Welcome back to Beyond Broccoli! Last month I posted about how the genus Brassica is classified and grouped, and where the plants come from in the world. Now let’s talk about what characteristics the brassicas have in common. Here’s some of what they share as a group:
An origin in temperate regions. These species originated in Europe and Asia, and most of them prefer to grow in cooler weather.
Thousands of years of cultivation and breeding. They’ve been part of humanity’s diet for a long time, and have great cultural significance in many regions.
Some physical similarities. I mentioned the cross-shaped (cruciferous) flower in the last post. Brassica seed leaves (cotyledons) have a characteristic heart shape, and seeds are generally small and round. We’ll explore leaf pigments and other commonalities in later posts.
Farmers, gardeners, and scientists have known for some time that tomato (Solanum lycopersicum) is sensitive to heat stress at flowering and fruiting. Pollination and fruit formation can be disrupted when temperatures >90⁰ F. during the day and >70⁰ F. at night. Other fruit problems like yellow shoulders and white internal tissue are also caused in large part by heat stress, especially when determinate (self-topping) varieties are grown and pruned heavily.
If you feel that high temperatures are reducing tomato flowering and fruiting in your garden you can try moving crops to spots receiving late afternoon shade or you can cover plants with 30% shade cloth (a mesh material that blocks about 30% of sunlight). Another option is to try some of the many heat-tolerant tomato varieties. Heat tolerance is a major focus for tomato breeders around the world.
This year, some HGIC staff tried four determinate, hybrid varieties developed by Southern breeders (the first three are from the University of Florida) that I started from seed at home. They all have excellent disease resistance:
Florida 91 (F1) 72 days (transplant to harvest). 9 to 11 oz. red tomatoes
Photo credit: Jon Traunfeld
Heatmaster (F1) 75 days (transplant to harvest). 7 to 8 oz. red tomatoes
Photo credit: Jon Traunfeld
Jamestown (F1) 80 days (transplant to harvest). 9 to 10 oz. fruit. Purported to have a deep red crimson gene and high lycopene content
Photo credit: Jon Traunfeld
Phoenix (F1) 72 days (transplant to harvest). 8 oz. red tomatoes
Nothing causes that sinking feeling like walking into the garden and seeing one or more tomato plants wilting. Not just some lower leaves that are yellowing, curling, or drying up from leaf spot diseases. No, I’m talking about healthy green leaves and stems that start to go limp. Oftentimes, this spells the beginning of the end for the affected plant(s) so it’s important to figure out what’s causing the wilting symptom. Even if you lose one or more plants this year you’ll want to prevent a recurrence next year. UME’s Home & Garden Information Center seems to be getting more tomato wilt questions this year than usual.
Wilting may indicate that roots or stems are injured, soil moisture has been too high or too low, or that the vascular tissue directly below the epidermis (skin) of tomato stems is blocked up with fungal or bacterial pathogens. Plants with disease-caused wilt should be removed. Here are some possible causes for wilted tomato plants in Maryland.
Fusarium wilt– this disease is caused by a soil-dwelling fungus. Lower leaves turn yellow and leaves and stems begin to wilt, often on one side of the plant. Leaves may revive overnight. Cutting affected stems lengthwise with a razor blade (directly below the surface) will reveal brown discoloration or streaking. The disease rarely infects all of the tomato plants in a row or a bed.
This fungus can survive in the soil for years even if the tomato is not grown in that location. One solution is to grow resistant varieties- look for those that are resistant to at least two of the three known races of fusarium wilt. Example:
Another option is to grow tomato plants in containers filled with compost and soilless growing media. Don’t set the containers on the garden soil that had the fusarium wilt problem last year.
Tender spring lettuce and spinach leaves are just a memory for many Maryland gardeners. As we move into the summer season the types and flavors of garden greens expands significantly. While some, like Swiss chard and kale, can be cut or torn and dropped into fresh salads and dishes, most will benefit from some level of cooking, like sautéing on their own or being added to stovetop or baked dishes. Most of the summer greens below grow quickly and have a long harvest period. They help us improve food security and adapt to climate change.
