By Penny Pawl, UC Master Gardener of Napa County
The tomato hornworm that so many gardeners detest has a beautiful future if we let it be. After a winter spent underground and when it is done with metamorphosis, it will become one of the loveliest and largest of the moth species.
We never get to see this moth because it only flies after dark. It is known as the sphinx moth or hummingbird moth. Some of them fly in a manner similar to the hummingbird.
During metamorphosis, a caterpillar transforms into a moth. The caterpillar's internal parts liquefy, reform and a moth is born. The same happens to butterflies and it is one of miracles of nature.
I found three of these giant worms the other day munching happily on one of my tomato plants. They blend in very well with the plant, and they are as big as my finger.
I gently pulled them off and inspected their grinding mouth parts. Then I put them under a large overturned bowl with some tomato leaves and the tomato they had been chewing on. The bow is resting on the garden soil.
Most people get upset when they see hornworms on their tomato plants. I get excited. I hate losing my precious tomatoes to them, but by putting them in a container, I give them a chance to complete their life cycle.
Many people agree with me. We like hornworms because they assist with Integrated Pest Management, a way of gardening and farming that relies on the good bugs to manage the bad bugs without the use of pesticides.
Hornworms eat your tomatoes, but in turn, the beneficial braconid wasp lays its eggs in many of the caterpillars. These tiny wasps develop within the caterpillar skin and eventually will kill their host. They emerge from the caterpillar looking rather like rice hulls on the back of the caterpillar.
This same process happens in other butterflies and moth larva and helps with pest management. Anise Swallowtail caterpillars, which feed on plants in the parsley and fennel family, also have parasitic wasps lay eggs in their eggs.
When the caterpillar completes its life cycle and transforms into a cocoon, it will drill into the soil to spend the next several months. I watched one do this and it was gone so quickly I was amazed. The following summer, when the weather warms, they will hatch and begin to fly around looking for places to lay their eggs. Tomato plants are a favorite host, but they like any plant in the nightshade family, including peppers, eggplants and potatoes
I have read that marigolds, basil, borage and mint will repel tomato hornworms if planted alongside the tomatoes. Their strong odors seem to repel the moth.
The hornworm begins life as a small egg laid on the underside of the leaf. The larva hatches and grows quickly, and as it grows it eats more and more of the host plant. After three to four weeks, it is ready to take that dive into the soil.
I raised two hornworm larvae in the house in a container a few years ago. The hornworms spent the winter in my refrigerator in a small jar with soil. When summer arrived, I moved them to the garden, but I fear the experiment was a failure. The three giants I just collected will be on their own when they decide to go into the next part of their life cycle.
UC IPM has this Pest Note on Tomato Hornworms:
The UC Master Gardeners of Napa County are volunteers who provide University of California research-based information on home gardening. To find out more about home gardening, upcoming events or to submit gardening questions, visit the Master Gardener website (napamg.ucanr.edu). Our office is temporarily closed to walk-in questions, but we are answering questions remotely and by phone or email. Submit your gardening questions through our website, by email email@example.com or leave a phone message at 707-253-4143. Master Gardeners will get back to you within a few days.
By Penny Pawl, UC Master Gardener of Napa County
Over the many years that I have been a Master Gardener, I have heard people talk about Nicotiana in the garden, but I didn't pay much attention. Then fellow Master Gardeners Gary Thompson and Noble Hamilton gave me a Nicotiana plant a couple of years ago. That's when the love affair began.
This plant is a member of the nightshade family (Solanaceae), a group that also includes tomatoes, potatoes, peppers and eggplant. It is one of the largest plant families.
Nicotiana is a showstopper in the garden as it grows about five feet tall and has beautiful blooms on the top of the stems. The white flowers grow in a cluster and they shine. The flowers set an enormous amount of tiny seeds.
Nicotiana's main pollinators are moths which come out at night, when the scent of the flowers is strongest.
In addition to the large white Nicotiana, I have a smaller version with green flowers (Nicotiana alata). It stays about two feet tall and is covered with small green blossoms.
Nicotiana is native to tropical and subtropical areas of North and South America. Some varieties also come from Australia. Although they are tropical, in my garden they have not frozen and are perennials. In cold climates they are treated as annuals and replanted each year.
Nicotiana plants bloom in a range of colors, including pink, pink with white, and rose. The plants are easily propagated by seed, and there are many seed sources online.
The seeds pods contain millions of tiny black seeds. I cut back a Nicotiana plant earlier this year and got countless black seeds in my hair and ears. The leaves are sticky, too, so I had leaves in my hair and ears as well. Luckily, they washed off. After the fires last year, the leaves were covered with soot and other debris floating in the air. That mess did not wash off, but those old leaves were eventually replaced by new ones.
If you deadhead the plant religiously, it will rebloom through summer and into fall. However, I would recommend not putting any of the spent blossoms in your compost pile to avoid spreading Nicotiana everywhere. You might end up with a Nicotiana forest.
The garden Nicotiana (also known as “flowering tobacco”) is related to the tobacco grown for cigarettes, but all parts of flowering tobacco are poisonous.
If you plant Nicotiana in a bed, put it in the middle or rear of the bed. It gets tall and as more branches form, it tends to bend over the plants around it. In my garden it does not demand a lot of water. It gets drip irrigation about once a week and worm compost for fertilizer once or twice a year. When winter arrives, I cut the plant back to about two feet.
If you purchase Nicotiana seed, sow it in seed-starting mix and watch the tiny seedlings emerge. Or you can scatter the seed directly in the planting bed. In either case, you will probably need to thin the seedlings as the plants require a lot of space when mature.
Next workshop: “Sustainable Vegetable Growing” (Four-Part Series) on Sundays February 23, March 1, March 8 and March 15, from 2 p.m. to 4 p.m., at the University of California Cooperative Extension, 1710 Soscol Avenue, Napa. For more details & online registration go to Online registration (credit card only) or call 707-253-4221.
The UC Master Gardeners of Napa County are volunteers who provide UC research-based information on home gardening and answer your questions. To find out more about upcoming programs or to ask a garden question, visit the Master Gardener website (http://napamg.ucanr.edu) or call (707) 253-4221 between 9 a.m. and noon on Mondays, Wednesdays or Fridays.