Expert players will be aware of the dual use for Crops in both Rune Factory 1 and 2, but beginners may not be familiar with the system and may not understand how it works. Runes are tiny orbs of brilliant light that can be found on a plot with 9 fully ripened Crops/Flowers. In both Rune Factory games, your character's energy levels are determined by two factors: HP (Health Points) and RP (Rune Points). When your character's RP bar reaches zero, any use of tools will begin to consume HP. This is the most simplistic explanation and in fact, there are other uses for Rune Points, such as the casting of Spells. At the start of the game, however, it is mainly in order to preserve your HP that you need to keep your RP at maximum.
Only an entire 3 x 3 plot filled with fully-ripened crops will produce 1 Rune Point daily. If you harvest ANY of the crops/flowers in that plot, a Rune Point no longer will appear. What this means in effect is that you need to have a strategy with respect to the crops that you grow throughout the map.
A Crop grown in any of the dungeons/caves may be more useful sometimes as a source of Rune Points than for the product it produces. Keep the 3 x 3 plot of crops intact and it will continue to produce 1 Rune Point daily. This can be very useful when your energy is depleted while fighting monsters and smashing rocks for treasure.
Don't forget to continue to water the crops that are fully ripened in any field if you choose not to harvest them.
Crops in Rune Factory, as in any Harvest Moon game, ripen at different rates and have different values. A crop with a high shipping value should be grown for shipment. One with a very low shipping value can be grown for Rune Point production instead.
For example, in Spring in Rune Factory 2, you can grow Pink Turnips. (Regular turnips, I believe, are the equivalent in Rune Factory 1.) They grow very quickly and have a fairly low shipping value compared to some of the other Spring Crops. Although you may be in need of money in the first Spring, you still should keep some 3 x 3 plots filled with fully ripened Turnips or Pink Turnips in order to have access to Rune Points on a daily basis.
There is a question of timing as well when considering when to harvest a crop. If you wish to harvest the crop and ship it, you still should wait until the Rune Point it has produced can be used effectively and not harvest it at 6.00 a.m. when both energy bars are filled. In Rune Factory 2, for example, shipments are collected by Mana at 3.00 p.m. It would be a waste of a good Rune Point to harvest a 3 x 3 square of fully ripened crops of any kind at 6.00 a.m. Better to use some energy either in chores or fighting monsters, then replenish the energy with the Rune Point before you finally harvest the Crop prior to 3.00 p.m.
Remember that you need to have fully-ripened Crops or Flowers in all 9 squares of any 3 x 3 plot in order to produce 1 Rune Point. If one square ripens more slowly or if you harvest one or two of the plants, no Rune Points will appear. It therefore requires an 'all or nothing' strategy where harvesting is concerned.
There is one further consideration or potential complication in both games. If you wish to keep fully-ripened Crops/Flowers in your field on the farm, you cannot set any Monsters the task of harvesting your Crops!