Garden Docs: Tips to keep onions from bolting

Jimmy C. asks: What causes onions to bolt? I’ve grown onions for years and never had a problem before.

When planting onion sets in mild areas, only the smallest sets should be planted. Larger sets often grow too fast, bolting into flower as soon as the weather warms up and before the bulbs have had a chance to mature.

Onion sets planted in October aren’t so likely to bolt since their growth is slower during the winter months.

Remember the warm days and sporadic temperature changes? It most likely caused the early bolting.

Remove the blooms and hope that the early flowering hasn’t drained too much nourishment from the onion bulb.

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Stephen H. asks: What can you tell me about gabions? A garden friend suggested I add a gabion as a garden element when I re-do the front yard and take out the turf.

A gabion is made of hog wire that is formed into a cage or multiple cages (sometimes called “baskets”) that can be used to create a retaining wall, base for a bench, a fence or a stand-alone, natural-appearing garden element. The ”big cage” interior is filled with fieldstone or other native stones that complement the surroundings. The top of the gabion can be of any height depending on its intended function and left open or capped off with more wire or even capped off with wood for a garden bench. Gabions are a creative application of rock/stone work that can be accomplished by most as long as there is some available muscle.

Ideas for using gabions in the garden can be found on the website pinterest.com. There is a wonderful little garden on Franklin Avenue in Santa Rosa that uses gabions as garden elements, and it is most effective as part of a drought-tolerant garden design.

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Anita asks: What is the scientific name for the strawberry begonia?

The scientific name is Saxifraga stolonifera. Another common name is “mother-of-thousands,” derived from the way it sends out runners with new plants attached. “Tricolor” is a good variety with smaller but very attractive green and white leaves with pink edges and purplish-rose undersides.

For those readers not familiar with this old-fashioned perennial shade plant, it forms a fine, dense ground cover that can be planted under trees, combined with ferns or positioned along a shady woodland path.

The Saxifraga stolonifera has wiry flower stalks topped with tiny and airy white blooms in the summer. It does die back in colder areas. Give it moderate water and fertilize sparingly in spring and late summer. Mulching around the plants should eliminate some of its moderate water requirements.

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Brian writes: I have a low, wet area (during the rainy season) that is part of a drainage swale. We have lost several trees due to root rot because of the poor drainage. The area can accommodate a good-sized tree. Any suggestions?

Yes, the bald cypress, Taxodium distichum, is a deciduous conifer that has cinnamon colored bark and beautiful soft green sprays of needle-like leaves and does well in our area. It should be good choice for your problem swale.

This is a tough tree that can take many types of soil, some wet and dry conditions and is not prone to diseases and pests. Extreme alkaline soil can be a problem. Because it is deciduous, it takes on an interesting winter form.

Juilliard Park has a fine example of a bald cypress tree that is admired for its soft green needles in the summer and its dramatic winter form.

Dana Lozano and Gwen Kilchherr are garden consultants. Send your gardening questions to The Garden Doctors, at pdgardendoctor@gmail.com. The Garden Doctors can answer questions only through their column, which appears twice a month in the newspaper and online at pressdemocrat.com.