General growing tips for summer greens:
Water, water, water and fertilize to promote rapid, healthy growth and maintain leaf and stem succulence
No row cover! They can cause a heat build-up. Instead, use insect netting to exclude insect pests
Plant summer greens in containers and move them to shady spots close to your front or back door
Create some shade for lettuces and other marginal crops like cilantro … plant on the north side of taller crops or try 30% to 50% shade cloth material
Most leafy greens below can be treated as cut-and-come-again crops: they put on new growth below each harvesting cut. Older, stressed foliage is less palatable
Explore seed racks and online seed catalogs for heat-tolerant crops and varieties
Leafy amaranth
Two well-adapted species for Maryland gardens are Amaranthus viridis (callaloo, also known as slender amaranth) and Amaranthus tricolor (Chinese spinach; leaves somewhat smaller than A. viridis).
Several species are very popular in Central and South America, India, Southeast Asia, and Africa. Nutritionally, they compare favorably with spinach and Swiss chard. Plants in this family use a special C4 photosynthetic pathway, also present in corn and sugarcane, which allows for vigorous growth under hot, dry growing conditions.
Leafy amaranth is basically a tasty and productive pigweed. Flowering accelerates with shorter days after the summer solstice. Frequent harvesting delays flowering and promotes branching. Immediately remove any flower stalks that emerge to prevent re-seeding.
Callaloo growing in 3-gallon bags in a high tunnel. UME Small Farms Program. Photo credit: Jon TraunfeldCallaloo can quickly become a weed problem. Don’t let plants flower. Each plant can produce >100,000 tiny seeds dispersed by water, wind, tools, and animals. Photo credit: Jon TraunfeldTri-color amaranth. Photo credit: Jon Traunfeld
Other heat-tolerant greens in the Amaranthus family:
Swiss chard and Perpetual Spinach (a.k.a. leaf beet) fall within the beet species- Beta vulgaris- and will produce large amounts of leafy goodness from spring through early fall. Orach (Atriplex hortensis) is another family member that grows best in spring and fall but can tolerate summer heat.
Two varieties of Swiss chard in the UMD Community Learning Garden. Photo credit: Jon Traunfeld
Leafy Brassicas
Several crops in the Brassicaceae plant family tolerate Maryland summers. Collard plants produce reliable and abundant harvests from summer through fall. ‘Morris Heading’ is an heirloom “cabbage-collard” variety found in Baltimore City community gardens throughout the growing season. ‘Green Glaze’ is touted as being heat-tolerant but I am not aware of studies that looked at temperature effects on the productivity of collard varieties.
Collard plant in late July surrounded by common purslane, and edible weed. Photo credit: Jon Traunfeld
Mustard and kale are somewhat less heat-tolerant than collards. ‘Green Wave’ and ‘Red Giant’ mustards and ‘Lacinato’ kale are common varieties grown in summer gardens in Maryland. I’m very curious about Portuguese kale (Couve tronchuda). It resembles collard and is described as sweet and tender and more heat-tolerant than other kales. If you grow it please leave a comment about your experience.
‘Lacinato’ kale (a.k.a Tuscan kale, dinosaur kale, black kale) growing in Baltimore City in late July. Leaves are harvested from the bottom. Photo credit: Jon Traunfeld
Check seed catalogs for mild-flavored leafy Asian greens that hold up well in warm weather like Tokyo Bekana (Brassica rapa var. Chinensis), ‘Komatsuna’ (Brassica rapa var. perviridis), Vitamin Green and Tatsoi (Brassica rapa Napa group), and ‘Chijimisai’ (tatsoi x komatsuna).
