The crop of the week is spinach, Spinacia oleracea, which is native to Central and Western Asia and was brought to the Americas via immigration/colonization from Eurasia. Spinach is a hardy, cool weather crop, grown for use as a cooked green vegetable or for salad greens. Spinach can be seeded in the spring as soon as the soil can be worked.
For spinach, the temperature for optimum production and high quality is 55º-60º F with day length of approximately 12 hours. Under certain conditions, spinach will bolt (develop a seed stalk and flower), reducing quality. During summer months, high temperatures and long days will result in bolting, depending on the variety used (see Table 2 for varieties that have an “S” under “Season” for summer production).
Spinach can overwinter in temperate regions of the world but will not survive the winters of Massachusetts; however, spinach can overwinter in greenhouses and “high tunnels”, which will be described in later articles.
There are two main types of traditional spinach, smooth leaf and savoy (crinkled leaf) and there are also ”Asian” types. All grow equally well and are marketed similarly, but the savoy type, because of its crinkled leaf, is more difficult to clean. Asian leaf types are relatively smooth with pointed leaves. Table 2 provides a list of recommended varieties, types and optimum times of the season for growth. (Modified from the New England Vegetable Management Guide for spinach.
Table 2. Spinach varieties and types recommended for New England* |
Spinach varieties |
Type** |
Season*** |
Acadia
|
Semi-savoy |
SF |
Carmel
|
Semi-savoy |
SF |
Corvair
|
Smooth |
W |
Emporer
|
Semi-savoy |
SFW |
Escalade
|
Semi-savoy |
SF |
Flamingo
|
Asian |
SFW |
Pigeon
|
Smooth |
W |
Gazelle
|
Smooth |
F |
* Taken from the New England Vegetable Management Guide. Many more varieties listed in the guide at https://nevegetable.org/crops/spinach
** There are two main types of spinach: smooth leaf and savoy (crinkled leaf) and also Asian types.
*** Optimum seasons of the year for varieties are listed for each variety: S=spring, F=fall, W=winter.
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Here are some pictures and information on spinach transplanted into Franco’s garden this spring. I started this garden in 2010 in Shutesbury, Massachusetts, which is 1,200 feet above sea level. This soil was somewhat rocky and sandy, from to which I removed larger rocks and added composted manure and also added as well as lime according to recommendations by the UMass Soil and Plant Nutrient Testing Laboratory. (See the section on soil testing in last week’s article on how to get your soil tested – it is the only way to know how much and what specific amendments you should add, if any. As of this writing [5/18/20], the UMass Soil Testing Lab is closed due to the coronoavirus pandemic, but the UConn Lab remains open.)
Figures 1 and 2 show spinach transplanted into Francos’ garden on April 10th; the transplants were from a local farm store. One can see that some of the spinach leaves are yellow, more so on May 14th than April 25th, suggesting the plants have not taken up sufficient nutrients needed for optimum plant growth. I have applied ample amounts of compost over the years which will in turn provide considerable amounts of the nutrients needed by vegetables and herbs grown in this soil over time. The most likely reason for the yellowing of the leaves is due, in part, to this year’s unseasonably cool and wet weather during April and May. Soil temperatures and water play and important roles in the availability of nutrients which are taken up by plants. Soil organisms feed on organic matter and this process releases nutrients which are readily available for uptake by plants. The warmer the soil, the more microbial activity takes place and the more nutrients used by plants are released into the soil. Soil microorganisms need a certain range of soil moisture for optimum activity and optimum release of nutrients for plant growth. Overly dry and or saturated soils will drastically reduce microbial activity and plants will suffer on multiple levels, including access to soil nutrients See Fundamentals of Soil Health and Fertility in the New England Vegetable Management Guide.
