How to Grow Pumpkins from Seed: Easy Steps for Cold Climate Gardens

Growing pumpkins from seed can be a fun and rewarding experience, especially if you’re gardening in colder, alpine regions. While pumpkins thrive in warm climates, with a few simple adjustments, you can enjoy a successful pumpkin harvest even in alpine conditions. Follow these easy steps to get started!

Step 1: Prepare Your Soil for Pumpkin Growing

Pumpkins love rich, well-draining soil that’s full of organic matter. Before planting, prepare your garden bed by adding plenty of compost or well-rotted manure to enrich the soil. Ensure the bed gets plenty of sun, as pumpkins need a good 6-8 hours of sunlight per day.

Our rocky mountain soil can be low on nutrients, and pumpkins are heavy feeders, so your pumpkins will appreciate whatever improvements you make to the soil they'll be growing in.

Tip: If your soil tends to hold water, consider building slightly raised mounds to ensure good drainage. Each mound should be about 30 cm high and 90 cm wide to give your plants space to spread out.

Step 2: Start Pumpkins from Seeds Indoors

To give your pumpkins a strong start, begin sowing seeds early indoors, around 4-6 weeks before the last expected frost date. We have a shorter growing season than other places so we need all the head starts we can get. Use biodegradable pots (like newspaper pots) to avoid disturbing the roots when transplanting. Plant 2-3 seeds per pot, about 1-2 cm deep.

Place your pots in a warm, sunny spot, and keep the soil consistently moist but not waterlogged. Seeds should germinate around the 10-14 day mark, depending on how warm they are.

Step 3: How to Transplant Pumpkins Outdoors

Before planting outdoors, 'harden off' your seedlings by placing them outside for a few hours each day, gradually increasing the time over a week until you can leave them outside in the all day sun. This helps them adjust to outdoor conditions without getting sun burnt. Just like you on the first sunny day since the cold winter, if you were out enjoying the sunny mountain air for 8hrs straight with no protection, you would get sun burnt too. Just remember to bring them inside at night though, our mountain regions can still get very chilly nights.

When transplanting outdoors, wait until the soil has warmed to at least 18°C (64°F) and all danger of frost has passed. For my alpine region, this is typically 2-3 weeks before the end of spring, any earlier than that and I'm still in potential frost danger. It's tempting to get excited and want to plant them out earlier, because that's what the rest of the country is doing, but trust me when I say, we are unique and our plants need to be treated differently.

Pumpkins grow big, not just the fruit but the vines and leaves too. If you are limited on space try going vertical. You could let them grow up a fence, an arch trellis, a strong teepee of tree trimmings, a dead tree or old washing line, get creative, have some fun! Just make sure it is strong, you are growing pumpkins remember, and pumpkins can get heavy.

Step 4: Watering and Mulching your Pumpkins

Pumpkins need consistent watering to thrive, especially during flowering and fruiting, which is typically when we experience the least rainfall. Water deeply at the base of the plant rather than from above, it's the roots that need a soak. Overhead watering may make you feel productive but you're just washing the leaves, and wet foliage can lead to fungal diseases.

In our alpine climates, where moisture can be variable, mulching around the base of your plants helps to retain moisture and regulate soil temperature. Use straw or old autumn leaves as mulch, but leave some space around the stem to prevent rot.

Step 5: Fertilise! Pumpkins are Hungry Beasts

Like I said earlier, pumpkins are heavy feeders. To keep your plants strong and productive, feed them with compost, well rotted manure, and worm castings throughout the season. It can be tempting to use the brightly coloured bags with pretty pictures from the garden centre that say N-P-K this that and the other, but to be honest pumpkins are happiest with composted food waste and what comes out of the back end of a sheep or worm. Keep it simple. Some of my best pumpkins were accidental plants that self sprouted from pumpkin waste which was literally thrown out with the scraps into the compost bin.

Step 6: Pollination

For pumpkins to produce fruit, they need pollination, which is typically done by bees and other insects. If you notice plenty of flowers but no fruit, it could be a lack of pollinators. Consider hand-pollinating by transferring pollen from the male flowers (the ones with long stems) to the female flowers (the ones with a small bulb at the base).

But if you have a lack of pollinating insects you've got bigger problems than not having your pumpkins pollinated. Seriously consider planting an array of flowering plants that pollinators love to encourage them into your garden. Also, talk to a local beekeeper to see if they can place a hive nearby.

Step 7: Harvesting Your Pumpkins

Pumpkins are usually ready to harvest 90-120 days after transplanting outside, depending on the variety. You’ll know they’re ready when the skin is hard, and the stem begins to dry out. A good rule of thumb is to harvest before the first frost, as cold temperatures can damage the fruit.

Use pruning shears to cut the pumpkin from the vine, leaving a few inches of stem attached. This helps extend the pumpkin’s shelf life.

With these simple steps, you’ll be well on your way to growing pumpkins in your alpine garden, even in cooler climates. Whether you’re planting for decoration or for delicious recipes, following these guidelines will set you up for success.