Malabar spinach
Basella alba (green stem) and Basella rubra (red stem) below are “summer spinaches” that produces a vigorous leafy vine. Leaves and stems can be sautéed or used to thicken soups and stews.
New Zealand spinach
New Zealand spinach (Tetragonia tetragonoides) below is a low growing annual with a spreading habit that has somewhat fuzzy, arrow shaped leaves, and mild spinach flavor.
Photo credits: Jon Traunfeld
Molokhia (Corchorus olitorius), known as Egyptian spinach and jute leaf, is an important food plant in the Middle East, Africa, and Asia. It’s higher in vitamins and minerals than most other leafy greens. This is the jute plant, known for its strong stem fibers. Young leaves can be eaten fresh, sautéed, or used to thicken soups and stews.
Sweet potato (Ipomoea batatas) – shoot tips, young leaves, and tender stems are excellent in many top-of-the-stove dishes. Harvesting young foliage, even on a regular basis, will not reduce your harvest of sweet potato roots later in the season.
Sweet potato plants with a less typical cut-leaf shape. Photo credit: Jon Traunfeld
Hibiscus as a Leafy Green?
Sunset hibiscus (Abelmoschus manihot) and roselle hibiscus (Hibiscus sabdariffa) leaves have a compelling lemon-sour flavor similar to garden sorrel. These plants are in the Malvaceae family along with cotton and okra, planted throughout the tropics and sub-tropics. Roselle is also grown for its strong fibers and its fleshy calyx which farmers and gardeners use to make tea, juice, and preserves.
Green stem hibiscus plant harvested for its leaves used in many Indian foods. Photo credit: Jon Traunfeld
Don’t Dismiss the Lettuces!
Lettuces are generally a cool-season crop but these varieties have demonstrated some level of heat tolerance:
‘Merlot,’ ‘Speckled Bibb,’ ‘Adriana,’ ‘Jericho,’, ‘Coastal Star,’ ‘New Red Fire,’ ‘Starfighter,’ ‘Tropicana,’ ‘Red Cross,’ ‘Magenta,’ ‘Cherokee,’ ‘Green Star,’ ‘Summer Crisp,’ ‘Little Gem,’ ‘Muir,’ ‘Burgundy,’ ‘Bronze Beauty,’ ‘Forlina,’ and most oakleaf types of leaf lettuce. Asian sword leaf lettuces, (pointed lettuce) have long, thin leaves and are described as crisp and tender with a mild bitterness.
One of the sword lettuces growing mid-summer in a Howard Co. community garden. Photo credit: Jon Traunfeld
An Auburn University study found that ‘Aerostar’, ‘Monte Carlo’, ‘Nevada’, ‘Parris Island’, ‘Rex’, ‘Salvius’, and ‘Sparx’ grown in a “hot greenhouse” out-performed 10 other heat-tolerant lettuce cultivars and received the highest flavor and texture ratings.
Give some of these greens a try this summer. The investment in seed, space, and time is minimal and you may discover some surprising new textures and flavors.
Resources:
Callaloo recipes– Dr.Nadine Burton, Alternative Crops Specialist, UMES Extension
Well, the short answer from a soil nerd (please note soil nerd is not the same as a soil scientist or soil chemist) is that yes it really does matter! Have you ever done the experiment with boiling red cabbage leaves and used that as a pH indicator? It’s a fun science experiment but probably wouldn’t work for determining an accurate soil pH.
People do not always see the benefit of getting their soil tested; however, if you take a good comprehensive soil sample, the information that you get from the analysis is invaluable. Not only will the results keep you from over-applying nutrients, which has economic and environmental benefits, but also it will ensure that your plants have all that they need right at their root tips.
In my opinion, the most helpful piece of information gained from conducting a soil analysis is the soil pH. PH is a measure of hydrogen ion concentration and tells you how acidic or basic/alkaline the soil is. Most vegetable garden plants prefer a pH between 6-7; therefore, acidic soils need to be amended with calcium carbonate (limestone). Acidic soils are indicated with numbers below 6 on the pH scale which ranges from 0 to 14. Soils in the Eastern US are often acidic, but the natural pH will depend on parent material and other soil factors, such as how the soil has been managed, what plants are growing there, etc.
