Whitefly Invasion

Dear Doyenne,
We live in Yakima, WA, Z5. We winter our hibiscus, tender herbs and Angel's Trumpet in our west facing windows until spring breaks, when we haul them all outside. We are plagued with whiteflies, both indoors and out - I'm thinking of donating our home to a research lab. We had started with the organic route, Safers insecticidal soap and other brands. We then made a mixture of alcohol, horticultural oil and water. Next we went to pyrethrum and then to diazinon.

I had read about companion plantings that whiteflies don't like pennyroyal, so I stuffed the bottom of my plants with the stuff. The whiteflies loved it! Short of quitting the plant business, what more can we do to get rid of the whiteflies?

Desperate in Washington,

Desperate,
What you describe is a problem common to outdoor plants that are housed inside during the winter. In general, it sounds like the plants have not gotten enough sun. I say this because your plants are not able to ward off insect attack, probably because of thin cuticles. They need full sun to toughen up.

Some other solutions (I'll skip the insecticidal soap rap, hoping you took care to treat the undersides of all leaves, and I'll refrain from screaming loudly about the diazinon!): yellow sticky traps staked at plant level and out of direct sun; nasturtiums, not as a preventative, but as a sacrificial crop, in order to keep them away from your good plants; the parasitic wasp, Encarsia formosa, which feeds on the whitefly in its nymph stages. I've also read that you can suck up many nymphs and adults using a small vacuum cleaner. Sounds improbable, but if you want to try it, be sure to vacuum up some boric acid first to kill the flues when they hit the bag.

I can't bring myself to say good luck, but I will say, hang in there! KL

Nasty Homemade Weed Killer

Dear Doyenne,
I am from Racine, WI. I found a weed killer mix in our newspaper, The Journal Times. The mix calls for 1 gallon of white vineagar, 1 pound table salt, and 1 tablespoon of dish washing soap. I would like to know why this mix should work.

Thank you.
Mr. Nelson

Mr. Nelson,
The mix you describe will kill just about anything, including weeds, insects, microbes, etc. It's got soap, which will destroy cuticle and other protective outside coverings; vinegar, a highly acidic substance; and salt, which will desiccate anything that's not already dead. It might be fine to use on sidewalk weeds (where presumably there isn't anything else alive), but bear in mind it's a broad spectrum killer. Homemade products aren't necessarily better or safer than commerical ones.

Thanks for writing,
Ketzel

Red Thread Fungal Disease in Lawn

Dear Doyenne,
I live in northeastern Washington State. Last summer something called "lawn and turf red thread" appeared in my lawn. It has spread over most of my lawn as dead looking areas with a red tinge. Have you any suggestions on eradicating it?

Thanks for any help,
O.C.

O.C.,
Although the lawn looks bad, the fungal disease you describe as "red thread" doesn't actually kill it -- it only parasitizes the leaves. The crowns will be able to regenerate new foliage with ample water. DO NOT USE A FUNGICIDE! This will just lead to the death of beneficial microbes, and probably cause more problems down the road. The best thing you can do is care for your lawn by using a high-nitrogen fertilzer in the spring, mowing with a mulching lawnmower, dethatching if needed (done in spring), and watering the lawn at least occasionally in the summer.

Hope this helps, KL

Bloomless Hydrangeas

Dear Doyenne,
My hydrangeas are growing like crazy, but they won't bloom. What am I doing wrong?

Thanks,
Pamela

Pamela,

My guess is that you've either been pruning them at the wrong time of the year, or that you live in a climate where the canes are killed back to the ground. Hydrangeas only bloom on the previous year's growth, so if the tops are pruned back in the spring or killed back by cold, they won't bloom. If you live in a very cold climate, you might want to move the hydrangea in fall to a more protected location.

Enjoy, KL

Topsoil a Dud

Dear Doyenne,
We live in a cold valley in the Sierras (-40°F winters, approx. USDA zone 3-4). My local nursery-guru says that the topsoil we purchased from the 100-year-old mill site has a "high carbon to nitrogen ratio" and that I'll "be feeding the microbes in the soil for years before they break down all that sawdust".

