Squashes and pumpkins are large plants which tend to sprawl or flop over into adjacent areas, so it's often a good idea to grow them at the edge of a bed to avoid potential problems with them growing over smaller or less vigorous plants like carrots.
Vining varieties of squash can be trained up supports to make it possible to fit them into a smaller space (and the default spacing in the Garden Planner assumes you'll be doing this). Make sure not to position these where they are likely to cast shade on other sun-loving crops.
If you'd prefer to let your squashes sprawl, you'll need to allow more space. You can adjust the spacings for the plant in the following way:
Double-click on the plant in your plan (or click on it once then click on the Edit Item button in your plan's toolbar).
Select your variety if necessary, then click on Customize Varieties.
Click Edit, then select the 'Use Custom Spacings' box. Enter the spacings you wish to use (spacing between plants for individual plants or blocks of plants, and spacing between plants in rows + spacing between rows for plants in rows).
Click Done.
Click Save All Changes.
Click Done.
