By all means go crazy. Add as much as you like to your order. It's only when the order gets too big or too heavy that overweight shipping applies.
Even then, I'll see if I can get standard rates for you first with some clever packaging. I often can and your order gets shipped as normal, nothing extra to pay :)
What makes an order overweight / oversize?
Overweight / oversize shipping rates apply for heavy orders, or very large boxes. It's normally when your order is over 10 litres of products combined (such as potting mix), but it can also be when you have a lot of large yet light items which have to be shipped in a very large box or two boxes. The overweight / oversize shipping rate is the same as the standard shipping rate, so instead of $5 for Auckland Standard for example, it would be $10 (2 x $5).
What if an order has free shipping but is also overweight / oversize?
Please note free shipping doesn't cover overweight / oversize orders, so if your order is large or heavy, and over $99, you don't pay the normal shipping rate, you only pay the overweight shipping rate. For example, instead of paying $10 for Auckland Standard for an overweight or oversize order, if your order is for over $99 of products, you'd only pay $5.
How do I know I need to pay extra for shipping?
If I can get your order in one box I will, and if that one box isn't too big or heavy I can often get you standard rates. In which case there's nothing extra to pay. Only if I hit overweight or oversize courier rates will I pop your order on hold and get in touch to let you know if any extra shipping is payable.
However, if your order is overweight, I'll email you a link to pay the extra, no bank transfer needed. It's just added to your order, so the same website payment methods apply (credit card, Afterpay etc). You don't have to pay however. You can adjust your order instead. Just let me know what you want taken out and I'll remove the extra products and refund you for them, then get your order on the way.
How much is overweight / oversize shipping?
Normally it's the same as the flat rate shipping for smaller orders. For example, if the flat rate is $5, overweight adds $5. You can check the flat rate shipping rates here If your order qualifies for free shipping, you only need to pay for overweight / oversize shipping.