The parent navel orange tree, which originally was planted in 1873, is still going strong on the southwest corner of Magnolia and Arlington avenues in Riverside. (Photo courtesy
The parent navel orange tree, which originally was planted in 1873, is still going strong on the southwest corner of Magnolia and Arlington avenues in Riverside. (Photo courtesy
‘Meyer’ lemon tree (Photo courtesy
‘Meyer’ lemon tree (Photo courtesy

To save an old tree, you may need to resort to inarching, which is the practice of grafting shoots from a young tree into an older one because the roots of the old tree are failing, usually because of disease.

You plant the young trees around the older one and bend shoots of the young tree toward healthy growth on the older tree, uniting them through grafting. Thus the healthy roots of the young trees sustain the older one.

The most famous case of inarching is found in Riverside, at 7115 Magnolia Ave., where California’s parent navel orange tree was planted in 1873. Several times since then, when the tree was dying from a root fungus, inarching was performed and the tree was saved. Every navel orange tree in California owes its origin to this tree.

Q I have a lemon tree that was planted in partial shade one year ago. My gardener claims it’s in too much shade. I was thinking I needed to wait for winter to transplant it to a sunny spot. Is this true?

— Marlene de Valera, Simi Valley

A You want to avoid citrus transplanting — or planting, for that matter — in winter because of the danger of frost. Citrus trees are evergreen, which means they are constantly putting out new growth, even if during the winter new growth slows down. In any event, you do not want to risk killing new growth from frost damage on a newly transplanted citrus since there is always some shock associated with transplanting, and you do not want to add to it.

Ideally, you would transplant in spring or early fall, just before or just after the onslaught of summer heat. Early morning is the best time to transplant as a precaution against desiccation of the root ball.

That being said, you really can transplant any time in our area as long as you take precautions when extreme weather is forecast. For instance, if a freeze was forecast soon after you transplanted your citrus tree in winter, you would want to cover your tree that evening with an old blanket that reached all the way to the ground, making sure to remove it in the morning. Or, if you planted this time of year and a sudden heat wave occurred, you would want to make sure to give your tree a nice shower with a hose several times during the day.

If you are moving from shade to sun, you have to be especially concerned about transplant shock. If you could initially provide some sort or screen or shade cloth canopy for the tree while it acclimated to the sunnier exposure, that would help it adapt to its new surroundings.

Anti-transparent sprays are also available. Anti-transparent spray covers foliage with a thin film that does not interfere with critical gas exchange between leaves and atmosphere even while it prevents transpiration or water loss from leaf surfaces. Aside from reducing transplant shock, anti-transparent spray is used for keeping needles on Christmas trees and for extending the longevity of cut flowers and vase arrangements. Anti-transparent spray is widely available through online vendors.

Application of root hormone, mixed in water, is another measure recommended to reduce transplant shock. Superthrive is a popular product, found in just about every nursery and garden center, that contains NAA (naphthyl acetic acid), a naturally occurring plant hormone that stimulates root growth.

Mulch is another safeguard for successful transplanting. Apply several inches of wood chips, hedge clippings, fallen leaves, or other garden debris between the trunk and drip line or canopy perimeter, making sure your mulch does…