Charity is the only mitzvah that has no limits. Unlike tzizit, for example, which have a fixed number of strings and knots, or the animals sacrificed in the Holy Temple, each of which must be a certain age, or even the succa, which cannot be more than 20 amot (around 30 feet) tall, charity has no limits. According to Shneur Zalman of Liadi, otherwise known as the Alter Rebbe, although twenty percent of income is customarily considered to be the maximum sum required for annual giving, this amount applies only to those who strictly keep all the commandments or mitzvot. For those of us who fall short in our observance - which includes just about everyone according to the Alter Rebbe's strict standards - there is no set limit to giving (Igeret HaKodesh, section 10). Moreover, if we truly want the Messiah to come, we may have to keep on giving charity until we are flat broke, "until the last penny has left our pocket." (Sanhedrin 97A) In order to understand what giving charity is all about, the Alter Rebbe provides a lesson in kabbalistic horticulture (Igeret HaKodesh, section 8). There, planting a seed is compared to giving a coin to a poor person. A plant's capacity for growth has little to do with the seed, which essentially rots after it makes contact with the earth. Instead, the seed simply activates the earth's vegetative power, which causes the plant to grow. In a similar fashion, giving a coin to a poor person activates God's charitable power, which benefits the donor and the world at large as much as the recipient of the coin. And giving charity in the Land of Israel, according to the Alter Rebbe, is most beneficial of all. The idea of a seed accessing the earth's latent vegetative power is summed up in the experienced gardener's admonition: "feed the soil in order to feed the plant." This refers to the rich microbial life upon which soil fertility and plant growth depend. Regular application of compost (rotting vegetation or aged manure) is the best way to feed the invisible soil organisms that, in the end, provide sustenance for plants. Decomposing bacteria and mycorrhizal fungi break down minerals into their ionic components, which are then absorbed by plant roots. There are thirteen earthbound mineral elements - in addition to hydrogen and oxygen from water, and carbon from air - upon which plant life depends. No matter how robust the seed, if any one of the earth's minerals needed by plants is absent from the soil or cannot be absorbed by roots, healthy vegetative growth cannot occur. Even when all these minerals are present, some of them - especially iron - may be locked up in the earth if the soil pH is too alkaline. This is often the case in areas where the climate is hot and dry, as in much of the Land of Israel. For this reason, when shopping for fertilizer, it is advisable to look for products that contain a full complement of the minerals - macronutrients and micronutrients - that plants require. The symptoms of mineral deficiency are often apparent in a plant's foliage. Nitrogen is the principal ingredient in most fertilizers. Nitrogen makes plants green, and when foliage turns yellow it is usually because of a lack of this element. Nitrogen is highly mobile and, when in short supply, will move into a plant's shoot tips where active growth is taking place and the need for nitrogen is most acute. Thus, if you notice a plant whose shoot tips or newest leaves are green, while older leaves are yellow, you almost surely have a nitrogen deficiency. By contrast, iron does not move easily in a plant and its deficiency, characterized by yellow foliage with green veins, is noticed on newer leaves. Can we grow a Fuji apple tree from a seed? How many years will it take until we get fruit? - Yehuda Nygate, Pardes Hanna Apple seeds may be germinated by chilling in a bag of moist peat moss in the refrigerator for two months. Upon removing the seeds, plant them in pots or paper cups next to a sunny window or, if the weather is mild, outdoors. Do not be disappointed if less than half of your apple seeds sprout, which is typical. It takes six years for an apple tree to produce fruit and, even then, the chances of the fruit being tasty are remote. The genes in apple seeds are wild and unpredictable and the fruit produced from seedling trees is usually bitter. Named fruit varities such as Fuji or Anna grow from cloned trees. The only way to make a Fuji apple tree is by rooting or grafting a shoot or bud from another Fuji tree. Still, every seed is different and, like children, you never know what they might become. There is always a chance that the apples from your seedling tree might be the sweetest ever grown. If you plant apple seeds, expect mature trees to grow thirty feet tall. Nursery grown apple trees, by contrast, whether for orchard or backyard use, are usually grafted onto dwarfing rootstocks and do not grow taller than fifteen feet. The writer welcomes gardening questions from readers and will answer each one, whether by e-mail or in this column. If you have a question, send an e-mail to email@example.com. Please include your full name and location.