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Q&A with Andrea Clapp, Tomato Breeder

World Tomato Society: What is the reason you started growing tomatoes? How long have you been doing it?

Andrea Clapp: I’ve loved tomatoes since as far back as my memory allows and have been growing them since then as well. I first started with my dad in our family garden, and when I was about 5, my dad built me my own garden.


WTS: Can you tell us a little bit about your setup?

AC: I grow in Back to Eden–style (mulched, no till) in-ground gardens, and also in cedar raised beds. I believe strongly in no-tilling methods whenever possible.



WTS: How many varieties are you growing, in greenhouses or outside?

AC: During the warm season, I grow 150 to 275 tomato plants. Many of them are varying generations of my breeding projects, but usually, 20 to 40 are stabilized open-pollinated varieties. In the winter, I grow in a small heated greenhouse to advance my breeding projects on a quicker timeline.


WTS: Any other produce that you are growing?

AC: I grow a wide variety of garden produce: peppers, eggplants, onions, garlic, pepinos, naranjila, litchi tomatoes, carrots, herbs, corn, beans, summer squash, winter squash, cowpeas, peas, melons, sweet potatoes, potatoes, beets, radish, several types of cruciferous crops (broccoli, cauliflower, kale, cabbage, etc.), mixed greens, peanuts, roselle, and pollinator flowering plants.


WTS: What is your climate type?

AC: I am in zone 5, so I have the scorching, humid summers as well as the sub-zero winters. It’s Iowa, so anything is possible weather-wise. I usually plant my warm-season crops around Mother’s Day and frost can sometimes come in mid-September or as late as the end of October.


WTS: What is your soil type?

AC: I have several different garden spaces with varying soil types. My ground soil consists of a good amount of clay, although it has been amended for over 16 years. Some of my raised beds were built over time with leaf mold and compost, so they can be dug with bare hands, and my most recent cedar raised beds are a custom blend mix of peat, compost, a bit of perlite, and some rabbit manure.

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WTS: What mistakes did you make starting out, and how did you learn from them?

AC: It’s hard to remember. I’ve been growing plants since I was about 3, and my dad was and still is a good teacher. I continually learn from what nature throws at me, because I believe you can gain a lot of insight if you allow nature to be your guide. I have also learned that instead of trying to defy nature, it’s best to mimic it. Nature always wins.


WTS: What is your favorite variety and why?

AC: I don’t have a favorite variety per se, but I enjoy varieties with a clear epidermis—purples, pinks, and whites primarily. The one and only variety that I plant every year is White Tomesol. It has a delicate, balanced flavor; the plants are robust with great disease resistance, so they hold up well during flooding and drought; they are usually the first plants to produce in the spring and the last plants left producing in the fall; and the production itself is very good, averaging 35 to 40 fruits per plant.


WTS: What is your favorite tomato dish to make?

AC: That is a hard question. I love tomatoes just about any way they come, but I guess I would say on a lazy Sunday afternoon I enjoy making braciole, an Italian dish—stuffed, rolled steak (rolled like a cinnamon roll) that simmers in a tomato-vegetable sauce bath for hours. The result is meat so tender you can cut it with the edge of a fork, like cake!


WTS: What advice would you give a beginner tomato grower?

AC: Pay attention to nature, and let it be your guide. When you make a mistake or something “bad” happens, record it in a journal with the date. Chances are it could be something that happens due to seasonal timing—you’ll be better prepared for the next growing season if you take good notes.


WTS: Are there any varieties that are easier to grow than others?

AC: Hybrids are more disease resistant, so they would be good for a novice grower. Also, hearts, pastes, and elongated tomatoes are trickier to grow because of their cell structure and flesh density. You have to know how to water appropriately and amend with the right fertilizers or you will have problems with blossom end rot.


WTS: What is the best way to transplant tomato plants?

AC: Tomatoes can be transplanted in several ways: straight up and down, sideways trenched, or at an angle. Any of these methods will work, but the key to transplanting is to plant them deep in the soil. Tomatoes will grow extra roots along any part of the stem that is in contact with soil.


WTS: And when is transplantation necessary?

AC: I pot up or transplant my tomatoes when they reach 2/3 the height of the container they are in. Tomatoes should not be planted outside until nighttime temperatures are consistently over 45 F.


WTS: Do you have any tips for growing tomatoes on a patio?

AC: Yes, dwarf, micro, and basket varieties are the best. The key to potted tomatoes is consistent watering and fertilization. In pots, the roots cannot reach deeper to seek out water and nutrients; they only have what is made available to them within the container.


WTS: What are your most common pest problems?

AC: Cutworms, cabbage worms, cucumber beetles, Japanese beetles, squash vine borers, stink and squash bugs, and occasionally hornworms.


WTS: What treatments have you found effective with these?

AC: Beneficial predators and a good pair of snips.


WTS: What are the most common disease issues you have dealt with?

AC: Septoria is prominent in the Midwest. Blight and bacterial issues can also be a problem some years.


WTS: What treatments have you found effective with these? 

AC: I recommend an aspirin spray in the early part of the season to boost their immunity (sometimes neem spray), copper fungicide, or mancozeb—in that order and also depending on which disease it is. Allowing the plants to dry out and keeping the soil covered also helps to keep soilborne pathogens down.


WTS: Are there any insects you welcome in your garden?

AC: Parasitic wasps, green lacewings, ladybugs, praying mantis, spiders, bees, and butterflies.


WTS: What do you do to avoid harming them or to create a welcoming environment?

AC: With the exception of occasional neem (I only use that when beneficials are less active and maybe once a season), I do not use chemical controls at all. I plant dill to draw predatory wasps, my gardens are covered in wood chips so they have a place to overwinter, and I have spirea and annual flowers on the edges of my garden to draw bees and act as a nesting site for mantids (spirea). Marigolds help with soil nematodes.


WTS: Are there any crops you like to plant near tomatoes that have a positive effect on them?

AC: I usually plant marigolds at the feet of tomatoes to control nematodes. They also help with some insects, and most importantly, they help build a good mycorrhizae population early in the season, which helps to feed and bring moisture to the root systems of young tomato seedlings. Onions and garlic help to keep the rabbits away from tender seedlings, and dill helps draw beneficials that prey on all different kinds of harmful “worms” (cutworms, hornworms, cabbage loopers, etc.).


WTS: Do you have any suggestions on procedures to incorporate at planting that will reduce disease or harmful bugs?

AC: Cover cropping or intercropping with mustard family plants will keep many harmful bugs away as well as control nematode populations. Cover cropping can also help to some extent with balancing the soil in terms of fungi and bacteria. And it may sound strange, but if I have had a particularly hard season with diseases, I treat my garden in the fall with a mixture of a fermentable product (kombucha, kefir, etc.), molasses, and water. I like to gather as many leaves as possible to cover my gardens and then spray with this mixture. It gives the leaves a jump start at breaking down and provides a positive fungal balance. My garden is also covered in wood chips, which helps control soil splash, keep the moisture where it needs to be, and prevent pathogens.



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