Saving Seed of Pumpkins, Squash, Cucumbers, Melons and Gourds
New gardeners often ask whether it’s alright to plant cucumbers, squash, or gourds next to each other. Their concern is whether cross-pollination will result in inedible fruit. Fortunately, the pollen source does not affect the current season’s fruit. However, if the seed from that cross-pollinated fruit is saved and planted the following year, the resulting plants can be very different, and may be inedible. (Gourds produce a toxin that is bitter, so if you have a squash that is bitter, discard it and remove the plant from the garden.)
Seed Saving Precautions
Saving seed from garden vegetables can be rewarding, but it also comes with challenges, especially with plants that are cross-pollinated.
If gardeners wish to save seed from cucurbits (squash, pumpkins, gourds, cucumbers, and melons), special precautions need to be observed, as these plants are insect-pollinated. Additionally, they have separate male and female flowers, which increases the chances that the female flower may be fertilized with pollen from a different variety of the same type or species. Unless you (and nearby neighbors) have grown only one of the types or varieties, you could end up with some very strange vegetables from seed saved from those plants.
Plants from within the following groups will cross with each other:
- Zucchini, Yellow Crookneck, Acorn, Spaghetti, Patty Pan, Delicata, Pumpkins and Gourds (except edible snake gourds) all may cross with each other.
- Butternut, Buttercup, Banana, Hubbard and Turban squashes may cross with each other.
- Muskmelon, Cantaloupe, Charentais; Honeydew; Casaba; Armenian Cucumber; Snake melon (gourd) can all cross with each other, but not with squashes, pumpkins, or cucumbers.
- The Buffalo gourd, a weed, is too distantly related to cultivated species to be a problem.
Cucumbers, watermelon, and Loofah gourds only cross only with themselves, so you don’t have to worry about isolating them unless you are growing several varieties of the same type.
To prevent cross-pollination between compatible types or varieties, they need to be separated by a distance of one-half to one mile. The presence of barriers such as large buildings, a thick stand of trees, or a hill can inhibit pollinator movement and allow for shorter isolation distances. However, since most gardeners don’t have adequate distance from other gardens or squash varieties within their own garden, the alternative is to (1) net or cage the entire plant to exclude insects or (2) bag or tape shut new male and female flowers as they are forming (before they open, but just beginning to show a bit of yellow or orange color) to prevent insect transfer of pollen. These methods require hand-pollination of the flowers. Early in the morning, a small paintbrush can be used to collect pollen from a male flower, and transfer it to a female flower. For best results, this should be done as soon as the female flower (identified by the miniature fruit just below the petals) first opens, within 4 hours of opening. Rebag or retape the female flower shut after you have pollinated it. Once you have fruit set, you can remove all the bags – just be sure to mark the fruit that you hand-pollinated.
Because pollen from the same plant can pollinate a flower, you only need to plant a single cucurbit plant in order to harvest viable seeds. However, to maintain a variety over time, save seeds from between 5-10 plants. If you’re saving seeds for genetic preservation of a rare variety, save seeds from 25 plants.
Seed Processing for Cucurbits
Pick fruit several weeks after it has matured to the point of changing color to yellow or orange. Scoop out the seeds and surrounding pulp, and place into a container, add water and let ferment 2-4 days at room temperature, stirring occasionally. Add more water, stir, and allow the nonviable seeds and pulp to float to the top, where they can be removed. Repeat if necessary to thoroughly clean the seed. When clean, spread seeds out to dry on coffee filters, paper towels, or screens. When sufficiently dry, they can be cleanly snapped in half.
For best results, store the fruit until it begins to lose eating quality; then ferment as above. Summer squash should be left on the plant until the rind hardens, then processed as above.
Allow fruit to remain on the plant for 1 to 2 weeks after maturity; alternatively, harvest reipened fruit and allow it to set for a few days prior to harvesting the seed. The seed can be simply washed by hand and then dried.
Once completely dry, seed should be stored in a cool dry location. If you have room, storing in your refrigerator is ideal. Make sure the storage containers are completely dry. Envelopes or ziplock bags work fine, as well as baby-food jars, etc. Most seed will stay good for at least 3-4 years. Don’t forget to label everything with both the plant name and date!
An Additional Caution
Some diseases can be spread through seed from infected plants. Following is a list of some of the diseases that can be spread through seed:
- All Cucurbits
- Angular Leaf spot (especially cucumber)
- Gummy stem blight
- Squash mosaic virus
If you know that your plants have any of these diseases, you should not save the seed. However, most people will have no idea whether their plants are infected with particular fungi, bacteria, or viruses. A good rule of thumb is to simply save seed only from plants that have healthy, normal-looking leaves and fruit.
How to grow pumpkins
Pumpkins are magnificent autumn vegetables that are fun to grow and delicious to eat. All you need is a packet of pumpkin seeds, a sunny position and lots of water. Children love growing their own Halloween decorations and the flesh is delicious roasted, mashed or used as part of a warm winter soup. An excellent source of vitamins A and C, the seeds can be eaten as a healthy snack too!
