I’ve sold heirloom tomato plants at the St. Paul Farmers’ Market since 2009. Every year I watch some people agonize over plant selection, sometimes spending an hour examining every seedling. Others look at the overwhelming amount of choice and say “just pick me a good one.”
Either approach works, but you do need to know what actually matters in young tomato plants. Healthy plants have specific characteristics: proportional pot size, thick stems, hardened-off foliage, and green color. Here’s what to look for and what to avoid.
Quick Summary: When buying tomato plants, look for: plants in 4-inch pots (not rootbound), thick stems (not leggy), hardened-off foliage (not wilting), green leaves (not yellow or purple), and healthy growing tips. Avoid plants already flowering or fruiting, large plants in small pots, and anything from big box stores where staff can’t answer growing questions. Buy from farmers markets where you can talk to the grower. Read time: 6 min | Experience level: Beginner
Jump to: Signs of Healthy Plants | What to Avoid | FAQ
Before moving to Minnesota, my husband and I ran a small Christmas tree farm in Oregon, and the process of selecting the perfect tomato plant is strikingly similar to finding the perfect Christmas tree.
Some people will spend a good part of the day worrying about details that only they can see, and some will just turn to me and say “pick me out a good one”.
In the end, the perfect plant is the one that will fit your specific growing conditions.
For tips on selecting plants based on specific flavors, review this guide on heirloom tomato flavor profiles.
The following list is just a set of tips for making sure your plant grows into a healthy expression of what it’s genes tell it to be.
What Makes a Healthy Tomato Plant?
Here are 7 key factors to look for when purchasing a tomato plant at the nursery or farmers’ market:
- Make sure the size of the pot is in proportion to the size of the plant; if you have a large plant in a small pot it is likely to be rootbound. I think the perfect pot size is a 4″ pot, as it has allowed the plant to gain height while comfortably spreading it’s roots. The example of the taller plant above is a 12″ plant in a 4″ pot. While some plants may be shorter than this due to variety, they would still be best in a 4″ pot which allows their roots to grow gradually until you get it into the ground.
- Look for a fairly thick stem; tall plants with thin stems have been stressed trying to reach the light and they will not stand up well to wind and rain in the garden;
- Make absolutely sure your plant has been hardened off. If you are buying it at an outdoor market, you will know by the fact that it is not drooping and wilting, but if you are buying from inside a nursery or a catalog…ask to make sure. Plants can look extremely healthy in a cultured environment and will fall over and wilt if you plant them outside without being hardened off;
- Small white nodes along the bottom of the stem is not a bad sign (see photo below). Those are trying to be roots. Plant the tomato deep enough to cover those white nodes and you will get more roots, and more tomatoes;
- Look at the growing whorl at the top of the plant; the bottom leaves of the plant may have suffered while hardening off, but if the top whorl is green and growing well, that is the main thing. You should plant your tomatoes fairly deep anyway and take off the bottom leaves if they touch the ground. The stem and the top are the two most important signs of health.
- Check the underside of the leaves to make sure there are no aphids or small bugs you would be bringing home;
- The color of the plant should be green (with the exception of any bottom leaves that have suffered windburn or sunburn while hardening off). If the plant is yellow it has probably been in the pot for too long and is lacking nitrogen; if the plant is somewhat maroon it has an iron deficiency. Green is good. You can fix the deficiencies with nutrition, but if it has gone too far the plant may be stunted;
What Should You Avoid When Buying Tomato Plants?
- Do not get great big plants that already have small tomatoes on them. They have already put a lot of energy into fruiting before their time and you will not get very many tomatoes from them. It’s fun to see tomatoes so early on a plant, but you will pay for it later with a poor yield.
- In the same vein, try to avoid plants that have blossoms; Early blossoms on a small plant means it has been stressed and feels it must hurry and produce. The yield will be poor.
- Small pots with large tomatoes will most likely mean the roots are tangled up into a ball in the pot. If you get one of these, be sure and break the roots gently apart and spread them out when planting;
- If you are going to grow your tomatoes in pots, ask for a variety that is determinate and you will likely have more success. Indeterminate plants will vine until frost and it is difficult to keep them upright in a pot without them breaking over the cage. A determinate plant will grow to a certain height and stay relatively stocky. With a determinate you will get a large yield over about a 3-week period, whereas with an indeterminate plant you will get a smaller yield but over a longer period of time. Not to say that you can’t grow indeterminates in pots…you can. It is just easier with determinate plants.
Where Should You Buy Tomato Plants?
Lastly, try and buy your tomato plants from a farmers’ market or somewhere where you have access to questioning a grower familiar with how the plant has been grown. The employees at many of the big box home stores may not be the best resource to help with any tomato questions you may have.
FAQ
4-inch pots are ideal. The plant has room to develop roots without becoming rootbound. Large plants in small pots are likely rootbound and will struggle after transplanting.
Early flowers on small plants indicate stress. The plant rushed to reproduce instead of building strong roots and stems. You’ll get poor yields. Healthy transplants should be vegetative, not flowering.
Those are root nodes. They’re a good sign. Plant the tomato deep enough to bury them, and they’ll develop into additional roots, producing a stronger plant.
Nitrogen deficiency, usually from being in the pot too long. You can correct it with fertilizer, but severely yellow plants may be permanently stunted. Choose green plants.
Determinate. They grow to a set height and stay compact, making them easier to support in pots. Indeterminate plants vine until frost and can break cages in containers.
You can ask the grower questions about hardening off, variety characteristics, and growing practices. Big box store employees often can’t help with tomato-specific questions, and plants may not be properly hardened off.
For a detailed guide and journal for growing tomatoes, check out my Tomato Workbook on Amazon for $11.99.
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