He said to use organic fertilizers with live bacteria and fungi and then add extra nitrogen (urea?) frequently to "increase the microbial populations" and that the plants will get a little of the nitrogen each time before the bacteria eat it all up.

I have noticed that no weeds have grown in the pile of topsoil that's been sitting here for 2 years. Could you explain this?

Thank you,
Erica

Erica,
Oh dear, the stuff you bought was indeed a dud because of its high sawdust content. Couple of problems here: first, plants will be unable to survive in such a low nitrogen environment without massive fertilizer additions. Second, the topsoil is likely to decompose by 50% or more total volume! You don't want to be planting shrubs and trees into a medium that will literally disappear over the next few years, leaving roots exposed and plants that will be blown down.

Ideal soil is only 5% organic matter (OM). My best advice, and you're not going to like it, is to find another topsoil source and insist on a low OM soil. Then use a nice topdressing of compost and/or wood chips to feed the soil from the top down. You can compost your topsoil and use it later as the sawdust level decreases. Or, if you have an area you are trying to keep weed-free, by all means use this as a top dressing; as you have noticed, nothing will grow in it.

My thoughts are with you! KL

Don't Move That Daphne

Dear Doyenne,
I live in Kent, Washington. And my concern is for a plant that belongs to a neighbor. She has a Winter Daphne which had thrived in the same place for 8-9 years. About 6 weeks ago, she redid the flower bed, moved the plant and changed the soil. When it first showed signs of wilt I told her to give it lots and lots of water, fertilize with acid mix and coffee grounds. Now the leaves are brown and she asked me if she should prune them off and I don't know what to tell her.

Thank you for your advice.
Cheryl

Cheryl,
Your friend is almost certainly going to lose her plant. As the great English gardener Vita Sackville-West once wrote (I might be paraphrasing here), "Never let a daphne see a spade." They cannot stand to have their roots disturbed, often succumb even when being transplanted from a nursery pot, and are difficult to dissuade out of a swan dive once they've jumped. Best bet is to leave it alone and see if any part of the plant pulls out of it.

So sorry! KL

Newsflash: Summer-planted Trees Need Water!

Dear Doyenne,
I have an apple tree, a Spitz, which I bought at the beginning of the summer. It's planted in our front yard and gets lots of sun. During weeks that it doesn't rain I water the tree with about a bucketful of water twice or three times a week. However, the leaves are curled up and dry and some of them have brown spots on them. The tree has grown since we planted it, but it doesn't look particularly healthy. Any suggestions?

Thanks!!!
Megan

Megan,
Surprisingly enough, your tree isn't getting nearly enough water. Keep in mind that when you bought it, it had already lost about 80% of its roots; add to that summer planting, and we're talking about a tree that needs more like 5 gallons of water at a time. If the area is well mulched (and not competing with surrounding grass, which will suck up water), you can get away with watering 2-3 times a week through the rest of summer. To save on labor, you might want to just put a hose end at the base of the tree and let it trickle for a few hours each time.

Best of luck, KL

Ill Lillies

Dear Doyenne,
I garden in Scituate MA, zone 6, near the Atlantic. I have many different asiatic lilies but there is a pair I am worried about. I think they are called "gold ring". The first two seasons were outstanding - they knocked my socks off! Last year after they had reached their height they dropped their leaves, but they managed to bloom, albeit not as mightily as previous seasons. So I fertilized them in the fall. This season they came up, dropped their leaves, had much smaller blooms, barely any scent and could not fully open, turned brown and drooped over. I was worried that the miserable red lily beetle had found its way to my gardens, but no other lily was acting this way and I could not find a beetle. These two sickies are quite near other healthy lilies, so I'm thinking I should be digging these two up, but I'm curious about what is going on.

Many thanks,
Kathleen

Kathleen,
Not to put too fine a point on it, but: Get those sickies out! Chances are they've contracted some sort of soil borne fungal disease to which many lillies are susceptible. Pull them out and do not compost them; instead, say a sad goodbye and chuck them in the garbage (perhaps along with a bit of the soil that was around them). Then go ahead and plant anything in that spot that ISN'T a lily!

Best, KL