How to cultivate and harvest summer and winter squash in Southcentral Alaska

Table of content

  • Where to grow
    • Greenhouse and hoop house bed preparation
    • Garden bed preparation
  • How to grow
    • Starting seedlings
    • Planting
    • Maintaining plants
  • How to harvest
    • Storage
    • Seed saving

Where to grow

If a you have greenhouse or hoop house that is best for winter squash. If you do not have a greenhouse or hoop house a garden bed with rich well drained soil and full sun will have to do for winter squash, and is preferable for summer squash. It is best if the greenhouse, hoop house, or garden bed is on top of a south facing hill instead of in a low spot or on a north facing hill.

Greenhouse and hoop house bed preparation

Does your greenhouse have a gravel or geo-mat floor, if so you will need to make a raised bed. To make a raised bed you will need a large wooden box about 18 inches tall and at least 3 feet by 3 feet, the box does not need a bottom. You can have as many boxes as you want beds, but keep in mind that you want to be able to reach the whole box so a long narrow one is best for most greenhouses. Once you have your boxes fill them most of the way up with rich fertile soil. If you want to make your own soil you can take some poor soil and mix in well rotted organic matter and partially rotted animal manure such as horse or cow manure.

If your greenhouse does not have a gravel or tarp floor or you are building your bed in a hoop house then you can build a bed straight into the ground. If the soil is poor use a nutrient test kit to see what the soil lacks. If the soil lacks nitrogen add partially rotted manure, if the soil lacks other nutrients I suggest you use the help of University of Alaska Fairbanks Cooperative Extension’s soil testing services and advice, to visit their site click here. If the soil is too sandy, has too much clay, or has too much silt then you should mix in well rotted organic matter. When building a garden bed inside you have to be very careful about digging near supports, if you dig too close to a support it could damage the structure.

Garden bed preparation

For your garden bed pick a spot with full sun and rich well drained soil on a south facing hill. If the soil in the spot is not already rich and fertile then make a large fertile mound bed. I like to make a hugelcultur style mound. Start with some mostly rotten wood, pile a mixture of well rotted organic matter, poor soil and animal manure on the wood. Spray it down with a hose to make the soil settle in the cracks between the wood, then shovel more mixture in the holes. This should make a large mound. This is best for summer squash but also works for winter squash if a green house or hoop house is not available.

How to grow

Starting seedlings

Start seedlings inside 2 weeks before the last frost of the spring. Pick varieties that have short growing seasons. Plant seeds in pots 4 inches wide and 3 or more inches tall, the pot should be full of soil that hold water well such as potting soil. Plant 2 seeds per-pot. Put the pots in a plastic seedling tray in a warm window sill with a lot of sun. Do not let the soil dry out in the pot.


If planting your winter squash in a greenhouse in raised beds wait until the temperature stays above 40 °F, put the seedling where they are going to be planted for a couple hours each day until they have had time to adjust to the lower temperature. This process is called hardening off. When the seedling are done hardening off plant them in the raised beds, if you are planting more then 1 seedling in each bed then plant the seedling 7 feet apart. Keep the soil moist until the seedlings are about 6 inches tall and have their first set of true leaves and gradually slow the watering.

If planting in the ground in a greenhouse or hoop house wait until it does not get below 40 °F and then harden off. Once hardened off plant the seedlings 7 feet apart in rows 7 feet wide, with a 2 foot wide path between rows. Keep the soil moist until the seedlings are about 6 inches tall and have their first set of true leaves and gradually slow the watering.

If planting out side wait until it does not get colder 40 °F then harden off. Once hardened off plant the seedlings 7 feet apart in rows 7 feet wide, with a 2 foot path between rows. Summer squash should be planted 3 feet apart in rows 3 feet wide.Put small arches of pipe or wooden cages over the plants and put floating row cover on to keep the seedling from getting sun burn. Gradually expose the seedlings to more and more sun light until they no longer need the cages. Keep the soil moist until the seedlings are about 6 inches tall and have their first set of true leaves and gradually slow the watering.

Maintaining plants

Water once a week or every time the soil is dry. If you have planted more than one variety there will be cross pollination problems especially if you are trying to save seeds, to deal with them you need to know how to tell a male flower from a female flower. You can tell a female flower from a male flower because the female flower will have a small fruit the shape of the squash it will grow into behind the flower but the male flower will not. Every time a female flower is about to open put a small plastic bag over the whole blossom and use a twisty tie to tie it shut at the back of the flower. Come back latter when the flower is open or has just closed, take an open male flower break the petals off, take the bag off the female flower and open the female flower then rub the insides of the male flower on the insides of the female flower and put the bag back on. When the female flower blossom has gotten droopy then take the bag off of it gentle remove the flower and do not put the bag back on. When a squash starts forming put a large ceramic tile under it so that it does not touch the soil. If ever a blossom, squash, or even a stem gets moldy then cut it off of the rest of the plant and discard. As vines get longer and hang off beds in the greenhouse pick them up and tuck them inside the edge of the greenhouse bed.

How to harvest

If you are harvesting a pumpkin for long term storage or seeds you want it as mature as possible. For such a pumpkin wait until it is the day before the first frost in the fall where the plant is, then cut all the pumpkins by using a very sharp clean knife and cutting the stem where it connects to the rest of the vine. Bring in all the pumpkin for storage or usage. For summer squash cut the summer squash off of the plant before the shell on a summer squash begins to harden, cut now because when the shell on a summer squash hardens the squash is not going to grow very much more and the frying quality will go down. If you are harvesting a summer squash for seeds wait until right before the first frost of the year and cut it off from the rest of the plant. When harvesting summer squash if there are fly or slug eggs on it that means it is or will soon rot and that you should cut it off the plant and discard.


Store pumpkins in a cool, dry, dark place on large shelves, on the shelves arrange pumpkins one pumpkin thick. The pumpkins can not get as cold as 40 °F. Check stock through out winter to make sure they are okay.

Saving seeds

To save pumpkin seeds cut the pumpkin in half with a clean knife then scoop out the seeds. On a different surface separate the seeds from the stringy flesh, pull out any small soft seeds. Put the remainder on a plate, towel, or small rack with close rungs. Put the plate or rack in a warm, dry, dark place until the seeds are dried. When the seeds are dry put them in a plastic zip lock bag, labile the bag with the variety of pumpkin and the date you put the seeds in the bag. If you are saving the seeds of more than one kind of pumpkin put them in different bags. It is the same procedure for summer squash.

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