10 Tips for Growing Heirloom Tomatoes
Recommendations
Heirloom tomatoes draw growers with their premium price and with shoppers hunting for old-time tomato flavor. They can be demanding, though, typically needing more labor and yielding less than modern varieties.
Disease is the main challenge. Most modern hybrids carry bred-in resistance, while the majority of old varieties have little. Heirlooms therefore often stop producing sooner than resistant types, and plants that lose much of their foliage also lose flavor, since leaves are what turn sunlight into sugars and aroma compounds. For a commercial heirloom crop, keeping disease out comes first.
Below are 10 practices that can help heirloom tomatoes earn their place on your farm.
1 • Learn to Graft
Grafting onto a resistant rootstock can raise heirloom yields considerably where soilborne disease is a problem.
Perhaps the most effective single practice for heirlooms is grafting: joining the heirloom scion to a vigorous rootstock that carries disease resistance.
University studies have reported large yield gains from grafted heirlooms, in some cases 30–50% or more, mainly where soilborne diseases are present. Grafting lowers the risk from those diseases, and many growers find the added vigor helps plants hold up against leaf diseases too.
More on grafting:
- Fundamentals of Tomato Grafting (webinar recording)
- Guide to Side-Grafting Tomatoes (tech sheet, PDF)
- Guide to Top-Grafting Tomatoes (tech sheet, PDF)
- Browse Tomato Rootstock
2 • Protect & Support
Many tomato diseases spread when leaves stay wet, so growing heirlooms under cover, where foliage stays dry, lowers disease risk.
Heirlooms tend to perform better in high tunnels, which keep the leaves dry. Many tomato diseases need moisture to spread, such as late blight, leaf mold, Botrytis and Alternaria.
Since most heirlooms make large, vigorous vines, they need a tall structure and a sturdy trellis. In greenhouses and tunnels, tomatoes are usually pruned to one leader tied to a string that can be let down as the season goes on, keeping the fruit within reach. Grafted plants can instead carry two leaders, which means buying fewer plants and helps cover the cost of grafting. To do this, remove every sucker except the one just below the first flower cluster; it becomes the second stem. Tools like the Rollerhook® and Tomahook make lowering and leaning the vines much easier.
More on trellising tomatoes:
- Trellising & Crop Support Systems for Tomatoes (article)
- Basket-weave Trellising Instructions (tech sheet, PDF)
- Greenhouse Tomato Pruning & Trellising (tech sheet, PDF)
- Browse crop supports and Trellising Supplies
3 • Prune Correctly
Vigorous heirloom vines need more frequent pruning. Taking off suckers opens up the canopy so air moves through it, which helps keep leaf diseases in check, and it also tends to push the plant toward larger fruit up top.
4 • Space Generously
Giving plants more room is another way to improve airflow and lower disease pressure. A common spacing for indeterminate tomatoes is 24–36" between plants and 4–6' between rows; for heirlooms, going wider in one or both directions lets the canopy dry faster.
5 • Grow on Mulch
Mulch warms the soil, holds moisture, smothers weeds and keeps soil from splashing onto leaves.
Field tomatoes benefit from mulch: it stops soil from splashing up, warms the ground, saves water and suppresses weeds, and together those improve marketable yield.
Black Solar Mulch, SRM Red Mulch, and Bio360 Biodegradable Mulch are all good choices for tomatoes.
6 • Lay Drip Lines
Drip irrigation keeps leaves drier than overhead watering.
Additionally, fertigation through the drip line is a better way to feed than spraying nutrients on the leaves.
7 • Prevent Disease
Where tomato diseases are common, plan a prevention program. Start by treating transplants with RootShield ® before planting. Its active ingredient is a beneficial fungus that colonizes the roots and helps protect them from root diseases. After planting, check the crop often for early signs of disease, which is easy with heirlooms since you're in the rows pruning regularly anyway.
More on tomato diseases:
8 • Choose Varieties with Care
We recommend 'German Johnson' is a dependable starting point. It grows more easily than many heirlooms, with strong vines, good yields and rich, tangy flavor.
Choose heirlooms methodically. Grow a range of varieties, keep notes, and narrow down to the ones that do best for you. For a quick look at color, maturity, size and texture, see the Heirloom Tomato Variety Comparison Chart.
Learn more:
- 3 Ways to Choose the Best Tomatoes(article)
9 • Water Judiciously
Many heirlooms have thin skins, which is part of their eating quality but also makes them crack on the vine. Avoiding overwatering reduces splitting, and extra water ends up in the fruit, where it waters down the flavor.
Giving water in several smaller doses as needed, rather than constantly, helps limit cracking and concentrates flavor. Some growers dry-farm tomatoes: they water deeply at planting to build a deep root system, then stop irrigating once the first fruits have set.
However you water, a handheld soil moisture meter gives fast readings. Record what you do so you can fine-tune timing and amounts.
10 • Consider Heirloom-like Tomato Varieties
Heirloom-style hybrids aim to combine heirloom flavor and texture with the disease resistance and yield of a hybrid.
These newer varieties were bred by conventional methods to give fruit with the look and taste of heirlooms on plants with more vigor and resistance. Their higher yield usually makes up for the somewhat higher seed price, since they keep producing instead of collapsing from disease as heirlooms can.
Three heirloom-style F1 hybrids worth a try:
- 'Marnero' closely resembles 'Cherokee Purple', widely considered one of the finest-tasting heirlooms.
- 'Margold' resembles 'Striped German', an heirloom revered for both its sweetness and its beautiful appearance.
- There are many 'Marmande'-type tomatoes, inspired by the old French heirloom, and 'Marbonne' is a well-regarded choice among them for flavor, vigor and disease resistance, in the field or under cover.
These hybrids keep much of the fruit quality of the heirlooms they resemble, while adding plant habits and disease resistances that support higher yields than true heirlooms, which often decline early in greenhouse conditions.
Grow the Best Heirlooms
Good heirloom growing comes from following new developments, trying things, and adjusting year by year. Review standard tomato practices before the season starts. ATTRA offers a free guide, Organic Tomato Production , that covers tomato growing in thorough detail.
With good production practices, and above all early disease prevention, heirlooms can become a profitable crop that your customers look forward to.
