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Hand-Pollinating Squash for Seed Saving
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Hand-Pollinating Squash for Seed Saving


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Hand-pollination of squash, including identifying male and female blossoms, pollinating, marking and recording. Hand-pollination may be necessary to preserve the characteristics of squash varieties in …

Hand-pollination of squash, including identifying male and female blossoms, pollinating, marking and recording. Hand-pollination may be necessary to preserve the characteristics of squash varieties in areas where other varieties of corn are being grown nearby. Video is here:

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  • One of the methods employed at Seed Savers that allows us to preserve this diverse array of genetic diversity is hand pollination.
  • Hand pollination allows us to maintain the traits of a individual varieties of squash while growing more than one species at a time. This is the Papago squash, a variety with green and cream stripes. In order to maintain these characteristics, the plants, and more specifically the female flowers, have to be isolated from the pollen of other varieties within the same species. Because insects can carry pollen between varieties over 1 mile away from each other, isolating by distance can be difficult. Hand pollination allows us to grow varieties close together and still prevent cross pollination.
  • As gardeners, it is important to have a basic understanding of plant taxonomy. On the screen now is the classification for a squash variety offered in our seed catalog, Yugoslavian Finger Fruit. The hierarchical structure probably looks familiar to you – this is the Linnaean classification system. This system categorizes plants into groups with similar characteristics, then breaks those groups into smaller, more specific categories, on and on, until a single species remains. As relatively new seed savers, it isn’t important to understand the whole system – we’ll only talk about the last three classifications: Family, Genus, and Species. [click] Gardeners should know the families of their garden plants for crop rotation and general growing guidelines – squash belongs to the Cucurbitaceae family, often referred to as the cucurbita, along with melons, watermelons, and cucumbers. At Heritage Farm our cucurbits are started in the greenhouse week 19 and week 20 (the system of using weeks to delineate time in the year can be found on a Growers Calendar and aids in consistency with planning) and transplanted to the field Week 21 or 22. Upon going into the ground they are immediately covered with remay, a light protective fabric suspended by wire hoops. This allows our plants to grow without the stress of insect pests until they reach a size where light feeding will not be of detriment to the overall health of the plant. Though knowledge of plant families is useful, seed savers can really get by if they only know their plants’ genus and species. Thankfully, this is easy to find out because most seed packets will list the plant’s genus and species. [click] A plant’s genus and species make up that plant’s binomial name, sometimes called the scientific or Latin name. The binomial name for this squash is Cucurbita pepo . Squash is an interesting crop type, because different varieties that we often lump together under the term ‘squash’ can actually belong to different species. Cross-pollination can only happen between plants in the same species. The four species of Cucurbits we are going to focus on for this discussion are pepo, maxima, argyrosperma, and moschata. Given that crossing will not happen between species, this means you could grow one variety within each of these 4 species in your garden and be able to save seed from each without worry. [click] This squash, C. pepo , will only cross with other squash belonging to the C. pepo species. It will not cross with C. maxima , C. argyrosperma , or C. moschata . (There is much debate about this next paragraph—it really depends on who you read) Of these four squash species, crossing will occur between C. argyrosperma and C. moschata , but only when C. argyrosperma is the female and C. moschata is the male parent. therefore, one variety each of C. pepo and C. maxima can be grown in the same garden along with one variety of either C. moschata or C. argyrosperma without crossing among varieties. It is interesting to note also that the term ‘pumpkin’ does not refer to a single species – the term is simply applied to any fruit that resembles what we think of as ‘pumpkin-like’. Additionally, some Cucurbita spp . varieties are classified as gourds along with varieties belonging to the genus Lagenaria.
  • Saving seeds of varieties you love can help safeguard those varieties against extinction. This graph illustrates the diverse availability of varieties available in 1903 through commercial seed houses. 80 years later, many of these varieties have disappeared. In 1903, for example, 341 different squash varieties were offered. Today, only 40 of those varieties can be found in the National Center for Genetic Resources Preservation, the USDA’s genebank where we back up our own collection.
  • Now we are ready to discuss the “meat” of hand polliation! Hand pollination commences once female flowers begin to be produced by the squash plants, this is usually around week 26/27 in NE Iowa (based around the start and transplant times discussed earlier). In most varieties a surge of male flowers precedes any female flower formation by 1-2 weeks—but once males begin showing up, the need for attentive scouting of the plants becomes crucial. Hand pollinations should not take place on rainy days, or days of excessive moisture.
  • Either before you begin to see that initial surge of males, or even earlier in the season, you will want to compile your list of needed materials. This is what we use here, you should not feel constricted by this list—if anything it should be a platform for your creativity! You will need the following items: READ LIST. Hand sanitizer is a MUST, regardless of your personal preferences. The hand sanitizer is crucial in preventing the transmission of pollen via your little fingers. It also will help prevent any transmission of viruses or fungal contaminants from variety to variety as well (via you).
  • Scouting, or looking for males and females, takes place at Seed Savers Monday through Thursday at 2:30 pm. Step one in this process is identifying females that are ready to be pollinated!