It should be noted that some plants actually prefer acidic soils, such as rhododendron, azaleas, and blueberries. Also, some plant diseases, such as scab in potatoes, are worse at a higher pH. Lowering soil pH (often done by adding sulfur) can take several months and may need to be a multi-step process. It is a great idea to test garden soils in the fall, so pH-altering amendments have time to do their job. Here is a great cheat sheet to help you understand what your soil analysis results mean.
Blueberry. Photo: C. CarignanTomato. Photo: A. BodkinsYellowing leaves may indicate a nutrient deficiency. Some soil nutrients may be unavailable to plants if the soil pH is not in the optimal range. Test your soil to find out the pH and nutrient content.
Another reason that pH is important is that it helps determine the availability of soil nutrients. Soil pH is linked to Cation Exchange Capacity (CEC), which is influenced by soil particle size and the type of parent material (rock). Clay soils will have a higher CEC (sites to hold onto nutrient ions) than sandy soils. CEC will be reported on most soil analyses. If the pH is not in the correct range, then many nutrients are not available to plants, even if you have applied ample nutrients. Thus, in order for the nutrients to support plant growth, it’s important to get that pH correct! This will provide both economic and environmental savings. Check out this link for a neat chart showing nutrients available and pH.
The third reason that it is important to check pH is because it can affect soil microorganisms, which are going to thrive at a near-neutral level. If the pH is too high or too low you will see a decrease in the number and activity of good soil bacteria, fungus, and more that help to break down organic matter and do amazing other things in the soil profile. (For more details on this topic, download PDF – Soil Acidity Impacts Beneficial Soil Microorganisms, from Washington State University Extension.)
Common questions about soil pH
Can pH change from year to year?
Some forms of nutrients —commercial fertilizers, compost, composted animal waste (cow, horse, pig, chicken manure), organic matter, the weathering of rocks, and even rainfall can alter pH. Fertilizers, depending on the type used, will alter soil pH at different rates. Refer to this PDF – Fertilizers and Soil pH from the University of California.
Can I use a home soil Testing kit?
I normally steer people away from these types of kits, just because there are so many inaccuracies, especially, if the kits were not stored at the proper temperature and the directions are not followed correctly, then the results may not be 100% accurate.
What about electronic soil testing probes?
I don’t have first-hand experience with these probes. I am sure that they do have a level of accuracy; however, I cannot justify the upfront cost. For most gardeners, soil testing every 3 years is sufficient, so in my opinion, it is easier to just collect the sample and send it to a laboratory.
By Ashley Bodkins, Senior Agent Associate and Master Gardener Coordinator, Garrett County, Maryland, edited by Christa Carignan, Coordinator, Home & Garden Information Center, University of Maryland Extension. See more posts by Ashley and Christa.
This year, the University of Maryland Extension Master Gardener Grow It Eat It Program celebrates the resource that supports all life on earth – soil! Look for soil education programs offered by your local Master Gardener program, and visit the Home & Garden Information Center website for more information about soil health.
Pollination is the movement of pollen from male to female flower parts of sexually reproducing plants. It is often accomplished by wind and insects and results in the development of some type of fruit containing seeds for the species’ continuation. Farmers and gardeners in the mid-Atlantic are finding that high day and evening temperatures can cause vegetable plants to drop flowers and small fruits or produce deformed and under-sized fruits. This problem has been observed in crops like bean, tomato, and pepper (mostly self-fertile; individual flowers can pollinate themselves), and in crops like squash and pumpkin (require cross-pollination between flowers).
How do high temperatures affect pollination?
