Thursday, August 25, 2011

We get questions...

In the flower garden:

geranium budworm

eggs of geranium budworm

Something is eating the flowers of my geraniums and petunias!

Geranium budworm is a caterpillar, the larva of a moth, which eats flower buds, petals, and leaves of common geraniums, petunias, callibrachoas, and related plants. It is hard to spot because it turns the color of what it is eating. Most people notice holes in the petals, and then the absence of flowers. Geranium budworm has a broad host range, and is also known as Tobacco budworm and Tomato fruitworm (not to be confused with tomato hornworm, which is more properly called Tobacco hornworm!).

Caterpillars can be controlled with an organic spray made from Bacillus thuringiensis (aka "BT"). The insect must feed on the material, so you have to tolerate some damage before you get control. The adults keep laying eggs all summer, so you have to spray about every week. Consider planting something that doesn't get budworm instead, such as ivy geranium.

Why is my Acanthus dying? It just finished flowering.

Acanthus mollis flowers

We get the same question about Alstroemeria. Both species are growing from a rhizome, and as with many bulb-like plants they have a short dormancy after the bloom. It is normal, but disconcerting. It's a good opportunity to cut the plant back. It will resprout right away.


Peruvian lily

In the orchard:

My citrus tree dropped most of the fruit right after it flowered!

Citrus produce an abundance of flowers, but the amount of fruit a tree can sustain is determined by the size and vigor of the tree. Many small fruit drop. This natural thinning is handy, because we don't have to worry about citrus trees over-producing and breaking the branches. Other fruit trees such as peaches and plums often set far more fruit than they 'should' and end up collapsing unless fruit is removed early in the season.

Why do my stone fruits have hardly any fruit this year?

We had 14 days of rain during the bloom period. Bees are finicky. High moisture caused fungus to blight the petals of apricots and plums. It's just been a tough year overall for fruit trees.

Figs are spoiling as they ripen: ok on the outside, yucky on the inside.

Figs set two crops in our area: the breba (spring) crop, and the fall crop. Figs are very soft and vulnerable to rot organisms if moisture is high, and this year we had over an inch of rain in the last week of June, which was very bad timing for the ripening breba crop. Hail damage in June allowed rot to set in. The fall crop, which is better and larger and arrives during reliably dry weather, should be fine.

Something is eating all the plums off my tree before they ripen!

Something is eating my young melons as they ripen!

Something is eating my oranges!

Management of tree rats and tree squirrels is very challenging. They move rapidly through the garden, damaging specific crops, and then move on. Basic animal management strategies usually involve:

removing habitat;

installing barriers;

applying repellents;

baits and traps.

Think like a rat. You are jumpy, want to keep moving and get some food without taking too much time about it because when you are out in the open you are vulnerable to predators. Prune to make the area more open. Slow them down with netting over and around the crop. Make noise somehow (wind chimes in the trees?). They may just go to your neighbor's yard.

One possible solution: a customer suggested sandwich bags to keep rats/squirrels away from pomegranates. You slip the developing fruit into a #4 sandwich bag and staple it closed.

In the landscape:

Newly seeded lawn areas suddenly died out after the rain in early June.

Seedling fungus diseases cause rapid die-off in warm weather, which is one of the reasons we get better results re-seeding lawns in the fall when nights are cooler and fungus isn't active. Rake out the area and add some more seed when weather cools off.

Problems with a redwood tree (Sequoia sempervirens): needles browning and dropping; needles scorched on surface; needles gray in appearance; no new growth.

Coast redwood needles

Most problems with Sequoia are related to watering. It is usually a problem with duration (not long enough), frequency (too often), or distribution (not enough emitters or sprinklers).
In this case, the tree was being watered with bubblers spaced at intervals around the drip line, PVC pipe with holes was installed vertically to promote deep watering. The bubblers were near the pipes so water flowed rapidly down. No spray or surface drippers.

It is normal for the older needles of coast redwood to turn brown and drop in late spring and more lightly throughout the year. The scorched needles and lack of new growth are signs that the tree is not happy. Here the problem wasn't lack of water, it was the distribution. Redwoods have many surface roots, so water needs to be distributed across the surface under the tree. Adding some mini-sprinklers to the system, or occasionally setting a sprinkler to augment the system, should restore the vigor.