  • The female flowers can be readily identified by the ovary located between the flower and the stem. The ovary will resemble a small squash; size, shape, and color will vary from variety to variety. Once a variety begins producing females we hang a very bright length of flagging tape from the field pole. This indicates to us that the variety is ready for HP to begin. For your purposes at home, this may not be necessary, but I am quite a visual person, and with the number of varieties we do, it is a necessary step. Tying the female at the appropriate stage is crucial to the success of the pollinations. The flower needs to be plump and puffy, soft when squeezed, and a peachy orange color at the tips. Each variety will display these characteristics in a slightly different manner, but all females of the varieties I’ve worked with do exhibit these signs when ready. You can see in this photo that the flowers on these females are blushing a yellow peach and the flower on the right is starting to separate at the tip just ever so slightly. These are females that will be open tomorrow morning. Absolutely do not tie any flowers that have already opened up.
  • Here we have found a female that is ready to be tied. The flower has begun flushing that lovely color and is softening up.
  • Using a brightly colored piece of flagging tape, I like to make a loop before sliding the knot over the tip of the flower. The flagging tape doesn’t need to go down the flower very far. Far enough that when she puffs open in the morning that the corners of the flower will not puff out and create holes for insects to go in, but not so far that the stigma is bruised by the tie.
  • We flag all the males and females we find in order to make retrieval the next morning more efficient. You may or may not want to do this.
  • Females that have already opened up, and are thus considered contaminated, are plucked off and tossed into the chum bucket (compost). If you are growing these squash to eat too (a summer squash for instance) you may want to leave these OP fruit on the vine so you get a tasty meal! We plant 36 plants of each variety in order to ensure we get a minimum of 18 fruit per variety. As a home seed saver, 1-2 fruit will probably yield more than a sufficient supply for you and your entire extended family and friends (or to take to a seed swap!)
  • I asked Grant to take this picture to show the vast array of ‘ripeness’ seen within the flower development. The left side shows flowers that are still quite green and undeveloped, progressing to the right where we have a male and females that have already opened and are thus considered no good for purposes of HP. The bottom row show an array of female flowers, with the second and third females as ones I would consider for the next days pollinations. Within that little box on the lower left side of the female row are some precautionary fruit! Flowers and fruits that are yellowing are generally a sign of abortion—do not tie these flowers closed as they are only going to fall off anyway and you shouldn’t waste your time! They are usually quite sensative to pressure and get knocked off the vine easily. While the aborter pictured here is quite far along in the process, the earlier stages mimic what you see here—yellowing of the ovary and a sickly yellowing of the flower. Here’s where you need to be careful. The flower will soften to the touch, like I was telling you to look for earlier. The thing that is different is that with a healthy female flower you will get spring and bounce back. With an aborting flower, the flower will stay squished and won’t bounce back to it’s original shape. I included the other female to the far left just to show the kinds of abnormalities that can be observed in the patch! While we are talking anomalies, during times of extreme heat some varieties will produce hermaphroditic males as a stress response. These male flowers will exhibit a swollen base, giving the allusion of a female flower (and, in fact, often do possess a stigma). The difference between a hermaphroditic male and a true female is the stalk and growing habit of the flower.
  • Step 2 of squash hand pollination involves finding and taping 3 males for every female flower found. For example, if 3 females were found, 9 males would need to be taped—ideally from different plants of the same variety, but there is no harm in selfing if you only grew one plant.
  • The top row are the male flowers, and the fourth and fifth males would be considered ready for pollination the next day. The last male in the row has already opened for the day and curled back up. Don’t be fooled by him! To the touch, the flower will be very soft and won’t maintain it’s shape very well. Do not use it!
  • Here is a closer look at the males that are ready to be taped. The male flowers should be exhibiting similar traits as the female flowers you just taped. They should be puffy and plump, have an orangey-yellow flush at the tips of the flower, and should be soft when squeezed, but not open. Again, do not tape any flowers that have opened! Once the total number of males has been determined for a variety, begin taping and flagging!
  • Here is a male that has been identified as ready.
  • A 2” piece of masking tape is applied to the flower to keep it closed until we are ready to expose it in the morning. The flowers are quite easy to tape, simply tear a piece of tape off roughly 4” long, put half under the flower, making sure the tip of the flower is slightly below the top of the tape, and fold over. Give a good press to the sides that you just stuck together so the seams are completely sealed, being careful that you do not damage your flower. The tape needs to effectively close all entry points to the flower. We then flag him, and continue our search until we have found the number of males necessary. In order to remember which varieties we need to visit in the morning, we rite down the pertinent information, which is the # females and # males, on yet another piece of flagging tape and hang it from the field pole. You are now done with the scouting process, and in the morning will be able to do your pollinations!
  • Pollinations need to take place in the morning, when the bees are out and about. This tends to be the time when the flowers are most receptive. We begin our pollinations when all the dew has dried so we are not transmitting fungal spores between plants. This is generally at 9am but may be different where you are. Before actually doing the pollinations you will want to gather all the males for the variety you are working with and set 3 males down by each female. When plucking off the males, be sure to leave a length of stem on them—this will act has your ‘paint brush’ handle and allow you to be more efficient when pollinating.
  • Here’s our female from the afternoon before. You can see that she puffed out and has created quite a nice star. This is good!
  • Having your chum bucket and masking tape ready, tear off the top portion of the female, just below where it was tied, and toss it in the chum bucket.
  • Briefly inspect for insect intruders (ants, cucumber beetles…); if there is any sign of insect activity, remove the female. If there are no signs of insects, devote an eye to watching the opening of the flower to make sure no bees or other insects go inside, or hold the flower closed.
  • While watching the female flower, begin removing the petals and sepals of the male flower. This is done by holding the part of the flower where the petals meet the hard, waxy bottom, and tearing the petals away from this portion of the flower with a slightly upward clockwise motion.
  • The exposed stamen should be dripping with bright yellow fluffy pollen.
  • Carefully rub the stamen over the pistil in the female flower, transferring as much pollen as possible. Repeat this with the remaining males.
  • When the three males have been used, you need to tape the female blossom closed.
  • Tape the flower closed with another piece of masking tape. Tape in the same manner in which the males were tape, but use a very delicate touch. At this point, you don’t want to press too hard, or twist the flower at all, or it may fall off.
  • Be sure to seal the tape tightly.
  • Loosely tie a piece of flagging tape around the stem of the female you just pollinated. We include information that is important to us, but you may just need a visual marker so you know that it is a fruit for seed and not for the eating!
  • Here is our finished product. Please remember to sanitize your hands before moving on to the next variety.
  • The task of hand pollination does not end at pollination! Continual monitoring of your fruit and the health of your plant/plants is critical to make sure that your fruit actually reaches maturity.
  • There are two factors that determine the harvest time of squash—these are color change and a hardening of the skin. We will briefly discuss harvesting, processing and basic seed storage to take the process from seed to seed.
  • In some varieties you will notice quite a significant color change, followed by the hardening of the skin coat to a point where a fingernail is unable to dent the skin. In other varieties the color change is much more subtle and maturity is marked more by the hardening of the skin coat. With summer squash, harvest time is pretty important. Fruit can generally remain on the plant until the plant starts to decline or succumb to death. Once harvested, they should be processed within a month. Winter squash will hold much longer in the field than the summer varieties. All winter varieties are left on the vine for as long as possible—few factors hasten the harvesting process—if a variety is succumbing to disease pressures, an impending frost, and severe deer damage being a few reasons we would bring fruit in early. Fruit can be stored and monitored for months. If you begin to see any sort of decline on the outside of the fruit, they should be processed immediately. Processing a summer squash can be a bit of a challenge, as the rind gets really hard to cut. We have created a machine we call “The Squasher”, which is a bit like a guillotine and crushes the fruit in half. Otherwise, a good sharp kitchen knife will work just fine. With squash, you can either cut across the equator or down the poles. Either way works just fine. Once you have opened the fruit, the only thing you need to do is extract the seed from the placenta and toss it in a bowl. Let the seeds sit in water over night to break down any sugars that surround the seed coat, and wash with a heavy stream of water the next day. Lay seed out on an old window screen or in a colander with a fan to dry for several days. Place in a sealed container in the fridge for later planting or sharing.
  • Questions?
  • Transcript

    • 1. Presented by Gabi Masek 2012 Seed Savers Exchange Webinar Series Squash Hand-Pollination
    • 2. Our mission is to save North America’s diverse, but endangered, garden heritage for future generations by building a network of people committed to collecting, conserving, and sharing heirloom seeds and plants, while educating people about the value of genetic and cultural diversity.
    • 3. Kingdom: Plantae Division: Magnoliophyta Class: Magnoliopsida Order: Cucurbitales common name: squash binomial name: Cucurbita pepo Family: Cucurbitaceae Genus: Cucurbita Species: pepo C. pepo will only cross with other C. pepo squash. It will not cross with C. maxima, C. argyrosperma, or C. moschata. Pumpkins belong to many different species, and some C. spp are listed as gourds. What is your squash’s Species?
    • 4. Colored flagging ribbon Wide masking tape Permanent markers Marking flags Hand sanitizer Apron (for carrying pollinating supplies) All-weather journal or spreadsheet for keeping track of pollinations in the field Materials
    • 5. Step 1 Identifying and Tying Female Blossoms
    • 6. Green unripe flowers “Over- ripe” flowers for HP purposes
    • 7. Step 2 Identifying and Taping Male Blossoms
    • 8. Green unripe flowers “Over- ripe” flowers for HP purposes
    • 9. Step 3 Opening and Pollinating Blossoms
    • 10. Step 4 Taping and Labeling Female Blossoms
    • 11. Harvesting, Processing, and Storing Seeds
    • 12. Thank you! Questions? 2012 Seed Savers Exchange Webinar Series For more information please visit these resources: Seed Savers Exchange website: Forum: Online Yearbook: To learn more about seed saving Read Suzanne Ashworth’s Seed-to-Seed Visit for the free publication, A Seed Saving Guide for Gardeners & Farmers