Which pumpkin variety is best?
This heavy-cropping variety is popular for its fairytale shape and excellent flavour
Image: Organic pumpkin ‘Cinderella’ from Thompson & Morgan
Pumpkins come in all sizes and shapes, from tiny fruits to the enormous Pumpkin ‘Big Max’ that grows to a prize-winning 45kg! But before you begin growing giant pumpkins it’s wise to think about how much space you have to spare.
If you prefer traditional sized vegetables then ‘Jack Of All Trades’ is the perfect choice. With sweet orange flesh it’s ideal for carving and making sweet dishes like pies and cakes. And for something slightly different, why not try the small, attractive fruits of Pumpkin ‘Wee Be Little’. Simply cut off the top, scoop out the seeds, season with salt and pepper and replace the top before cooking in the microwave until soft. Delicious!
When to sow pumpkins
Ideal for Halloween, these warty pumpkins make an excellent display
Image: Pumpkin ‘Zombie’ F1 Hybrid from Thompson & Morgan
Pumpkins require warm daytime temperatures of between 18 – 30C (68F) and prefer a minimum night temperature of 16C (61F), at least until they’re planted out. In cooler areas pumpkins can be sown indoors from April to mid May for transplanting outside later, when temperatures have risen.
However if you’re short of indoor space, you may prefer to wait until the soil has warmed up in late May or early June and sow your seeds directly outdoors. Wherever you choose to start them, it’s best to sow two seeds per hole and thin the weakest plant out later on. And if you choose to direct sow outdoors, start your pumpkins off under cloches to give them the best start.
How to sow pumpkin seeds
Watch our short video above to see how resident horticulturist, Sue Sanderson, sows her ‘Jack of all Trades’ pumpkin seeds. Here’s a quick recap:
- You can wait until the soil has warmed up in late May, early June, and then direct sow your pumpkins outdoors. However I prefer to start mine indoors from mid-April, and then plant them out later on.
- Fill a small 7.5cm diameter pot with a good quality potting compost. Make sure you press the compost down gently to fill in any air gaps. It’s a good idea to use potting compost for pumpkins rather than seed sowing compost because it gives the plants more nutrients from the very start. Because pumpkin seeds are quite large, they won’t mind the coarser texture.
- Make a planting hole to a depth of about 2.5cm. Sow your pumpkin seeds on their sides to reduce the risk of rotting. And it’s a good idea to sow two seeds per hole in case one doesn’t germinate. If both come up you can just pinch one out, or transplant it into a separate pot.
- Water the compost well and then put your pots in a propagator, or seal them inside a plastic bag, at a temperature of about 20 degrees celsius until germination.
- Pumpkins are really vigorous growers and will literally burst from the soil within five to seven days. Once germinated they can be removed from the plastic bag or propagator, and grown on in cooler conditions until they’re ready to be planted outdoors.
- Make sure they receive plenty of light. The secret to success with pumpkins is to keep them well watered and nice and warm – between 18 and 25 degrees celsius – at least until you plant them outdoors.
How to plant out your pumpkins
To see how to plant out your pumpkins, watch the short video above. Here’s a quick recap:
- Gradually acclimatise your pumpkins to outdoor conditions over 7-10 days before transplanting them out into warm, well drained, humus rich soil. They prefer a position in full sun that’s sheltered from the wind. Choose a spot that receives at least 6 hours of direct sun per day and prepare the soil in advance, adding plenty of well rotted manure or compost.
- Planting distances can range from 90cm apart to 3m apart depending on the variety, so you’ll need to check the seed packet. At each planting station, pile the soil into mounds about 15cm (6″) high. Plant each pumpkin plant on top of a mound to ensure good drainage and keep them well watered until they’re established.
- Pumpkins enjoy plenty of nitrogen so they appreciate a feed of general fertiliser a few weeks after planting. They will begin to produce long stems which can be trained in a circle around the plant to prevent them spreading too far. They have deep roots and are normally quite capable of finding their own water within the soil, but in very dry periods some supplementary watering may be required.
How feed and pollinate pumpkins
Pumpkins are very vigorous growers, so they need a lot of fertiliser throughout the season to keep them healthy. The video above shares lots of top tips to help with feeding and pollinating. Here’s a quick recap:
- Use a high nitrogen feed every week until the flowers start to appear, then switch to a high phosphorous feed. When the fruits begin to develop, switch back to a high potassium feed again. Pumpkins are thirsty plants too, and regular watering is essential if you want to produce a decent crop.
- Pumpkins are normally insect pollinated, but if the fruits aren’t setting then you may need to hand pollinate them. Female pumpkin flowers can be identified by a swollen bump at the base of the bloom, which the male flowers don’t have. Don’t be alarmed if the first few flowers are all male. This is normal, and you’ll start to find female flowers developing soon after.