Redwoods are never drought-tolerant trees, preferring evenly-distributed water every week or so throughout the summer.

Curled, distorted leaves on bay laurel.

A psyllid insect arrived in California's Bay Area a decade or so ago, and sometimes shows up here in the Valley. It is an aphid-like insect that sucks the leaves, and the leaf edges curl around it. If you carefully unroll the leaf edge you will find the culprits. Psyllids only harm the new growth, for a rather short period in the spring, and the damage is cosmetic. Bay trees that are pruned lightly are less affected, as the psyllid can't damage thicker mature leaves. Prune bay laurel seasonally for size control, if at all, and avoid shearing them.

My neighbor has planted "horsetail bamboo" and it is spreading into my yard. Can I sue him?

You can sue anybody. The question is whether you would prevail in court. Most judges aren't horticultural experts. I can tell you that horsetail (Equisetum species) is very invasive. It is NOT a bamboo, but has a growth habit similar to running bamboos: rhizomes spread quickly through moist soil into nearby beds and lawns. Herbicides won't kill it. Digging it out is difficult because it breaks and resprouts. A rhizome barrier will contain it until it goes over or under; barriers for spreading plants must be monitored seasonally.

People like the look of horsetail as an accent plant. Offer to buy your neighbor an ornamental grass, a phormium, or iris, and help to dig out the offending invader. In extreme cases a physical barrier (sold by bamboo supply specialists) and heavy-duty landscape fabric can hold it back.

General and wacky:

Do you have a product to control frogs? They're keeping me awake at night.

A set of earplugs is less than $10.

How do I kill the bees that are all around my shrub?

Don't kill bees!

What happened to all the ants?!?

They drowned. At least, that is my assumption. We normally get lots of questions about how to control ants as summer begins. This year, hardly any. The soil was saturated in December, again in March, and cold rainy weather continued into May and June.

They'll be back. Trust me on this.

What is the deal with olives? Fruitless? Sterile? Huh? I want one that won't make a mess.

There are self-sterile olives which can be cross-pollinated by other varieties, but which consequently set much smaller crops than self-fertile types. Olive pollen is very tiny, light, and wind-blown for a mile or more. So it isn't unusual for a “fruitless” type to set some crops of fruit. One variety called Swan Hill is self-sterile for both male and female flowers, so it is incapable of setting fruit. The patent on that variety has finally worn off, so it has become more readily available as other growers begin propagating it.

1. Why can't I find Scottish broom anywhere?

2. I was browsing your website and noticed that St. John's wort can't be sold in Yolo and was wondering why. I have some seeds of another Hypericum (punctatum) and want to know if I should worry about planting them or not, since it seems like a similar species.

Scotch broom (Cytisus scoparius) and St. Johnswort (Hypericum perforatum, aka Klamathweed) are both invasive species in the true sense of the word: non-native plants which reseed out into wild areas, displacing native vegetation, and possibly causing economic harm to farmland or rangeland. Scotch broom has become so familiar as an invasive that most wholesalers have stopped growing it; most have even stopped growing related broom species!

St. Johnswort is restricted from sale in Yolo County. Local agricultural commissioners have discretion about how they prevent the spread of invasive weeds that are listed on the state's official list. Our ag commissioner has decided to prohibit retail sales of Klamathweed. The restriction is specific and does not apply to other species of Hypericum.

A cautionary note:

A customer walked in waving a pest sample on a branch from an apple tree, from the Bay Area. Oh, my. We are in a quarantine district for Light Brown Apple Moth (LBAM), which is fully established in the Bay Area. There have been a few finds in Yolo County, though not in nurseries. Thank goodness. According to nursery folks in the Bay Area, a find prompts closure of the nursery, the whole place has to be sprayed, and then re-inspection is required before they can re-open.

Please don't bring plant materials into Yolo County from anywhere in the Bay Area other than from nurseries that have been certified as free of LBAM. Nothing from Aunt Minnie's backyard, please! That is how pests spread.

For more information about Light Brown Apple Moth, visit the state agriculture department web site: