Question: Can I plant some coriander in a container on a sunny patio? Also I have a potted mint plant growing for the last two or three years which was doing well, but not now. What more can I do? Florence Salama, via email
Answer: Coriander would do well in a container on your sunny patio. Soil should be rich and well-drained.
It's easy to sow coriander too thickly. If it's spaced 12 to 15 centimetres (five to six inches) apart, the plants are stronger and leafier. But some people sow thickly anyway, then thin and eat the plants as they develop.
Coriander can survive through a mild winter. If you want to try this, you could move it in late fall into a sheltered spot.
Mint likes part shade, moisture and rich soil. But no matter how well you treat it, potted mint left unrenovated starts dying out after a while.
You can keep mint fresh and growing in a container by cutting one or two pie wedges out of the existing growth, removing the roots and that portion of the soil. Old mint roots are thick and tough, so you need a very sharp knife or a serrated freezer knife.
Discard the old roots you've lifted out of your wedges. Don't compost the roots because parts of them may begin growing. City green waste bins are the best place for aged mint.
You can compost the old soil if you can separate it from the roots. But the wedge holes should be filled with compost. The mint will quickly occupy the space. Mint needs a constant supply of new, fresh soil to grow well. That's why it's invasive in the open garden.
If your mint pot is on soil, mint roots may reach out through drainage holes.
Question: I have a wonderful tomato plant with a dozen or more tomatoes getting ripe. But a fat, green worm fell off a leaf. I saw another one today, and they are hard to kill. I tried an insecticide and finally used hair spray. What else can I do, and how can I tell if there are any more? Eileen, via email
Answer: This sounds like the tomato hornworm. It's active at night. You could go out with a flashlight and hunt for more.
If you could bring yourself to handpick them and stomp on them, this would be a quick, organic, easy and safe solution. Safe for you and safe for the fruit.
Some gardeners throw slugs on the road in hopes a car will squish them. This would also work for hornworms. Hornworms could also be euthanized in the freezer inside a sealable plastic bag. I have heard of this being done with slugs. It's said to be relatively humane.
If any insecticide and hair spray got on the tomato fruit, I don't recommend eating it.
Spray tends to drift on the air and doesn't always end up where you're aiming.
Sprayed fruit would likely have a nasty taste, and insecticides can make people sick.
Insecticidal soap will kill hornworms. But it needs great care. It's harmful in eyes and mustn't get on tomato fruit.
A substance called Btk will work on hornworms when they're small and young. You can find both in garden centres.
Be sure to thoroughly dig the tomato soil this winter. Hornworm cocoons overwinter in the soil.
Anne Marrison is happy to answer garden questions. Send them to her by email, firstname.lastname@example.org.
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