Growing Greens in the Heat of Summer
The abundant summer heat and sunshine is notorious for drying up soils and baking the life out of tender greens. While it might feel impossible to get your salads at the same time as your okra and tomatoes, growing greens in the summer is an option in almost every region. With a few management techniques, the right varieties and some real or engineered shade, greens can be planted in successions, all season long.
Below we'll cover some of the basics of growing greens in the heat of summer.
Start with Heat Tolerant Varieties
One thing you can do as a grower to get the most out of your summer beds of greens is to aim for varieties that have been selected based on their ability to handle and even thrive through heat stress. These varieties are often labeled heat tolerant, mention that they are slow to bolt, and may even have an added note about their use in summer production. At High Mowing, we have a great selection of heat tolerant lettuces, specialty greens, and Asian and mustard greens that fit this seasonal slot. All of these varieties have been trialed in our summer trials farm program and have proven to be all star performers when things heat up.
Manage Your Water
Water is an essential aspect of maintaining a healthy crop of greens. Most greens have a water content that meets or exceeds 90% and they will need ample water to produce during times of heat stress. It is important not to overhead water greens during the heat of day, as the cold water can be a shock to their already stressed system and can cause physical damage or even cause greens to bolt. Watering with drip tape can be a great method for getting greens through rough dry patches. If the weather is especially hot and dry, watering at night can allow the soil to hold onto moisture and provide your crops with a longer window of refreshment.
When direct seeding greens in the heat of summer, it is important to keep the beds consistently moist for even germination. Sometimes it can be helpful to throw row cover over a freshly seeded bed as an added layer of protection from the drying powers of the sun. If transplanting in the summer, make sure that you are only planting in the early morning, or better yet, in the late afternoon and evening. Ensure that each plug is completely saturated before being placed in the soil and cover all pieces of the soil mix attached to the plant to ensure the plug doesn't dry out when the sun returns. For 5 water retention methods, read this blog.
Up Your Soil Fertility
Greens generally prefer high organic matter to reach their full potential and this is especially the case in the summer. When the plant begins to experience stress from the hot summer weather, it will rely on the soil for an ample supply of nutrients and minerals to keep growing and developing sugars and flavor. The soil in your growing beds should be tested and amended with the proper ratios of minerals to provide the plants with what they need to grow and fully mature. If your plants are drooping during the heat of the day, this can be an indicator that your soil minerals need some help.
When adding compost as a means of increasing organic matter, it can be helpful to mix the compost into the top layer of topsoil during the summer months to prevent carbon burn off from the sun. Even if you've added compost to your garden or farm beds in the spring, adding more when planting new beds can give your crops easy access to the nutrients and stored water they need to thrive.
While this won't necessarily work in every system, sometimes it can be useful to utilize the size of one crop to help nurse another along. This is commonly used in cover cropping where a plant like buckwheat that will germinate without rain or irrigation, will be sown along with another cover crop. The buckwheat attracts water and creates shade, allowing the other seeds to germinate during times where heat and lack of moisture would otherwise prevent it. This same idea can be applied to greens in a slightly different way.
Some farms and gardens have ample shade which can help hold onto moisture, but in open fields it can be useful to interplant greens with taller crops. Planting greens alongside taller crops, or even among them, can create a microclimate that is more tolerable to the baby greens plants. For instance a head lettuce planted at the base of a pepper plant will not interfere with the growth of the peppers, but will benefit from the partial shade it will receive during the day.
Use Shade or Shade Cloth
If you happen to have a part of your garden or farm that receives partial shade when the leaves of the trees fill out in the summer, it can be a good strategy to reserve some of that space for your summer greens patch. For those of us that aren't that lucky, creating partial shade is an option for keeping your greens thriving when the heat is on. Shade cloth or shade nets can be used to prevent the sun from crisping your plants. This permeable material reduces the amount of sunlight that reaches your crops by 50% and allows ample air flow so that your crops can breathe.
Harvest Early and Often
While summer greens are definitely possible with lots of TLC, it is a bit trickier than cool season growing and being realistic about your expectations is important. As you fine tune your systems, you will get closer to perfecting your lush summer greens game, but a good motto for your first trials of summer greens is "harvest early and often". This means not only pick them in the morning (or evening) when the sun is not taxing the plants, but also harvest them on the younger side. If you harvest your greens when they're still in their growing or baby phase, they are more likely to resemble the luscious spring greens you remember fondly from earlier in the season.
If you wait too long, they may lose quality more quickly in the heat of summer than they would when grown in one of the cool seasons. If you are using row cover to protect your greens from insect invaders, it is important to harvest your greens early in the morning because the direct sunlight will be especially damaging to the newly uncovered, tender plants beneath.