All fruiting plants have an optimal temperature range for the pollination/fertilization process. High temperatures can reduce pollen production, prevent anthers from releasing pollen, kill pollen outright, and interfere with the pollen tubes that serve as conduits for uniting sperm cells and eggs (fertilization) inside undeveloped seeds (ovules). High temperatures can even injure flowers before they open. Night temperatures are increasing at a faster rate than day temperatures as a result of climate change, and seem to be most responsible for these pollination problems.
Q: I’d like to eventually grow some of my own fruit. What’s a good starting point and what do I need to consider?
A: It’s fun to try growing your own food, though fruit trees require the greatest amount of commitment and patience to be rewarding. Ill-prepared first attempts can easily end in failure. We suggest inexperienced gardeners or anyone short on time try small-fruit (berry) cultivation first before diving into fruit trees – they’re much simpler to grow, need little to no spraying, and take up less space – but if you do enough research to know what to expect, you can certainly start small so it’s not overwhelming.
Blueberry – Vaccinium corymbosum ‘Elliott’Blueberry – Vaccinium corymbosum ‘Jersey’Blueberry plants not only provide fruit but also have beautiful fall color. Blueberries also can be grown in containers in small-space gardens. Photos: M. Talabac
Easier crops for a novice grower to start with include fig, persimmon, and some of the more esoteric fruits like jujube, serviceberry, and pawpaw. Ironically, the most popular fruits – apple, pear, peach, plum, cherry – are the hardest to grow well in our mid-Atlantic conditions. This is not due to temperature hardiness but rather disease and pest pressures.
Plan as much as possible first: where do you have enough space and the best conditions, how will they be cared for year-round, what problems should you anticipate, and how will you process the perishable harvest? Even when grown organically, there’s a lot of intervention and preventative treatments that will typically be needed to produce a useful harvest and to keep the tree healthy. After a problem arises, curative options are few, so knowing ahead of time what to look for and when is important in avoiding plant damage or a ruined crop for that year.
“Location, location, location” applies in gardening too. Fruit-bearing plants usually require full sun (6+ hours daily in summer) and well-drained soil to perform well. A site with good air circulation reduces disease, and proper pruning and training will make harvesting easier. Choose an area where you have enough space to avoid crowding and competition between plants. Different varieties mature at different sizes, and training style will also impact how much room trees use.
Most fruit trees are propagated by grafting. That means the variety you want is joined to a rootstock of a related variety for the purposes of improving hardiness, disease resistance, and/or dwarfing the plant’s stature for ease of maintenance and harvest. Terms like semi-dwarf, dwarf, and miniature refer to the overall growth habit compared to a full-size tree, not the fruit size itself.
Check which varieties need cross-pollination to fruit well, as some will not produce fruit if planted alone. Self-fruitful groups include figs, peaches, nectarines, and apricots, plus some varieties of apple, cherry, pear, persimmon, and plum. Keep like with like when you can, because cross-compatibility may not occur; for instance, don’t rely on pollination between an Asian and a European pear, or an early-blooming apple with a late-blooming apple. Web-based suppliers sometimes provide cross-pollination charts to illustrate compatible pairings. Avoid multi-graft plants (trees with several varieties grafted onto a shared trunk) unless you’re quite experienced because they run the risk of increased maintenance headaches or the loss of an entire variety’s crop.
Fig fruits.
Good inherent disease resistance goes a long way to reducing pesticide use and lowering the risk of bad outbreaks. No varieties are immune to problems, but those with noted resistance aid your efforts tremendously. It may surprise you to learn that some of the most popular varieties found at supermarkets are not the more disease-resistant options or even easy to grow overall. Ideally, narrow your options down by resistance traits first, desired flavor and other traits second.
Our website has a lot of information about growing fruit. You can search for a specific fruit type and find information on plant selection and good care practices.
By Miri Talabac, Horticulturist, University of Maryland Extension Home & Garden Information Center. Miri writes the Garden Q&A for The Baltimore Sun. Read more by Miri.
