When planning our gardens and choosing varieties, we might make choices by the color of foliage or flowers, the shape and characteristics of the fruits and vegetables, or even just on a whim. But for many gardeners, our local climate can pose problems. 

Matching the right plant to the right place is part of good gardening practice. Here are a few points to consider when selecting your varieties, and how to apply them.  

Understanding your local gardening climate

Many gardeners confuse their local gardening climate with the USDA Plant Hardiness Zones, which are based on average minimum winter temperatures and used to choose perennials that can survive your winters. Hardiness zones are helpful for shrubs and trees. They don’t tell you how long your growing season is, how hot your summers get, or how much heat your annual vegetables will actually receive.

To better choose annual plant varieties that will perform well for you, consider other factors, including heat and cold, moisture or drought, and growing season length.

Heat and cold don’t necessarily mean the minimum and maximums each year, but more the overall amount of heat or lack thereof. Do you live in an area with extremely hot summers, or are you gardening near the coast where the average high temperature in July rarely exceeds 80℉? Are your nights warm, or does it still drop into the 60s, making you think to reach for a shirt many evenings? The amount of heat a plant receives is a key factor in growth. 

Moisture and drought are other aspects of your local gardening climate. For many of us, the driest period of the growing season corresponds to the hottest weather. The two factors can combine to stress plants, reducing growth and yields, and even making them more susceptible to disease. 

Growing season length is also an important factor for many gardeners when choosing varieties. Usually, we’re talking about the number of days between your last frost in spring and the first frost of autumn, and of course, that is more restrictive for northern climates.  Athens, GA gardeners have about 200+ days of growing season, while gardeners in Springfield, MA have only about 145 days. But growing season length can also be a problem for southern gardeners. Due to extreme heat, you may essentially have a spring and a fall growing season, with the summer being too hot for many crops to do well. Long stretches of 100+ ℉ heat are stifling to plants and humans alike.

Here’s a look at how each of these climatic factors can be planned for when selecting annual plant varieties. 

Heat Tolerance

Some plants just don’t like the heat. Plants have a maximum temperature beyond which they stop conducting photosynthesis. It’s not the same for every plant, but for many, growth and fruit set stall when daytime temperatures reach the low to mid 90s. Even heat-loving crops like peppers have an upper limit beyond which they stop setting fruit. High temperatures earlier in the season can also lead many plants to bolt. The stress of overheating triggers the plant to enter reproductive mode, so it can try to produce seeds before it dies. 

Over the years, plant breeders have tracked which varieties perform better under the intense summer sun and have continued selecting for that trait to develop new varieties that hold up better and continue to grow even in extreme weather. If your summer days are typically above the mid 90s, you may have better success with varieties labeled as heat-tolerant. 

If a variety is described as heat-loving, heat-tolerant, or bolt-resistant, it’s better suited to hot‑summer gardens and may not perform as well in cooler climates. Page 13 of our Spring 2026 catalog features a great selection of tomatoes that do well in hot, humid climates, including ‘Heatmaster’ and ‘Florida 91’.

Lettuces are not fans of hot weather and commonly bolt early as temps rise, ruining their flavor. However, 'Black-seeded Simpson' is known for its superb heat tolerance. If your summers get hot early and you’d like a chance at some lettuce even after beach season arrives, it might be a good choice.

Cool Summer Nights

Cold tolerance isn’t just for traditional cool-season crops like lettuces, brassicas, or peas. Like too much heat, cool nights, or low average temperatures can slow or stop photosynthesis and fruit set for plants. Gardeners with lower summer temperatures, like those near the coast, at elevation, or farther north, may need to seek varieties that keep working even when temperatures drop during cool weather.

Tomatoes are known as warm-weather crops, and many varieties will clam up and refuse to do much when the overnight temperatures drop into the 50s. But ‘Siberian’ is a determinate tomato well suited to cooler summers, and can set fruit even when temps dip down to the high 30s. 

Sweet corn can be especially tough to grow successfully in areas with cool summer nights. Even if the days-to-maturity fall within the growing season, growth can be poor, and ears can be sporadically filled. If that’s your problem, look for varieties that are not only quick to mature, but also adapted to cool overnight temperatures.  

Drought tolerance

Normally, we water our vegetable gardens during dry periods, and we might also irrigate our flower beds. But if your summers often include a long, dry period, choosing varieties bred for drought tolerance can reduce stress on the plants, especially if you forget to grab the hose.

When moisture is low, plant roots release hormones that cause the stomata in the leaves to close, sealing in the water the plant has. With the stomata closed, photosynthesis slows dramatically. Drought-tolerant varieties will keep growing longer in drier conditions. They suffer less stress and rebound more quickly. 

Dry weather can cause many problems with sweet corn, but ‘Iochief’ is our most drought-resistant variety. Even within species, some varieties will be more tolerant of drought than others. If your soil dries out between waterings and some varieties seem to stall, switching to drought‑tolerant types can mean plants that keep growing and recover quickly once rain returns.

Growing Season Length

Instead of the absolute number of days between the last spring frost and the first fall frost, we might consider growing season length in a different way, namely, effective growing season length. How many days were useful for the plant, allowing it to grow and mature instead of just surviving? Many days in spring and fall are not very useful, from a garden plant perspective, for growth. 

Horticulturists (and plant pathologists and entomologists) often discuss a measurement called growing degree days (GDD). Basically, a growing degree day is a measure of how much useful warmth a plant has received, based on daily high and low temperatures. Understanding growing degree days helps us to adjust our expectations and to select more appropriate varieties for our local climate.

For most of our summer garden crops, the baseline at which we start counting GDDs is 50℉. If the average daily temperature is cooler, little or no plant growth occurs. The baseline for cool-season crops like spinach or kale is usually 32℉, reflecting their ability to grow with less heat.

For example, using tomatoes, a spring day with a high of 60℉ and a low of 40℉ averages 50℉. Not much growth or progress toward making ripe tomatoes. But a day with a high of 85℉ and a low of 65℉ results in 25 GDDs. If you need about 1,800 GDD (base 50℉) for a big, beefsteak tomato, and cool spring or fall days add little to that total, you really depend on a solid stretch of consistently warm weather in the middle of the season for fruit to ripen. No problem in Athens, GA, but that could present an issue in the north.

For gardeners with cooler summers or chilly summer evenings, you’ll have better success with varieties better adapted to cool climates. Since we don’t have many tables available to us listing exactly how many growing degree days a particular variety needs, we can approximate and choose a variety with a shorter maturity timeframe. For example, switching from ‘Waltham’ butternut squash to ‘Early Nutter’ reduces the days to maturity by 15-20 days.

Because vegetable development is driven by accumulated heat units (GDD) rather than the elapsed calendar days, an ‘early’ cultivar with fewer days to maturity generally needs less heat to finish and is usually a better choice for cool‑summer or short‑season gardens, even though seed packets don’t list exact growing degree‑day requirements.

Matching your annual vegetable and flower selections to your local climate will result in better growth and likely higher yields. You’ll have fewer disappointing or failed crops and a more resilient garden.