores are typically open all winter, they are typically only selling off their remaining inventory from the previous season and frequently lack essential components. Your best option is definitely to purchase organic potting soil from a reputable garden center’s indoor section, but by all means, add some compost, organic fertilizer, or perhaps both. Alliums are nutrient-demanding plants that require fertile soil for the best results; mixtures supplied in tiny bags for houseplants and similar plants typically have insufficient nourishment.
When growing alliums from seed, how long does it take?
Alliums, which include onions, leeks, shallots, chives, and garlic, were once only considered to be vegetables, but today’s taller species with their enormous spherical flowerheads are among the most prominent members of the architectural plant community. Their stiff lollipop-shaped heads are ideal for counterbalancing tall, poker-shaped flowers, softer flowing grasses, and sharp vertical leaves, while their rich color—typically purple—looks stunning either in contrast to warm reds, yellows, and oranges or mixed with cooler tones of lilac, blue, and white.
Alliums can reach heights of up to 200 cm, with flowerheads ranging in size from small pompoms to enormous spheres of star-shaped blooms. For rock gardens and the front of the border, the diminutive varieties work great. Garlic and chives grow well in these conditions, and they have the added benefit of confusing aphids and other bothersome insects so they go for food elsewhere. To ward against pests, surround other veggies and delicate plants like roses with these smelly plants.
Alliums are attractive not just when they are fully bloomed; the fallen flowerheads can also be left on the plant to dry and add architectural interest in the fall and winter. Hard frost will make the globes, especially those of Allium christophii, look gorgeous. For an eye-catching interior arrangement, you may also cut the flowers fresh and combine them with iris and thousand-flowered Gypsophilla.
Growing guide
Alliums prefer a warm, sunny location with healthy, rich soil. They can live in a more sandy area, but they will need to be well mulched if they want the truly magnificent huge heads. Since they are perennial bulbous plants, you can either plant them as potted plants year-round or as bulbs in the fall, putting them up to 15 cm deep. The plants will quickly take root and typically bloom the following year. Being bulbous also means that plants will eventually generate small offsets around the parent, forming large clumps.
Propagation
Any very big clumps can be separated into smaller portions in the late summer and replanted. Additionally, offset bulbils can be used to propagate new plants (newly formed, little bulbs). The majority of bulbils develop underground around the initial bulb. These can be carefully broken off and buried 1 cm deep in grittier compost. Aerial bulbils are produced by the Allium sphaerocephalon variation and emerge from the flowerhead. The same procedure as above can be used to plant these.
A content allium will freely self-seed. You can gather the seeds from the plant before they fall if you like to control where your new plants will sprout up (as opposed to leaving it up to chance and chaos). As soon as the heads (and stems) start to turn brown, remove them. Place in a paper bag so you can catch the seeds as the pods split open. The seeds can be kept in the bag in a cold location until the following spring, or they can be sown straight into the soil where you want them to grow. It can take up to a year for some alliums to germinate, so patience is essential.
Pest alert
Alliums are typically healthy plants, yet during a humid time they might get white rot and downy mildew. Since they belong to the onion family, they may experience onion fly attacks. Yellowing leaves are a typical early sign, and as white maggots eat away at the roots, the plant will abruptly collapse. Because the maggots are so deeply embedded in the soil and even in the bulb itself, this pest is particularly challenging to eradicate. Dig up any afflicted plants to get rid of onion flies so that the maggots can’t develop into adults, pupate, and create more grubs.
Variety guide
The most well-known flowering allium is undoubtedly A. giganteum, which grows up to 1.8m and produces 10-15cm-diameter spherical heads of purplish-pink flowers. Despite their size, almost never do they need to be staked. It looks lovely placed beside another monster, the grass Stipa gigantean, in the back of a border as a focus point. Another choice is the 80cm tall cultivar “Globemaster,” which grows best between shrubs in a sunny border and adds a dash of deep violet to the season with its enormous 15cm wide spherical flowerheads. Allium sphaerocephalon, which has stunning two-tone maroon and green flowerheads, may be the prettiest member of the clan. When combined with grasses or other globe-headed flowers like Echinops and Eryngium, it makes a stunning border plant.
The rich rosy-purple flowers of Allium hollandicum ‘Purple Sensation’ make it a charming addition to a sunny border. It will reach a height of 1 m. It looks especially beautiful when planted with fennel with feathery leaves. A. karataviense is ideal for the rock garden because it only grows to a height of 25 cm. Large, delicate pink blooms with unique leaves with dark crimson edges adorn the plant. Another option for a rock garden or for growing in a pot on the patio is the variety “Ivory Queen,” which is even shorter at 20cm tall and thrives in dry soil in a sunny location.
Crocus tip
Many of the taller alliums’ foliage will already be starting to die back by the time the blooms bloom, but if they are surrounded by perennials with appealing foliage (such herbaceous geraniums), these unkempt leaves can be covered.
Container plants
Alliums prefer a sunny location with well-drained soil, but if they are planted in pots, they must not be allowed to dry out in the spring as this can prevent the flower buds from opening.
Can allium flowers be grown from seed?
After the foliage and blooms have faded, you can lift, divide, and replant clumps of older plants if they are getting too crowded.
There are numerous allium species that generate offsets, or young plants. You can lift the bulbs and separate the offsets when flowering is over and the leaves have stopped growing. Either directly plant them in their ultimate locations, or let them grow outdoors in pots with grittier compost.
Some alliums (including Allium roseum, Allium sphaerocephalon, and Allium vineale) generate aerial bulbils in the flower head instead of flowers. These bulbils can be delicately taken out and divided. Planting the bulbils in wet, well-draining compost that is spaced 2.5 cm (1 in) apart and covered with a 1 cm (3/8 in) layer of compost is possible. They will not achieve blossoming size for a few of years.
Alliums can be propagated by seed, however hybrids won’t ‘come true’ (i.e., they can differ in color and shape from the parents) with this technique. Ripe seeds should be sown as soon as possible. Put the seeds into grit-filled compost trays and top with 5 mm of grit. Put the containers in a shaded area of the yard. Alternately, keep seeds chilled and plant them in the spring at about 13C. (55F). Most seeds ought to germinate in about a month. It will grow to flowering size over a number of years.
How long does it take alliums to mature from a seed?
Scoop a soilless seeding mixture into a flat or tray for beginning seeds. Peat moss, vermiculite or perlite, sand, and occasionally a little amount of lime and compost are included in a soilless mix. Make sure the mixture is also sterilized for the greatest outcomes.
Allium seeds should be liberally scattered around the mixture’s surface in the tray or flat. For a more precise planting, you can use a pair of tweezers or forceps or pinch a group of seeds together between your thumb and index finger. The allium seeds should be placed 1/4 to 1/2 inch apart.
- The allium seeds should be spread out on paper towels to air dry for about a day.
- Peat moss, vermiculite or perlite, sand, and occasionally a little amount of lime and compost are included in a soilless mix.
Using a spoon or a tiny piece of wood, press the allium seeds into the seeding mixture approximately 1/8 of an inch deep.
Place the tray in a location that will stay at a temperature of about 70 degrees F for three weeks. At least once per day, check on the tray. Keep the allium seeds moist by spritzing the seeding mixture with a thin mist of water as needed rather than drowning them in water to the point where they become sodden and soaked.
After three weeks, move the tray and put it somewhere where the temperature won’t drop below 50 degrees or rise above 70 degrees. For the remainder of the germination period, keep the tray in this position. Germination can start in about a year, depending on the allium variety you are growing.
The majority of alliums produced from seed will start blooming in two to three years, according to the University of Maryland Fact Sheet on Alliums.