Paul James answers questions about ferns, mints, self-watering containers and more.
Master gardener Paul James answers some questions from gardeners:
Q. Help! The undersides of my fern fronds are covered with weird spots.
A. What you're seeing is perfectly normal. Those intriguing geometrically-arranged spots are known botanically as sporangea and each one of them contains seeds. In fact, you can collect the spores and use them to propagate new ferns. The process is tedious and the success rate is less than gratifying, though, so when I need new ferns, I buy them.
Q. Do ferns need fertilizer?
A. No, ferns don't need fertilizer. As a matter of fact, most commercial fertilizers are way too strong for ferns and will either severely damage them or kill them outright. The only food ferns need is an annual side-dressing of compost or shredded leaves.
Q. I like mint. Is it easy to grow?
A. If you can grow weeds, you can grow mint. There are all kinds of mints to consider, from the familiar peppermints and spearmints to the more unusual kinds like apple mint and variegated pineapple mint. Mint, when given a fair amount of shade and plenty of moisture, can spread very quickly in a garden. So I suggest you consider growing it in a pot. I also suggest you experiment with using it in the kitchen, because mint — in my opinion — is one of the most under-used culinary herbs of all.
Q. What does LD-50 mean?
A. The expression LD-50 is the most commonly used method of measuring the acute toxicity of pesticides. "LD" refers to lethal dose and "50" refers to the dose of a particular pesticide that kills 50 percent of the organisms exposed to it in laboratory tests. The higher the LD-50 rating, the safer the pesticide is to use. Dursban, which was banned in this country a few years ago, has an LD-50 rating of 163, which means it is extremely toxic. Insecticidal soap, by contrast, has an LD-50 rating of greater than 10,000, which means it's virtually non-toxic. Unfortunately, the ratings are based on the oral ingestion of pesticides but most pesticides are absorbed through the skin or inhaled. So don't assume that a particular product with a high LD-50 rating is necessarily safe. And as always, make sure you read the label instructions carefully and follow them to the letter.
Q. Is boric acid safe to use?
A. Boric acid, with an LD-50 rating of between 3,200 and 6,000, is relatively safe to use in low doses, and it's extremely effective against ants, cockroaches, fleas and silverfish. In fact, it's the active ingredient found in most off-the-shelf cockroach and ant-control products. However, in its powdered form, boric acid can irritate the nose, throat and lungs, so it's a good idea to wear a mask when applying the stuff.
Q. Can you make your own insecticidal soap?
A. You bet you can. A one- to two-percent solution of liquid hand-soap mixed with water works reasonably well, although homemade concoctions are often less reliable and more likely to burn plants than commercial formulations. Besides, if you buy insecticidal soap in concentrate and dilute it with water, you'll actually save more money in the long run than if you made the stuff from scratch.
Q. How are your tomatoes — the ones you planted in the self-watering planters?
A. They and the eggplant are doing better than I expected, despite the fact that 75-mph winds knocked them flat to the ground last week. I planted those four tomatoes and one eggplant in special containers just six weeks ago, and now the tomatoes are extremely healthy and show no signs of bacteria or viral blight, which is rare for my region. They're flowering now and should set fruit soon. The eggplant is looking good, and has been left unharmed by flea beetles, which are notorious pests around here. The self-watering feature of these planters is great, and despite warm temperatures, I haven't had to fill the reservoirs more than once a week, which is a real timesaver. In fact, this fall I'm going to re-use the planters and grow greens in them. Then I'll set them up on a potting bench where rabbits can't get to the goods.