Oxalis Can Give Weeds a Good Name

QUESTION: Why is oxalis referred to as a weed? I’d be willing to pay, if need be, for the bright, effortless color it brings to my garden, which is mostly native plants, each spring.

--F.B., Sherman Oaks

ANSWER: Not all oxalis plants are weeds, and one person’s weed is another’s wildflower. A weed, after all, is simply something growing where it’s not wanted.

I’m not sure which oxalis you’re referring to, but I suspect it is the Bermuda buttercup, Oxalis pes-caprae, with its bright yellow flowers. Clusters of these come on top of stems up to a foot tall, and the leaves are bright green and cloverlike, often with dark brown spots. Kids often chew on the leaves and in my neighborhood call it “sourgrass.”

The Sunset Western Garden Book lists Oxalis pes-caprae as an ornamental, and it is very pretty. But the book suggests growing it in pots and cautions against planting it out in the garden, since it spreads very rapidly.

I would add that it is impossible to get rid of, since it is growing from a deep and easily detached bulb. The only way is to keep trying--never leaving any above-ground growth. After several years, it will exhaust the energy stored in the bulb and “starve” to death.

The Grand Duchess strain of Oxalis purpurea is also sold as an ornamental plant. It has glistening pink, white or lavender flowers more than an inch across. It’s the first thing to bloom in the new year in my garden, dying completely back by summer.

It too grows from bulbs and can become weedy, but it is less likely to spread from where it is planted and is not difficult to dig up should you decide to get rid of it.

You occasionally see several others grown as ornamentals, such as O. crassipes and the native redwood sorrel.

I suspect, however, that very few gardeners consider the kinds commonly called weeds--such as the flat, spreading Oxalis corniculata or the taller one that roots as it spreads--as anything but persistent, irksome weeds. Spend a weekend trying to dig them out of an otherwise handsome clump of native iris or from a ground cover planting of the tidy little dymondia or even lamb’s ears, and I think you’ll agree.

One clever gardener did use the weedy red-leaved kind between paving stones, mixed with clumps of bright green Scotch moss, a handsome combination. As I said, one person’s weed is another’s treasure.

Don’t Hedge About Using Guavas, Plums

Q: I live in Baldwin Hills (in Sunset’s Zone 22, I believe) and would like to make a hedge with strawberry guavas, pineapple guavas and natal plums. I’d like to keep it 5 feet tall and 2 feet wide. Is it possible, and how far apart should I plant them?

--M.B., Los Angeles

A: Sounds like a great idea--an edible hedge--and there should be no problem planting it. All three plants are tough and grow easily in your climate zone.

The variety of Natal plum, Carissa, named ‘Fancy,’ is an upright shrub that will easily grow to 5 feet and is often pruned into a hedge, as are all the other Natal plums. It also has the largest fruit of the commonly available kinds.

The pineapple guava (Feijoa sellowiana) is of similar size and can be pruned into a hedge. The variety ‘Nazemetz’ is supposed to be self-fertile, but it still produces better crops if there are others planted nearby, so be sure to include two of these in your hedge. The fleshy flower petals are also edible and deliciously sweet.

I’ve seen strawberry guavas, Psidium cattleianum, pruned so hard they might as well have been a hedge, which is a shame, since this 10- to 15-foot tree can be majestic with its beautiful bark and multiple trunks. The yellow strawberry guava, the variety ‘Lucidum,’ has the densest growth and would make the best hedge.

Although all three of these can grow quite large (to 15 or more feet), I see no trouble keeping them as a 5-foot hedge, though you may have to let them get a little more than 2 feet wide. I’d plant them about 3 feet apart, though they could be planted farther apart than that.

Time to Take Stalk of Japanese, Bearded Iris

Q: Now that the Japanese iris and bearded iris have finished blooming, what should I do about the tall stalks and leaves? Do I need to lift the Japanese iris bulbs? Also, what should I do about the bearded iris that didn’t bloom this year? Should I yank them out?

--T.D., Camarillo

A: Once an iris has bloomed, you should cut off the stalk and the attached leaf. Both of these irises are perennials, so don’t dig up or disturb the rhizomes. The Japanese iris need plenty of moisture (many people grow them with their roots submerged in a pond), so keep them moist this summer and fall.

Bearded iris like a little late-summer drought, so after July, water less often or not at all, then begin watering again in early fall.

Don’t pull out those rhizomes that didn’t flower this year; they will make next year’s flowers. After about three years, you will need to dig up the rhizomes and respace them, usually in August.

Discard the old, rotted rhizomes and save only the healthiest. Cut back the roots and the leaves so they are about 6 inches long, and replant the rhizomes in clumps of three so they are about 4 to 6 inches apart. The clumps should be about 12 to 18 inches apart. Don’tbury them; the top of the rhizome should be at soil level.

To Seed or Sod: Both Have Advantages

Q: We’ve recently remodeled and would like to replace the old Bermuda grass lawn with a new lawn but don’t know whether to sod or seed. What do you think?

--C.Y., Villa Park

A: Sod is nearly instant and seed much less expensive, but both make a long-lasting lawn if installed properly.

Many people think you can just lay sod over the dirt and it will grow, but both sod and seed require the same kind of extensive soil preparation: Amendments must be added and the soil thoroughly tilled and raked as flat as a pool table.

Unless you plan to plant another Bermuda grass lawn in its place, you also need to be concerned about the old Bermuda. It must be completely killed or it will come back from the roots and rhizomes through the sod or sprout with the seed.

The herbicide Roundup is frequently used for this purpose, but it may take several tries, and it does not kill seed lying in the soil. The directions explain how to best use it.

The easiest and cheapest way to redo your lawn would be to till the soil and sow seed of common Bermuda grass. The old Bermuda stolons will sprout along with the new seed, and you’ll have a lawn you can walk on in about two months.

But sod does have several advantages. It can be walked on almost immediately and will keep most weed seeds lying on the soil from germinating, though sod installers often spread a pre-emergent herbicide to make sure no weed seeds sprout.

Also, it can be laid at any time, while seed can be sown only during certain seasons. Bermuda seed is usually sown in late spring or early fall, while seed of fescues and other cool-season grasses must be sown earlier in spring or later in fall. Neither does well sown in midsummer.

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