Thanks to John Harrison of Allotment & Gardens
In April, take a seed and gently file it along the edges so that it will be easier for it to break through when it germinates. You can start them off by placing between some damp (not wet) paper towel, or sow direct in a 5 litre pot filled with seed compost with the pointed end down. They won’t germinate well at room temperature, so place them in a warmer environment at 25-28C. Germination will take 1-4 days, at which point the temperature needs to go down to 18-20C. Then the young plant can grow on in the pot which needs to be placed somewhere sunny. After 7-10 days it will need to be transplanted to a ‘pumpkin patch’ outdoors or in a large polytunnel.
The Pumpkin Patch – Preparation
Pumpkin plants are fast growers and heavy feeders. They will need 300-600 sq feet, ideally with some kind of fence or barrier to provide protection from the wind. A loamy soil is best, and it’s always a good idea to dig in plenty of well-rotted cow manure during the previous autumn. The ideal pH is between 6.5 and 7.2.
Transplanting Pumpkins
When transplanting, you need to bear in mind that a huge plant will grow outwards with a long main vine and with many secondary vines coming off it. The first 2 leaves on the plant are the cotyledons, the next one is the first “true” leaf. The main vine will run in the opposite direction from the first true leaf, so when transplanting make sure it’s facing the right way for it to grow in the desired direction. Like all curcurbits, they are not frost hardy so protection from cold nights and frost up until the end of May is vital. A mini cloche built from a wooden frame and clear plastic sheeting will do the job.
Pruning Pumpkins And Vine Maintenance
As June progresses, a high nitrogen feed is a good idea to promote leafy growth. The main vine will grow outwards towards the centre of the patch. If it grows wayward, train it by placing bamboo sticks either side. As it grows longer, secondary vines will appear at the nodes where the leaves appear.
Using bamboo canes again, train each of the secondary vines to grow away at 90 degrees from the main vine. As the secondary vines grow, they in turn will produce tertiary fines at the leaf nodes – these should be pinched off. If you don’t pinch them off, the plant will rapidly turn into a tangled mass of leaves, which will encourage disease and rot. You’ll also find rogue pumpkins lurking in there too, taking energy from the main one! So it’s important to keep up with this work, because at this stage of growth the plant is growing rapidly, with vines increasing in length from 4 – 8 inches per day!
Also at each node will appear a male flower, a tendril, and a tap root. The tap roots can appear from above and below the node, so bury each node under some soil, so that they both have a good chance of rooting. The more roots the plant has, the more water and nutrients it can take up, and the bigger the pumpkin! They will also help to stabilise the plant during windy days.
The main and secondaries should grow out in the shape of a Christmas tree; terminate the first secondaries when they are 15 to 20′ long and then as you go up the main make them progressively shorter.
Pumpkin Pollination
You’ll notice that there are two different types of flowers on your pumpkin plant. At each node there is a male flower, but sometimes you will notice it’s a little different – it’ll have a ‘baby pumpkin’ about the size of a golf ball at its base. This is a female flower, and when pollinated they’ll go on to form pumpkins.
However, you need to pinch off ALL the female flowers, apart from one on the main vine when it appears at a minimum of 10 feet out. The female flowers usually open at sunrise just over a week after they first appear. When they do open, pollinate it as early as possible in the morning with one or more of the male flowers, either from the same plant or another Atlantic Giant. Make sure plenty of pollen is rubbed over the stamen. Then tie up the flower petals with some string to prevent water getting in, contamination, dehydration etc.
If the pollination has succeeded (and sometimes they don’t), you’ll see the fruit swell day by day. When it’s about the size of an orange it will need piece of plywood covered in sand to lie on. This might need to be adjusted on a daily basis as the fruit grows. Try and manoeuvre the vine so the fruit is on the outside of a curve. You can remove secondary vines if necessary – think 2 months ahead when there is potentially a huge pumpkin there – it will need the space, and you don’t want it growing on top of the vines. While it’s still big enough to lift, carefully place it so it will grow on a large piece of plywood covered with an inch of sand.
The Fruit
It’s possible that the first one will abort, or the pollination didn’t take, so it’s a good idea to pollinate a few ‘spare’ pumpkins further up the vine. These can be removed when you’re sure the first one has taken, which is usually when it gets to about 40 inches in circumference.
As it grows, the pumpkin will need some protection from the wind and sun so that the skin does not dry out and remains supple enough for growth. Cover it with a white sheet, or erect a mini tent or umbrella shade over it.
Continue to pinch out rogue tertiary vines and bury nodes as the summer progresses. Keep the whole plant, including the buried nodes, well watered especially during hot and dry periods. Foliar feed is always a bonus. High potassium feed is good for fruiting. Be prepared for blackfly in July, and powdery mildew in August. The pumpkin itself should stop growing and be ready for harvest around the end of September.