I love winter squash, especially butternut. But squash plants can take up a LOT of room in your garden. One squash plant on the ground can easily exceed 15 feet across. Because most of my gardens have been small, I didn't grow many squash plants until I started to use trellises.
I now grow 2 large butternut squash plants in a 4 foot by 4 foot area, giving each of them large 4 foot wide by 7 foot tall trellises – and I can harvest as much as 40 pounds (one full bushel) of squash from that tiny area! But to produce this much harvest in a small bed requires fairly deep soil, as squash plants have massive root systems.
I prefer to use large, sturdy trellises that I can move around the garden as I rotate my crops. My current trellises are made from livestock panels cut in half with bolt cutters, supported on t-posts pounded into the garden bed, and secured with strong zip ties.
You have a choice of weaving the vines within the trellis to support them as they grow, or you can tie the vines to the trellis. I do a little of both. Just don't expect the tendrils on the vines alone to support the heavy load of squashes as they mature.
This trellis is just over 4 feet wide and 7 feet high. I plant about 3 squash seeds at the base of each trellis, and thin them down to ONE squash plant that looks the most vigorous. I train about 6-8 vines from that one plant to grow up each trellis. I don't want to overcrowd them, as I want good ventilation to reduce disease, and I want it to be easier for me to search for squash bugs.
I cut off all other vines at the base of the plant. I don't let any vines grow on the ground, as they tend to hide a lot of squash bugs. You will also see side-shoots form on most of the vines on the trellis, and I just prune them off, too. You will get plenty of squash from the main vines on the trellis. My plants usually grow 1-2 feet beyond the height of my 7 foot trellises, and just dangle down from the top.
Squash plants grown on trellises need more irrigation that those growing on the ground. The higher leaves lose more moisture to evaporation. In addition, because the vines are not growing on the ground, they cannot sink more roots into the soil along their vines as they are usually able to.
Butternut squash and some other winter squashes don't need any extra support for their fruit, unlike melons (which do need the support of slings to keep from falling off the trellised vines). But I probably wouldn't try trellising squashes that will exceed 10 pounds or so. But if you have success trellising larger squashes, let me know!
This year, in 2012, we had a wonderful growing season, and our squash ripened early. They usually develop mildew and die down by mid-September, but we picked this harvest just before Sept. 1st.
Use a sharp pruning shear, and cut the squash carefully from the vines. Leave about 2 inches of stem attached to each squash. If you break this piece off, the squash will usually rot early, instead of lasting all winter. Eat them first. Don't drop or toss the squash during harvest or storage, as they can bruise and won't store as well as a result.
I didn't find any immature squash this year. Mature butternut squash are a solid tan color, and the skin resists being punctured by a fingernail. I don't usually do the fingernail test, as I just harvest the squash when the vines have died back or just before a frost. Immature squash are usually a pale green color. They won't store well, and their flavor is poor.
In the past, I have planted 4 squash in 16 square feet, training 2 plants each on the 2 trellises. I harvested about the same number of squash, but they ended up being much smaller fruit. So, for now, unless future experiments show me otherwise, I plan to grow just one vigorous plant per trellis, and enjoy larger squashes.
These 17 squash weighed 40 pounds, and filled a bushel basket. I spread them out in a warm, dry room in my house and will let them cure for a few weeks. Then, as the weather cools down, I will put them on shelves in a cool room for storage – usually around 55-60 degrees. These squash become sweeter after curing, and I usually start eating them by Thanksgiving, if not a couple of weeks sooner. If I haven't finished eating them by the end of winter, they are still usually in good condition by late May or so.
Well-grown squash from my garden tastes better than anything I can get in the stores. The rich flavor has spoiled me, and I now refuse to buy store squash because I am so disappointed in the taste. Growing squash on trellises has been very successful for me. I urge you to give it a try yourself!
Related Article: Growing Watermelon on Trellises