The virtue of tree onions greater than at first sniff

A few weeks back I wrote about the virtue of Egyptian onions -- also called top or tree onions -- which grow a small bulb on the bottom and smaller, miniature onions in place of seeds on the top.

The column triggered numerous inquiries, mainly requests for seed sources (more about that later), and one phone call from a reader who said, in effect: "You didn't tell the half of it."

To my chagrin this person's name and telephone number have disappeared from the note pad alongside the telephone -- my fault entirely because I should have transferred it to a safer place. It was obvious that my informant was an experienced gardener, so I will try to capsulize our discussion, although the promised visit to his garden has still to take place.

From the conversation I quickly learned that, yes indeed, there is more to the tree-onion story. The caller told me he had been growing tree onions for decades and that he just wouldn't be without them in his garden. Over the years he has learned a trick or two, so that the tree onions he harvests are considerably larger than the oversize scallions most Egyptian onion growers bring in.

His secret is simple and logical: When the seed heads are pruned off as they form, the plant is forced to store all its energy in the only remaining place for it do so -- in the bulb at the base. The result is considerably larger onions for cooking and eating.

Another option is to prune off most of the flowers on the top of each seed stalk, leaving only one bulb to form. This produces an improved bulb at the base of the plant and a good pickling-size onion on top.

Quite inadvertently, I confirmed my caller's experience this year. A carelessly swung garden tool snapped off the flower heads of a couple of tree onions just after the top onions had formed. Recalling this, I went out to inspect the onions immediately after the telephone conversation. To my intense satisfaction the onion bulbs were oval-shaped and the size of a small egg.

In my previous column, I mentioned that by mounding up soil or mulch around the tree onions in the fall, the stalk is blanched and the onions can be eaten, white stalk and all, like miniature leeks come spring.

Once the seed stalks start maturing, however, the center of the stalk cooks up like wood, so that the onion is no longer edible until the fall, when it will have divided at the base and sent up new stalks.

This is true, my caller agreed, but only the stem is affected.

"You can still eat the bulb itself," he pointed out. "Just cut the stem off right at the base."

Meanwhile, there is still time to plant tree-onion bulbs this fall. If nothing else they will send out roots in the coming cool weeks and be established enough to take off readily in the spring. Mulch the onion bed so that the bulbs are not subjected to constant heaving from the freeze-thaw cycles of winter.

Otherwise, you can plant the little bulbs in the spring just as soon as the soil can be worked.

Here are some sources of tree-onion bulbs:

Comstock, Ferre Company, Wethersfield, Conn. 06109.

Farmer Seed & Nursery Company, 12 Northwest 34th Street, Faribault, Minn. 55021.

Le Jardin du Gourmet, West Danville, Vt. 05873.

Nichols Garden Nursery, Albany, Ore. 97321.

Well Sweep Herb Farm, 317 Mount Bethel Road, Port Murray, N.J. 07865.

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