- As the flowers develop, pick a single male flower and remove its petals. Press it against the centre of each female flower. If you prefer, you can tickle the centre of each flower with a small paintbrush to transfer the pollen from the male flower.
- If you’re growing pumpkins for Halloween then you’ll be hoping for the largest fruits possible. Select just two or three pumpkins per plant and remove all the others to focus the plant’s energy on your chosen fruit.
How and when to harvest pumpkins
Leave your pumpkins on the plant for as long as possible until the skin has hardened and the fruits start to crack near to the stem. But be sure to harvest them before the first frost. Cut each fruit from the stem, leaving several inches of the stem attached. Watch the video above for more harvesting advice.
Pumpkin growing tips
These flavoursome miniature pumpkins are perfect for carving and cooking
Image: Pumpkin ‘Wee be Little’ from Thompson & Morgan
- Pumpkins can be prone to rot if left to sit on wet ground so it’s a good idea to raise the fruits off the damp floor using a wooden board or a large upturned seed tray.
- They need lots of sun to ripen, so remove any foliage that’s casting shade.
- If you need your pumpkins for Halloween, you may need to harvest them a few weeks before and bring them into a warm room to help them ripen in time.
How to use pumpkins
Delicious to eat, pumpkins have plenty of decorative uses too
Image: Thompson & Morgan
- Table decorations – Use small pumpkins as table decorations along with a display of colourful autumn leaves. Or, if you’re really creative, make individual place settings for your dinner party guests!
- Halloween carvings – Small pumpkins can look very effective and are easier for young children to handle. There are lots of free templates online that you can download to really impress your neighbours.
- Soup bowls – Pumpkin soup is delicious and looks really effective presented in hollowed-out pumpkins. Simply scoop out the flesh, making sure that the ‘bowl’ is sturdy enough to hold the soup. Take a look at our home-grown recipes page, where you’ll find some great ideas for spicy pumpkin and butternut squash soups.
- Pumpkin seeds – Don’t throw away your scooped out pumpkin innards! Simply wash and dry the seeds, sprinkle them with oil and a little salt and pepper before roasting in the oven. Use them as a garnish on soups and salads or enjoy as a tasty snack.
We hope this has answered all your pumpkin questions. Now all you need to do is decide which new variety of pumpkin seeds to try! Post your images on social and remember to tag us in using #YourTMGarden. Find more pumpkin advice and plenty about sowing and growing squashes too at our pumpkin and squash hub page.
An Essential Guide to Growing Pumpkins—From Planting Seeds to Harvest
One of the best things about Halloween is choosing the perfect pumpkin at the patch or store, then spending the afternoon deciding how to carve it, drinking apple cider, and pondering how you plan to craft your costume. But if you want to save yourself a trip (and test your green thumb), you can also opt to grow your very own pumpkins.
Caring for homegrown pumpkins when they’re in the ground can be a time-intensive process, but as long as you set a routine, there will be big orange gourds in your garden in just a few months. Here, Danny Watson, a garden center associate at The Home Depot, shares his best tips for planting and growing pumpkins from seeds.
When to Plant Pumpkins
The best time to plant pumpkin seeds is from late May to early July, so you can enjoy them in the fall. You can choose store-bought seeds that are ready for planting or collect the seeds from a pumpkin you just carved—it’s a pretty easy task. Before you plant pumpkin seeds, keep in mind that you’ll need plenty of room in your backyard to space out the seeds, so aspiring pumpkin growers who lack substantial outdoor space might want to stick to the pumpkin patch or store.
How to Plant Pumpkin Seeds
Prep Your Seeds
If you’re planting seeds that you removed from the inside of a fresh pumpkin, there’s some prepping you’ll need to do before you plant them in the ground.
First, you’ll need to clean off the pulp. Place the seeds in a colander and rinse them with cold water. “Once you’ve rinsed all the seeds, separate and select the biggest seeds,” Watson says. “They have a better chance to grow and flower. Space them out on a paper towel, so they can air-dry.”
If you’re not ready to plant them just yet, you can store the seeds by putting them in an envelope and placing them in the back of your refrigerator.
For store-bought seeds, Watson suggests choosing between these three varieties: Autumn Gold if you’re looking to grow pumpkins you can carve; Dill’s Atlantic Giant if you want to grow giant pumpkins upwards to 200 pounds; and Casper if you like all-white versions.
Pick a Planting Site
“Pick a planting site with full sun to light shade,” Watson recommends. “Keep in mind that the soil should be able to drain because pumpkins prefer soil that is not too soggy.”
Pumpkins need room to grow, so you’ll need to clear a big spot in your yard. “Due to large vines, it is best to plant your pumpkin seeds five feet apart,” Watson says. “If you are growing a smaller variety of pumpkins, the spacing changes—instead, space them three feet apart.”
Check the pH level of your soil (which you can do with a kit)—it should read between 6 and 6.8. Make sure the area is clear of any pests, insects, and weeds: “You can use weed block two weeks ahead of planting, which will allow the weeds to die naturally,” Watson suggests. Another option? All-natural weed killers.